Nanomaterials and advanced characterizationI
Advanced functional films grown by pulsed deposition methods
There is a growing interest towards pulsed methods like High Power Impulse Magnetron Sputtering (HiPIMS), Pulsed Laser Deposition (PLD), Pulsed Electron Beam Deposition (PED), etc. for thin films and nanostructures synthesis. Indeed, unique properties can be obtained thanks to the specific characteristics of pulsed processes.
Advanced functional thin films require specific properties and their performances are tightly related to their composition, structure, surface morphology and interface properties which, in turn, are dictated by the film growth environment. Pulsed deposition methods of thin films offer unique opportunities to obtain high performance materials.
The symposium aims at discussing cutting edge research on pulsed deposition techniques such as HiPIMS, PLD, PED as well as pulsed RF/DC magnetron sputtering, arc discharges and other processes for which the pulsed characteristics play a key role in the film growth. The goal is to better understand the relationship between parameters such as the high kinetic energy of film forming species, pulse width and pulse repetition rate, ionization of plasma species, transport phenomena, non- equilibrium growth, etc. and the film properties. Whatever the pulsed deposition process, this symposium aims at discussing the growth of oxides, nitrides, carbides and related thin films which cover a wide range of controllable properties. Specificities of the pulsed methods effects on thin film stoichiometry, structure and surface morphology will be addressed with particular emphasis on low temperature crystallization and epitaxy, metastable phase stabilization, self-assembled nanostructures, nanocomposites, nanosheets on rigid/flexible substrates, etc. The effect of pulsed deposition methods on the films quality and the promotion of novel or substantially improved structural, chemical, optical, electrical, magnetic, mechanical, biocompatible, bioactive, catalytic properties, etc. will be highlighted. Applications in transparent electronics, spintronics, resistive switching, renewable energy, tribology, catalysis, and sensing are meaningful illustrations of the expected results from the research carried out on films grown by pulsed methods.
Hot topics to be covered by the symposium:
- Advanced functional thin films by pulsed deposition methods with emphasis on the role of process parameters (high kinetic energy of species, pulse width, growth rate, etc.)
- Focus on the relationship between the thin films structure and physical properties
- Oxide, nitride, carbide and related thin films for a wide range of advanced applications
- Nanocomposite and metastable phase thin films
- Self-assembled nanostructures, growth and novel properties
- Low / room temperature epitaxial growth of thin films by pulsed methods
- Van der Waals epitaxy on 2D materials and flexible substrates.
List of invited speakers:
- Amaël Caillard, GREMI, CNRS/University of Orléans, France
- Carles Corbella Roca, Department of Mechanical & Aerospace Engineering, The George Washington University, USA
- David B. Geohegan, Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, USA
- Ulf Helmersson, Linkoping University, Sweden
- Michael Lorentz, Felix-Bloch-Institut für Festkörperphysik, Halbleiterphysik/Semiconductor Physics Group, University of Leipzig, Germany
- Francesco Pattini, Institute of Materials for Electronics and Magnetism, CNR, Italy
- Tetsuhide Shimizu, Tokyo Metropolitan University, Japan
- Nathalie Viart, Institut de Physique et Chimie des Matériaux de Strasbourg, Ecole Européenne de Chimie, Polymères et Matériaux - Université de Strasbourg, France
One invited talk will be selected amongst submitted oral contributions to bring to the stage younger researchers who make significant contributions to the field of the symposium, and to also promote the participation of the less represented gender.
Scientific committee members:
- Jacques Perriere, Sorbonne Universities, UPMC Paris 06 & CNRS, Paris, France
- Manfred Martin, RWTH Aachen University, Germany
- Eric Millon, GREMI, University of Orléans, France
- Maryline Guilloux-Viry, University of Rennes 1, France
- Rosalia Serna, Spanish National Research Council, Madrid, Spain
- Maria Luisa Grilli, ENEA Casaccia Research Centre, Italy
- David Babonneau, University of Poitiers-ENSMA, France
- Peter Kelly, Manchester Metropolitan University, UK
- Damien Thiry, University of Mons, Belgium
- Daniel Lundin, University Paris Sud, France
- Anke Weidenkaff, Technical University of Darmstadt, Germany
Papers will be published in Thin Solid Films (Elsevier Ltd.).
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|09:35||Welcome - N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis|
Fundamentals of pulsed deposition methods : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : Amaël Caillard
Affiliations : GREMI, CNRS/Université d’Orleans, UMR 7344, 14 rue d'Issoudun, 45067 Orleans Cedex 2, France
Resume : The HiPIMS (high-power impulse magnetron sputtering) technology has been developed over the two decades, and it is now widely used for the deposition of various thin films. This PVD method is a derivative process of conventional magnetron sputtering (MS). MS is based on the formation of a plasma created by the bombardment of a target by energetic ions (Ar+) leading to the sputtering of atoms that are deposited on a substrate. The plasma density is controlled by the electrical power applied to the target from a continuous current and voltage supplier. In HiPIMS, the use of a high power density around several kW/cm2 with short pulses in the 1 to 100 s range allows to get higher plasma densities and ionization degrees, compared to direct current (DC) magnetron discharges. In this paper, we will describe the physical phenomena involved in HiPIMS process with a particular focus on the nature of sputtered species in the deposition chamber, their nature (ions, neutrals), and their spatial and energy distributions regarding the applied experimental conditions (voltage, current, pulse duration, plasma gases…). A comparison will then be made with two other well-known deposition methods that use pulsed sources : pulsed-laser deposition (PLD) and pulsed-electron beam deposition (PED). In the most common configuration, PLD uses lasers that deliver pulses with a few ns duration focused on the target while, in PED experiments, the electron beam pulse width is in the order of several tens ns. Regarding these 3 techniques, the nature, the density, the energy and spatial distributions of the emitted species will be compared and related to the chemical and physical properties (composition, morphology, crystalline quality..) of the obtained thin films.
Authors : D. Dellasega (1), F. Mirani (1), D. Vavassori (1), A. Maffini (1), D. Orecchia(1), C. Conti (2), D. Loiacono(1), M. Beghi (1), M. Passoni (1)
Affiliations : (1) Department of Energy, Politecnico di Milano, Milan, Italy; (2) ISPC, National Research Council, Milan, Italy
Resume : In the present work the formation dynamics of non-equilibrium hexagonal and face-centered cubic crystallographic phases in titanium (Ti) coatings, comparing HiPIMS and PLD pulsed techniques, is presented. Thanks to their exceptional material properties Ti films have been extensively studied and exploited in various technological fields. In addition to the common hcp (α) and bcc (β) crystalline phases, a high pressure metastable simple hexagonal (ω) phase has been obtained in bulk Ti by high pressure torsion . Epitaxial growth of ω-Ti is also possible . In addition, a face-centered cubic (fcc) phase, not predicted by the equilibrium phase diagram of Ti, was firstly observed in thin epitaxial films evaporated on NaCl single crystals . As reported in literature, the fcc phase is unstable and its transition to the α-phase takes place beyond a critical thickness around 1-20 nm. Exploiting the features of HiPIMS, we report the deposition of Ti films on Si containing showing the presence of the ω and fcc phases. This was achieved by tailoring the energy of the impinging species via substrate bias. HiPIMS pulse parameters have been optimized to maximize the amount of Ti ions. Films deposited in low energy ion conditions (bias = 0 V) exhibit the Ti fcc phase up to a maximum thickness of about 370 nm. Its evolution is correlated to the evolution of the intensity of the stress field in the film. Differently, films deposited under high energy conditions (bias = 300 - 500 V) show the nucleation of the Ti ω-phase for thicknesses greater than 260 and 330 nm, respectively. Its appearance is also related to the formation of elongated grains 100s nm long. A compressive-tensile-compressive (CTC) behavior is observed for residual stresses as thickness increases. To compare HiPIMS with other pulsed deposition techniques, Ti films have been deposited also by nanosecond- and femtosecond- PLD in a low and high fluence regime (1 - 10 J/cm^2). The deposited films have been characterized by XRD and SEM. Stress state and elastic properties of the deposited films have been assessed respectively by Stoney curvature method and Brillouin spectroscopy.  M. Tane, Acta Materialia 61 (2013) 7543  Y. Cheng, PRL 76 (1996) 21  F. E. Wawner, J. Vac. Sci.Technol. 6 (1969) 588
Authors : Benjamin Dey1, Simon Bulou1, Thomas Gaulain1, William Ravisy2, Mireille Richard-Plouet2, Antoine Goullet2, Agnès Granier2, Patrick Choquet1
Affiliations : 1 Luxembourg Institute of Science and Technology (LIST), Luxembourg 2 Institut des Matériaux Jean Rouxel (IMN), France
Resume : Thin films of titanium dioxide TiO2 are of major interest due to their valuable properties: photocatalysis under UV exposure, self-cleaning, anti-fogging, and anti-bacterial. Among the different TiO2 polymorphs, anatase is by far the most interesting for photocatalytic applications. The conventional deposition processes usually require deposition of several hours and/or a step of annealing above 250°C to get the anatase phase. Nowadays, the demand of flexible devices is soaring for various applications. Therefore, there is a high interest to synthesize anatase TiO2 films on thermally labile substrates. In this work, we study the interest of pulsing a high-density ECWR plasma source compared to its use in continuous mode with the aim of obtaining crystallized anatase TiO2 layers at low substrate temperature (< 100°C) using an organometallic TTIP as precursor. TiO2 thin films were characterized by means of Raman Spectroscopy, XRD analysis, Scanning and Transmission Electron Microscopy. Their photocatalytic performances were evaluated by measuring their ability to decompose stearic acid under 365 nm UV-light. This presentation will demonstrate the strong interest of using a pulsed plasma. Indeed, a fine tuning of pulsing parameters (pulses length, frequency and crest) is necessary to enable the synthesis of high photocatalytic films based on a high density of crystallised anatase grains. Every evidences brought in light, that a thin film growth happens even during time off , indicating different growth mechanisms between CW and pulsed plasma.
Authors : Florian Jung (a), Ralph Delmdahl (b), Andreas Heymann (b), Max Fischer (b), Helmut Karl (a)
Affiliations : (a) University of Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany (b) Coherent LaserSystems GmbH & Co. KG, Hans-Böckler-Str. 12, 37079 Göttingen, Germany
Resume : Pulsed laser deposition finds application in a variety of technological and scientific fields. In particular, precise control of the laser target interaction is crucial for achieving reproducible epitaxial thin film growth. For that, a homogeneous and defined energy density distribution at the ablation target plane has to be targeted not only for optimal stoichiometry transfer and reproducibility, but also for meaningful study of laser target interaction effects. In this work we discuss and correlate morphology and crack formation together with compositional changes of the laser ablated target areas by using a KrF excimer laser beam delivery system consisting of an adjustable aperture homogeneously illuminated by a focused laser beam. The aperture opening is demagnified imaged onto the target producing a rectangular homogenously irradiated area. The aperture size and a continuously variable attenuator allow precise adjustment of both the ablation area and energy density at fixed laser working parameters. A polycarbonate target was used for benchmarking the energy density distribution and image quality at the ablation target. We investigated ablation in an oxygen atmosphere at different pressures of single crystalline (001) oriented SrTiO3, LaAlO3, Y3Fe5O12 and amorphous SiO2 targets. The energy density was varied from 6 J/cm2 to 0.6 J/cm2 and correlated to ablation target surface roughening, preferential ablation effects and decomposition. The target surface morphology has been imaged by LSM, AFM and SEM. Compositional changes have been identified and characterized by optical imaging and µ-Raman spectroscopy.
Authors : Sergei Chertopalov, Tomas Zikmund, Jiri Bulir, Michal Novotny, Eva Maresova, Lenka Volfova, Stefan Andrei Irimiciuc and Jan Lancok
Affiliations : Institute of Physics of the Czech Academy of Sciences, Na Slovance, 182 21 Prague, Czech Republic
Resume : Fluoride materials occupy an original and strategic position in modern optics. The fluorides exhibit unique optical features associated with the presence, low phonon energy, high optical transparency from deep ultraviolet up to far infrared spectral ranges as well as of the rare-earth (RE) ions, low phonon energy which make them excellent candidate for variety of optoelectronics and photonics applications. Several Physical Vapour Deposition (PVD) techniques has been tried to fabricate fluoride thin films. The common crucial problem of the plasma techniques is especially fluorine deficiency caused by breaking of the fluorine bonds by energetic plasma species . We propose to use a novel hybrid deposition technique based on a suitable combination of Electron-beam evaporation (EBE) either with Pulsed laser deposition (PLD) to fabricate nanostructural thin films with outstanding optical and magnetooptical properties. The main idea is to join the particular deposition techniques, exploit their advantages and choose the best method or combination for the fabrication of nanogranular nanostructures with outstanding optical and magneto-optical properties suitable for integrated part of the photonic devises. We will present the overview of fabrication methods (i) plasmonic properties of Ag, Al and Bi nanoparticles inside rare earth doped CaF2 and LaF3 matrices in UV and visible range and enhancement of luminescence properties by local surface plasmon resonance (ii) magnetooptics materials combine ferromagnetic nanoparticles with plasmonic nanostructures in fluoride glasses  T. Yoshida, et. all Fluoride antireflection coatings for deep ultraviolet optics deposited by ion-beam sputtering Appl. Opt. 45 (2006) 1375
Authors : P. Gomez(1), E. Soria(1), S. Camelio(2), Ch. Thomas(2), J. Margueritat(3), D. Babonneau(2), J. Gonzalo(1)
Affiliations : (1) Laser Processing Group, Instituto de Optica, IO-CSIC, Serrano 121, 28006 Madrid, Spain; (2) Institut P', Dept. of Physics and Mechanics of Materials, UPR 3346 CNRS-Université de Poitiers-ENSMA, SP2MI, 11 Bvd. M. & P. Curie, BP 30179, 86962 Futuroscope Chasseneuil Cedex, France; (3) Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, UMR CNRS 5306, 69622 Villeurbanne, France.
Resume : Metal-dielectric nanostructures containing metal nanoparticles (NPs) present exciting optical properties, which make them ideal candidates for the development of nanoscale electronic and optical devices, due to the possibility of generating large electromagnetic field enhancement via Surface Plasmon Resonance (SPR). However, most practical applications require a fine control of the NP morphology and orientation. Sequential pulsed laser deposition (PLD) is a versatile technique which provides an excellent control over the amount of deposited metal, as well as reduced NP size dispersion. However, the Volmer-Weber nucleation and growth mode of metal NPs on a dielectric surface, along with surface processes, such as sputtering or sub-surface implantation associated to the presence of energetic ions in the laser generated plasma, hinder the production of NPs with well-defined symmetry. In this work, we show how these shortcomings can be tackled by exploiting the pulsed character of the PLD, appropriately designing the deposition sequence and geometry, and combining it with rippled substrates to produce oriented and elongated NPs along the direction of growth (nanocolumns, NCls) or parallel to the substrate plane (nanowires, NWs) with small diameters (D≈ 3 nm, D≈ 12 nm, respectively) and large aspect ratios (≈20 for NCls, ≈50 for Nos), that lead to a clear polarization dependence of the localized SPR modes.
Authors : Stefan Andrei Irimiciuc(1), Michal Novotny(2), Lenka Volfova(2), Joris More Chevalier(2), Ladislav Fekete(2), Jan Fara (2,3), Craciun Valentin(1), Jan Lancok(2)
Affiliations : 1National Institute for Laser, Plasma and Radiation Physics – NILPRP, 409 Atomistilor Street, Bucharest, Romania 2 Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, Prague, Czech Republic 3 University of Chemistry and Technology, Technicka 5, Prague, Czech Republic
Resume : Optical emission spectroscopy (OES) measurements were performed during the pulsed laser deposition (PLD) of Cu2O, Lu2O2:Eu and (PO2)4(WO3)2 (PWO) in various O2 atmospheres. The aim of the study was to generate spatial maps of the main elements of the transient plasmas generated in UV ns laser ablation on CuO, Lu2O2:Eu and PWO targets. In situ plasma monitoring of the laser produced plasma plays an important role as a feedback and control mechanism in order to adjust the technological processes. OES is the best candidate for plasma monitoring as it is a non-invasive technique and has abilities for quantitative and qualitative analyses. PLD of the aforementioned targets was performed on a wide range of O2 pressures (from 10-3 up to 20 Pa) in order to achieve stoichiometric transfer and tailor the properties of the thin films. A 10-fiber bundle was used to collect the optical emission spectra from the full width of the plasma and then moved in various positions to analyses different points from the target to the substrate. From each investigated plasma volume, we extracted a series of plasma parameters like excitation temperature, electron density, collision frequency, and mean free path. For each independent deposition conditions, we recreated the spatial distribution of all the parameters. The formation of molecular oxides was also seen through their spectral signature and their roto-vibrational temperature estimated. The nature of molecular emission is discussed in the framework of recombination mechanisms induced by the relatively increased background pressure. The results are compared with the properties of the deposited thin films determined by surface analysis techniques like, AFM, SEM, XPS, Raman Spectroscopy or XRD.
Authors : Joelle ZGHEIB, Ahmed RHALLABI, Pierre-Yves JOUAN
Affiliations : Université de Nantes, Institut des Matériaux Jean Rouxel (IMN), 2 rue de la Houssinière 44322 Nantes, France
Resume : A classical magnetron plasma discharge is widely used in several technological applications, especially in semiconductor manufacturing. Metallic, oxide and nitride thin film depositions under sputtering are used in different steps of device manufacturing. Due to the increment of supplied power, the increased heat of metallic target electrode (cathode) is considered as a limitation factor to improve the deposition rate and the deposited thin film performances. To avoid these limitations, one of the avenues explored is the application of power in the form of very short pulses High Power Impulse Magnetron Sputtering HiPIMS. It represents an alternative to DC or RF PVD processes. Therefore, the injection of a high power about 150 Watts/cm2 (vs 10 Watts/cm2 in DC case) during a very short pulse time allows to avoid the high heat growth during the thin film deposition process. It also allows the improvement of the ionization degree and the dissociation rate of injected gaz. To understand more about the pulsed high power discharge, we have developed a kinetic model of Ar/Cr pulsed plasma mixture. The model is based on the solving of the mass balance equations coupled to the power balance equation. The advantage of our kinetic model is its ability to quantify the densities of neutrals and ions considered in the reaction scheme as well as their fluxes into the substrate. The simulations results show the effects of the main machine parameters, such as the pressure, the flow rate of Ar, and the duty cycle on the neutral and the ion densities evolution versus time. On the other hand, the simulations show that, for the same average power, the dissociation and ionization rates in HiPIMS process are more efficient than in RF PVD process.
Carbon-based & 2D materials : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : Carles Corbella1, Sabine Portal1, Madhusudhan N. Kundrapu2, Michael Keidar1
Affiliations : 1 George Washington University; 2 Tech-X Corporation
Resume : Pulsed anodic arc discharge is a novel synthesis method of nanomaterials by means of low-temperature atmospheric plasma. The technique consists in periodically supplying DC power to two vertically aligned electrodes in the form of short unipolar pulses with peak currents of a few Amperes in Helium atmosphere. The pulsed arc plasmas are sustained at frequencies of the order of 1 Hz with 10% of duty cycle. It constitutes a versatile technique thanks to many advantages compared to steady DC arc processes, in particular: flexibility in the experimental conditions, process stability and repeatability, better use of ablating anode, lower production of macroparticles, and lower thermal loads. Such features will be discussed in this presentation. Also, an overview concerning the recent accomplishments of pulsed arc discharge on deposition of carbon nanostructures (graphene and carbon nanotubes) and few-layer flakes of MoS2 will be provided, as well as an outlook on future applications of this method for the discovery of new materials with tailored functional properties.
