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2020 Spring Meeting

Nanomaterials and advanced characterization


Current trends in optical and X-ray metrology of advanced materials for nanoscale devices VI

Photonic probes are an essential tool to characterize novel materials, since they can be non-destructive and are sensitive to many of the critical characteristics of the materials. This symposium will: i) explore the use of photons from terahertz to x-ray to characterize materials essential for many emerging technologies; ii)give an overview of the current status of optical and x-ray metrology for materials characterization and quality assurance of thin films, layer-structured materials, and one-dimensional nanomaterials, with a particular emphasis on state-of-the-art metrology; iii) promote and encourage the interaction between academic and industrial research to address scientific and technological challenges associated with the improvement of standard analytical methods and qualification of newer techniques with a particular emphasis for ICT, Microwave/Terahertz, Renewable Energy and Energy storage, health and heritage conservation; iv)promoting and encouraging young researches and academics interaction with industry to address scientific and technological challenges associated with the improvement of standard analytical methods and qualification of newer techniques suitable for addressing the needs for the emerging technologies of the future at nanoscale; v)foster networking activities within all these emerging fields of science and technologies that are expected to have a significant societal impact.


This symposium will explore recent advances in photonic characterization of novel materials used in applications as varied as renewable energy, medical applications, and art restoration. Visible photons are very easy to produce and manipulate, and have the proper energy to characterize semiconductor materials, such as might be found in solar cells. Infrared and terahertz photons much lower energy and are harder to produce and manipulate, but give information about lattice vibrations and impurities in materials. X-rays are much higher energy, and therefore can explore material characteristics such as lattice spacing and atom identification.

This international symposium is intended to give an overview of the current status and future trends of optical, terahertz, infrared and x-ray metrology used to characterize nanoscale and other materials essential for many emerging technologies such as ICT, Microwave/Terahertz, Renewable Energy and Energy storage, health and heritage conservation. Another emphasis of the symposium will be on the use of larger facilities, such as synchrotrons, which produce x-rays with characteristics beyond the capability of laboratory light sources. An important consideration in this symposium will be on the actual characteristics measured, as well as the limits of the technique.

In addition to the scientific objectives, we will promote and encourage the interaction between worldwide academics, National lab scientists and scientific instrument manufacturer to improve standard analytical methods and qualification of newer techniques suitable for addressing the needs for the emerging technologies of the future. A special networking event between Europe and Japan will be organised as part of this symposium.

Hot topics to be covered by the symposium:

  • Ellipsometric techniques (Mueller Matrix, Infrared, THz, time-resolved and in-situ)
  • X-ray diffuse scattering
  • THz spectroscopy
  • Spatially resolved optical and x-ray techniques at nanoscale.
  • Characterization of complex materials such as halide peroskites, graphene, graphene oxide, 2D semiconductor materials, nanotubes and nanowires, nanoporous materials and composites.
  • Emerging novel materials: Catalysts, Nanocarbons, 2D Materials, Thermoelectrics, β-Ga2O3,
  • e-Ga2O3,Perovskites, SiC;
  • Bio-related materials (Proteins, Cancer Cells, in-vivo and ex-vivo characterization)
  • Materials for New Mobility (Batteries, Supercapacitors, 5G/6G, Fuel cells, CFRPs)
  • Nanostructures, photonic crystals, and metamaterials; transparent conductive materials
  • Dielectrics and ceramics: low- and high-k materials; transparent semiconductors
  • Novel functional materials: Ferroelectrics, ferromagnetics and multiferroics
  • Emerging X-ray Techniques: Coherent imaging; Ultrafast timing fs (FEL)
  • Novel imaging and mapping capabilities and high spatial resolution: Nanoscale Raman (TERS/ SERS), IR and Photoluminescence Spectroscopies
  • Ultrafast Spectroscopy/ Optical Pump-probe techniques
  • High Resolution Transmission Electron Microscopy
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08:40 Welcome address/Symposium Q Organizers    
Q.I Current trends in spectroscopic ellipsometry : G.E. Jellison, M. Modreanu
Authors : Kurt Hingerl
Affiliations : Center for Surface- and Nanoanalytics, Johannes Kepler Universität Linz, 4040 Linz, Austria,

Resume : Rayleigh and Abbe derived formula for the diffraction limit, which is due to the finite width of each imaging system, because the optical near fields cannot be transmitted through it. The intensity overlaps on the screen and it cannot be any more unambiguously decided if the image stems from one or from two distinct points or areas. With the appearance of spectroscopic imaging ellipsometers (SIE) especially applied to structured samples, and capable of imaging the ellipsometric angles or Mueller Matrix elements the problem above cannot be solved in direct way, i.e. the angular resolution cannot be changed. However, with a slight reformulation the number (and size) of the contributing points or areas can be determined with an imaging ellipsometer on a field of view of e.g. 50 x 50 µm area with resolution of a few µm by a few µm (for numerical purposes we assume 2 x 2 µm). In our contribution we will first discuss, how ellipsometric measurements with an imaging ellipsometer shall be interpreted in the case of no depolarisation and with depolarisation. Then it is shown with numerical techniques based on finite element methods or rigorous coupled wave analysis. 1) that the presence of subwavelength defects or structures (Au) of an areal size of e.g. 50 x 50 nm and 10 nm height on Si can be easily detected by SIE, provided the two ellipsometric angles and are measured with an accuracy of 0.01°. This result proves that the well known sensitivity of ellipsometry on the thickness of vertical overlayers can be extended also to the horizontal dimensions. 2) Knowing that there is more than one structure with the given size in the real plane even closer than the Abbe formula can resolve in the image plane, SIE will immediately determine this number by measuring  and 3) In addition we show that extremely high precision SIEs will allow to estimate the approximate distance between the different structures. The ellipsometric response depends, due to the existence of evanescent fields in plane [5], on the distance between the single structures. A matrix of in total 9 structures (i.e. a field of 3 x 3) of 20 nm x 20 nm structures a distance p apart will yield different SEI responses depending on the distance.

Authors : Biwas Subedi, Indra Subedi, Prakash Uprety, Dipendra Adhikari, Niva Jayswal, Marie Solange Tumusange, Maxwell M. Junda, Kiran Ghimire, Prakash Koirala, Robert W. Collins, Yanfa Yan, and Nikolas J. Podraza
Affiliations : University of Toledo

Resume : Opto-electronic devices like photovoltaics (PV) depend on both optical response of component materials to control how incident light is collected as well as material electronic transport properties to utilize that absorbed light. Millimeter (THz) to ultraviolet range spectroscopic ellipsometry measures the complex optical response of materials for and within solar cells. Layer thickness, interfacial formation, structure, electronic transitions, bandgap, Urbach tails, and relative defect density are identified optically for components of silicon wafer, polycrystalline organic-inorganic lead halide perovskite, and other thin film PV technologies. THz optical Hall effect measures majority and minority carrier transport properties of semiconductors within solar cells. Open circuit voltage and fill factor simulated using those transport properties agree with direct measurement. Spectroscopic ellipsometry measurements of complete single and tandem junction PV generate structure and optical property input parameters for simulations of external quantum efficiency (EQE) and short circuit current density. Sources of optical and electronic losses are identified through quantification of parasitic absorption in non-current generating layers and carrier collection profiles of PV devices. Non-contacting optical measurements provide a means of full PV device property prediction and loss diagnosis.

Authors : M. Fried a,b, Z. Lábadi b, Z. E. Horvath b, Z. Zolnai b
Affiliations : a Institute of Microelectronics and Technology, Óbuda University, Tavaszmezo u. 17, H-1084 Budapest, Hungary b Institute of Technical Physics and Materials Science (MFA), Centre for Energy Research, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary

Resume : Reactive (Ar-O2 plasma) magnetron sputtered non-stoichiometric tungsten molybdenum oxide mixed layers were investigated and mapped by Spectroscopic Ellipsometry (SE). The W- and Mo-targets were placed separately and 30x30 cm glass substrates were moved under the two (W and Mo) separated targets. We used different (oscillator- and Effective Medium Approximation, EMA-based) optical models to obtain the thickness and composition map of the sample layer relatively quickly, and in a cheap and contactless way. We have also used Rutherford Backscattering Spectrometry and XRD to check the SE results. We compare the “goodness” of the different optical models depending upon the sample preparation conditions, for instance the speed and cycle number of the substrate motion. Authors acknowledge the funding of Hungarian National Science Fund OTKA NN131269 and K129009

Authors : Manuela Schiek (1), S. Funke (2), F. Balzer (3), M. Duwe (2), K. Hingerl (4), Peter H. Thiesen (2).
Affiliations : (1) University of Oldenburg, D; (2) Accurion GmbH, Göttingen, D; (3) University of Southern Denmark, DK; (4) JKU Linz, A.

Resume : Semiconductor thin films are technologically relevant materials for opto-electronics and photonics. Typically, they are micro- or nano-textured and anisotropic in their structural and resulting opto-electronic properties. This asks for microscopic tools such as imaging Mueller matrix ellipsometry combining the power of Mueller matrix ellipsometry and optical microscopy to obtain the complete complex dielectric tensor. Here we utilize Nanofilm_EP4 instrumentation by Accurion. We present the biaxial dielectric tensor for a polycrystalline, orthorhombic organic thin films consisting of birefringent and pleochroic rotational platelet-like domains [1]. [1] Balzer, Lützen, Schiek et al. Cryst. Growth Des. 17 (2017) 6455.

10:20 Coffee Break    
Q. II. Terahertz spectroscopies and applications : T.Kiwa, N. J. Podraza
Authors : Masayoshi Tonouchi
Affiliations : Osaka University

Resume : Laser Terahertz (THz) Emission Microscope (LTEM) is our original microscope which enables us to visualize temporal carrier transport of photoexcited electronic materials. LTEM has been proven as a new promising tool in the evaluation platform for semiconductor R&D, which visualizes the temporal photoexcitd carrier transport with a resolution of laser beam diameter. The waveforms of LTEM unveil the nature of carrier dynamics in various materials such as wide-gap semiconductors, and also can tell the type of carriers i.e. p or n without any contacts. In this talk, we will show examples of the application of THz emission spectroscopy to GaN and some nano materials.