Authors : T. Amelal, M.H. Futscher, J. Sastre, Y.E. Romanyuk, S. Siol
Affiliations : Empa - Swiss Federal Laboratories for Materials Science and Technology
Resume : Mankind's increasing hunger for energy and the imperative for sustainability drive the search for rechargeable batteries with high energy density and cyclability. One of the most promising routes to improve Li-ion batteries is the use of metallic lithium anodes. The development of such batteries has proven to be challenging due to non-uniform plating of Li metal, resulting in the formation of dendrites. Recent research from Samsung demonstrated that Ag-C composite interlayers could effectively suppress dendrite growth in Li-ion-batteries, significantly increasing battery life . However, it remains unclear which properties of the interlayers cause this effect. To study the effect of interlayer properties on Li-plating, we deposited amorphous carbon (a-C) films via DC magnetron sputtering (DCMS) as well as high power impulse magnetron sputtering (HiPIMS) on metallic electrodes. We demonstrate that the ability of these a-C films to promote homogeneous Li plating on the electrode depends on their thickness, conductivity and microstructure. The a-C films conductivity and microstructure can be adjusted in a large range by varying the deposition temperature, working pressure, and ion bombardment conditions. Compared to DCMS, the HiPIMS process allows varying the a-C film properties in a wider range, thereby deepening our understanding of the underlying effects. References:  Y.-G. Lee et al., High-energy long-cycling all-solid-state lithium metal batteries enabled by silver–carbon composite anodes, Nat. Energy 5, 299–308, 2020
Authors : Laura Cacot, Erika Loranger, Myrtil Kahn, Richard Clergereaux, Nicolas Naudé, Luc Stafford
Affiliations : (Cacot, Naudé, Clergereaux)LAPLACE, Université de Toulouse, CNRS - Toulouse (France); (Kahn) CNRS, LCC (Laboratoire de Chimie de Coordination) - Toulouse (France); (Cacot, Loranger, Stafford) Département de Physique - Université de Montréal - Montréal (Canada)
Resume : Aerosol-assisted plasmas can be used to produce a wide variety of thin films, including homogeneous, nanotextured and/or nanocomposite coatings. For example, the nebulization of colloidal solutions, i.e. liquid solutions containing nanoparticles, in plane-to-plane dielectric barrier discharge (DBD) at atmospheric pressure has been used for nanocomposite thin film deposition . However, nanoparticles-loaded droplets in the aerosol lead to the deposition of aggregated nanoparticles embedded in the matrix . Recently, a new process of nanoparticles injection in plasmas has been developed . This method consists in synthesizing the nanoparticles prior to their injection in the plasma in a pulsed injection regime. However, the composition of the aerosol as well as the impact of the pulsed injection on the DBD are still opening questions. This work aims to study a pulsed-aerosol-assisted DBD deposition process. In contrast with the continuous nebulization of solutions, pulsed injection causes a sudden increase of the quantity of precursor in the inter-electrode space as droplets – their velocity being in the 10 m.s-1 range. We observed that depending on the process parameters (injection, time, pulse frequency, continuous gas flow rate, etc.), the discharge stability and, consequently, the thin film deposition (here ppHMDSO or amorphous carbon) are modified. It is shown that this pulsed injection of either HMDSO or pentane plays a very critical role on the formation of plasma-polymerized coatings. References  J. Profili, O. Levasseur, J.-B. Blaisot, A. Koronai, L. Stafford, and N. Gherardi, “Nebulization of Nanocolloidal Suspensions for the Growth of Nanocomposite Coatings in Dielectric Barrier Discharges,” Plasma Process. Polym., vol. 13, no. 10, pp. 981–989, Oct. 2016.  M. Khan, Y. Champouret, R. Clergereaux, C. Vahlas, and A.-F. Mingotaud, “Process for the preparation of nanoparticles,” EP 16305977.7, 2016.
Non oxide functional materials : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : Ganesh Kumar Nayak, David Holec
Affiliations : Department of Materials Science, Montanuniversität Leoben, Franz-Josef-Straße 18, A-8700, Leoben, Austria
Resume : Materials with suitable long-duration wear and friction properties require coatings that must be hard, tough, thermally stable, and oxidation resistive. Self-lubricant coating systems with the release of the lubricious species have the above-desired potential. Nanocrystalline (nc)-TiN/SiNx coatings have proven extremely successful in combining these desirable characteristics. The lubricious ability is attained by alloying V to create Ti(V)N/SiNx nanocomposites which form V2O5 surface oxide acting as a solid lubricant. In the present work, we report on state-of-the-art density functional theory (DFT) and molecular dynamics (MD) calculations revealing the structure and stability of the Ti(V)N/SiN interfaces. Special attention is given to the microstructures, mechanical properties, and bonding mechanisms of the interface between nc-TiN and different thicknesses of amorphous (a)-SiNx. The detailed analysis of the structure, stability, and mechanical anisotropy of layered Ti(V)N/SiNx films with amorphous SiNx (with various thickness) will be discussed with a special focus on the distribution of different species at the interface. The mean square displacements, interfacial atomic concentrations, and the radial distribution function of the nc-Ti(V)N/a-SiNx interface will be calculated and correlated with the overall mechanical properties.
Authors : Angélique Chabanon, Alexandre Michau, Michel L. Schlegel, Frédéric Schuster, Srikanth Narasimalu, Bingqing Yao, Hicham Maskrot, Zhili Dong, Fanny Balbaud
Affiliations : Université Paris-Saclay, CEA, Service d'Etudes Analytiques et de Réactivité des Surfaces, 91191, Gif-sur-Yvette, France/Interdisciplinary Graduate School, Nanyang Technological University, Singapore 637371, Singapore ; Université Paris-Saclay, CEA, Service d'Etudes Analytiques et de Réactivité des Surfaces, 91191, Gif-sur-Yvette, France ; Université Paris-Saclay, CEA, Service d'Etudes Analytiques et de Réactivité des Surfaces, 91191, Gif-sur-Yvette, France ; Université Paris-Saclay, CEA, Cross-Cutting Program on Materials and Processes Skills, 91191 Gif-sur-Yvette, France ; Energy Research Institute @ NTU (ERI@N), CleanTech One, Singapore 637141, Singapore ; School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore ; Université Paris-Saclay, CEA, Service d'Etudes Analytiques et de Réactivité des Surfaces, 91191, Gif-sur-Yvette, France ; School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore ; Université Paris-Saclay, CEA, Service de la Corrosion et du Comportement des Matériaux dans leur Environnement, 91191, Gif-sur-Yvette, France
Resume : The lifespan enhancement in corrosive (marine and spent fuel reprocessing) environments of 304L stainless steel infrastructures and tools was achieved by synthesizing dense Ti and Zr coatings by high power impulse magnetron sputtering (HiPIMS). The effect of Ar, Ti and Zr in-situ ion etching pretreatments on the substrate-coating interface and coating properties was investigated by varying three process parameters: etching duration, ion energy and ion flux. Characterization by XRD, SEM and TEM showed high density, columnar and polycrystalline structures for both Ti and Zr metal coatings. Study of the interface revealed the good adhesion of these coatings on the substrate and the absence of impurities at the substrate-coating interface. Chemical analysis by TEM-EDX showed the presence of Ar in all the interfaces and the implantation of Ti and Zr ions in the substrate during metal ion etchings. XPS analysis revealed surface modifications such as change in the surface-formed natural oxide layer as related to etching pretreatments, and confirmed ion implantation. Nanoindentation tests showed that the hardness of the etched samples increased due to these surface modifications. Electrochemical measurements assessed the improvement in corrosion resistance of etched substrate and a 200-nm-thick metal layer in saline and spent fuel reprocessing environments due to optimized etching and coating. In addition, immersion tests in seawater and spent fuel reprocessing solution were performed to observe the coatings behavior under service conditions.
Authors : Rui Shu1, Daniel Lundin2,5, Mauricio A. Sortica3, Daniel Primetzhofer3,4, Arnaud le Febvrier1, Per Eklund1
Affiliations : 1Thin Film Physics Division, Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping, Sweden 2Plasma and Coatings Physics Division, Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden 3The Tandem Laboratory, Uppsala University, Uppsala, Sweden. 4Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden 5Laboratoire de Physique des Gaz et Plasmas—LPGP, UMR 8578 CNRS, Université Paris-Sud, Université Paris Saclay, 91405 Orsay CEDEX, France
Resume : Understoichiometric high-entropy nitride (TiZrTaMe)N1-x (Me= Hf, Nb, Mo, or Cr) films were deposited on Si(100) substrates at 400 C by reactive magnetron sputtering using single elemental targets. Different negative substrate bias voltages ranging from 0 to 130 V were employed. The composition was determined by a combination of EDS and ToF-ERDA, and the crystal orientation and morphology of the studied films have been investigated by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The nitrogen content for the samples varied from 34.9 at.% to 43.8 at.%, indicating that all the TiZrTaMeN1-x films were understoichiometric (0.12 ≤ x ≤ 0.32). The metalic compositions were near-equimolar and not be affected by substrate bias. When increasing the substrate bias, the phase structures of TiZrTaMeN1-x (Me=Hf, Nb or Mo) films evolved from a polycrystalline fcc phase to a (002) preferred orientation, along with a change in the surface morphologies from faceted triangular mounds to a dense and smooth structure. All the four series of (TiZrTaMe)N1-x (Me= Hf, Nb, Mo, or Cr) films showed an increasing trend of intrinsic stress when the substrate bias increased. The maximum compressive stress reached maximum values of ~3.1 GPa for Hf and Cr-containing films deposited at -130 V. The hardness reached a maximum value 28.0 1.0 GPa at bias 100 V for all the four series of films. The observed effects of bias on (TiNbZrMe)N1-x films provide important information for the development and mechanical properties of high entropy nitride films.
Authors : Niemczyk, A.(1), Brajnicov, S. (2), Satulu, V. (2), Bonciu, A. (2), Baranowska, J. (1) Mitu, B. (2), Dinescu, M. (2).
Affiliations : (1) West Pomeranian University of Technology, Szczecin, Faculty of Mechanical Engineering and Mechatronics, Department of Materials Technology; al. Piastów 19; 70-310 Szczecin, Poland (2) National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., Magurele Bucharest 077125 Romania
Resume : Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique is lately receiving considerable attention due to its possibility to obtain a large variety of materials, such as delicate polymers, proteins, or biomaterials in the form of thin films. In this context, copolymers which present a particular complexity due to the diversity of the polymer chains are excellent candidates for synthesis using MAPLE technique. In this work, we present the results on the synthesis of poly(ethylene-co-vinyl acetate) (EVA) copolymer using a Nd:YAG laser with a repetition rate of 10 Hz which was irradiating the EVA copolymer dissolved in chloroform and frozen in liquid nitrogen. The influence of the laser wavelength, fluence, number of pulses and the concentration of EVA in the target on the thin film properties was investigated. The morphology and topography of thin films were evaluated by means of Scanning Electron Microscopy and Atomic Force Microscopy techniques. The composition and chemical bonding was revealed upon using Fourier Transformed IR Spectroscopy and X-ray Photoelectron Spectroscopy. This approach allowed us to optimize the experimental conditions in order to obtain depositions of EVA thin films with high degree of resemblance to the target composition.
Authors : K. Thorwarth(1) S. Siol(1), C. Voisard (2), M. Kraft (2), G. Thorwarth (2)
Affiliations : 1 Empa, Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland 2 DePuy Synthes GmbH, Dübendorf, CH-8600 Switzerland
Resume : Simultaneously meeting the technical requirements for both surface and bulk properties is a key challenge in the development of medical implants. For example, PEEK (Polyetheretherketone) is a radio-lucent alternative to metallic implants and well established for applications in spine surgery. While hav-ing excellent bulk properties like a modulus closely matching cortical bone (18 GPa), an unconditioned PEEK surface is known to display poor bone integration. To enhance the osseointegration and biocompatibility of PEEK, Titanium coatings are well established on the market. Plasma spraying of titanium is commonly used for the coating of these implants. However, the resulting thick coatings (30-800μm) lead to a loss of primary substrate features, necessary for implant stability and exact placement of the implant. Standard PVD processes offer the promise of high-quality coatings at much lower film thicknesses. Unfortunately, conventional sputtering or evaporation techniques do not provide an adequate adhesion of the titanium coating on PEEK. Here we demonstrate that using ionized physical vapor deposition techniques such as high power im-pulse magnetron sputtering (HiPIMS) it is possible to directly metallize the polymer with excellently adhering films while also maintaining the original surface structure. High adhesion strength values (>30 MPa) can be obtained with HiPIMS, including penetration into narrow trenches and on surfaces with a shallow deposition angles . These findings are supported by finite Element simulations, which illustrate that standard adhesion testing according to ASTM D4541 is not applicable to polymer substrates as a strong deformation of the soft substrates leads to incorrect adhesion strength values. It is shown that a tailored surface pre-treatment is essential to secure layer adhesion to the PEEK surface. XPS and ToF-SIMS measurements confirm film qualities compliant to surgical grade II Titanium (ISO 5832-2). SEM is used to study the layer structure with respect to the HiPIMS parameters. Overall, these results highlight the merit of pulsed sputtering techniques for coatings on PEEK even for demanding bio-medical applications.
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Functional oxides : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : Tetsuhide Shimizu
Affiliations : Tokyo Metropolitan University
Resume : A simple and cost-effective approach to stabilize the sputtering process in the transition zone during reactive high-power impulse magnetron sputtering (HiPIMS) is proposed. The method is based on real-time monitoring and control of the discharge current waveforms. To stabilize the process conditions at a given set point, a feedback control system was implemented that automatically regulates the pulse frequency, and thereby the average sputtering power, to maintain a constant maximum discharge current. Another approach using this regulation process is to tailor the film chemistry and microstructure during the deposition process, by adjusting the setpoint of peak current and range of the controlled HiPIMS pulse frequency. The present study overviews the controllability in obtaining a variety of sub-stochiometric compositions and different microstructures of TiOx, AlOx, ZrOx and MgOx by using this flexible process control.
Authors : Jiri Rezek,Nirmal Kumar,Stanislav Haviar,Tomas Kozak
Affiliations : University of West Bohemia, Plzen, Czech Republic
Resume : Nowadays, tungsten oxide is widely studied as a promising material for hydrogen gas sensing, electrochromic or photocatalytic applications. However, there are only few works focused on utilization of reactive HiPIMS (high-power impulse magnetron sputtering) process for WOx films preparation. Despite the fact, reactive HiPIMS could enhance deposition rate  or allow to prepare quality oxide films at low temperatures . In this work, we present results obtained during reactive HiPIMS deposition of thin WOx film with different stoichiometry and structure. Effect of oxygen partial pressure, value of pulse-averaged target power density and pule length will be discussed. Results obtained from an improved version of our global model of reactive HiPIMS  will be also presented. Hydrogen sensing response will be shown for selected films. It is demonstrated, sensitivity towards hydrogen gas is highly increased for a proper nanostructure.  J. Vlček, J. Rezek, J. Houška, R. Čerstvý, R. Bugyi, Surf. Coat. Technol. 236 (2013)  J. Rezek, P. Novák, J. Houška, A.D. Pajdarová, T. Kozák, , Thin Solid Films 679 (2019) 35–41.  T. Kozák, J. Vlček, J. Phys. D. Appl. Phys. 49 (2016) 55202.
Authors : Guillaume Krieger(1), Nathalie Viart(1), Daniele Preziosi(1)
Affiliations : (1) Institut de Physique et Chimie des Matériaux de Strasbourg, Strasbourg, France
Resume : Perovskite rare-earth nickelates RNiO3 (R being a rare-earth) have been the leitmotiv of intense theoretical and experimental research efforts assuming that they could mimic the high-Tc superconductivity of cuprates for which a Cu 3d-eg orbital selective Cooper pairing is supposed to be responsible of the zero-resistance state. Recently, such a zero-resistance state was obtained in Sr-doped NdNiO2 thin films (isostructural to cuprates), where the pristine (Nd,Sr)NiO3 thin film was reduced by a CaH2 powder via a so-called topotactic process. Here, we will introduce our efforts to reproduce such a result for 5% and 20% Sr-doping of NdNiO3 thin films grown via by Pulsed Laser Deposition technique. We comprehensively studied the influence of the oxygen partial pressure during ablation to minimize the strain relaxation state of the perovskite phase onto SrTiO3 single crystals. Transport and electronic properties will be also discussed.
Authors : T. H. Wang1,2, P. C. Hsu1,3, M. Korytov1, Robert Gehlhaar1, J. Genoe1,2, C. Merckling1,3
Affiliations : 1 Imec, Kapeldreef 75, B-3001 Leuven, Belgium; 2 ESAT Department, KU Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium; 3 Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium
Resume : Future applications such as high-speed chip-to-chip optical interconnects, compact high-resolution beam steering and video-rate RGB hologram generation require the integration of fast and efficient optical modulators on top of silicon CMOS devices. For these applications the integration of high quality electro-optical materials on silicon wafers is hence required. Among the possible material options, barium titanate (BaTiO3) is one promising candidate due to its large intrinsic Pockels coefficients. However, the reported Pockels coefficients in literature strongly depend on the obtained crystal lattice stress and axis orientation. In this work, we demonstrate an epitaxial PLD-grown BaTiO3 (BTO) on top of a SrTiO3 /Si(001) pseudo-substrate grown by molecular beam epitaxy(MBE). We investigated the polarization axis orientation of BTO films under different growth conditions by X-ray diffraction. The control of growth conditions enables us to change polarization by selecting between c- and a-axis orientation with tetragonality control ranging from 0.98 to 1.02. For the a-BTO, the out-of-plane ω-scan shows good crystalline quality with FWHM of 0.37˚. The change of polarization axis was confirmed by both electrical and PFM results, which correlated well with the XRD results. Using STEM and NBD, we related the crystalline orientation switch to lattice mismatch relaxation inside BTO films. Furthermore, the polarization change also showed impact on optical behavior, which was explored by using Mueller matrix Ellipsometry. The optical indices were compared with MBE-grown BaTiO3, and the deviations could be linked to the differences using these two techniques.
Authors : Michiels, M.*(1-6), Hemberg, A. (1), T. Godfroid (1), Panepinto, A. (1), Douheret O. (1), Colaux, J.L. (2), Moskovkin, P. (2), Lucas, S. (2), Caillard, A. (3), Thomann, A-L. (3), Voué, M. (4), Laha P. (5), Terryn H. (5), Snyders, R. (1-6) and Konstantinidis, S. (6).
Affiliations : (1) Materia Nova Research Center, 3 Avenue Nicolas Copernic, Parc Initialis, 7000 Mons, Belgium; (2) Laboratory of Analysis by Nuclear Reaction (LARN / PMR),NARILIS, University of Namur - 61, Rue de Bruxelles, B-5000 Namur, Belgium; (3) Groupe de Recherches sur l'Energétique des Milieux Ionisés (GREMI), UMR7344 Université d'Orléans, CNRS BP6744, F-45067 Orléans Cedex 2, France; (4) Materials Physics and Optics, University of Mons, 20 Place du Parc, Mons 7000, Belgium; (5) Electrochemical and Surface Engineering (SURF), Vrije Universiteit Brussel – 2, Pleinlaan, B-1050 Brussel, Belgium; (6) Chimie des Interactions Plasma-Surface (ChIPS), CIRMAP, University of Mons, 23 Place du Parc, B-7000 Mons, Belgium;
Resume : In this work, a titanium target is reactively sputtered in an Ar/O2 atmosphere by i) conventional direct current magnetron sputtering (DCMS), ii) high-power impulse magnetron sputtering (HiPIMS), and iii) bipolar HiPIMS discharges (BPH). Energy-resolved mass spectrometry analysis has shown low-energy peak for DCMS while a high energy tail extending in the range of several tens of eV was observed with HiPIMS. In the BPH discharge, plasma ions reached up to ≈300 eV for Ti+ ions in line with the applied positive potential. The plasma diagnostic results serve as input data for kinetic Monte Carlo-based simulations performed with the NAnoSCAle Modeling (NASCAM) code. In a second step, TiO2 coatings are characterized in order to unravel how the plasma properties influence film composition, microstructure, phase constitution, density and optical properties. The optical data are compared with results extracted from the NASCAM simulations. Among others, we show that applying a too high positive voltage (300V) during bipolar HiPIMS provokes the reduction of the apparent film growth rate. This observation is combined with a decrease of the X-Ray diffraction peak intensities as compared to results obtained with classic HiPIMS. According to XRD, anatase phase is observed for DCMS while rutile phase is obtained in HiPIMS regime. Rutherford Backscattering Spectroscopy analysis also shows that a higher amount of argon atoms is incorporated in the TiO2 films grown by bipolar HiPIMS.
Authors : Antonio Pena-Corredor*, Daniele Preziosi, François Roulland, Nathalie Viart, Christophe Lefevre
Affiliations : Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504, University of Strasbourg, CNRS
Resume : Oxide thin films are a topic of increasing research relevance owing to their potential applications in spintronics and orbitronics. The properties of these films can be highly affected by the film’s crystallography  and, as a result, there is a great interest in deciphering the atomic distribution inside the film. In bulk materials, Synchrotron X-ray Diffraction and Neutron Diffraction techniques allow to locate the different atoms which compose the crystal . However, thin films have much fewer matter to probe, so these techniques have difficulties in giving a whole picture of the film’s crystal structure. An alternative for such an issue is the use of Resonant X-ray Scattering (REXS) via X-ray Absorption Near Edge Structure (XANES) experiments. This technique has been shown successful in probing the metallic cations in the oxide thin film . Direct resonance at the oxygen absorption edge is however not practically feasible, due to the low energy of this edge and the too strong absorption issues it implies. Oxygen positions are hence much harder to probe. This is all the more unfortunate when considering oxides with a ferro-orbital ordering because the exact position of each atom must be known for the study of the orbital state . To achieve the determination of the oxygen positions, we propose the study of the REXS spectra acquired for the metallic cations beyond the edge surroundings, in the Extended X-ray Absorption Fine Structure (EXAFS) domain. This part of the spectra is sensitive to the atom’s electronic environment  and, as a result, will be influenced by the neighbouring oxygens’ positions. Using the FMDNES software , we have proved the possibility to fit the EXAFS spectra and determine the position of the oxygen ions positions via REXS on the spinel oxide FeV2O4, as a showcase. This approach, valid for both bulk and thin-film materials, has the aim of being generalised to all systems. The development of this technique will enable the complete determination of the atomic positions and orbital state in a crystal film, and will necessarily ease the conception of future orbitronic thin-film-based devices.  G. Tan et al., «Crystallographic contributions to piezoelectric properties in PZT thin films», Sci. Rep., vol. 9, n. 1, 2019.  M. Woińska et al., «Hydrogen atoms can be located accurately and precisely by x-ray crystallography», Sci. Adv., vol. 2, n. 5, 2016.  C. Lefevre et al., «Potentialities offered by the Resonant X-ray Scattering to the crystallographic study of oxide thin films», Conference: Rayons X & Matière 2017.  S. Kawaguchi et al., «Orthorhombic distortion and orbital order in the vanadium spinel FeV2O4», Phys. Rev. B, vol. 93, n. 2. 2016.  V. Favre-Nicolin, «Développement de la Diffraction Anomale Dispersive», PhD thesis, p. 20. 2011.  O. Bunău et al, «Self-consistent aspects of x-ray absorption calculations», J. Phys. Condens. Matter, vol. 21, n. 34, 2009.