Authors : M. Helm, I. Fotev, L. Balaghi, D. Lang, R. Rana, S. Winnerl, H. Schneider, E. Dimakis, A. Pashkin
Affiliations : Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany

Resume : We study the plasmonic response of free charge carriers in GaAs/InGaAs core/shell nanowires by means of THz spectroscopy. In the first set of experiments, we generate an electron-hole plasma in an ensemble of nanowires using photoexcitation by a femtosecond optical pump pulse. Fitting the plasmon peak measured in the linear low-field regime allows us to deduce room-temperature mobilities around 4000 cm2/Vs. Besides that, we drive the plasmon in nanowires with intense THz pulses generated in an organic DSTMS crystal. In a THz field of >MV/cm the plasmon peak is red shifted, indicating intervalley transfer of the electrons. In the second experiment, we investigate a single, highly electron doped nanowire by scattering infrared near-field infrared microscopy (s-SNIM). Here we observe a red shift of the mid-infrared plasma resonance from 125 meV to 95 meV at a peak power of 0.5-1 kW (pulse energy of 2-3.5 nJ) from our free-electron laser, which can be explained by heating the electron system in the nonparabolic conducting band. We gratefully acknowledge contributions from S. Shan, J. Schmidt, R. Hübner, S. C. Kehr, and L. M. Eng

Authors : Hitoshi TABATA
Affiliations : The University of Tokyo

Resume : The surfaces of topological insulators contain two dimensional massless Dirac electrons. Plasmon can be excited using coupled electrons of top and bottom surfaces and shows resonance in the terahertz frequency rage with exceptionally large mode indices and long lifetimes. In the range of terahertz wave length, there are a number of important resonance absorption modes caused by intermolecular coupling and it enables us to directly observe the specific binding state of a bio-related molecular system without modifying fluorescent molecules. However, in general, it is necessary to amplify the signal intensity by some techniques. Two-dimensional Dirac plasmons can be excited from these surface electrons. These plasmons are expected to exhibit resonances in the terahertz (THz), a frequency range of interest for bio-medical sensing and chemical identification. Topological insulators (TIs) are materials having a bulk bandgap crossed by linearly-dispersing two-dimensional surface states and are expected to show surface plasmon in the THz wave length range. In addition, TI plasmons should also exhibit spin-momentum locking, leading to a reduction in scattering and an increased plasmon lifetime. In this study, we have focused on TIs of Bi2(Te,Se)3 as topological insulators those generate surface plasmon resonance in the terahertz range, and fabricated thin films on sapphire substrates by a pulsed laser deposition (PLD). Crystallographic, nano-micro structural properties are discussed. And their physical, electrical and optical properties are also presented in a view point of the terahertz plasmonics.

Authors : Sean Knight(1), Megan Stokey(1), Vallery Stanishev(2), Philipp Kühne(2), Christian Binek(3), Tino Hofmann(4), Vanya Darakchieva(2), Mathias Schubert(1)
Affiliations : Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, U.S.A.(1), Department of Physics, Chemistry and Biology, Linköping University, Sweden(2), Department of Physics and Astronomy, University of Nebraska-Lincoln, U.S.A.(3), Department of Physics and Optical Science, University of North Carolina at Charlotte, U.S.A.(4)

Resume : Terahertz Mueller matrix ellipsometry is a powerful technique for materials characterization, which has been used to determine the complex dielectric tensor of thin films and substrates in the spectral range of 0.1 THz to 1 THz[1,2]. Its sensitivity can be greatly enhanced by utilizing Fabry-Pérot interferences that occur between multiple reflections off of the sample's interfaces for samples containing THz-transparent substrates. Further enhancement is possible by creating an external Fabry-Pérot cavity via adding a reflective metal surface behind such samples[3]. These techniques, for example, have enabled the detection of optical Hall effect signatures in two-dimensional electron gases, and recently, were used to detect the electron paramagnetic resonance (EPR) signal in Ce-doped lutetium oxyorthosilicate. [1] Philipp Kühne, et al., ‎IEEE Trans. Terahertz Sci. Technol 8, 257 (2018). [2] Sean Knight et al., Sci. Rep. 9, 1353 (2019) [3] Sean Knight et al., Opt. Lett. 40, 2688 (2015).

12:45 Lunch break    
Q. III. Advanced characterization techniques: Biomaterials : M.Tonouchi, S.Knight
Authors : Eva Bittrich (1), Petra Uhlmann (1), Klaus-Jochen Eichhorn (1), Dieter Jehnichen (1), Mathias Schubert (1,2,3), Marieta Levichkova (4), Karsten Walzer (4), Mahmoud Al-Hussein (5)
Affiliations : (1) Leibniz-Institut für Polymerforschung Dresden e.V. Hohe Str. 6, 01069 Dresden, Germany; (2) Department of Electrical & Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588-0511, USA; (3) Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden; (4) Heliatek GmbH, Treidlerstr. 3, 01139 Dresden, Germany; (5) Department of Physics, University of Jordan, Amman 11942, Jordan

Resume : Nanostructured surfaces and thin films of small organic molecules, polymers or hybrid materials are promising interfaces for versatile applications like sensing, water purification, nanoelectronics, energy production, and energy storage devices. In this presentation we present aspects from our research, ranging from switchable responsive polymer brushes for biosensing to thin films of small organic molecules for organic photovoltaic applications. For smart polymer brush-bio-interfaces we discuss the quantification of the adsorbed amount of biomolecules by in-situ ellipsometric measurements. Additionally, the swelling of these nm-thin films is visualized by polarization modulation-based anisotropic optical contrast microscopy, utilizing slanted columnar thin films of silicon (SCTF) as birefringent substrates for brush grafting. Furthermore, we present the effect of employing thin alignment layers on controlling the morphology and optical properties of semiconducting thiophene thin films for organic photovoltaics. Here, we used a combination of spectroscopic ellipsometry (SE) and grazing incidence wide angle X-ray scattering (GIWAXS) to characterize the optical properties and morphology of these films, respectively.

Authors : Joo-Hiuk Son, Hwayeong Cheon, Donggun Lee, Seo-Yeon Jeong
Affiliations : Deparment of Physics University of Seoul

Resume : Carcinogenesis involves DNA methylation which is a primary alteration in DNA in the development of cancer before genetic mutation. Because the abnormal DNA methylation is found in the most of cancer cells, assessment of DNA methylation using terahertz radiation can be a novel optical method to detect and control cancer. The methylation has been directly observed by terahertz spectroscopy at around 1.6-1.7 THz and this epigenetic chemical change could be manipulated to the state of demethylation using high-power terahertz radiation. Demethylation of cancer DNA is a key issue in epigenetic cancer therapy and our results may lead to the treatment of cancer using electromagnetic waves. In the presentation, the manipulation of biological molecules and cells toward cancer treatment using intense terahertz radiation will be explained in detail.

Authors : Hiromichi Hoshina(1), Shota Yamazaki(1)(2), Chiko Otani*(1)(3)
Affiliations : (1) RIKEN Center for Advanced Photonics, RIKEN, Japan (2) Department of Agriculture, Tohoku University, Japan (3) Department of Physics, Tohoku University, Japan * lead presenter

Resume : High-power sources in terahertz (THz) region opens the possibility of the activation to change macromolecular structures. Because such structures are directly connected to their functions, the development of new functions of macromolecules by THz irradiation is expected. We demonstrated the irradiation of the intense THz wave to a biodegradable polymer, poly-hydroxybutyrate (PHB), as well as Actin protein. We clearly observed the enhancement of crystallinity by THz irradiation image for PHB by intense THz irradiation from a free electron laser (FEL) of Osaka University. Following the results, the irradiation of the intense THz wave to the Actin solution was performed by using a Gyrotron source of Fukui University, and the elongation of Actin fiber by THz irradiation was also clearly observed, showing the possibility of structural control of protein by the irradiation. We will summarize our recent results related to the controls of chemical and biological intermolecular structures by intense THz sources.

Authors : Alexander Ebner (1); Robert Zimmerleiter (1); Jakob Kilgus (1); Ivan Zorin (1); Christoph Cobet (2); Kurt Hingerl (3); Christian Rankl (1); Markus Brandstetter (1);
Affiliations : (1) RECENDT – Research Center for Non-Destructive Testing GmbH, Science Park 2, Altenberger Str. 69, 4040 Linz, Austria; (2) Linz School of Education, Johannes Kepler Universität, Altenberger Str. 69, 4040 Linz, Austria; (3) Center for Surface and Nanoanalytics, Johannes Kepler Universität, Altenberger Str. 69, 4040 Linz, Austria;

Resume : Conventional optical techniques applied in the fingerprint region of the mid-infrared (MIR) spectral range typically rely on thermal emitters. Such sources are characterized by low brightness, which finds expression in poor signal-to-noise ratios (SNR), long acquisition times and insufficient spatial resolution. By exploiting high-brightness broadband MIR laser sources, however, the limits of conventional instruments can be exceeded by orders of magnitude. The application of a spectrally tunable MIR quantum cascade laser (QCL) for spectroscopic ellipsometry is presented. The QCL based ellipsometer is outperforming state-of-the-art FTIR ellipsometers in terms of SNR by a factor of 290. This exceptional noise performance allows to acquire high-resolution (1 cm-1) broadband (900 cm-1 – 1204 cm-1) ellipsometry spectra in less than a second (887 ms), which designates a reduction in acquisition time by a factor of 66,000 compared to reference measurements performed with a state-of-the-art instrument. The benefit of this approach is illustrated by monitoring molecular reorientation during the stretching of a 6 µm Polypropylene film at sub-second temporal resolution. Additionally, chemical mapping studies performed with a MIR supercontinuum laser based microspectroscopy setup at diffraction limited spatial resolution are presented. The achieved results were outperforming reference measurements obtained with a conventional FTIR microscope in terms of both spatial resolution and SNR.