Authors : Daniel Pfützenreuter, Martina Zupancic, Zbigniew Galazka, Martin Albrecht, Jutta Schwarzkopf
Affiliations : Leibniz-Institut für Kristallzüchtung, Max-Born-Str. 2, 12489 Berlin, Germany
Resume : BaSnO3 is a semiconducting perovskite material offering a high charge carrier mobility of up to 320 cm2/Vs . This is higher than for most transparent conducting oxides and furthermore highest for perovskite materials, which makes it very interesting regarding an application as field effect transistor. Usually, BaSnO3 films are grown on SrTiO3 or MgO substrates both exhibiting a lattice mismatch of more than 5%. This leads to high defect density in the films, and consequently to a reduced charge carrier mobility. Our approach to improve structural and electrical properties of BaSnO3 films is to use (110) LaInO3 substrates which have a lattice mismatch of only -0.03% to BaSnO3. LaInO3 substrates are newly developed  and surface preparation for the use in epitaxy is investigated by means of in-situ RHEED. It could be shown that doping the substrate with Ba or Ce  stabilizes the surface at elevated temperature and low pressure compared to undoped LaInO3 substrates. Based on these results we have grown epitaxial BaSnO3 films with high structural quality by pulsed laser deposition on LaInO3 substrates. Compared to the growth on SrTiO3 substrates, the electric properties of La-doped BaSnO3 thin films could be improved. An electron mobility of 76 cm2/Vs could be measured at a charge carrier density of 3.5 10^19 cm-3. Further reduction of the La-doping concentration is expected to result in even higher carrier mobility.  H. J. Kim et al.; Appl. Phys. Express 5 (2012) 061102  Z. Galazka et al.; Phys. Status Solidi (2021) submitted
Authors : Petr Novák (1)*, Jiří Rezek (2), Tomáš Kozák (2), Jarmila Savková (1),
Affiliations : (1) New Technologies – Research Centre, University of West Bohemia, Plzeň, Czech Republic, (2) Department of Physics and NTIS - European Centre of Excellence, University of West Bohemia, Plzeň, Czech Republic
Resume : The aluminium-doped zinc oxide (AZO) may have comparable electrical and optical properties to more expensive Indium-tin oxide (ITO), which is the mostly used material for transparent conductive electrodes. Nevertheless, it is difficult to obtain suitable conductivity at low deposition temperatures as the best electrical properties are obtained above 300°C . The resistivity of AZO films is also strongly related to the oxygen conditions during the film growth. Generally, the low-oxygen conditions lead to lower resistivity, but may also cause deterioration in optical properties and vice versa. Generally it is assumed that the oxygen conditions affect the concentration of intrinsic defects in the ZnO film, which result in a change of a carrier concentration. The oxygen interstitials (Oi) and zinc vacancies (VZn), which dominates at oxygen rich conditions, act as single- and double-charged acceptors, respectively. On the other hand, oxygen-poor conditions dominantly result in formation of oxygen vacancies (VO) and zinc interstitials (Zni). While Zni are shallow donors and lead to increasing of carrier concentrations, oxygen vacancies are deep donors and do not contribute to the electrical properties. Our research was mainly focused on the possibility to control oxygen content in the AZO films by the reactive high-power impulse magnetron sputtering (HiPIMS) at room temperature, which allows the deposition to temperature sensitive substrates. The electrical properties was analysed by Hall measurements and ellipsometry. Main aim was to study influence of several discharge parameters on the properties of extensively researched material. It was found that oxygen conditions can be finely controlled by different discharge parameters such as pulse length or average power density  during deposition. The electron microscopy was used to investigate the film structure, which influences mainly the carrier mobility. Obtained results shows the benefits and also limitations of the reactive high-power impulse magnetron sputtering for a high-rate deposition of transparent conductive films onto heat-sensitive substrates.  P. Novák, Phys. Status Solidi. (2019) pssa.201800814.  J. Rezek, P. Novák, J. Houška, A.D. Pajdarová, T. Kozák, Thin Solid Films. 679 (2019) 35–41
Multiferroic, ferreoelectric & magnetic oxides : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : Suvidyakumar Homkar1, Daniele Preziosi1, Xavier Devaux3, Corinne Bouillet1, Johanna Nordlander2, Morgan Trassin2, François Roulland1, Christophe Lefèvre1, Gilles Versini1, Sophie Barre1, Cédric Leuvrey1, Marc Lenertz1, Manfred Fiebig2, Geneviève Pourroy1, Nathalie Viart1
Affiliations : 1 IPCMS, UMR Unistra-CNRS 7504, 23 rue du Lœss, BP 43, 67034 Strasbourg cedex 2, France; 2 Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland; 3 Institut Jean Lamour, CNRS, Nancy-Université, UMR 7198, CAMPUS ARTEM, 54000 Nancy, France
Resume : Gallium ferrite, Ga2-xFexO3 (GFO), is, for x=1.4, one of the very rare room temperature multiferroic oxides, and is therefore of high interest for electronics, and in particular, spintronics applications. We have studied the very early steps of its growth by pulsed laser deposition onto SrTiO3 (STO) (111) substrates. The films show, for thicknesses as low as 7 nm, an out-of-plane electric polarization, evidenced by second harmonic generation and confirmed by the cationic displacements observed by high resolution transmission electron microscopy (HR-TEM). While the polarization points towards the substrate for the first ca. 5 nm, it abruptly reverses and points outwards from the substrate for the rest of the deposited film, revealing very clear tail-to-tail configuration of the polarization domains. Thickness dependent electric polarization orientations have already been observed in the literature, but the phenomenon has then been ascribed to strain-driven effects. Here the strain-relaxed nature of the GFO films excludes such an explanation. Instead, we show by atomically resolved electron energy loss spectroscopy (EELS) that this polarization reversal is related to the oxygen availability during the growth and is controlled by important ionic migration processes at the substrate-film interface. Such a chemistry-driven effect gives us a glimpse of new levers for the manipulation of the polarization.
Authors : J. Garot (1), J.-B. Moussy (1), H. Magnan (1), A. Vlad (2), C. Mocuta (2), P. Ohresser (2), R. Belkhou (2), A. Barbier (1)
Affiliations : (1) Service de Physique de l'Etat Condensé, UMR 3680 CEA-CNRS, Gif-sur-Yvette, France ; (2) Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin BP48, 91192 Gif-sur-Yvette, France
Resume : Magneto-electric multiferroics materials, having simultaneous ferromagnetic and ferroelectric long range orderings, are of high technological interest to realize future key components of new devices in important technological fields like spintronics, sensors, multiple state memory cells, energy harvesting etc. Artificial multiferroics obtained by combining ferroelectric and ferromagnetic materials are a seductive route to overcome the lack of intrinsic single phase multiferroics. For practical applications, high flux deposition methods like pulsed laser deposition (PLD) are appropriate to realize thick layers. However suitable compounds are complex oxides that may raise specific elaboration issues. We considered the PLD deposition of thick (80 nm) ferrimagnetic CoFe2O4 layers on thin epitaxial films (10 nm) of BaTiO3 deposited by atomic oxygen assisted molecular beam epitaxy on SrTiO3(001) single crystalline substrates. Depositions were realized using reactive nano (YAG) and femto second pulsed lasers ablating a sintered CoFe2O4 target with the substrate held at 300 K and 750 K. Deposition at 300 K leads to an amorphous layer while at 750 K epitaxial and polycrystalline layers are observed for ns and fs lasers respectively. The layers as well as their recrystallization by air annealing up to 1300 K were investigated by electron and X-ray diffraction, photoemission as well as synchrotron radiation X-ray diffraction (XRD), magnetic dichroism (XMCD), spectromicroscopy (XPEEM) exploiting photon energy and light polarization tuning at beamlines SIXS, DEIMOS and HERMES respectively. The as deposited films were all inhomogeneous with a strong Co surface depletion. Annealing up to 850 K leads to more homogeneous, better crystallized and smoother films. To the contrary higher temperatures annealing reveal epitaxial strain release, and chemical reduction accompanied by the occurrence of surface magnetic domains. The overall magnetic properties evolve to reach an isotropic final state. Our observations show that the chemical, morphologic and magnetic behaviors are strongly dependent on the deposition conditions and post-deposition thermal treatments.
Authors : Dallocchio M.*(1), Boileau A.(1), Mercey B.(1),David A.(1), Lüders U.(1), Sandrine Froissart.(1), Xavier Larose.(1), Bérini B.(2), Dumont Y.(2), Pautrat A.(1), Prellier W.(1), Fouchet A.(1)
Affiliations : (1)NORMANDIE UNIV, ENSICAEN, UNICAEN, CNRS, CRISMAT, 14000 CAEN, FRANCE. (2)Groupe d’Etude de la Matière Condensée (GEMaC), UMR 8635 Université de Versailles Saint-Quentin en Yvelines & CNRS Université Paris-Saclay.
Resume : Colossal magnetoresistance La0.66Sr0.33MnO3 (LSMO) thin films have been grown by pulsed laser deposition on SrTiO3 using combinatorial substrate epitaxy (CSE) approach. These polycrystalline substrates have been synthesized by spark plasma sintering (SPS) and polished in order to obtain mirror surface. They present micrometer-size grains with different crystallographic orientations where each grain acts as a single crystal to promote local epitaxy with all the different crystallographic orientations in only one sample. The size of the crystallographic domains can be controlled from 2 to 40 µm depending of annealing temperature during synthesis by SPS. A complete study of grain size, orientation, local epitaxy, and morphology have been investigated by electron backscatter diffraction (EBSD) and atomic force microscopy (AFM) measurements. The study of the magnetic and transport properties shows an increase of the Curie temperature of the LSMO films deposited onto polycrystalline substrates, compare to films deposited on single-crystal SrTiO3 substrate. We show that magnetotransport is strongly affected by CSE approach depending on the crystallographic domain size. A constant high magnetoresistance (MR) appears in the CSE approach from 5 to 320K compare to single-crystal We have also evidenced the apparition of a low field magnetoresistance (LFMR) below 200K. This effect is strongly reinforced by the shrinking of the size domain, related to the presence of the grain boundaries. Finally, we study hysteretic magnetotransport which is also sensitive to domain size and anisotropy. CSE approach is therefore a new way to tune the magnetotransport of complex oxides. Thanks to the PolyNASH project ANR-17-CE08-0012.
Authors : D.E. Dogaru1*, A. Brunier1, A. Manolescu2, M. Alexe1
Affiliations : 1 Department of Physics, University of Warwick, Coventry CV4 7AL, UK 2 Department of Engineering, Reykjavik University, Menntavegur 1, IS-101 Reykjavik, Iceland
Resume : SrRuO3 is one of the few itinerant (4d) ferromagnetic oxides with ferromagnetism emerging from double exchange interactions. Epitaxial SrRuO3 thin films on (100)-oriented SrTiO3 substrate show orthorhombic symmetry with the orthorhombic o direction normal to the substrate surface. Whereas several studies have confirmed an out-of-plane component of the easy axis, the magneto-crystalline anisotropy of SrRuO3 thin films is still under investigation. Here we show intriguing magneto-transport properties of ferromagnetic SrRuO3 thin films grown on (100) SrTiO3 substrates by pulsed laser deposition techniques. The in-plane strain imposed by narrow substrate terraces alters the magnetic anisotropy energy of the system and results in a negative magnetoresistance (MR) below the coercive field. This negative-MR effect occurs in a perpendicular magnetic-field measurement geometry, it is dependent on the direction of the electrical current with respect to the in-plane crystallographic axes and it is restricted to a small range of SrRuO3 film thicknesses (4-12nm). We discuss experimental conditions including growth parameters, measurement geometrical configurations, scaling factors, thickness dependence, etc. and propose a model for the origin of this thin film magneto-transport property.
Poster Session : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : Alina Vladescu, Mihaela Dinu, Lidia R. Constantin, Mariana Braic
Affiliations : National Institute of Research and Development for Optoelectronics - INOE 2000, 409 Atomistilor St., 077125, Magurele, Romania
Resume : Biomedical fields used various materials with a wide of characteristics. Transition metal carbides or nitrides or carbonitrides have attracted great interest in biomedical applications, especially for load bearing implants, due to their greater properties such as chemical inertness, high hardness, high wear and corrosion resistance, low friction, good biocompatibility. Among various carbides, TiC and ZrC are the most investigated as possible candidate in medical field due to their superior biocompatibility. Nevertheless, the anticorrosive properties and biocompatibility of TiC and ZrC coatings are not fully understood. Consequently, it is worth to investigate the corrosion, biomineralization, degradation rate, tribological performance, protein adsorption, cell attachment, and antibacterial properties of TiC and ZrC coatings, properties crucial in biomedical applications. The aim of the present paper is to investigate three types of carbide coatings (TiC, ZrC and TiNbC) as possible candidate for load bearing implants. For this study, the deposition and characterization of TiC, ZrC and TiNbC coatings are performed on 316L stainless steel substrates. The coatings were prepared by cathodic arc evaporation method. The coatings were investigated in terms of microchemical, microstructural and mechanical properties, corrosion resistance and tribological performance in SBF at 37°C, as well as the biocompatibility with human osteosarcoma cell line MG63. We acknowledge the support of the Romanian projects: no. 60PCCDI/2018 (PN-III-P1-1.2-PCCDI-2017-0239); Core Program-2020; no. 19PFE/2018 (PROINSTITUTIO).
Authors : Alina Vladescu, Mihaela Dinu, Lidia R. Constantin, Catalin Vitelaru
Affiliations : National Institute of Research and Development for Optoelectronics - INOE 2000, 409 Atomistilor St., 077125, Magurele, Romania
Resume : During the years, as compared to the transition metal nitrides or carbides, the corresponding carbonitrides were found to exhibit better mechanical properties, corrosion and wear resistance as well biocompatibility. The goal of the current work is to comparatively investigate the mechanical characteristics (roughness, hardness, adhesion, elastic modulus), corrosion resistance in DMEM at 37C and biocompatible characteristics of TiSiCN coatings as possible candidate for load bearing implants. TiCN will be used as reference coating. The coatings are deposited by cathodic arc evaporation method on CoCr alloy, common alloy used in orthopaedic surgery. We acknowledge the support of the Romanian projects: no. 60PCCDI/2018 (PN-III-P1-1.2-PCCDI-2017-0239); Core Program-2020; no. 19PFE/2018 (PROINSTITUTIO).
Authors : Ilyes MITICHE 1 2, Nadhira BENSAADA LAIDANI 1, Omar LAMROUS 2, Said MAKHLOUF 3
Affiliations : 1 Center for Materials and Microsystems, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Povo, Trento, Italy; 2 Laboratoire de Physique et Chimie Quantique, Mouloud Mammeri University of Tizi-Ouzou, BP 17 RP, 15000 Tizi-Ouzou, Algeria; 3 Laboratoire de Mécanique, Structure et Énergétique, Mouloud Mammeri University of Tizi-Ouzou, BP 17 RP, 15000 Tizi-Ouzou, Algeria
Resume : The goal of this work is to synthetize and characterize stable colloidal metallic nanoparticles during sputtering onto liquid substrates for thermal conversion applications. For this purpose, sputtering targets of copper and gold were used and polyethylene glycol with average molar mass 600 g/mol was taken as liquid substrate for its very low vapor pressure allowing to maintain low pressure levels in the deposition chamber, as well as for its low toxicity and cost. The structure of the obtained nanofluids were characterized using X-ray photoelectron spectroscopy and X-ray diffraction spectroscopy and the shape and the size of the NPs were determined by atomic force microscope (AFM) and dynamic light scattering technique. Finally, spectrophotometry analysis was carried out in order to determine the UV-visible absorption spectra of these nanofluids. The effects of the process parameters such as discharge voltage and deposition time on the properties of the nanofluid are analyzed and discussed. Among others, AFM reveals that the size of the nanoparticles varies between 30 and 160 nm. We also observed that the discharge voltage affected the range of light absorption wavelengths.
Authors : Laura Sauze, Nicolas Vaxelaire, Nicolas Bernier, Roselyne Templier, Denis Rouchon, François Pierre, Denis Remiens, Guillaume Rodriguez, Florian Dupont
Affiliations : CEA-LETI; CEA-LETI; CEA-LETI; CEA-LETI; CEA-LETI; CEA-LETI; IEMN-DOAE; CEA-LETI; CEA-LETI;
Resume : Piezoelectric materials are used in a wide range of application based on their electric, acoustic or optical properties. The upcoming 5th Generation of mobile applications (5G) requires higher performances for RF filters like Surface Acoustic Waves (SAW) resonators. Lithium niobate (LiNbO3) monocrystalline substrates are commonly used for the manufacturing of SAW devices. However, the thickness which conditions the performances of the resonator, cannot be tuned easily. Even though LiNbO3 is a good candidate, its growth remains very challenging. Therefore, layer transfer from monocrystalline LiNbO3 substrates is the most common approach. The growth of stoichiometric, single-phased and crystalline (either epitaxial or textured) lithium niobate thin films is challenging. To ease the synthesis of crystalline LiNbO3, an alternative way of deposition is explored here: the Pulsed Laser Deposition (PLD). In this work, 200 nm-thick LiNbO3 films have been grown by PLD on pure congruent LiNbO3 substrates with various orientations: X-cut (or (110) plane), Y-cut (or (100) plane) and Z-cut (or (001) plane). The morphological properties of the films were analysed by Atomic Force Microscopy (AFM), high-resolution X-Ray diffraction (HRXRD) and scanning transmission electron microscopy (STEM). The chemical properties of the films were investigated by Raman spectroscopy and by Secondary Ion Mass Spectrometry (SIMS). These results could be the first step towards a new generation of high-performance SAW filters based on epitaxially grown LiNbO3 thin films.
Authors : Kyeong-Keun Choi, Seongjeen Kim
Affiliations : Pohang University of Science and Technology (POSTECH); Kyungnam University
Resume : Palladium (Pd) thin films have been used for hydrogen (H2) sensing applications. There are several reports the Pd on H2 sensing at below 150 °C. However, the sensing property, change of morphology, temperature coefficient of resistance (TCR), thermal stability and the reaction of Pd films have not been studied systematically at above 300 °C and is not yet fully understood. In this study, Pd thin films were deposited on 10nm titanium (Ti) film/100nm thermal oxide/Si (or SiC) substrates for application in hydrogen sensor with high temperature stability. The temperature-dependent sheet resistance measurements of Pd (top)/Ti stacked films with 50 – 300 nm thicknesses of Pd films were studied as a function of temperature at the temperature range of 25°C (room temperature) – 550 °C with heating rate of 20 °C/min. Rapid thermal anneal (RTA) process was applied to get high thermal stability, faster response and high repeatability of Pd thin films. As the temperature increases, the resistivity of Pd (top)/ Ti stacked film increases, and the resistivity showed sharply decreased at temperature of ~ 150 °C and ~ 520 °C, respectively, with increasing temperature. This means we need more higher anneal temperature to get thermal stability film. The hydrogen sensing properties of the annealed films increased the repeatability of the hydrogen sensing at above 300°C, but response time (~ 4 s) and recovery time(~64 s) are almost same compared with a as the deposited film.
Authors : Simon Kos, Jindrich Musil
Affiliations : University of West Bohemia, Plzen, Czech Republic
Resume : The strongly non-equilibrium processes used at an atomic level in a new sputtering technology of coatings are: (1) heating to high temperatures without slow substrate heating, (2) high pressures (>1000 GPa) used in the coating formation, and (3) extremely fast cooling (> 10^10 K/s) of the created coating material. The principle of this technology is explained. The technology is suitable for deposition of advanced coatings with new unique properties as demonstrated by the following examples: (1) alloy coatings with a high-temperature beta phase sputtered at low temperatures close to room temperature , (2) overstoichiometric nitrides which exhibit high hardness due to the presence of the singly bonded pernitride structural unit [2,3], and (3) superhard flexible Ti coatings with high hardness (up to 20 GPa) several times higher than that of the bulk Ti metal . The technology may be used for depositions not only on large areas such as sheets but also on parts of complex shapes, and hence it has a high application potential.
Authors : Tien-Chai Lin1, Ping-Chin Kuo1, Wen-Chang Huang1,2
Affiliations : 1Department of Electrical Engineering, Kun Shan University, No. 195, Kun-Da Rd., Yung-Kang Dist., Tainan, 71003, Taiwan, ROC 2Green Energy Technology Research Center, Kun Shan University, No. 195, Kun-Da Rd., Yung-Kang Dist., Tainan, 71003, Taiwan, ROC
Resume : In the research, we present a co-sputtering technique to deposit indium magnesium zinc oxide (IMZO) thin film with various deposited time and various power ratios toward MgO and IZO ceramic targets. The doping effect of Mg on the IMZO thin film is considered. X-ray diffraction (XRD), scanning electron microscopy (SEM), Hall measurement and UV–vis spectrophotometer characterizations were carried out for microstructural, electrical, and optical properties of the samples. It shows an improvement of the resistivity at high doping of Mg. This also leads to an increase of carrier mobility of the film. The crystalline of the film is amorphous and shows a high transmittance of above 80% for all the sample of various Mg doping. A good response of the film as it was applied to be a hydrogen sensor. The IMZO film shows an n-type semiconductor property at the sensing of hydrogen and its resistance decreases obviously through the response.
Authors : Bianca Cristiana Hodoroaba(1) Stefan Andrei Irimiciuc(2) Gabriela Dorcioman(2), Petronela Garoi(2), Doina Craciun(2), Valentin Craciun(2,3)
Affiliations : 1University of Bucharest, Faculty of Physics, Bucharest-Magurele, Romania 2National Institute for Laser, Plasma and Radiation Physics – NILPRP, 409 Atomistilor Street, Bucharest, Romania 3Extreme Light Infrastructure for Nuclear Physics, Magurele, Romania
Resume : Low-density materials represent a strong interest for a wide range of applications as well as for fundamental physics in light of recent developments of extreme high-power fs lasers. . Several applications are identified like microsensor pre-concentrators, bone implantation, scaffold for tissue regeneration, electrochemical supercapacitors and lightweight microwave shielding structures. Carbonaceous foams show unique properties: black-body-like absorption, an anomalous ferromagnetic behavior, additionally an increased gas and liquid adsorption and storage capability. The absorption of intense and short laser pulses by matter is observed to significantly increase in such density range. The advantage of using PLD for the deposition of such complex structure comes from inner properties of transient plasmas which present strong gradient in density, particle energy and in the case of carbon the presence of complex molecular structures even in the plasma form. We report here on the generation of complex carbonaceous structure generated on silica substrates by pulsed laser deposition of graphite target in controlled environment. A novel deposition geometry was attempted in order to take into account the flip-over effect and the strong asymmetries from the carbon generated plasma. The deposition process was calibrated by adjusting the laser beam energy, frequency, and deposition time on a wide range of values. Various background gasses (Ar, CH4) and pressure were used in order to find the best media that could aid the generation of complex carbon structures. The obtained films were investigated by complimentary surface analysis methods like XRD, XRR, XPS, SEM and EDS in order to accurately describe the structure and composition of the films.
Authors : Devanshi Bhardwaj, Deependra Kumar Singh, S.B. Krupanidhi, A. M. Umarji
Affiliations : Materials Research Centre, Indian Institute of Science, Bengaluru, India - 560012
Resume : Vanadium oxides are the most interesting materials because of its varying oxidation states between V2 and V5 , out of which, the most famous compounds being V2O5 and VO2. VO2 has an interesting semiconducting to metal transition (SMT) property where it changes its phase structure from low-temperature insulating state to high-temperature (T>68°C) metallic state. Because of this, VO2 has wide applications. Pulsed laser deposition (PLD) has been used to fabricate vanadium oxide thin films for several applications, since the method has several advantages including easily controllable film composition by deposition parameters, a good repetition of stoichiometry of the target material in the films deposited on the substrate, and epitaxial growth of thin films. We report the synthesis of vanadium oxide thin films (PLD) under different parameter conditions on Si/SiO2 substrate using V2O5 target. The aim of the work was to get smother films of VO2 with a single step synthesis process. The microstructure and crystal symmetry of the deposited films were studied with X-ray diffraction, scanning electron microscopy (SEM), and Raman spectroscopy. The film obtained were phase pure as determined from XRD and Raman data. The films smoothness and surface morphology were examined by atomic force microscopy where the roughness was reduced to about 4 nm as compared to other synthesis process used before in the group. SMT was studied by I-V measurements on different films where 3-4 orders of resistance change were observed for the best condition. Thus, we were able to successfully synthesise VO2 thin films with reduced roughness thus making it suitable for optical applications.
Authors : A. Bellucci1, M. Mastellone1-2, M. Girolami1, V. Serpente1, V. Valentini1, E. Bolli3, A. Mezzi3, S. Kaciulis3, S. Orlando4, A. Santagata4, R. Polini1-5, E. Sani6, and D. M. Trucchi1
Affiliations : 1Istituto di Struttura della Materia (ISM-CNR), Via Salaria km 29.300, Monterotondo Scalo (RM), 00015, Italy; 2Dipartimento di Scienze di Base ed Applicate per l'Ingegneria, Università di Roma "La Sapienza", Via A. Scarpa 14, 00161, Roma, Italy; 3Istituto per lo Studio dei Materiali Nanostrutturati (ISMN-CNR), Via Salaria km 29.300, Monterotondo Scalo (RM), 00015, Italy; 4Istituto di Struttura della Materia (ISM-CNR), Contrada Santa Loja, Tito Scalo (PZ), 85050, Italy; 5Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, Rome, 00133, Italy; 6Istituto Nazionale di Ottica (INO-CNR), Largo E. Fermi, 6 Firenze (FI), I-50125, Italy.
Resume : Double fs-pulse experiments were performed on the overall surface of different semiconductors (Si, InP, SiC, diamond) to finely control their optical properties inducing 2D-nanostructured morphologies. By tuning both the pulse delay and polarization of the incident laser beams, the formation of regular laser-induced periodic surface structures (LIPSS) able to attribute the desired properties of absorption and selectivity to the semiconductor, have been observed. The configuration employed for the double-fs-laser pulse (Ti:Sapphire, 800 nm) sequences was collinear and both beams were focused, by both 4x and 40x microscope objective, on the sample surface that was moved, according to a raster path, in order to fully treat it. The inter-pulse delay of the individual 100-fs-duration pulses was varied from 50 fs up to 30 ps, whereas the double pulse laser beam vertical and horizontal polarizations were combined each other. In order to guarantee the most proper dose of laser beams impinging on the sample surface, this was moved continuously with speeds ranging from 0.1 to 5 mm/s under the laser repetition rate of 1 kHz. The resulting treated samples were analyzed by scanning electron microscopy, Raman, XPS, UV-visible-IR spectroscopy to finely tune the treatment parameters for each different semiconductor. The obtained results allow a clear identification of the advantages connected to the double-pulse treatment with respect to the single pulse irradiation. The effectiveness of the double-fs-pulse used in the present work in controlling the resulting nanometer 2D-textures of the samples’ surface and, as a consequence, the semiconductors’ optical absorption and selectivity is thus provided.
Authors : M. Nistor 1, E. Millon 2, C. Ghica 3, C. Hébert 4,5, J. Perrière 4,5
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics (NILPRP), L22, P.O. Box. MG-36, 77125 Bucharest-Magurele, Romania; 2 GREMI, UMR 7344 CNRS-Université d'Orléans, 45067 Orléans Cedex 2, France; 3 National Institute of Materials Physics (NIMP), Atomistilor Str. 105 bis, PO Box MG-7, 77125 Magurele-Ilfov, Romania; 4 Sorbonne Universités, UPMC Univ Paris 06, UMR 7588, INSP, F-75005, Paris, France; 5 CNRS, UMR 7588, INSP, F-75005, Paris, France
Resume : The microstructure and physical properties of Nd doped ZnO films grown on c-cut sapphire substrate by the pulsed-electron beam deposition (PED) at 500°C and 10-2 Ar pressure, under oblique incidence, were investigated. RBS, TEM, XRD and pole figures analyses were carried out to characterize the film microstructure, while the electrical resistivity and optical characteristics of the films were also studied. A (00l) texture is always observed for pure or doped ZnO films grown by PED on c-cut sapphire substrate. Besides this classical aspect, for PED under oblique incidence a tilted growth mode was observed, with the presence of Nd:ZnO columns inclined by about 17° /- 3°, with respect to the normal to the substrate. Moreover, the (002) ZnO plane was tilted by about 35° with respect to the (002) Al2O3 plane. The 17° tilt of the ZnO column is the result of the «shadowing effect» related to the oblique incidence; while the specific 35° tilt of the (002) ZnO plane has to be related to the epitaxial growth of the film on the substrate. An epitaxial relationship showing that the (229) plane of ZnO grows on top of the substrate surface was deduced from the pole figures. The origin of this specific texture will be discussed, as well as the consequences of the tilted growth on the electrical and optical properties of Nd doped ZnO films.
Authors : Jae-Yeol Hwang
Affiliations : Department of Physics, Pukyong National University, Busan 48513, Republic of Korea
Resume : Two-dimensional (2D) chalcogenide materials have been focused as new candidates beyond predecessor graphene due to the discoveries of interesting physical properties, such as high-performance thermoelectricity, superior carrier mobility, ultrafast charge transfer, topological insulator, and superconductivity. In particular, the demands on high-quality 2D chalcogenide films for device applications are increasing since such properties are strongly correlated with their unique structural ordering and crystal quality. However, the difficulties in controlling epitaxy with low defect density, the lack of appropriate substrate, and a little understanding of growth mechanism for 2D chalcogenide film have been major obstacles for the further advances of these materials. We demonstrate novel concepts enabling the van der Waals epitaxy (vdWE) of 2D chalcogenide films on conventional substrates. As a proof of concept, highly-oriented pnictogen chalcogenide films were epitaxially grown on graphene (2D) and sapphire (3D) substrates by pulsed laser deposition via spontaneous vdWE utilizing the surface reaction of the substrate with chalcogen. It was found that spontaneous vdWE promotes the high-quality 2D chalcogenide film with high carrier mobility and low defect density. [References] Hwang et al. Nano Letters, 17, 6140 (2017). Hwang et al. Advanced Materials, 29, 1604899 (2017)
Authors : M. Rusu, L. Choubrac, J. Márquez-Prieto, T. Unold
Affiliations : Struktur und Dynamik von Energiematerialien, Helmholtz-Zentrum Berlin für Materialien und Energie, Lise-Meitner Campus, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
Resume : BaZrO3 thin films have a high application potential, in particular, in solid oxide fuel cells as well as precursor layers for the preparation of novel unconventional semiconductor materials such as chalcogenide perovskites. These applications require the investigation of a wide range of the material physical properties as a function of elemental stoichiometry and crystalline phases. The goal of this work is therefore to prepare BaZrO3 thin films with controllable/tunable physical properties. Uniform, striped, and wedge-shaped BaZrO3 thin films on areas as large as 2x2 inch2 were prepared on quartz glass substrates by pulsed laser deposition. The preferential ablation of elements was investigated as a function of background pressure between 1x10-1 mbar and 5x10-7 mbar. Stoichiometric transfer to the substrate was studied for laser fluences ranging between 0.7–3.5 J/cm2. Thin films with a [Zr]/[Ba] ratio in the range of 0.8–1.3 were obtained. The thermal stability was investigated on thin films prepared either on uniformly heated substrates at temperatures ranging from 25°C to 600°C or on substrates with thermal gradients of 200°C. Selected samples were post-sulfurized to form BaZrS3-BaZrO3 chalcogenide perovskites thin-films with tunable bandgaps in a range from ~2.0 eV to ~3.4 eV. Their potential use as absorbers and as functional layers for solar energy harvesting is also discussed.
Authors : AlYemni, Sarah N., AlBrithen, Hamad A., AlYamani, Ahmed Y., AlAnzi, Ali Z., AlQahtani, Hadba, H., AlBadri, Abdulrahman M., AlHazaa, Abdulaziz N., AlShammari, Abeer F., AlOdhayb, Abdullah N., Shamma, Khaled Z., AlNjiman, Fahad M.
Affiliations : King Saud University (KSU), King Abdulaziz City for Science and Technology (KACST), King Abdullah Institute for Nanotechnology (KAIN).
Resume : In this work, Zrx Ti1-x O2 alloy thin films were grown by pulsed laser deposition (PLD) technique. The intended stoichiometry of films was obtained by using prepared targets with different concentrations of ZrO2 in ZrO2-TiO2 powder mixture (0%, 15%, 20%), then compressed by a hydraulic press, followed by annealing. Samples are categorized into three sets depending on target concentrations. Thin films were deposited on Si substrates, at two temperatures 500 °C and 600 °C. The deposition process was under the oxygen gas background at a flow rate of 5 sccm. The optical properties of the grown films were investigated by spectroscopic ellipsometry (SE) and photoluminescence spectroscopy (PL). From the data fitting of the SE, it is found that the index of refraction varies as a function of the depth, indicating either a change in the film phase structure or stoichiometry. Further optical and structural measurements are carried on to explore ZrTiO2 alloy properties and the effects of the growth temperature on these properties.
Authors : P. Gomez, A Mariscal, J. Gonzalo, R. Serna
Affiliations : Laser Processing Group, Instituto de Optica, IO-CSIC, Serrano 121, 28006 Madrid, Spain
Resume : White light LEDs (WL-LEDs) are replacing conventional lighting sources due to its high energy efficiency and reduced power consumption. However, current technology, based on encapsulated crystalline phosphors, is expensive for large scale production and may present thermal constraints. An alternative are rare-earth (RE) doped phosphors. In particular, Europium possesses two oxidation states with different photoluminescence (PL) emission characteristics: 4f intra-transitions (red) in the case of Eu3 , while Eu2 shows a broadband emission in the blue-visible spectrum. Thus, the combination of both ions is an appealing possibility for WL-LEDs, yet the long-lifetime of Eu excited states reduces the PL emission brightness. A possible solution is to combine them with metallic nanostructures to enhance their emission due to plasmonic effects. We will show that the inclusion of Ag nanoparticles (NPs) in europium oxide (EuOx) thin films leads to a broad PL emission band. Nanostructured thin films consisting of EuOx layers on top of self-organized Ag NPs layers were produced by PLD in vacuum at room temperature. PL emission is activated by post-deposition annealing in air at 300ºC. PL characteristics range from a narrow red emission in absence of Ag NPs to a broad white band when they are present, although the Eu2 /Eu3 ratio in similar in both cases. The enhancement and modification of spectral response is discussed in terms of coupling of Eu ions with Ag NPs.
Authors : Joris More-Chevalier1, Elen Duverger-Nédellec2, Stefan Andrei Irimiciuc3, Lenka Volfova1, Sergii Cherpalov1, Olivier Perez4, Laurence Herve4, Eva Maresova1, Jan Lancok1
Affiliations : 1 Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 182 21 Prague, Czech Republic; 2 CNRS, Université de Bordeaux, ICMCB, UMR 5026, F-33600 Pessac, France; 3 National Institute for Laser, Plasma and Radiation Physics – NILPRP, 409 Atomistilor Street, Bucharest, Romania; 4 ENSICAEN, UNICAEN, CNRS, CRISMAT, Normandie University, 14000 Caen, France
Resume : Phosphate tungsten bronzes have been shown to be low-dimensional conductors. Several families are described including monophosphate tungsten bronzes (PO2)4(WO3)2m, (PWO) and diphosphate tungsten bronzes (P2O4)2(WO3)2m. These materials present some specific electronic properties as spin density waves, charge density waves and superconductivity. In this study we presented fabrication of the PWO thin films from ceramic targets by means of pulsed laser deposition (PLD) using Nd:YAG laser operated at 266 nm wavelength on fused silica substrate. Plasma monitoring was performed as a function of the oxygen pressure and a correlation was done between chemical composition of films and the plasma ions distribution. Our attention was focused on the influence of the oxygen pressure as well as the temperature deposition on the optical and electrical properties of films was studied. The surface morphology and composition were characterised by AFM, SEM/EDX and XPS, respectively. A change in the electrical properties varying from metallic to dielectric was observed with the oxygen concentration in the PWO films. Equivalent variation in the optical properties was observed for PWO films presenting a metallic behavior when oxygen concentration was low. Finally, the increase of the oxygen concentration tends to change optical properties from semiconductors, presenting a band gap in the visible range varying from 400 nm to 450 nm, to an insulator layer with a large band gap in the UV range.
Authors : Raúl Zazo, Antonio Mariscal Jiménez, Ivan Camps, Pilar Gómez-Rodríguez, R. Peláez, J. Gonzalo, Rosalía Serna and Jan Siegel
Affiliations : Laser Processing Group, Instituto de Optica, IO,CSIC, Madrid 28006, Spain
Resume : Silicon oxynitrides are highly versatile because their composition can be varied from oxygen‐rich compositions, close to that of SiO2, to a nitrogen‐rich composition, close to that of Si3N4, which enables control of their optical and electrical performance. Among them, oxynitride phosphors based on so called SiAlONs have widely been investigated when doped with Eu2 for green color conversion, field emission lamps and display applications. Moreover, these materials show excellent thermal stability and durability against moisture. Previously, we have reported the successful growth of amorphous SiAlON-Eu doped thin films prepared by pulsed laser deposition, and their photoluminescence (PL) and cathodoluminescence (CL) properties [1,2]. Upon photon and electron excitation, films showed light emission dominated by a spectral band covering the whole visible (VIS) wavelength range that is associated to the Eu2 5d-to-4f electronic transition [1,2]. However, to achieve such emission furnace annealing treatments at temperatures in the range of 600-700 ºC were needed to reduce defects in the films and enhance PL efficiency. In this work we demonstrate the achievement of efficient PL broadband emission after ns-pulsed laser annealing in localized areas of the SiAlON-Eu doped films. Laser irradiation is performed with an ArF excimer laser. We are able to achieve a higher PL intensity after laser irradiation than with conventional furnace annealing, and succeed to suppress unwanted narrowband Eu3 emission. We will discuss the effect of the laser pulse energy and number of pulses on the PL intensity enhancement and the involved underlying associated physical mechanisms. //  I. Camps, A. Mariscal, and R. Serna, J. of Lumin. 191, 97(2017).  I. Camps, A. Mariscal and R. Serna, Phys. Stat. Solidii 215, 1800260 (2018).
Authors : C. W. Bond(1), Y. Jin(2,3) , R. L. Leonard(1), P. Gómez-Rodríguez(4), E. Nieto-Pinero(4), J. Gonzalo(4), R. Serna(4), A. Petford-Long(2,3), J. A. Johnson(1)
Affiliations : 1Mechanical, Aerospace, and Biomedical Engineering Department, University of Tennessee Space Institute, Tullahoma, TN 37388, USA 2 Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA 3 Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA 4Laser Processing Group, Instituto de Optica CSIC, Madrid 28006, Spain
Resume : Light emission from rare-earth (RE) ion doped thin films is attractive for applications in optoelectronics, and bio-imaging. However, RE performance depends critically on the composition of the material. Fluoride crystals are excellent hosts due their low phonon-energy; this minimizes the multiphonon relaxation thus improving the RE luminescence efficiency. When these RE-doped crystalline fluorides are embedded in an oxide glass matrix, forming a glass-ceramic, the composite profits from robust mechanical and optical properties. However, developing these nanocomposite materials in thin film configuration, for integration in a device, is a challenge. In this work we show the successful preparation of glass-ceramic films consisting of Eu-doped BaF2 active nanocrystalline layers separated by amorphous Al2O3 layers using ArF alternate pulsed laser deposition. We used Al2O3, BaF2 and Eu2O3 targets, and different deposition conditions; in order to achieve precise control of the Eu doped BaF2 distribution at the nanoscale level within the film. Noteworthy is that the Al2O3 layers and Eu doping where prepared in the usual on-axis substrate configuration, while for the BaF2 deposition the off-axis configuration was used to minimize fluorine loss. By alternate deposition of the targets, nanostructured multilayer films with different Al2O3 and BaF2 layer thicknesses and Eu doping were prepared. TEM analysis shows the formation of BaF2 nanocrystals within the Al2O3 amorphous layers. The films show good transparency and broadband visible luminescence that is related to Eu2 emission. // This research was supported by the National Science Foundation under grants DMR 1600783 and DMR 1600837, and the Spanish National Research Council under grants LINKA20044 and RTI2018-096498-B-I00 (MCIU/AEI/FEDER, UE).
Authors : Suvidyakumar Homkar1, Johanna Nordlander2, Daniele Preziosi1, Christophe Lefevre1, François Roulland1, Geneviève Pourroy1, Manfred Fiebig2, Morgan Trassin2, Nathalie Viart1
Affiliations : 1 IPCMS, UMR Unistra-CNRS 7504, 23 rue du Lœss, BP 43, 67034 Strasbourg cedex 2, France 2 Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland
Resume : Ga2-xFexO3 (GFO) is a promising material for developing low power consuming devices since at x=1.4 it boasts a room-temperature multiferroic nature with coupled magneto-electric properties. There exist a few reported characterizations of multiferroicity in GFO. Most have been done either on bulk or thick films, but none addresses the evolution of ferromagnetism and ferroelectricity in the technologically relevant ultra-thin regime. In this study, we report the magnetic characterization and optical in situ second harmonic generation (ISHG) study of GFO films, starting from the very first few unit cells grown with Pulsed Laser Deposition onto SrTiO3 substrate. GFO films show perpendicular magnetic anisotropy for thicknesses as low as 7 nm and parallel magnetic anisotropy for above 32 nm. Observation of SHG signal during the growth of GFO films (800°C) indicates a high polar ordering temperature. SHG at ultra-thin regime suggests a critical thickness of 6 u.c. for the onset of polarization. Another remarkable observation is the stabilization of single polar state in GFO films, interestingly retained even in the absence of charge screening environment, probably related to its high coercive field. In contrast, other ferroelectric oxides easily break down into domains and require charge screening to stabilize a single polar state. GFO thin films with single polar state and perpendicular moment could thus yield applications in the capacitor and low power switching devices.