15:45 Coffee break    
Q.IV Microwave and functional materials : T.Kiwa, O.Durand
Authors : Takashi Teranishi, Akira Kishimoto
Affiliations : Okayama University

Resume : DC bias characteristics of ferroelectrics is described by the combination of two phenomena; 1) tunability as a short time range dielectric response and 2) aging characteristics as long time range response over several hours. The tunability in ferroelectrics is interpreted as permittivity depression due to hardening in domain wall vibrations as well as the freezing of the optical phonon modes. The tunability phenomenon can be observed within microseconds or shorter time range. On the other hand, the later aging effect of normal ferroelectrics is derived from configuration change in the ferroelectric domains due to the domain wall shift under the DC field application for hours. We developed the technique of quantification to the dipole contribution in tunable characteristics by employing the broadband dielectric spectroscopy from low to microwave frequencies. The apparent tunability T in BaTiO3 (BTO)-based ferroelectrics significantly increased as the domain size, DS, decreases. This phenomenon was mainly attributed to an increase in the density of the 90°-domain wall vibrations. We also found a relationship between aging effect in ferroelectrics and its domain size; as BTO DS reduces, the decrease in apparent permittivity by DC electric field becomes larger. The investigation of the microwave dielectric spectra revealed the dipole polarization governs the overall aging effect irrespective of the BTO domain size, while the ionic and electronic polarizations contributions are small.

Authors : Daniela Dragoman
Affiliations : (1) Univ. of Bucharest, Physics Faculty, P.O. Box MG-11, 077125 Bucharest, Romania

Resume : The talk will focus on the emerging area of metasurfaces, which are increasingly replacing conventional optical components in optics and optoelectronics applications due to their miniature size and flexibility in design. In particular, the talk will concentrate on the design of metasurfaces for imaging applications in the infrared spectral region. Different configurations of all-dielectric metasurfaces will be presented, the emphasis being on providing solutions for imaging/focusing devices with variable focus and reduced aberrations and/or for handling partially coherent light fields. Limitations imposed by implementations of the designed metasurfaces will be also addressed. The research leading to these results has received funding from the EEA Grants 2014-2021, under project no. EEA-RO-NO-2018-0438 - ElastoMETA

Authors : Mircea Dragoman (1)*, Daniela Dragoman (2), Adrian Dinescu (1)
Affiliations : (1)National Institute for Research and Development in Microtechnologies (IMT Bucharest), Erou Iancu Nicolae Street 126A, 077190 Voluntari (Ilfov), Romania (2)Univ. of Bucharest, Physics Faculty, P.O. Box MG-11, 077125 Bucharest, Romania

Resume : This talk will be dedicated to the new and emerging area of 2D materials having important applications in nanoelectronics. The discovery of HfO2- based ferroelectrics has as the main impact the CMOS compatible fabrication of high frequency HfO2-based devices such as phase-shifters, antenna arrays or filters with a high degree of tunability and miniaturization. The transfer of 2D materials on HfO2 ferroelectrics has demonstrated new physical effects such as the opening of the bandagap in graphene monolayers of 0.2 eV, very high mobility of FETs based on graphene/HfZrO ,enhanced memory performances and memrsistive effects. The authors acknowledge the financial support via project no.. PN-III-P4-ID-PCCF-2016-0033 –GRAPHENEFERRO.

Authors : Marco Farina(1), James C. M. Hwang(2), Eleonora Pavoni(1), Gianluca Fabi(1), Andrea Di Donato(1), Antonio Morini(1), Xin Jin(3), Xiaopeng Wang(2), Joseph C. Hardly(1), Davide Mencarelli(1).
Affiliations : (1) Università Politecnica delle Marche, Dipartimento di Ingegneria dell'Informazione, Ancona 60131, Italy (2) Cornell University, Department of Materials Science and Engineering, Ithaca, NY 14850 USA (3) Lehigh University, Department of Electrical and Computer Engineering,Bethlehem, PA 18015, USA

Resume : Scanning Microwave Microscopy (SMM) is approaching technological maturity and gaining popularity in material science, allowing to investigate for example semiconductors, 2D materials, topological insulators, superconductors and ferro-electrics at nanoscale. Nonetheless spectroscopy, requiring a large bandwidth, is precluded by current single-frequency or narrowband approaches, and several kinds of measurements are limited by the low signal-to-noise ratio of SMM. Here we discuss a novel approach, the inverted SMM, where the sample is no longer illuminated by a probe but is sitting on a waveguide, and the probe is only a perturbation of the field and a return-to-ground path. The proposed approach solves the bandwidth and sensitivity problems while allowing to convert any existing scanning probe microscope (AFM, STM, SNOM) into an i-SMM.