Authors : V. Satulu, V. Marascu, A. Moldovan, V. Ion, B. Mitu, G. Dinescu
Affiliations : National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., Magurele Bucharest 077125 Romania
Resume : Fluorocarbon materials present interesting properties like low dielectric constant (<2.5), very good resistance for anticorrosion, as well as low friction coefficient which makes them promising candidates in various applications, like dielectric layers for the ultra-large-scale integration devices or anti-static friction and self-lubrication coating in magnetic storage devices [1,2]. In this work, results on the synthesis of fluorocarbon thin films by means of pulsed- plasma approaches, namely, RF magnetron sputtering of polytetrafluorethylene target and PECVD starting from fluorine containing precursors (SF6/CH4) are reported. Deposition of fluorocarbon thin films was performed in a spherical vacuum chamber provided with 1” RF magnetron gun and a PECVD sources, each of them mounted at 45o in respect to the substrate holder plane and 9 cm distance from it. Filling factors in the range 20-100% were used. Topographical aspects and the chemical composition of the fluorine-based layers were assessed by means of AFM and XPS investigations, respectively. The dielectric function of fluorocarbon thin films was determined in two frequency regimes: in the low frequency range by dielectric spectroscopy and in the optical range by spectroscopic ellipsometry. The obtained results are encouraging for the usage of fluorocarbon thin films as dielectric film in multilayer devices.
Authors : E. Millon 1, C. Cachoncinlle 1, V. Demange 2, S. Ollivier 2, M. Guilloux-Viry 2, X. Portier 3, M. Nistor 4, C. Hebert 5,6, J. Perrière 5,6
Affiliations : 1 GREMI UMR 7344 CNRS-Université d'Orléans, 45067 Orléans Cedex 2, France; 2 Univ. Rennes, CNRS, ISCR - UMR 6226, ScanMAT UMS 2001, F- 35000 Rennes, France; 3 Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), CEA/UMR CNRS 6252, Normandie Université, ENSICAEN, 6 Boulevard du Maréchal Juin, 14050 Caen Cedex, France; 4 National Institute for Lasers, Plasma and Radiation Physics (NILPRP), L22, P.O. Box. MG-36, 77125 Bucharest-Magurele, Romania; 5 Sorbonne Universités, UPMC Univ Paris 06, UMR 7588, INSP, F-75005, Paris, France; 6 CNRS, UMR 7588, INSP, F-75005, Paris, France;
Resume : Up to now, the room temperature (RT) epitaxy of oxide thin films is obtained by pulsed laser deposition (PLD) on atomically stepped (001) sapphire substrates. The c-cut substrate terraces are typically obtained via a high thermal annealing (1000°C) of the substrate before the growth . In the present work, the RT epitaxial growth of pure or doped iron oxide films was obtained on c-cut, a-cut and r-cut sapphire substrates without any high T tratments before the growth. AFM measurements do not show the presence of straight atomic steps and atomically flat terraces on these substrates. RT PLD of a Zn:Fe3O4 target leads to the formation of the wustite (Zn:FeO) and/or spinel (Zn:Fe3O4) phases depending upon the oxygen pressure during the RT growth. Rutherford backscattering spectrometry, transmission electron microscopy, X-ray diffraction and pole figure measurements were used to determine the precise texture and in-plane epitaxial relationships between film and substrate. On c-cut and a-cut substrate the wustite and spinel phases were (111) textured. Differently, on the r-cut substrates the iron oxide films show a (001) texture. The in-plane epitaxial relationships observed in these three cases were interpreted in the frame of the domain matching epitaxy. The possible mechanisms of the RT epitaxial growth of oxide films on these c-cut, a-cut and r-cut sapphire substrates will be presented and discussed.  R; Yamauchi et al, Scientific Reports 5 (2015) 14385.
Authors : M. Dinu (1), I. Pana (1), A. E. Kiss (1), L. R. Constantin (1), X. Almandoz (2), A. López-Ortega (2), Arcadie Sobetkii (4), M. Mondragon (3), C. E. A. Grigorescu (1), C. Vitelaru (1), A-M. Iordache (1), J. M. Izurrategi (3), Arcadii Sobetkii (4), V. Capatana (4), C. Bidalach (4), N. C. Zoita (1)
Affiliations : (1) National Institute of Research and Development for Optoelectronics, 409 Atomistilor Str., 077125 Magurele, Romania; (2) TEKNIKER, Tribology Unit, Iñaki Goenaga 5, 20600 Eibar, Spain; (3) GOIZPER S. Coop., Antigua 4, 20577 Antzuola, Spain; (4) SC MGM STAR CONSTRUCT SRL, 7 Pancota St, Bucharest 022773, Romania.
Resume : High-entropy alloys (HEAs) are metallic alloys containing at least five principal elements with equiatomic or near-equiatomic ratio. HEAs have attracted a lot of attentions and showed great application expectancy, especially as coating materials, due to their special physical, chemical, and mechanical properties, such as superior corrosion resistance, excellent thermal stability, high hardness, and better wear performance in comparison with conventional alloys. In this work, TiAlxCrNbY high-entropy alloy coatings were prepared by co-sputtering of Ti, Al, Cr, Nb and Y targets in an Ar atmosphere by a hybrid HiPIMS/DCMS/RFMS technique (Al and Cr by HiPIMS, Ti and Nb by DCMS, Y by RFMS). The effect of Al content, from 3 at. % to 22 at. %, on the adhesion, structural, morphological, tribological, mechanical and corrosion resistance properties was studied by scratch testing, HR-XRD, SEM, AFM, pin-on-disk testing, nanoindentation, electrochemical and corrosion tests. The best wear and corrosion performances were obtained for a concentration of Al in the range of 6 at.% - 12 at.%. This work was supported by ERANET-M.-TriboHEA project - grant no. 113/2019 of CCDI-UEFISCDI, PNCDI III, and grant no. ZL-2019/00622 of INNOBASQUE - and by Core Project 18N/08.02.2019 of the Romanian Ministry of Research and Innovation.
Authors : N. C. Zoita (1), M. Dinu (1), I. Pana (1), A. E. Kiss (1), L. R. Constantin (1), X. Almandoz (2), A. López-Ortega (2), Arcadie Sobetkii (4), M. Mondragon (3), C. E. A. Grigorescu (1), C. Vitelaru (1), A-M. Iordache (1), J. M. Izurrategi (3), Arcadii Sobetkii (4), V. Capatana (4), C. Bidalach (4)
Affiliations : (1) National Institute of Research and Development for Optoelectronics, 409 Atomistilor Str., 077125 Magurele, Romania; (2) TEKNIKER, Tribology Unit, Iñaki Goenaga 5, 20600 Eibar, Spain; (3) GOIZPER S. Coop., Antigua 4, 20577 Antzuola, Spain; (4) SC MGM STAR CONSTRUCT SRL, 7 Pancota St, Bucharest 022773, Romania.
Resume : Compositionally complex alloys consisting of five or more principal elements in equimolar or near-equimolar ratios, also referred to as high-entropy alloys (HEAs), have received considerable attention in the last decade due to their special physical, chemical, and mechanical properties, such as superior corrosion resistance, ductility and fracture toughness, thermal stability, hardness, and wear performance in comparison with conventional alloys. These superior characteristics are due to HEAs specific nanostructure, consisting of nanoscale particles embedded in an amorphous and/or crystalline matrix, which are in turn strongly dependent on the processing technology. A hybrid HiPIMS/DCMS/RFMS technique in inert and reactive atmospheres of Ar and Ar/CH4/N2 was used in this work for the development of TiCrCoNiV high-entropy alloys coatings with low content of carbon and nitrogen for machine and automotive applications, that require medium-to-high friction and wear resistant surfaces. The adhesion, structural, morphological, mechanical, tribological, and corrosion resistance properties of the coatings were evaluated by scratch testing, HR-XRD, cross-sectional SEM, AFM, nanoindentation, pin-on-disk, and electrochemical corrosion tests. The best tribological properties for the targeted applications were obtained for a coating presenting a coefficient of friction of about µ = 0.61, a wear rate of K = 2.3*10-6 mm3/Nm, and a hardness value of H = 18.0 GPa. This work was supported by ERANET-M.-TriboHEA project (grant no. 113/2019 of CCDI-UEFISCDI, PNCDI III, and grant no. ZL-2019/00622 of INNOBASQUE) and by the Romanian Ministry of Research and Innovation Core Project, grant no. 18N/08.02.2019.
Authors : Sang A Lee1*, Jae-Yeol Hwang1, Jong-Seong Bae2, Jegon Lee3, and Woo Seok Choi3
Affiliations : 1Department of Physics, Pukyong National University, Busan, 48513, Korea; 2Busan Center, Korea Basic Science Institute, Busan 46742, Korea; 3Department of Physics, Sungkyunkwan University, Suwon, 16419, Korea
Resume : Transition metal oxides (TMOs) with strong hybridization between the transition metal and oxygen give rise to a variety of functionalities associated with their structural, electrical, magnetic, and chemical properties. Among them, perovskite ruthenates (ARuO3, A = Ca, Sr, and Ba) are rare metallic oxide materials that can be used as conducting layers or electrodes in electronic devices. The alteration of the A-site ion of perovskite ruthenates can result in different magnetic properties, even though they have the same B-site ion with the same Ru4 valence state. While CaRuO3 and SrRuO3 have a similar orthorhombic structure with distorted RuO6 octahedra, the magnetic ground state of CaRuO3 and SrRuO3 are paramagnetic and ferromagnetic, respectively. On the other hand, BaRuO3 in bulk can be stabilized into four different crystal structures, i.e., nine-layered rhombohedral (9R), four-layered hexagonal (4H), six-layered hexagonal (6H), and cubic perovskite structure (3C). The ferromagnetic bulk 3C BaRuO3 is only stabilized under extremely high pressure. In this study, we demonstrate epitaxially stabilized cubic BaRuO3 thin film on SrTiO3 (001) substrate via pulsed laser deposition (PLD). Also, pseudo-cubic Ruthenates are systematically investigated the electronic structure using x-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. The BaRuO3 thin film shows four-fold symmetry without RuO6 octahedral distortion contrary to other Ruthenates. We note that the electronic structure is significantly different from that of 9R BaRuO3 thin film but shows a similarity to its structural analogues (SrRuO3 and CaRuO3), suggesting the importance of the lattice structure in determining the electronic structure. The cubic BaRuO3 thin film shows metallic nature, with the Hall coefficient and carrier concentration is 1.32 × 10−8 Ωcm/T and 4.73 × 1022 holes/cm3 at 25 K, respectively. Finally, the magnetic ground state of the thin film is ferromagnetic with a transition temperature of ~50 K.
Authors : I.O. Kruhlov, L.M. Kapitanchuk, S.I. Sidorenko, S.M. Voloshko
Affiliations : Metal Physics Department, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Prospect Peremogy 37, 03056 Kyiv, Ukraine
Resume : The problem of humid corrosion in metallic thin-film elements of microelectronics devices is of high relevance. The application of low-energy Ar+ ion pre-irradiation is proposed in present study to struggle this issue, which was revealed for Ni/Cu/Cr/Si(001) tri-layer films. As-deposited and irradiated samples were exposed to RT water vapor produced by an ultrasonic generator. Exposure in such 100% humid environment ranged from 2 to 7 hours at a constant vapor pressure of 1.5 atm. Depth distribution of the main components (Ni, Cu, Cr) and impurities (O, C, N, K, Na, Cl, Ca, S) wsa studied using Jamp-9500F (Jeol) Auger spectrometer. Craters after profiling were also examined by scanning electron microscopy at an 30° angle collecting both secondary and Auger electrons. Threefold increase of C amount in the near-surface area is found in the sample after the vapor exposure. Furthermore, the thickness of the oxidized surface layer on the chemical maps in Auger electrons increases up to 5 times. Significant accumulation and redistribution of other impurities is observed as well. Simultaneously, the surface structure is substantially damaged and a lot of macrodefects are observed. Ion pre-irradiation with 800 eV energy for 20 minutes impedes the development of these processes after the water vapor exposure. The amount of O and C impurity atoms (as well as all others except of N) in the near-surface area is similar to their content in as-deposited non-exposed sample. The same affect is also characteristic to the surface morphology. This data indicate on the feasibility of applying the low-energy ion irradiation to enhance the corrosion resistance of metallic thin films.
Authors : E. Millon (1), C-E Bejjit (1), C. Cachoncinlle (1), J. Perriere (2,3), E. Briand (2,3), X. Portier (4)
Affiliations : (1) GREMI, UMR 7344 CNRS / Universite d’Orleans, 14 Rue Issoudun, 45067 Orleans Cedex 2, France (2) Sorbonne Universités, UPMC Paris 06, UMR 7588, INSP, 4 Place Jussieu, 75005 Paris, France (3) CNRS, UMR 7588, INSP, 4 Place Jussieu,75005 Paris, France (4) CIMAP, UMR 6252 CNRS / CEA / Université Basse Normandie, 6 bvd Marechal Juin, 14050 Caen Cedex, France
Resume : Magnetite (Fe3O4) and wustite (FeO) are well-known oxides for their tremendous magnetic properties. However, being able to grow stable FexOy thin films with controlled iron oxidation states could be of interest for further applications. In this work, we highlight the formation of different FexOy based thin films grown by pulsed-laser deposition (PLD) from Fe or Fe3O4 targets onto sapphire or MgO substrates. Based on XRD and RBS analysis, we point out that, by controlling both the substrate temperature and the oxygen pressure in the 10-7 – 0,1 mbar range during the PLD growth, films with various Fe/O ratios may be prepared. Thus, the different crystalline phases of the Fe-O system may be obtained: Fe2O3, Fe3O4, and the thermodynamically metastable FeO. In particular we show that at low pressure (10-6 mbar) Fe3O4/Fe composite thin films for which both metallic Fe and Fe3O4 phase are epitaxially grown on the sapphire substrates even at room temperature. This result is interpreted as a possible phase separation from the FeO metastable phase. The precise growth conditions leading to the formation of FeO-based film are also discussed.
Authors : Sizhao Huang*1, Evert Houwman1, Kurt Vergeer1, Nicolas Gauquelin2, Andrey Orekhov2, Dmitry Chezganov2, Johan Verbeeck2, Sixia Hu3, Gaokuo Zhong4, Jani Peräntie5, Yukuai Liu6, Frans Blom7, Gertjan Koster*1, Guus Rijnders1
Affiliations : 1. MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands, E-mail: email@example.com, firstname.lastname@example.org 2. Electron Microscopy for Materials Science (EMAT) University of Antwerp 2020 Antwerp, Belgium, E-mail: Nicolas.Gauquelin@uantwerpen.be 3. S. Hu,Core Research Facilities, Southern University of Science and Technology, Shenzhen, China, E-mail: email@example.com 4. Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, China, E-mail: firstname.lastname@example.org 5. Microelectronics Research Unit, University of Oulu, P.O. Box 4500, FI-90014 Oulu, Finland, E-mail: email@example.com 7. Canon Production Printing Netherlands B.V., P.O. Box 101, Venlo 5900MA, The Netherlands, E-mail: firstname.lastname@example.org
Resume : Lead based bulk piezoelectrical materials, e.g. PbZrxTi1-xO3(PZT), in sensors and transducers nowadays are widely used in electromechanical applications, for which optimally performing thin films are needed. Several theoretical reports were published on the influence of thermal strain on the piezoelectric properties (d33) in PZT thin films, also predicting significant enhancement of this property. In this work, we successfully demonstrate the applicability of these models for PZT(x=0.6) thin films grown on CaF2, SrTiO3(STO) and 70% PbMg1/3Nb2/3O3-30%PbTiO3(PMN-PT) substrates by pulsed laser deposition. The different substrates provide different thermal misfit strains, leading to experimentally observed and theoretically predicted d33 values of 32 pm/V, 140 pm/V and 81 pm/V, respectively. We characterised the PZT films with temperature dependent X-ray reciprocal space mapping (RSM) and grazing incidence diffraction (GID), transmission electron microscopy (TEM) in bright field (BF) and dark field (DF) modes as well as selected area diffraction (SEAD) convergent beam electron diffraction (CBED) and piezoresponse force microscopy (PFM). The Zr/Ti ratio has been confirmed by Rutherford Backscattering Spectrometry (RBS). The PZT(x=0.6) film which in bulk has a rhombohedral lattice symmetry, is at room temperature on STO in a relaxed monoclinic phase, which is the first has been observed for this composition. With this research we demonstrate that the thermal misfit strain has a significant effect on the structural and piezoelectric properties of PZT films.
Authors : S. Ni, prof.dr.ir. G. Koster, dr.ir. E.P. Houwman, prof.dr.ing. A.J.H.M. Rijnders
Affiliations : Inorganic Material Science, University of Twente
Resume : Due to the high dielectric constant, low dielectric loss, high piezoelectric response, and optical transparency, PMN-PT thin films have attracted tremendous attention for PiezoMEMS, Field Effect Transistors (FETs), energy harvesting and storage, and haptic sensors and actuators. However, it remains a great challenge to fabricate phase-pure pyrochlore-free PMN-PT thin films. In this work, we demonstrate that high-quality PMN-PT thin films are grown on SrTiO3 (STO) substrates using LBSO as the buffer electrode. It is found that whether nucleation of the pyrochlore phases occurs or not depends on the strain state of the initial growth layer. Direct growth of PMN-PT films on STO gives rise to a large compressive strain in the initial growth layer, and the resulting PMN-PT films contain pyrochlore phases. Already optimizing the deposition conditions, the compressive strain in the initial layer can be reduced, which also reduces the amount of pyrochlore phases in the films. By using La doped BaSnO3 (LBSO) as the buffer electrode, the initial growth layer of PMN-PT is under a large tensile strain, and the resulting PMN-PT films are in a pure perovskite phase and show high crystalline quality (FWHM of (002) peak≤ 0.05). The resulting films also show smooth morphology, with a Root Mean Square (RMS) roughness of less than 0.25 % of the film thickness. This study demonstrates that the use of a tensile lattice mismatch between the template layer and the PMN-PT tends to prevent the nucleation and growth of pyrochlore phases in favour of the perovskite phase and enhances the crystalline quality of the PMN-PT significantly.
Authors : M.Kiaba, T.Číž, O.Caha, A.Dubroka
Affiliations : Institute of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, Brno, Czech Republic; Institute of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, Brno, Czech Republic; Institute of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, Brno, Czech Republic; Institute of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, Brno, Czech Republic
Resume : We report on deposition and structural characterization of superlattices composed of antiferromagnetic LaFeO3 and semiconducting SrTiO3. The samples were grown by pulsed laser deposition with in-situ reflection high-energy electron diffraction (RHEED). The individual layers in superlattices are only a few momonolayers thick (between 1 to 10). The thickness was in situ controlled by RHEED in order to ensure that each layer had an integer number of monolayers. All films were deposited on SrTiO3(100) substrate with TiO termination. The superlattices have a flat surface with vicinal steps as observed by atomic force microscopy. The superlattice structure was explored by X-ray diffraction and reflection. Remarkably, we have observed a first order diffraction on the bilayer in the [(LaFeO3)1u.c. +(SrTiO3)1u.c.]x10 superlattice demonstrating that our superlattices are well ordered down to the monolayer scale. We have performed the temperature dependent transport measurements and NIR-UV ellipsometry in order to characterize the electronic state of the superlattices. The superlattices are highly resistive and exhibit semiconducting behavior at high temperatures.
Authors : M.L. Grilli1, D. Valerini2, A. Rizzo2, C. Song3, G. Hu3, M. Yilmaz4, R. Chierchia1, A. Rinaldi1
Affiliations : 1 ENEA - Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Casaccia Research Centre, Via Anguillarese 301, 00123 Roma, Italy 2 ENEA - Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Brindisi Research Centre, S.S. 7 Appia - km 706, 72100 Brindisi, Italy 3 Key Laboratory of Materials for High Power Laser, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China 4 Department of Science Teaching, K. K. Education Faculty, Atatürk University, 25240 Erzurum, Turkey
Resume : Al2O3 coatings deposited by Atomic Layer Deposition (ALD) have attracted considerable attention in the past years, due to the ability to coat complex geometries with very high aspect ratio for application in several technological fields. In this work we compare the structural, mechanical and tribological characteristics of 150 nm thick Al2O3 coatings fabricated by ALD and radio frequency sputtering, as deposited and annealed @900°C in N2 for 90 minutes. ALD coatings were deposited on Si substrates at 300 °C starting from tri-methylaluminum (TMA) precursors. Radio frequency sputtered Al2O3 films were grown at room temperature at a radio frequency power of 300 W in pure Ar atmosphere. X-ray diffraction, SEM-EDS, nano-hardness and friction measurements were used to infer the structural, morphological, mechanical and wear properties of the as deposited and annealed films. Results show superior mechanical performances for annealed alumina coatings under low loads, while the resistance against wear under higher load was higher for the sputtered annealed alumina coatings.
Authors : L. A. Martínez-Ara, P. Maldonado-Altamirano, M. A. Hernández-Pérez, J. Sastré-Hernández, J. R. Aguilar-Hernández, G. S. Contreras-Puente, J. Santoyo-Salazar
Affiliations : Departamento de Física, CINVESTAV-IPN, CDMX, Mexico; Doctorado en nanociencias y nanotecnología, CINVESTAV-IPN, CDMX, Mexico; ESIQIE-IPN, CDMX, Mexico; ESFM-IPN, CDMX, Mexico; Mexico; ESFM-IPN, CDMX, Mexico; ESFM-IPN, CDMX, Mexico; Departamento de Física, CINVESTAV-IPN, CDMX, Mexico.
Resume : Al_xGa_1-xN films on different substrates, Si (111), Al_2O_3 (0001) and amorphous quartz were grown by Pulsed Laser Deposition (PLD). A Nd-YAG laser tuned at 1064 nm wavelength, 12 ns pulse duration and a repetition rate of 50 Hz, was used for the ablation process. The energy of the laser beam focused at the target surface was 50 mJ/pulse. Aluminum concentration was determined by photoluminescence (PL) and Raman spectroscopy. Photoluminescence (PL) measurements were carried out with a He-Cd laser as exciting light, tuned at 325 nm, with a power of 40 mW. The PL at 10 K shows that the yellow band (YL) has a shift of 170 meV at higher energy in the ternary in comparation with the gallium nitride (GaN). Such shift of the PL maximun together with the widening of the YL band is related to the formation of the ternary compound. Raman spectra were mesured at room temperature by using a He-Ne laser, 633 nm, it with an output power of 30 mW, in a LabRam HR Evolution system. The Raman spectra show peaks at 569 and 655 cm-1 modes associated to GaN and AlN respectively, and a peak at 772 cm-1, this frequency corresponds to the vibrational mode A1(LO), this increases continuously from the mode of GaN to the corresponding A1(LO) mode of the AlN when the aluminum concentration increases. Beginning with displacement of the vibrational mode the aluminum concentration was determined, it turned out to be 15 %.
Authors : L. A. Bibiano-Salas, G. Eboli-Castro, L. A. Martínez-Ara, M. A. Hernández-Pérez, J. R. Aguilar-Hernández, , J. Santoyo-Salazar
Affiliations : ESFM-IPN, CDMX, Mexico; ESFM-IPN, CDMX, Mexico, Departamento de Física, CINVESTAV-IPN, CDMX, Mexico; ESIQIE-IPN, CDMX, Mexico; ESFM-IPN, CDMX, Mexico; Departamento de Física, CINVESTAV-IPN, CDMX, Mexico.
Resume : CdS, CdSe and CdS_0.5Se_0.5 alloy films have been deposited on glass, quartz and silicon (111) substrates by means of pulsed laser deposition technique. A Nd:YAG laser tuned at 1064 nm, 12 ns pulse duration and a repetition rate of 50 Hz, was used in the process. The energy of the laser beam focused on the target surface was 50 mJ/pulse. The deposition chamber was evacuated at the pressure of about Torr. The substrates were heated at 500°C and the deposition time was fixed at 30 minutes. We obtained high quality polycrystalline films, all the peaks refer to the (002) orientation corresponding to the hexagonal phase. The diffraction peak of the ternary is between the corresponding to CdS an CdSe. The lattice plane distance and the lattice parameter were calculated, resulting 3.54 A and 6.85 A respectively. By the transmittance spectra the band-gap were determinated, 2.39 eV for CdS, 1.9 eV for CdS_0.5Se_0.5 and 1.68 eV for CdSe. The photoluminescence spectra were taked at room temperature, they show emission related to the near band edge (NBE), centered at 2.4 eV for CdS, 1.68 eV for CdSe, and the emission of the ternary, at 1.9 eV, is according to the composition and the reported in the literature.
Authors : E. Azrak (1)*; L. Michaud (1); N. Vaxelaire (1); M. Bousquet (1); J. Eymery (2); F. Fournel (1); A. Reinhardt (1); S. Tardif (2) ; P. Montméat (1)
Affiliations : (1) Univ. Grenoble Alpes, CEA, LETI, 17 Avenu e des Martyrs, 38000 Grenoble, France (2) Univ. Grenoble Alpes, CEA, IRIG, MEM, 17 Avenue des Martyrs, 38000 Grenoble, France * lead presenter
Resume : AlN is commonly used as an active material in optoelectronics1 devices and microelectromechanical systems2. Due to its wurtzite structure, AlN is highly sensitive to external stresses. A first principle study theoretically showed that stresses should have an impact on the properties of AlN thin-films, with for instance an improvement of piezoelectric coefficients3. We have thus optimized the transfer process of poly-crystalline AlN (pc-AlN) thin-films sputtered on Si substrates onto flexible polymer substrates. The objective was to engineer the induced deformation of AlN films, and therefore tailor their properties. Growth of pc-AlN films on Si substrates was performed at 350°C by magnetron sputtering, with thicknesses between 200 nm and 1600 nm. There were two transferring steps after deposition: (1) pc-AlN on Si was bonded to another Si substrate called “carrier”, with an adhesive polymer on its surface. This transfer step was a temporary polymer bonding. After thinning then completely etching the original Si substrate, we then had a pc-AlN on Si carrier stack. (2) The AlN film was then detached from the carrier and bonded onto a flexible 230 µm thick polymer. This stretchable polymer was, then, used to controllably stress the AlN film. X-ray diffraction was performed after each fabrication step to assess the structural changes the AlN went through. In-situ Raman spectroscopy was used during the uniaxial straining of the AlN film to monitor the stress-induced E2 peak shift.
Authors : Raul Ramos, Diego Aparecido Carvalho Albuquerque, Everson Martins, Steven F. Durrant, José Roberto Ribeiro Bortoleto
Affiliations : Sao Paulo State University - UNESP, ICTS, Sorocaba, SP, Brasil.
Resume : This work reports a study of the room-temperature synthesis of a SnO2/ZnO bilayer by Pulsed Magnetron Sputtering. Morphological, optical, and electrical properties of the bilayer were investigated for different thicknesses of SnO2. Morphology was studied using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FE-SEM), the optical properties were analyzed by UV-Vis-NIR spectroscopy and the electrical properties were investigated by Linear Voltammetry. The optical transmittances of the ZnO films and the SnO2/ZnO combination were high (about 80%) in the visible, and the SnO2 film did not alter the optical properties of the ZnO, which would act as a transparent contact electrode in a Perovskite Solar Cell.
Authors : Gianina Popescu-Pelin1, Carmen Ristoscu1, Liviu Duta1, Iuliana Pasuk2, George E. Stan2, Miruna Silvia Stan3, Marcela Popa4,5, Mariana C. Chifiriuc4,5,6, Claudiu Hapenciuc1, Faik N. Oktar7,8, Anca Nicarel9 and Ion N. Mihailescu1
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, RO-077125 Magurele, Romania; 2 National Institute of Materials Physics, RO-077125 Magurele, Romania; 3 Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Bucharest, RO-050095 Bucharest, Romania 4 Microbiology Department, Faculty of Biology, University of Bucharest, RO-060101 Bucharest, Romania; 5 Research Institute of the University of Bucharest (ICUB), University of Bucharest, RO-050095 Bucharest, Romania 6 Academy of Romanian Scientists, Ilfov Street no. 3, RO-050711 Bucharest, Romania 7 Department of Bioengineering, Faculty of Engineering, Goztepe Campus, University of Marmara, Kadikoy, 34722 Istanbul, Turkey 8 Center for Nanotechnology & Biomaterials Research, Goztepe Campus, University of Marmara, Kadikoy, 34722 Istanbul, Turkey 9 Physics Department, University of Bucharest, RO-077125 Magurele, Romania;
Resume : Thin films from fish bones-derived (Sparus aurata and Salmo salar species) bi-phasic calcium phosphate materials were fabricated via pulsed laser deposition with a KrF* excimer laser source (λ = 248 nm, τFWHM ≤ 25 ns). Physical–chemical characteristics of targets and deposited nanostructures were assessed by SEM and XRD, and also by Energy Dispersive X-ray (EDX) and FTIR spectroscopy. Films were Ca-deficient and contained a significant fraction of β-tricalcium phosphate apart from hydroxyapatite, which could contribute to an increased solubility and an improved biocompatibility for bone regeneration applications. The synthetized coatings proved efficient against Escherichia coli colonization, while presenting unchanged cytocompatibility with human gingival fibroblast cells in respect to the biological control, making them promising for fast osseointegration implants. Progress is therefore expected in the realm of multifunctional thin film biomaterials, combining antimicrobial, anti-inflammatory and regenerative properties for advanced implant coatings.
Authors : Wolfgang Stein
Affiliations : SURFACE systems+technology GmbH+Co KG
Resume : New materials or advanced functional films are always dedicated for specific aplications. Very often either the substrate material or the film material are strongly sensitive against normal environmetal conditions. Even if the components of such deposition are not sensitiv against such attac, the interfacing between substrate and film is effected from such influence. The solution in material research for such problems is an isolation of such substrate under strongly controlled atmosphere, which can be achieved with the use of glove boxes with integrated gas cleaning systems. The user interacts via isolation gloves to handle sensitive materials in the glove box wich are introduced to it via integrated load lock ports. The combination of such controlled work bench to any kind of deposition system is a problem, because normally no easy way exist to transfer such materials from a glove box into separate deposition systems. Only a fully protected connection from such glove box to the deposition system allows an undisturbed transfer. But standard deposition systems are not prepared for such transfer. SURFACE offers now fully integrated process systems which have a complete glovebox built in. In addition the complete design of such system recognizes the reduction of handling performance of the user caused by the thick gloves and its limited taktile sensitivities. Any services on such deposition system is generated from the atmosphere side, without disturbing the conditions of the contolled atmoshere in the glove box. The fully integrated style of the glove box reduces also the necessary floor space of such comlete set-up in the lab. As an excample : the total foot print of a complet PLD Glove Box system including big Excimer laser, its gas cabinet, the process automation system with user interface, the vacuum chamber, cooling chiller and the gas control cabinet fits to a floor space of 2,5m x 0,8m and includes already the glove box workstation with a working width of 1 to 1,5 m. Exambles for such integrated systems are presented.
Authors : Faezeh.A.F.Lahiji*, Roger Magnusson, Arnaud le Febvrier, Per Eklund
Affiliations : Department of Physics, Chemistry and Biology, ( IFM), Linköping University, SE-58183 Linköping, Sweden
Resume : NiO thin films are important for a wide range of applications like transparent conductors in inorganic smart windows, photovoltaics, chemical sensors, and resistive random-access memory device technology. Understanding the deposition process for NiO thin films is therefore of broad importance. In the present work, NiO film were grown on the sapphire substrate with different orientation (c-plane, m-plane, and r-plane) and silicon substrate (Si) (100). The deposition process was carried out at 300oC temperature by pulsed-DC reactive magnetron sputtering with an oxygen flow ratio varying from 4% to 51%. The XRD analysis indicated a NiO textured/epitaxially grown on all substrates. For example, on c-plane sapphire, the films deposited under high oxygen ratio (> 35% O2) have NiO (111) preferred orientation, while a mixture of NiO (111), and Ni (111) was obtained for lower ratio of oxygen. The morphology of NiO films deposited at high oxygen ratio in the plasma have nanocrystalline grains with uniform and smooth surface. A pyramidal NiO surface is observed on c-plane sapphire substrate with lower oxygen flow. The pyramids have three-fold symmetry axis perpendicular to the (111) plane and confirms by the analysis of the XRD. NiO film deposited on r- and m-plane sapphire show rice husk shaped morphology. The optical properties of the film measured by spectroscopic ellipsometry like refractive index (n), extinction coefficient (k), and band gap energy of NiO films were also influenced by different oxygen flow in the plasma as well as on different substrate.
Authors : Gianina F. Popescu-Pelin1, Dorel F. Albu2, Jeanina Lungu2, Adrian Georgescu2, Ion. N. Mihăilescu1, Mihai A. Gîrțu2 and Gabriel Socol1
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, Magurele 077125, Ilfov, Romania 2Department of Physics, Ovidius University of Constanța, Constanta 900527, Romania
Resume : We report on the pulsed laser deposition (PLD) synthesis of four batches of TiO2 coatings in different gaseous atmospheres (O2, N2, Ar și He) as photoanodes in the structure of dye-sensitized solar cells (DSSC). Two TiO2 layers were deposited for each batch (a thin nanostructed one and a high density one) by using a KrF* excimer laser (λ= 248 nm și τFWHM = 10 ns) and applying a 10 and 40 Hz laser repetition rate. The morphology, topography and crystalline structure of the coating were evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-Ray Diffraction (XRD), respectively. Depending on the ambient gas pressure during the PLD depositions, the SEM micrographs revealed morphological differences between samples. Furthermore, the AFM results are in good agreement with the SEM ones. The crystallographic assessment of the TiO2 samples highlighted the presence of a mixture of anatase and rutile with low crystallinity. The photovoltaic performance studies were carried out to understand and evaluate the effect of the TiO2 bilayer (the interaction with the dye molecules) on the cells efficiency.
Authors : Smita G. Rao, Robert Boyd, Rui Shu, Arnaud le Febvrier, Per Eklund
Affiliations : Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping SE-581 83, Sweden
Resume : The Cantor alloy CoCrFeMnNi and its variants, in bulk as well as thin films, have been extensively studied during the past decade. The remarkable mechanical, electrical, and magnetic properties that are exhibited by these materials can be influenced by their microstructure, phase, and constituent elements. The addition of light elements, such as nitrogen, can further improve these properties through processes such as amorphization and nitride-compound formation. The aim of the present study is to understand the changes in the phase composition and microstructure to a Cantor variant system caused by addition of a transition metal that reacts poorly with nitrogen. Under stochiometric nitride (CrFeCoCux)N0.3 films were grown by reactive magnetron sputtering onto silicon substrates. The amount of copper in the films was increased from 0 at. % to 12 at. % in order to study the effects on the resulting phase composition. Without Cu, two-phase fcc+bcc films were obtained. The addition of Cu was found to stabilize the bcc structure despite the fact that Cu as a pure metal is fcc. Nanoindentation tests revealed a slight increase in hardness with Cu addition from 11.0±0.2 GPa for the films without Cu to 13.7±0.2 GPa for the film with 4.4 at. % Cu.
Authors : Dhaifallah R. Almalawi,1,2 Sergei Lopatin,3 Paul Edwards,4 Ram Chandra Subedi,5 Boon Ooi,5 Nimer Wehbe,3 Robert W Martin4, Iman S. Roqan1,*
Affiliations : 1Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia 2 Physics Department, Faculty of Science, Taif University, 21974 Taif, Saudi Arabia. 3Imaging and Characterization Core Laboratory, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia 4 Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, United Kingdom 5 Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia.
Resume : We present a new strategy of high-quality GaN growth on any substrates. Specifically, we successfully obtained self-assembled threading dislocation (TD)-free vertical GaN nanowires (NWs) on a wide range of substrates using a pulsed laser deposition (PLD) method without the need for a metal catalyst using an oxygen-doped GaN target. A polycrystalline-GaN (poly-GaN) layer, as well as an oxygen-rich nanolayer, are formed during the one-step growth underneath the GaN NWs. Advanced optical and structural characterizations reveal the mechanism of such NW formation on common and emerging bulk (Si, sapphire and GaN, and Ga2O3) and two-dimensional (graphene, MXene, MoS2, and WSe2) emerging substrates without a need to altering the PLD conditions for each substrate. All samples are characterized by high optical and structural quality. Optimizing the PLD growth conditions to obtain GaN NWs will be discussed based on surface energy theory. Scanning electron microscopy (SEM) shows the length of GaN ranges from 1.5 to 3 µm. Secondary-ion mass spectrometry (SIMS) measurements show high oxygen content in all samples. High-resolution scanning transmission electron microscopy (HR-STEM) images and compositional maps demonstrate that the polycrystalline nature of the poly-GaN layer prohibits the lattice-mismatch effect, leading to a complete absence of TDs at the interface between GaN and substrate. HR-STEM further revealed that the in-situ oxide nanolayer (~ 1 nm) is formed between the poly-GaN layers and substrates during the one-step growth. This nanolayer may assist in the formation of the single-crystal GaN NWs via Stranski–Krastanov growth mode. X-ray diffraction measurements also indicate that hexagonal GaN wurtzite structure is attained on different substrates, while photoluminescence (PL), including temperature and power-dependent PL measurements, reveal an intense GaN band edge emission at 3.5 eV dominated by radiative recombination, whereas a negligible yellow band is observed. A high internal quantum efficiency (~ 65 %) is demonstrated, confirming the high optical quality of GaN NWs. Cathodoluminescence maps reveal that the sample emission comprises GaN NW band edge peak and a broad peak originated from GaN poly-GaN exhibits at 3.8 eV. We will discuss the origin of the peak blue-shift. The strategy presented here paves the way for the production of cost-effective high-efficiency GaN-based devices suited for flexible and large-scale applications.
Authors : L. Duta1, V. Grumezescu1, M.C. Chifiriuc2,3, G.E Stan4, O. Gherasim1,5, D. Chioibasu6, A.C. Popescu6, F.N. Oktar7,8
Affiliations : 1Lasers Department, National Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania 2Department of Microbiology, Faculty of Biology, University of Bucharest, Bucharest, Romania 3Research Institute of the University of Bucharest (ICUB), Earth, Environmental and Life Sciences Division, Bucharest, Romania 4National Institute of Materials Physics, Magurele, Romania 5Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, Politehnica University of Bucharest, Bucharest, Romania 6Center for Advanced Laser Technologies (CETAL), National, Institute for Lasers, Plasma and Radiation Physics, Magurele, Romania 7Department of Bioengineering, Faculty of Engineering, University of Marmara, Istanbul, Turkey 8Advanced Nanomaterials Research Laboratory (ANRL), University of Marmara, Istanbul, Turkey
Resume : Simple and doped biological-derived hydroxyapatite (BioHA) coatings were synthesized by Pulsed Laser Deposition onto Ti6Al4V implants, fabricated by additive manufacturing technique. The effect of doping reagents on the physical-chemical, mechanical and biological properties of these structures was assessed. The morphological investigations evidenced the fabrication of rough surfaces, which are ideal for the good adhesion of cells and in situ anchorage of implants. Structural evaluation demonstrated a monophasic apatite-like nature of the synthesized BioHA coatings. Compositional analyses revealed the presence of typical doping elements of natural bone, along with a quasi-stoichiometric target-to-substrate transfer. This is consistent with the biological nature of pristine materials. The inferred bonding strength values were superior in the case of functionalized Ti implants, when compared both to simple (uncoated) Ti ones and to the threshold imposed by ISO standard regulating load-bearing implant coatings. The synthesized layers exhibited low cytotoxicity on human cell lines, along with a long-lasting effect against bacterial and fungal biofilm development. The good cytocompatibility corroborated with an efficient antimicrobial activity suggest that the herein proposed BioHA coatings, derived from renewable and inexpensive materials, could stand as innovative and viable alternatives to synthetic HA coatings for the fabrication of a new generation of medical devices. Acknowledgements: Project number PN-III-P1-1.1-TE2019-1449 (TE 189/2021) and Core Programme 16N/2019.
Authors : L. Duta1, V. Grumezescu1, G.E Stan2, O. Gherasim1,3, G. Popescu-Pelin1, F.N. Oktar4,5
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, Magurele, Romania 2National Institute of Materials Physics, Magurele, Romania 3Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, Politehnica University of Bucharest, Bucharest, Romania 4Department of Bioengineering, Faculty of Engineering, University of Marmara, Istanbul, Turkey 5Advanced Nanomaterials Research Laboratory (ANRL), University of Marmara, Istanbul, Turkey
Resume : We report on simple and doped hydroxyapatite (HA) coatings of biological-origin (BioHA) synthesized by Pulsed laser deposition onto titanium substrates. A comparison between structures not subjected and those subjected to post-deposition thermal treatments (at temperatures ranging from 400 to 700 °C, respectively), aimed to indicate the influence of the applied temperature on the morphology, structure, chemical composition, wetting behaviour and bonding strength characteristics of the synthesized BioHA structures. SEM micrographs revealed surfaces with rough and irregular morphologies, which consisted of spherical formations (“particulates”). Compositional analyzes indicated the presence of trace-elements generally found in the composition of the bone mineral phase, which play a key-role in its functionality. The inferred values of the Ca/P molar ratios corresponded to the ones reported in literature in the case of biological-origin apatites. GIXRD investigations showed that the synthesized BioHA coatings consisted of a hexagonal HA phase, with different degrees of crystallinity, mainly influenced by the applied post-deposition thermal treatments. The FTIR-ATR spectra highlighted the main bands specific to the phosphate groups, which corresponded to a HA-type structure. When increasing the temperature, a narrower aspect of the spectral lines could be observed, which was indicative to a HA structure with a much higher degree of crystallinity. All functionalized Ti implants presented hydrophilic behavior to the difference of simple (non-deposited) Ti ones, which were hydrophobic. An increase of the pull-out bonding strength adherence values with the applied temperature was attributed to the processes of atomic inter-diffusion at the coating‒Ti substrate interface, which occurred during post-deposition thermal treatments. The improved morpho-structural, compositional and mechanical properties of the BioHA coatings, along with the fact that these materials were fabricated from sustainable, low-cost resources, could offer guidance towards the replacement of HA synthetic structures for future implantological applications. Acknowledgements: Project no. PN-III-P1-1.1-TE2019-1449 (TE 189/2021) and Core Programme 16N/2019.