Authors : C.H. Joseph, Nicola Pelagalli, Davide Mencarelli and Luca Pierantoni
Affiliations : Department of Information Engineering, Universita Politecnica delle Marche, Ancona, Italy

Resume : Novel metamaterial designs are gaining attention in recent years as practical implementations of these artificial materials starts to emerge. Metamaterials are artificial medium which offers negative permittivity and permeability in finite frequency ranges depending on their designs. Metamaterials properties are mostly studied and utilized in the microwave regime and it makes important to study its characteristics at extreme high frequencies. In this work, we explore the new designs of metamaterials works at upper mm-wave (120-300 GHz). The electromagnetic response of these structures are studied using commercial full wave simulator. Moreover, the additional practical solutions to realize these novel structures in mm-wave devices will be discussed.

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Q. V. Advanced characterisations of photovoltaics : O.Durand, N. J. Podraza
Authors : N. Barreau (1), E. Gautron (1), O. Durand (2), A. Létoublon (2), C. Cornet (2), R. Bernard (2), D. Lincot (3)
Affiliations : (1) Université de Nantes, CNRS, Institut des Matériaux Jean Rouxel, IMN, F-44000 Nantes, France (2) Université de Rennes, INSA Rennes, CNRS, Institut FOTON – UMR 6082, F-35000 Rennes, France (3) CNRS, Institut Photovoltaïque d'Ile de France (IPVF), 18 boulevard Thomas Gobert, 91120 Palaiseau, France

Resume : Fabrication of tandem solar cells by combining mature c-Si and Cu(In,Ga)Se2 (CIGSe) thin film photovoltaic technologies is among the valuable routes to achieve 30 % efficiency within the next decade. This approach can be successful only if (i) devices based on 1.6-1.7 eV bandgap C(I)GSe absorber layers reach efficiencies higher than 15 % (ii) Si/C(I)GSe heterointerface are optimized. So far, the main drawback to CuIn1-xGaxSe2-based devices is the relatively low efficiency achieved with absorbers whoe bandgap is wider than 1.5 eV (i.e. x > 0.7). Many models were proposed during the last decades to explain the origins of those lowered performance; most of them blame detrimental grain boundaries, local inhomogeneities, and recombinative heterointerfaces. To overcome these issues, we propose an orignal approach consisting in growing by coevaporation CuIn1-xGaxSe2 (with x > 0.8) onto epi-III-V/c-Si plateforms. This approch offers at least two advantages, namely minimizing the density of crystalline defects thanks to epitaxial growth, and use the epi-III-V as selective contact to minimize detrimental heterointerface recombinations. For our first attempts, we used epi-GaP/c-Si(001) as plateform and we could achieve epitaxial CuIn0.1Ga0.9Se2 growth. The presentation will give an overview of the process used, the results of characterizations, as well as the first device performance.

Authors : Jacky Even
Affiliations : Univ Rennes, INSA Rennes, CNRS, Institut FOTON - UMR 6082, F-35000 Rennes, France

Resume : The presentation will describe recent experimental and theoretical results for 3D and 2D bulk halide perovskites and QD nanostructures, including symmetry analyses and DFT computations of electronic states coupled with spectrocopy (PL, TRPL) and diffraction (X-Ray, Neutrons) studies. The presentation will adress the ongoing debate about the nature of the exciton ground state in perovskite QD.

Authors : Jean-Christophe BLANCON
Affiliations : Chemical and Biomolecular Engineering, Rice University, 77005 Houston, TX, USA.

Resume : Organic-inorganic halide perovskites (HP) are remarkable semiconductors that combine features of hard and soft matter and have potential applications in many areas. Two-dimensional (2D) HPs – where organic spacer cations can be engineered to microscopically isolate nanometer-thick HP layers, offers tunable physical properties and improved device stability [Nature 536, 312 (2016)]. Recent studies have hinted at the importance of dynamic interactions between electronic states and the lattice in these materials. It is thus critical to understand the interplay between structure and properties in 2D-HPs during light excitation and in device operation conditions. Here, we investigate these effects by exploring the 2D-HP phase space both in terms of HP layer thickness and organic spacer rigidity. We reveal the structure-properties interplay by correlating state-of-the-art characterization tools, i.e. grazing-angle wide angle x-ray diffraction, ultrafast electron-diffraction, and optoelectronic spectroscopy at the sub-micron scale. Our work demonstrates that the characteristics of excitons can be modulated not only by the thickness of the HP layers as in classic quantum-wells but also through structural distortions. Similar effects are linked to local compositional changes or artificial interfaces in heterostructures of 2D-HP and WS2 [Nano Lett. 19, 4852 (2019)]. We also report on the transient structural changes under light excitation and discuss their implications for applications.