Authors : L. Khomenkova1,2, D. Lehninger3, V. Yukhymchuk1, X. Portier4, P. Petrik5, F. Gourbilleau4, S. Ponomaryov1, N. Korsunska1, J. Heitmann3
Affiliations : 1) V. Lashkaryov Institute of Semiconductor Physics, 45 Pr. Nauki, Kyiv 03028, Ukraine; 2) National University “Kyiv-Mohyla Academy”, 2 Skovorody str., Kyiv 04070, Ukraine; 3) Institute of Applied Physics, TU Bergakademie, Freiberg, Germany; 4) CIMAP, Normandie Univ, ENSICAEN, UNICAEN, CEA, CNRS, Caen, France; 5) Institute for Technical Physics and Materials Science (MFA), Center for Energy Research (EK), Hungarian Academy of Sciences (MTA), Budapest, Hungary
Resume : The impact of isovalent dopants on optical and structural properties of HfO2 matrix attracts significant attention due to the unique optical and electrical properties of such materials. In the present work, the effect of annealing temperature on the properties of Ge-doped HfO2 thin films is investigated by spectroscopic ellipsometry, Raman scattering, XRD and TEM methods. The films were grown by radio-frequency top-down magnetron co-sputtering of pure Ge and HfO2 space-apart targets. The Ge content in the films was varied in the range 0-60 at % via power density applied on Ge target. Besides, pure Ge and pure HfO2 films were prepared for comparison. The samples were annealed in at T=300–1000 °C for 30 s in a nitrogen atmosphere. As-deposited homogeneous Ge-HfO2 films were found to be amorphous contrary to pure HfO2 films. This fact confirms that Ge incorporation stabilizes the amorphous HfO2 phase that was found to be stable up to T=600 °C. The T increase up to 800°C results in the formation of pure Ge nanocrystallites as well as tetragonal HfO2 grains. Further T rise favors considerable Ge out-diffusion from the films followed by the appearance of the monoclinic HfO2 phase. At the same time, no Si presence was revealed in the film volume testifying on the stability of these films in direct contact with Si substrate. The mechanism of the film phase transformation is discussed.
Authors : G.G. Lobachоva, Ie.V. Ivashchenko
Affiliations : Metal Physics Department, Igor Sikorsky Kyiv Polytechnic Institute, Ukraine
Resume : Electrik-spark alloying (ESA) and subsequent shot blasting are promising methods of combined processing, which allows to obtain a high density of defects in the crystal structure and thus creates favorable conditions for the processes of diffusion and phase transformations and formation in the surface layer of high wear resistance. Purpose: to study the kinetics of formation, phase composition, structure, microhardness, wear resistance of coatings on HVG steel after ESA (Cu-, Al-anodes) and the impact of shot blasting. To achieve this goal, ESA of steel HVG by Al- and Cu-anodes with subsequent shot blasting with a duration of 60 s, 120 c, 180 s was performed. Cu- and Al-anodes were chosen due to the formation with the base iron of limited solid solutions or intermetallics to increase the surface microhardness. The "ELITRON-26A" unit was used at ESA. Shot blasting of samples with applied electrospark coatings was performed with steel balls with a diameter of 0.5 - 1 mm It was found that ESA of HVG steel by Al- and Cu-anodes allows to create a coating with a thickness of 10 to 24 μm with a microhardness of 4.9 GPa due to the formation of solid solutions of electrode materials and intermetallic Al8Cr5. The shot blasting carried out after ESA allows to give uniformity to coverings and to increase microhardness of an Al-coating from 4,9 to 12,4 GPa, and for Cu-coating from 4,48 to 7 GPa at increase in time of shot blasting from 60 with to 180 s with and increase the wear resistance of Al-coating by 15.2 times and Cu-coating by 7.6 times.
Authors : A. Giradeau (1,2,3), G. Carnide (1,2,4), A.F. Mingotaud (4), M. Cavarroc (3), M.L. Kahn (2) and R. Clergereaux (1)
Affiliations : 1 LAPLACE, CNRS UMR5213, Université de Toulouse, 118 route de Narbonne, 31062, Toulouse, France 2 LCC, CNRS UPR8241, Université de Toulouse, 205 route de Narbonne, 31077 Toulouse, France 3 Safran Tech, Pôle M&P, Rue des Jeunes Bois, 78772 Magny les Hameaux, France 4 IMRCP, Université de Toulouse, CNRS UMR 5623, Université Toulouse III - Paul Sabatier, 118 route de Narbonne, 31062, Toulouse, France.
Resume : Aerosol-assisted processes enable to deposit thin films, homogeneous [1,2] or nanocomposite [3,4,5,6]. For example, the nebulization of colloidal solutions, i.e. liquid solutions containing nanoparticles, in different plasma processes has been widely used for nanocomposite thin film deposition. However, nanoparticles loaded droplets in the aerosol lead to the deposition of aggregated nanoparticles embedded in the matrix. Recently, a new process of nanoparticles injection has been developed . This method, called reactor-injector of nanoparticles, consists in synthesizing nanoparticles prior to their injection in the plasma in a pulsed injection regime. It enables to form nanocomposite thin films with really small (<10 nm in diameter) and highly dispersed nanoparticles embedded in the matrix . This work aims to study the deposition of ZnO/DLC nanocomposite thin films in a low-pressure RF plasma. The main challenge of this process is to find the best compromise between the parameters for an efficient synthesis of ZnO nanoparticles and an optimal behaviour of low-pressure RF plasmas in a pulsed regime. It is shown that the operating window enables to deposit nanocomposite thin films with an extended range of volume fraction. References  X. Hou, et al. Chem. Vapor Dep, 12, 583-596, (2006).  F. Palumbo, et al. Coatings, 10, 440 (2020).  R.G. Palgrave, et al. J. Am. Chem. Soc., 128, 1587 (2006).  M. Mitronika, et al. J. Phys. D: Appl. Phys., 54, 085206 (2020
Authors : M. Nistor 1, F. Gherendi 1 and J. Perrière 2,3
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics (NILPRP), L22, PO Box. MG-36, 77125 Bucharest-Magurele, Romania 2 Sorbonne Universités, UPMC Univ Paris 06, UMR 7588, INSP, F-75005, Paris, France ; 3 CNRS, UMR 7588, INSP, F-75005, Paris, France
Resume : Wurtzite ZnO has alternating atomic layers of Zn and O ions along the c-axis with cationic (Zn-face) or anionic (O-face) surface termination, this crystallographic polarity influencing its optoelectronic properties. With the purpose of studying this particularity, ZnO thin films were grown by pulsed electron beam deposition (PED) on c-cut single crystal substrates at different temperatures and gas pressures. Epitaxial thin films with tunable optical and electrical properties were obtained by varying the film growth conditions, even starting from relatively low substrate temperatures. X-ray photoelectron spectroscopy (XPS) was performed both for determining the chemical composition and in order to investigate the valence-band structure of films and in particular to determine the polarity in the case of these wurtzite-type thin films. These results about the dominant polar face of ZnO films will be discussed in correlation with degenerate or non-degenerate semiconductor electrical properties that we have put into evidence for these films and the pulsed aspect of the film growth (kinetic energies of species arriving at the substrate and the deposition rate). Hall effect and optical measurements will be used in this purpose.
Authors : N. Rochdi, S. Atmane, A. Caillard
Affiliations : GREMI, UMR 7344 CNRS/Université d’Orleans, 14 rue d'Issoudun, 45067 Orleans Cedex 2, France
Resume : The bipolar HiPIMS (high-power impulse magnetron sputtering) technology has been recently developed for tailoring ions energies in thin film deposition. The effects of a positive pulse following the negative HiPIMS pulse have been intensively studied using energy-resolved mass spectrometry whereas few papers deal with the effect of this pulse on the properties of hard coatings. In this study, we investigated its effect on the filling of silicon trenches and on the penetration inside porous substrate (silicon), the filling and the penetration being characterized by scanning electron microscopy and Rutherford backscattering spectroscopy. We correlated these results to the time integrated (and time resolved) ion energy distribution obtained by an energy-resolved mass spectrometry and by a retarding field energy analyzer, to the energy influx incoming onto the substrate measured by a thermal probe.
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Nanoscale materials, nanostructures and methods : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : Ulf Helmersson
Affiliations : Linköping University, IFM Materials Physics, Linköping, Sweden
Resume : Bipolar high-power impulse magnetron sputtering (HiPIMS) can be used to achieve ion acceleration for ion-bombardment of insulating thin films. A rising plasma potential (Up), in-between the HiPIMS-pulses, are obtained using a reversed positive target potential. This can result in ion-acceleration of ions reaching the film surface as long as the surface potential (Us) is maintained low, as it is for conducting substrates connected to ground. For insulating substrates or insulating thin film surfaces, Us will vary depending on the net charge collected by the surface. During the positive bipolar pulse ions will cause an increase in Us reducing the accelerating voltage Up - Us. How the collected charge affects Us depends on the capacitive coupling between the film surface and ground. For a films surface that has a high capacitance to ground, Us will stay close to ground potential for an extended time in-between the HiPIMS pulses, while if the capacitance is low, Us will quickly attain a potential close to Up. To mimic this, we have used a conductive substrate connected to ground via an externally applied capacitor. In this way Us could be measured for different capacitance values. In this way we conclude that significant ion bombardment can be maintained for insulating films of several µm thickness as long as the substrate is conducting and connected to ground. For insulating substrate, Us quickly attains a potential close to Up and effective ion bombardment cannot be obtained.
Authors : Johann Toudert, Rosalía Serna, Antonio Mariscal
Affiliations : Laser Processing Group, Instituto de Óptica, IO-CSIC, Madrid, Spain
Resume : Thin-film metamaterials are cornerstone for the design of photonic, optoelectronic and energy conversion devices with ultra-small footprint because they enable unprecedented optical effects in subwavelength dimensions. To fabricate them, the current standard is a top-down approach, in which a thin film (usually evaporated or sputtered) is structured by lithography to produce a tailor-made assembly of metal, semiconductor or dielectric nanostructures that is the core of the metamaterial. The optical properties of the initial thin film drive those of the nanostructures and are thus crucial to the metamaterial performance. Therefore, there is a strong interest in growing thin films with optical properties superior to those of the currently used. In addition, because of the low-throughput nature of lithography, finding alternative fabrication approaches enabling the self-assembly of the nanostructures is essential for upscaling. Herein, the importance of pulsed laser deposition (PLD) to address these needs will be demonstrated. First, it will be shown that PLD enables the growth of ultrathin semi-metal films presenting a giant refractive index (n~10, higher than any other) and unconventional interband-induced plasmonic properties [1,2]. By harnessing these features, thin-film metamaterials showing tunable perfect absorption of light in the UV, visible and IR for solar energy conversion and photodetection have been demonstrated [3,4]. Second, the potential of PLD to grow large-area thin-film metamaterials will be demonstrated. In particular, it will be explained how to engineer the nanoscale order of self-assembled plasmonic nanostructures in an oxide matrix for applications in sensors, switches and broadband optical elements [5-7].  Toudert, J. Phys. Chem. C 121, 3511 (2017) and 116, 20530 (2012);  Toudert, Opt. Mater. Express 7, 2299 (2017) [INVITED] and 9, 2924 (2019);  Toudert, Opt. Express 26, 34043 (2018);  Ghobadi, ACS Photon. 5, 4203 (2018);  Toudert, ACS Photon. 2, 1443 (2015);  Baraldi, Adv. Mater. Interfaces 5, 1870058 (2018);  Garcia-Pardo, arXiv:1912.01120 (2019).
Authors : Aida Serrano1, Juan Rubio-Zuazo2, Jesús Lopez-Sanchez3, Esther Enriquez1, Sara Román-Sanchez1, Eduardo Salas-Cólera2, German R. Castro2
Affiliations : 1 Departamento de Electrocéramica, Instituto de Cerámica y Vidrio, CSIC, 28049 Madrid, Spain; 2 Spanish CRG-Spline, The European Synchrotron (ESRF), 38000 Grenoble, France and Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, 28049 Madrid, Spain 3 Instituto de Magnetismo Aplicado CSIC-ADIF, P.O. Box 155, Las Rozas, Madrid 28230, Spain
Resume : In this work we present a strategy for developing epitaxial incommensurate Au(111) nanostructures on oxide heterostructures with tunable plasmonic activity. For that, high quality single phase and oriented α-Fe2O3(0001) thin films have been used as a template for the noble metal epitaxial deposition. The complex systems have been grown by pulsed laser deposition on oxide substrates. For the Au nanostructuration a one-step solid-state dewetting procedure has been achieved tailoring the isolated character and the morphological features of Au nanoparticles through the substrate temperature during the Au growth, without altering the structural characteristics of the hematite layer that is identified as single iron oxide phase. The epitaxial character and the lattice coupling of Au/oxide bilayers are mediated through the sort of oxide substrate. The crystallographic domain size and crystalline order of Au nanostructured-layer are dependent on the Au growth temperature. Besides, controlling the substrate temperature in the Au growth a tailorable response of the localized surface plasmons related to Au nanoparticles is mediated through the morphological characteristics of Au islands and the proximity effect of the hematite layer. This processing route allows obtaining ensembles of plasmonic islands on oxide surface with an epitaxial character, allowing the combination of multiples functions of these hybrid nanomaterials and increasing highly their value for several applications.
Authors : A. Bercea (1,2), C. Champeaux (1), C. Constantinescu (1), F. Dumas-Bouchiat (1)
Affiliations : (1) University of Limoges, CNRS, IRCER, UMR7315, 12 rue Atlantis, F-87000 LIMOGES, France. (2) National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, Magurele, Romania. Corresponding author email address: email@example.com; firstname.lastname@example.org
Resume : With its discovery, Pulsed Laser Deposition (PLD) has rapidly become relevant in the deposition of thin films with complex stoichiometry and manufacturing nanostructures. In PLD, the ablated material expands and forms a plasma plume that travels towards the substrate. This particular motion of a high directionality of the ablated material is one of the characteristics of PLD. Here, taking advantage of this high directionality of the ablated material, we propose a way to develop tunable localized surface plasmon resonances (LSPR)-devices with a particular architecture based on metallic nanoparticle arrays. The nanoparticle arrays are made using a combination of colloidal lithography and the PLD technique. The colloidal lithography is performed with a Langmuir Blodgett deposition system, consists of using colloidal masks made with polystyrene spheres of 3 µm in diameter deposited on c-sapphire. Then, by PLD with KrF laser (fluence: 2-3 J/cm2), a thin metallic film is deposited on the spheres. After removing the polystyrene, organized metallic quasi-triangular nanoplatelets (QTP) arrays of the metallic layer are revealed. Through additional thermal treatments, the specific shape of the QTPs evolves to quasi-spherical particles and permits the modulation of LSPR peak position between mid-infrared (~ 4.5 µm) and near-infrared (~1.5 µm). The Au QTP are embedded into an active “phase-transition” 200 nm vanadium dioxide (vo2) matrix. The temperature driven reversible metal-to-insulator transition of vo2 ( ~ 68 °C), accompanied by a change in dielectric permittivity that induces an active modulation (for more than 500 nm) of the resulting Au QTP-vo2 nanocomposite LSPR. This resonance modulation originates in the creation of a temperature dependent core-shell structure consisting of QTP (core) surrounded by a metallic vo2 (shell) and embedded into a vo2 dielectric matrix brought out by fine specific investigations by local Raman spectroscopy mapping, High-Resolution X-ray diffraction, UV-Vis-NIR Spectroscopy, FTIR spectroscopy, Scanning electron microscopy. These experimental data are correlated with a theoretical approach using a simplified finite difference time domain method. By rigorously solving Maxwell's equations, it describes the LSPR peak for the different configurations of QTPs and QTP-vo2 nanocomposite. Acknowledgment: The work presented is realized entirely at the IRCER laboratory, France under financing supports from the French MESRI Ministery and the Labex – _LIM (ANR-10-LABX-0074-01). References: Packed colloidal spheres for thin film structuration; towards modulation and tunability of surface plasmon resonance A. BERCEA, C. CONSTANTINESCU, F. DUMAS-BOUCHIAT, C. CHAMPEAUX, PLUMEE 9 (1) (2019) , http://pubs.ub.ro/?pg=revues&rev=plumee&num=201901&vol=9&aid=4970
Authors : Carlota Ruiz de Galarreta, Eva Nieto-Pinero, Jan Siegel, C. David Wright, Rosalia Serna and Johann Toudert
Affiliations : College of Engineering, Mathematics & Physical Scienes, Department of Nano Engineering Science and Technology, University of Exeter, Exeter EX4 4QF, UK Laser Processing Group, Instituto de Optica, IO, CSIC, Serrano 121, 28006, Madrid, Spain
Resume : Due to their ability to absorb, manipulate and confine light in volumes much smaller than the wavelength, plasmonics and plasmonic metasurfaces made of metallic nanoparticles are becoming a strong platform for the development of photonic devices. This includes, for instance, structural colour generators, high sensitivity detectors or super absorbers for photovoltaic purposes . Typically, metals such as gold, silver or aluminium are used for the development of such devices. Nevertheless, bismuth has been also recently proved also as an excellent material for plasmonics  and for perfect absorbers . As an additional advantage, bismuth exhibits a relatively low melting temperature (~270 ºC), with its solid-to-liquid phase transition being accompanied by a pronounced change in its permittivity function . In this work we explore the potential of bismuth plasmonic metasurfaces as reconfigurable structural colour generators via melting and solidification of encapsulated bismuth meta-atoms prepared by pulsed laser deposition. We study the effect of the solid-to-liquid phase transition on the metasurface colour appearance. Finally, we demonstrate control over the switching time between laser-induced melting and subsequent re-solidification. Our results underline the potential of bismuth plasmonic metasurfaces for a new concept of volatile reconfigurable plasmonics.  H. Yu, Y. Peng, Y. Yang and Z-Y. Li, npj Comp. Mater. 4, 45 (2019).  J. Toudert et al., J. Phys. Chem. C, 121, 3511−3521 (2017).  J. Toudert et al., Opt. Express, 27, 34043 (2018).  M. Jimenez de Castro et al., Appl. Phys. Lett., 105, 16, 113102 (2014).
Authors : T. NGUYEN VAN (1,3), N.M. DEMPSEY (2), C. CHAMPEAUX (1) and F. DUMAS-BOUCHIAT (1)
Affiliations : (1) Univ. Limoges, CNRS, IRCER, UMR 7315, 87068 Limoges, France (2) Univ. Grenoble Alpes, CNRS, Institut NEEL, 38000 Grenoble, France (3) Department of Physics, Le Quy Don Technical University, 100000 Hanoi, VietNam Corresponding authors: email@example.com, firstname.lastname@example.org
Resume : In the last decades, Pulsed Laser Deposition (PLD) has emerged as one of the most elegant and straightforward methods to deposit complex materials. The congruent process in PLD, specially favored in the UV regime (KrF laser, 248 nm), allows stoichiometry transfer from the target to the opposite substrate for thin film growth. Here, the high quality NdFeB and FePt magnets with good magnetic properties have been developed, from each time of single compound targets, using in situ or ex situ annealing process. For NdFeB thin films, the influence of the Nd/Fe atomic ratio ranging from 0.18 to 0.47, on structural, microstructural and magnetic properties has been examined . In-depth investigations from the chosen composition permit to extract optimal conditions of temperatures (590 °C ± 40 °C) for NdFeB films and reveal excellent magnetic properties with (BH)max ~290 kJ/m³, among the best magnets in the market. Equivalent magnetic properties for such films have been observed on both kinds of Si and c-sapphire substrates. In order to further improve the quality of the magnet, e. g., (BH)max product, theoretical modeling suggests that soft-hard magnetic nanocomposites , with the dimensions of the soft phase smaller than twice the domain wall width of the hard phase, could achieve up to 1 MJ/m³. A homemade Pulsed Laser Nanoparticle Source  (PLNS, using Nd:YAG laser, 532 nm) was developed and coupled with the conventional PLD system. The reactor allows to fabricate nanocomposites, composed of soft magnetic nanoparticles (NPs) with controllable size in the range 2 nm – 8 nm with a very narrow size distribution (i. e., 4.1 nm ± 0.3 nm) and hard magnetic thin films presented before. Thus, a variety of magnetic nanocomposite configurations can be synthesized thanks to the flexibility of independent and/or simultaneous deposition from the combination of PLD and PLNS. The overall magnetic nanocomposite behaviors are influenced from both the hard and soft magnetic elements. Acknowledgement: The presented work is realized entirely at the IRCER and Néel Laboratories, France, within the framework of ANR-16-CE09-0019-SHAMAN. References:  T. Nguyen Van, I. de Moraes, N.M. Dempsey, C. Champeaux, and F. Dumas-Bouchiat, J. Magn. Magn. Mater. 520, 167584 (2021).  R. Skomski and J.M.D. Coey, Phys. Rev. B 48, 15812 (1993).  M. Gaudin, P. Carles, E. Laborde, C. Champeaux, and F. Dumas-Bouchiat, J. Appl. Phys. 125, 054301 (2019).
Authors : Wolfgang Stein, Marc Pohlmann
Affiliations : SURFACE systems+technology GmbH+Co KG, D-41836 Hückelhoven,Rheinstr.7
Resume : PLD belongs to the field of physical deposition processes and has been in use for several decades. The use of the specific advantages of laser emission found its way into materials research from the very beginning of this technology. The unique combination of direct interaction of a local high energy density pulse in a short time scale with the irradiated material led to multiple uses of this process. The multiple use cases of this technology allow for commercial use in addition to scientific use. Each technology has strengths and weaknesses. The latter are often tolerable in the field of research, but are a criterion for exclusion in commercial applications. In almost 30 years of PLD plant production, SURFACE has repeatedly improved the process technology through innovations and thus supplied its customers with high-performance plant technology. New solutions are presented, which will contribute to the further spread of PLD technology. In addition to the scientific field of application with small substrates, industrial applications in the field of large-area applications are also made possible. Examples are presented for the specific applications in reserach and production.