Authors : Laurent Lombez,1,3, Adrien Bercegol,1,4, Stefania Cacovich,1,3, Armelle Yaiche,1,2, Guillaume Vidon,1,4, Jean-Baptiste Puel,1,4, Christophe Longeaud,1, Sébastien Jutteau,1,4, Daniel Suchet,1,2,3, Jean-François Guillemoles,1,3, Jean Rousset,1,4, Daniel Ory,1,4
Affiliations : 1 Institut Photovoltaique d’Ile de France (IPVF), 18 boulevard Thomas Gobert, Palaiseau, France; 2 CNRS, Ecole Polytechnique, Institut Photovoltaïque d’Ile-de-France UMR 9006, 18 boulevard Thomas Gobert, 91120, Palaiseau, France; 3 CNRS-Institut Photovoltaique d’Ile de France (IPVF), UMR 9006, 18 boulevard Thomas Gobert, Palaiseau, France; 4 EDF R&D, 18, boulevard Thomas Gobert, 91120, Palaiseau, France;

Resume : The excellent photovoltaic performance of halide perovskites goes along with a high photoluminescence yield (PL) that makes them suitable for a wide range of photonic devices and various optoelectronic applications, such as photodetectors, lasers and light emitting diodes. However, due to the complexity of the materials and the related devices, often traditional macroscopic characterization tools are not able to unveil the physical processes underlying the working principles of the solar cells, especially transport properties. Indeed, electronic as well as ionic transport are still under investigation and can be blurred by photonic effect. Here we quantify in depth transport then in plane transport by means of multidimensional imaging techniques. To go further in the in plane case we investigate electrons, holes and ions transport. We used innovative characterisation methods that combine hyperspectral imaging system (HI) and a time-resolved fluorescence imaging (TR-FLIM) set-ups. We employed these optical techniques to study charge carriers transport in hybrid perovskites and probe a large variety of transport parameters (diffusion length, mobility, lifetimes…) which are often cross-linked. Photonic transport is also observed and the experimental impact will be discussed. Besides, measuring the local variations of time resolved luminescence in the nanosecond scale under lateral electric bias allows a direct access to charge carrier collection and transport properties for each kind of charge carrier –electrons and holes-. At long time scale such experiment allows to probe the ionic transport, especially associated with iodine species. More precisely, the iodine seems to affect the band structure and locally modify the bandgap; it also degrades the local quasi Fermi level splitting (i.e. the internal bias). The novel experimental approach, can thus image and quantify the transport mechanisms occurring within the material (even under aging procedure), providing new insights on these complex transport phenomena.

Authors : Marie Legrand * (1)(2), Adrien Bercegol (1)(2), Laurent Lombez (1)(4), Jean-François Guillemoles (2)(3), Daniel Ory (1,2)
Affiliations : (1) EDF R&D, France (2) Institut Photovoltaïque d’Ile de France (IPVF), France (3) CNRS, Ecole Polytechnique, UMR IPVF, France (4) Laboratoire de Physique et Chimie des Nano-objets, France

Resume : Analyzing the photoluminescence (PL) of semiconductors complementarily in time and wavelength allows to derive their key optoelectronic and transport properties. Up to now, separate acquisitions have to be performed. We developed a 4D imaging set-up that allows the acquisition of spectral and temporal luminescence intensity with micrometric spatial resolution. Very notably, this dataset is acquired simultaneously and hence with exact same experimental conditions. This novel set-up relies on single pixel imaging technology, an approach that enables the reconstruction of the spatial information recorded from a higher resolution non-imaging detector. The sample PL signal is spatially modulated with different patterns by a digital micro-mirror device1. We make use of this technique for the first time with a streak camera as a detector, allowing to record the PL intensity decays and spectrum for each pixel with very high temporal (<100ps) and spectral resolutions (< 1nm). A patent application has been filled. We already performed successful measurements and 4D numerical reconstructions and we demonstrate the use of this setup by characterizing hybrid mixed halide perovskite samples. We extract and analyze the material properties (gap) at different time scales as well as the carrier recombination (lifetime, radiative coefficient) and transport (diffusion coefficient) properties with a single experiment. 1 Duarte et al, IEEE Signal Process. Mag. 25, 83 (2008).

12:15 Lunch break    
Q.VI Current trends in optical spectroscopy : G.E. Jellison, M. Modreanu
Authors : C. Sturm (1), K. Hingerl (2), V. Zviagin (1), R. Schmidt-Grund (1,3), T. G. Mayerhöfer (4), M. Grundmann (1)
Affiliations : (1) Felix Bloch Institute for Solid State Physics, Universität Leipzig, Germany (2) Center for Surface and Nanoanalytics, Johannes Kepler University Linz, Austria (3) now at: Institute for Physics, Universität Ilmenau, Germany (4) Leibniz-Institut für Photonische Technologien e.V., Germany

Resume : Wide-bandgap materials, which are interesting for opto-electronic devices, like Ga2O3, exhibit often a low crystal symmetry. Here, we present the determination of the optical properties of such materials by spectroscopic ellipsometry. For the investigation of the nature of the underlying excitations, we present a general approach for the decomposition of the dielectric function by taking into account the dipole orientation distribution of each excitation into account. The application of this approach is demonstrated exemplary on an orthorhombic KTiOPO4, monoclininc Ga2O3 and triclinic K2Cr2O7. Without making any assumptions, we show that the tensor elements of the dielectric function in general are not independent of each other. The dielectric function can be described by a superposition of electronic transitions. For each transition an eigensystem exists in which the contribution to the dielectric function is given by a diagonal susceptibility tensor. The relative magnitude of these tensor elements is given by the dipole orientation distribution of the corresponding transition. In the limiting case, the oriented dipole approach is obtained as well as the tensor for uniaxial and isotropic materials. It is also shown that the imaginary part of the non-diagonal tensor elements can become negative, which is forbidden in scalar systems.