2D-Interfaces & Heterostructures : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : David B. Geohegan,(1) Yu-Chuan Lin,(1) Chenze Liu,(3) Yiling Yu,(1) Eva Zarkadoula,(2) Mina Yoon,(1) Alexander A. Puretzky,(1) Liangbo Liang,(1) Xiangru Kong,(1) Yiyi Gu,(1) Alex Strasser,(1) Harry M. Meyer,(2) Matthias Lorenz,(1) Matthew F. Chisholm,(2) Ilia Ivanov,(1) Christopher M. Rouleau,(1) Gerd Duscher,(3) Kai Xiao(1)
Affiliations : 1) Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA 2) Materials Science and Technology Div., Oak Ridge National Laboratory, Oak Ridge, TN, USA 3) Dept. of Materials Science and Engineering, University of Tennessee, Knoxville, TN, USA
Resume : Atomically-thin two-dimensional (2D) materials face significant energy barriers for synthesis and processing into metastable phases for functional quantum materials, such as Janus structures. Pulsed laser deposition (PLD) plasmas inherently imbue species with hyperthermal kinetic energies (KEs) ranging up to 100 eV/atom to easily overcome these barriers, however such energies can easily damage 2D crystals as they grow. Here we explore the synthesis and conversion of few-layer atomically-thin 2D transition metal dichalcogenide crystalline films by controlling PLD using in situ diagnostics to KEs < 10 eV/atom, a regime that excludes other techniques such as sputtering or MBE. In this talk, we introduce and characterize the controllable implantation of hyperthermal species from pulsed laser deposition (PLD) plasmas as a top-down method to compositionally engineer 2D monolayers. Using in situ plasma diagnostics the kinetic energies of Se clusters in the plume (Se2-Se9) impinging on monolayer WS2 (and MoS2) crystals were controlled in the <10 eV/atom range to determine the thresholds for selective top layer replacement of sulfur by selenium for the formation of high quality WSSe (and MoSSe) Janus monolayers at low (300 °C) temperatures, and bottom layer replacement for complete conversion to WSe2 (and MoSe2). Atomic-resolution electron microscopy and spectroscopy in tilted geometry confirmed the WSSe Janus monolayers for KE’s between 3-5 eV/atom, with all the Se atoms on one side and all the S atoms on the other. Molecular dynamics simulations reveal how Se clusters at these energies implant to form disordered metastable alloy regions, which then recrystallize to form highly ordered structures, opening the door for low-energy implantation by PLD as a novel method to explore the synthesis of 2D Janus layers and alloys of variable composition. More generally, these experiments reveal principles to guide the direct PLD synthesis of atomically-thin 2D materials. By controllably tuning the “building blocks” delivered to the substrate during PLD using time-resolved in situ diagnostics, and by then using nonequilibrium techniques such as pulsed plasma irradiation or laser crystallization to understand their conversion into 2D crystals, one can begin to unravel and understand some of the classical and non-classical crystallization pathways and time scales responsible for the assembly of atomically-thin 2D crystals. A general perspective will be provided with examples from recent experiments as time permits. Research was sponsored by the U.S. Dept. of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Div. and was conducted at CNMS, a U.S. DOE Office of Science User Facility. Novel PLD facilities under development in the Functional Hybrid Nanomaterials Group at CNMS that are available for worldwide users will be described.  Y.-C. Lin, C. Liu, et al., ACS Nano 14, 3896 (2020).
Authors : R. Dittmann, F. Hensling, T. Heisig, C. Xu, F. Gunkel
Affiliations : Peter Grünberg Institut 7, Forschungszentrum Jülich GmbH, Jülich, Germany
Resume : The functional properties of complex transition metal oxides are strongly influenced by the elemental composition and the lattice disorder. Although device materials typically require unparalleled levels of purity and perfection, the presence of point and extended defects in oxides have been identified to be advantageous for a variety of applications. Therefore, the precise control over the defect configuration is one of the key challenges for the oxide thin film growth community. Defect formation during pulsed laser deposition growth can be either governed by the defect equilibria at the given growth conditions or by the plume dynamics, the presence of UV-irradiation  or by the growth kinetics. We will present detailed studies on selected prototypical oxide thin film systems which enabled us to disentangle the different factors influencing the formation of both, oxygen and cation vacancies. We observe a significant influence of the surface termination of SrTiO3 single crystal substrates on the formation of oxygen vacancies during annealing and growth and attribute it to the inhibited surface exchange for SrO-terminated SrTiO3 . By investigating the early stage of growth by in situ AFM and RHEED we could reveal the complex interplay between non-stoichiometry, growth mode and the formation of extended defects such as antiphase boundaries and Ruddlesden-Popper-type of defects . We will furthermore give examples how defect engineering can be employed to fabricate thin film heterostructures and devices with tailored functional properties .  F. V. E. Hensling, D. J. Keeble, J. Zhu, S. Brose, C. Xu, F. Gunkel, S. Danylyuk, S. S. Nonnenmann, W. Egger and R. Dittmann, “UV radiation enhanced oxygen vacancy formation caused by the PLD plasma plume”, Scientific reports, 8846 (2018)  F. V. E. Hensling, C. Baeumer, M.-A. Rose, F. Gunkel and R. Dittmann, “SrTiO3 termination control: A method to tailor the oxygen exchange”, arXiv:1907.06095  C. Xu, H. Du, A. J. H. van der Torren, J. Aarts, C. L. Jia and R. Dittmann,“Formation mechanism of Ruddlesden-Popper-type antiphase boundaries during the kinetically limited growth of Sr rich SrTiO3 thin films“, Scientific Reports 6, 38296 (2016),  F.V.E. Hensling, T. Heisig, N. Raab, C. Baeumer and R. Dittmann, “Tailoring the switching performance of resistive switching SrTiO3 devices by SrO interface engineering”, Solid State Ionics 325, 247 (2018)
Authors : Binbin Chen,1 Nicolas Gauquelin,2 Robert J. Green,3,4, Jin Hong Lee,5 Cinthia Piamonteze,6 Matjaž Spreitzer,7 Daen Jannis,2 Johan Verbeeck,2 Manuel Bibes,5 Mark Huijben,1 Guus Rijnders,1 Gertjan Koster1
Affiliations : 1MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands 2Electron Microscopy for Materials Science (EMAT), University of Antwerp, 2020 Antwerp, Belgium 3Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Pl, Saskatoon, Saskatchewan S7N 5E2, Canada 4Stewart Blusson Quantum Matter Institute, University of British Columbia, 111-2355 E Mall, Vancouver, British Columbia V6T 1Z4, Canada 5Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767 Palaiseau, France 6Swiss Light Source, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland 7Advanced Materials Department, Jožef Stefan Institute, 1000 Ljubljana, Slovenia
Resume : The properties of correlated oxides can be largely manipulated by forming short-period superlattices since the layer thicknesses are comparable with the typical length scales of the involved correlations and interface effects. Herein, we studied the metal-insulator transitions (MITs) in NdNiO3/SrTiO3 superlattices by controlling the NdNiO3 layer thickness, n in unit cell, spanning the length scale of the interfacial octahedral coupling. Scanning transmission electron microscopy reveals a crossover from a modulated octahedral superstructure at n = 8 to a uniform non-tilt pattern at n = 4, accompanied by a drastically weakened insulating ground state. Upon further reducing n the predominant dimensionality effect continuously raises the MIT temperature, while leaves the antiferromagnetic transition temperature unaltered down to n = 2. Particularly, the MIT can be enhanced by imposing a sufficiently large strain even with strongly suppressed octahedral tilting. Our results demonstrate the relevance for the control of oxide functionalities at reduced dimensions.
Authors : S. Chromik (1), M. Spankova (1), E. Dobročka (1), A. Koos (2), M. Nemeth (2), B. Pecz (2), A. Michon (3), M. Al Khalfioui (3), E. Frayssinet (3), Y. Cordier (3), M. Cannas (4), S. Agnello (4), S.E. Panasci (5&6), E. Schilirò (6), P. Fiorenza (6), F. Roccaforte (6), F. Giannazzo (6)
Affiliations : (1) IEE-SAS, Bratislava, Slovak Republic; (2) MFA-EK, Budapest, Hungary; (3) Université Côte d’Azur, CNRS, CRHEA, Valbonne, France; (4) Department of Physics and Chemistry, University of Palermo, Italy; (5) Department of Physics and Astronomy, University of Catania, Italy; (6) CNR-IMM, Catania, Italy
Resume : In the last years, the integration of MoS2 on GaN has been explored by different groups, as a platform for the implementation of advanced electronic and optoelectronic devices, such as band-to-band diodes and self-powered UV-photodetectors . Particularly, the low lattice mismatch (<1%) and thermal expansion coefficients difference between MoS2 and GaN hexagonal crystals are favourable for a good quality epitaxial interface. Among the different MoS2 growth methods available, pulsed laser deposition (PLD) has been recently successfully employed to obtain few layers of MoS2 with excellent epitaxial alignment on GaN substrates . In this work, the PLD process has been carefully optimized to achieve uniform deposition of ultra-thin MoS2 films on GaN/sapphire and GaN/Si templates, as well as on sapphire substrates. The structural, chemical and electrical properties of the samples were extensively investigated by the combination of several characterization techniques. Atomic force microscopy analyses revealed a smooth surface morphology of deposited MoS2 on all the considered substrates. A bilayer thickness was evaluated by Raman spectroscopy, and confirmed by high resolution transmission electron microscopy analyses, showing also a sharp interface with GaN. The excellent epitaxial alignment with the substrate was demonstrated also by X-ray diffraction. Furthermore, a nearly ideal stoichiometry of the films was demonstrated by X-ray photoemission spectroscopy. Finally the electronic transport properties of the MoS2 layers and the vertical current injection at MoS2/GaN heterostructures have been investigated both at nanoscale by conductive atomic force microscopy (C-AFM) and by characterization of device test structures. These research activities are funded by the FlagERA-2019 project “ETMOS”.  F. Giannazzo, E. Schilirò, R. Lo Nigro, P. Prystawko, Y. Cordier Y, “Integration of 2D materials with nitrides for novel electronic and optoelectronic applications”, Chapt. 11 of “Nitride Semiconductor Technology: Power Electronics and Optoelectronic Devices”, Ed. F. Roccaforte, M. Leszczynski, Wiley-VCH Verlag, 2020.  S. Chromik, et al., “Influence of GaN/AlGaN/GaN (0001) and Si (100) substrates on structural properties of extremely thin MoS2 films grown by pulsed laser deposition”, Appl. Surf. Sci. 395, 232–236 (2017).
Authors : Lorenzo Pasanisi, Jacqueline Marie Börgers, Sebastian Hambsch, Alexander Gutsche, Regina Dittmann
Affiliations : Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich, Germany; Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich, Germany and Institute of Physical Chemistry, RWTH Aachen University, Aachen, Germany ; Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich, Germany; Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich, Germany; Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich, Germany; Peter Grünberg Institut, Forschungszentrum Jülich GmbH, Jülich, Germany;
Resume : (La,Sr)MnO3 (LSMO) is one of various materials which exhibit resistive switching behaviour and are thus being investigated for future use in both non-volatile memory and neuromorphic computing applications. The volume type and multi-level switching of LSMO make it a particularly interesting candidate within the field of neuromorphic computing. The primary focus of our investigation is to study the resistive switching behaviour of LSMO. We have found this behaviour to be heavily influenced by the choice of top and bottom electrodes and to be particularly enhanced by the addition of an Al interlayer between the LSMO and the top electrode. In addition, we focus on the influence of various material properties such as Sr-dopant concentration, strain, oxidative state and the presence of one- or two-dimensional lattice defects (like dislocations or grain boundaries). In particular we have found the Sr dopant concentration in conjunction to particular top electrode compositions to have a significant effect on the resistive switching of LSMO. In order to study these effects on the switching behaviour, we prepare LSMO thin films with defined properties by Pulsed Laser Deposition (PLD) to structure these into devices, which we can characterize electrically. Our goal is to understand the switching mechanism of LSMO, to be able to tune its switching properties.
Devices & applications : N.Laidani, M. Nistor, J. Gonzalo, S. Konstantinidis
Authors : Mehmet Alper Sahiner, Faith Akinlade, Jasmyne Emerson, Stephane Arsharuni, Matthew Herington, Venise Castillon
Affiliations : Seton Hall University, Physics Department
Resume : We have used pulsed laser deposition to deposit nanoparticles (Ag, Au, and Si) to investigate the effects of these impurities on the photovoltaic properties of the CdS/CdTe based thin films. The main objective was to investigate how the inclusion of nanoparticles will affect light scattering in the at the interfaces and whether the different size and shape of nanoparticles will have a positive effect on the overall electrical performance of these thin film solar cells. In our previous studies, we have investigated the effects of the embedded Ag nanoparticles on the photoelectric conversion efficiency on CdS/CdTe based thin film solar cells as synthesized by Pulsed Laser Deposition (PLD). Silver was shown to enhance the photovoltaic performance by almost doubling the photovoltaic conversion efficiency of the conventional CdS/CdTe films . A careful comparison of photovoltaic performance of Au/Si versus Ag embedded thin films of CdS/CdTe on indium tin oxide coated glass substrates have been performed. Our results on the Ag case revealed electrical performance of these cells have correlates with the particles density and the particle size on the CdS/CdTe interface. This study concentrates on the Au and Si nanoparticle deposition on the CdS/CdTe interface with varying particle size and distributions. Structural and compositional characterization were performed using XRD, AFM, and SEM/EDX. Photovoltaic properties were measured using a LabView assisted Keithley Sourcemeter set-up. The comparison of Ag vs Au/Si nanoparticles on the structure and photovoltaic conversion efficiency will be presented. Ag and Au/Si nanoparticles have contrasting effects on the photovoltaic conversion efficiency in terms of their relative coverage at the interface, This will be discussed in the light of plasmonic resonances and effective light scattering for Ag and Au/Si particles.  Olivia Rodgers, Anthony Viscovich, Yunis Yilmaz, Mehmet Sahiner, “The Effect of Embedded Ag Nanoparticle on the Photovoltaic Conversion Efficiency in CdTe/CdS Thin Films”, American Physical Society Bulletin, X17.13 (2018). This work is supported by NSF Award #:DMI-0420952
Authors : Curcio M. (1)*, Brutti S. (2), De Bonis A. (1), Santagata A. (3), Teghil R. (1)
Affiliations : (1) Department of Science, University of Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Italy; (2) Department of Chemistry, University of Rome ‘‘La Sapienza’’, Piazzale Aldo Moro 5, 00185 Rome, Italy; (3) CNR-ISM, UOS Tito Scalo, C/da S. Loja, 85050 Tito Scalo, Potenza, Italy
Resume : With the development of innovative portable technological devices the needs of scalable high power density miniaturized energy storage devices, such as microbatteries (MBs), is increasingly urgent. Li-ion systems are the most used in batteries for portable devices therefore the re-shaping of this technology into MBs is the focus of many studies. The production of 2D electrodes by the means of thin film deposition techniques has several advantages both in terms of manufacture and electrochemical properties. For this purpose, Pulsed Laser Deposition (PLD) is a promising technique thanks to the possibility to produce compact and dense films with a controlled thickness and preserved target material stoichiometry. Here PLD has been successfully employed to produce both cathode and anode thin films. In particular, a Nd:glass femtosecond-pulsed laser (524 nm, 250 fs, 10 Hz) was employed for the deposition in vacuum of anatase target materials for the production of the anode, while a Nd:YAG nanosecond-pulsed laser (532nm, 7ns, 10Hz). was used for deposition of the Lithium iron phosphate (LFP) in presence of buffer gas. Different post-deposition treatments were evaluated and films structure and composition were investigated with a multi-technique approach, cyclic voltammetry and galvanostatic technique were used to demonstrate the electrochemical activity of the obtained thin films in Lithium half cells.
Authors : Gianina Popescu-Pelin1, Cristian Butnaru1, Izabela Jinga1, Livia Sima2, Marioara Chiritoiu2, Gabriela Chiritoiu2, Felix Sima1, Gabriel Socol1
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, Magurele 077125, Ilfov, Romania 2Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
Resume : We report on the development of novel coatings with improved composition and structure that enhance bone structure restoring properties of titanium (Ti) implants. Ti implants functionalized with Se and Sr doped HA/β-TCP coatings (HA/β-TCP:Se/Sr) were achieved by combinatorial pulsed laser deposition (c-PLD) technique in order to identify the optimum elemental composition with respect to their biological performances. FTIR evaluation of HA/β-TCP:Se/Sr samples offered information’s about the functional groups and covalent bonding and confirmed the stoichiometric transfer of compounds. The elemental composition of the as-deposited coatings was determined from EDS and XPS measurements and pointed out the Se and Sr dopants content. The morphological features and the crystalline state of the as-deposited coatings was evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, respectively. The cytotoxicity, viability and proliferation of HA/β-TCP:Se/Sr were evaluated in order to establish the optimal Se/Sr ratio for which the proliferation of osteoblasts precursors is ensured. The ELISA measurements showed that M2 polarization of mouse primary macrophages is diminished on HA/β-TCP coated Ti. Moreover, an attenuation of inflammatory response on areas with increased Se content was observed. The aim of this study was to fabricate metallic implantable devices covered with thin films of HA/β-TCP:Se/Sr composite designed for bone tissue therapy that stimulate the osseointegration.
Authors : Iman Roqan1,*, Dhaifallah R. Almalawi,2 Bin Xin,1 Somak Mitra,1 Norah Alwadai,3
Affiliations : 1Physical Science and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955, Saudi Arabia. 2Physics Department, Faculty of Science, Taif University, 21974 Taif, P. O. Box 888, Saudi Arabia. 3Department of Physics, College of Sciences, Princess Nourah bint Abdulrahman University (PNU), Riyadh 11671, Saudi Arabia.
Resume : Room-temperature broadband photodetectors are potential candidates for a wide range of space science, chemical detection and optical communication applications. In this work, pulsed laser deposition (PLD) was used to successfully grow catalyst-free high optical and structural GaN NWs on a p-type Si substrate. The optimized PLD growth conditions for these high-quality NWs will be presented. All-inorganic perovskite, CsPbBr3 attracted considerable attention due to its large absorption coefficient, high charge carrier mobility, and long-range balanced electron- and hole-transport lengths. CsPbBr3 nanocrystals (NCs) are synthesized by the solution-processed method. In this work, we will present UV−visible broadband photodetectors fabricated by depositing CsPbBr3 perovskite NCs on GaN NWs. Our findings show that GaN NW hybridization with perovskite allows high-performance self-powered characteristics that can be used for photovoltaic applications, operating in a broad spectral range. After illuminating the device with white light under 0 V, the photo-responsivity of 200 mA/W is obtained, indicating superior-performance self-powered broadband photodetector operating under ambient conditions.
Authors : Matthäus Siebenhofer, Tobias Huber, Gernot Friedbacher, Werner Artner, Jürgen Fleig, Markus Kubicek
Affiliations : Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria & Kyushu University, Japan; Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria; Institute of Chemical Technologies and Analytics, TU Wien, Austria
Resume : The mixed conducting perovskite material La0.6Sr0.4CoO3−δ (LSC) is a very promising cathode material for application in a solid oxide fuel cell (SOFC) due to its catalytic properties for the oxygen surface exchange reaction and its high electronic conductivity. However, one of the remaining obstacles in the broader use of LSC is its susceptibility to changes of the surface structure due to various environmental factors. To further deepen the understanding of these degradation mechanisms and possible countermeasures, it is necessary to retrace the properties and the structure of LSC to a point before degradation starts. La0.6Sr0.4CoO3-δ thin films grown on YSZ single crystals were investigated directly in the stage of deposition by means of In-Situ Impedance Spectroscopy during Pulsed Laser Deposition (IPLD). This method allows the investigation of dense thin films unaltered by degradation and provides information about the oxygen exchange kinetics as well as the defect chemistry of pristine LSC thin films. Our measurements revealed remarkably low surface resistance values (1.3 Ωcm² at 600 °C and 0.04 mbar O2) compared to films measured outside the PLD chamber (20 Ωcm² at 600 °C and 0.04 mbar O2). Also the activation energy of the surface exchange resistance at 0.04 mbar p(O2) is significantly lower than at ambient conditions (1 eV vs. 1.3 eV) and degradation happens considerably slower than in air. The experiments further showed that the initial surface exchange resistance of LSC grown on YSZ is not influenced by the grain size of the columnar film. Additionally the chemical capacitance of LSC thin films was linked to the concentration of oxygen vacancies and shows that LSC thin films exhibit lower oxygen vacancy concentrations than the corresponding bulk material.
Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spainj.email@example.com
L22, 409 Atomistilor Street, 77125 Bucharest-Magurele, Romaniamnistor@infim.ro
Centro Materiali e Microsistemi, 18 Via Sommarive, 38123 Trento, Italylaidani@fbk.eu
National Fund for Scientific Research (FNRS), Mons, BelgiumStephanos.Konstantinidis@umons.ac.be