Authors : Zapien, J.A.*(1), Huqe, M.R.(1), & Foo, Y.(1).
Affiliations : (1) Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong, SAR, PRC. * lead presenter

Resume : NIR to UV characterization strategies have paramount importance because of their simple implementation, non-invasive, non-destructive, fast, and contactless advantages. Among them, spectroscopic ellipsometry (SE), as a self-referenced and phase-sensitive technique, provides superb sensitivity to the sample characteristics. However, information about the sample’s characteristics are only accessible via detailed mathematical modeling. While the Rigorous Coupled-Wave Analysis (RCWA) is the preferred strategy for modeling the optical response of structured 1D periodic structures; as the complexity in size and dimensionality increases, it becomes important to find complementary numerical tools to accomplish this task. The Finite Difference Time Domain (FDTD) method provides attractive advantages that include generality of the method, capacity to model single and non-periodic structures, and natural suitability to address non-linear phenomena. We will discuss the use of the FDTD method as an alternative to model the broad band spectroscopic ellipsometry (SE) data of real structures. Particular attention will be given to the computational demands, time-to-result, and its capabilities and limitations to enable a quantitative search for best-fit parameters of an optical model with spectral density comparable to the experimental data. This work was supported by a grant from the Research Grants Council, University Grants Committee, Hong Kong SAR, PRC (Project No. CityU 11210218).

Authors : E. Krüger* (1), S. Henn (1), C. Sturm (1), S. Richter (1,2), H.-G. Zirnstein (3), J. Zúñiga-Pérez (4), C. Deparis (4), L. Trefflich (1), B. Rosenow (3), R. Schmidt-Grund (1,5) & M. Grundmann (1)
Affiliations : (1) Universität Leipzig, Faculty of Physics and Earth Sciences, Felix Bloch Institute for Solid State Physics, Germany (2) Now at: Linköping University, Department of Physics, Chemistry and Biology (IFM), Semiconductor Materials (HALV), Sweden (3) Universität Leipzig, Faculty of Physics and Earth Sciences, Institute for Theoretical Physics, Germany (4) CRHEA-CNRS / Université Côte d'Azur, France (5) Universität Illmenau, Institute for Physics, Germany

Resume : Exceptional points (EPs) correspond to non-Hermitian degeneracies and represent topological charges, being of great interest in the context of research on topologically non-trivial photonic systems due to their possible applications for e.g. optical isolators. EPs can occur in the momentum space of a photonic system, representing directions along which the eigenmodes coalesce, yielding a degeneracy in energy, broadening and polarization. Furthermore, the eigenenergies exhibit a complex-square-root topology around such EPs. A well-known related phenomenon is the splitting of each classic optic axes of optically biaxial material into two singular optic axes, in the absorptive regime [1,2]. However, the presence of such EPs is not limited to bulk single crystals but can occur in a variety of systems described by non-Hermitian Hamiltonians [3]. Here, we report on EPs in planar dielectric heterostructures with broken cylindrical symmetry, realized by using anisotropic cavity layer materials, and present different approaches for experimental proving of the EPs in such photonic systems. Furthermore, we show how the occurrence and direction of EPs can be controlled by the structure design. Finally, we describe approaches for breaking the in-plane reciprocity of the system, thereby paving the way for more complex topologically non-trivial photonic systems. [1] W. Voigt, ‎Ann.Phys 314 (1902) [2] C.Sturm, M. Grundmann, Phys.Rev.A 93 (2016) [3] S. Richter et. al., Phys.Rev.Lett. 123 (2019)

Authors : Manuela Schiek (1 4), J. Zablocki (2), F. Balzer (3), K. Meerholz (4), A. Lützen (2), O. Arteaga (5).
Affiliations : (1) University of Oldenburg, D; (2) University of Bonn, D; (3) University of Southern Denmark, DK; (4) University of Cologne, D; (5) University of Barcelona, ES.

Resume : Chiral organic semiconductors offer unique potential for chiroptical applications when the thin film semiconducting properties combine with a sizable excitonic circular dichroism. This is the case for a series of naturally chiral prolinol-derived squaraines with variable side chain length for fine-tunability of the chiroptical responsen [1]. For an accurate, quantitative determination of the chiroptical response from their homogeneous thin films, a partial Mueller matrix polarimetry measurement is sufficient. Many modern ellipsometers are capable of measuring 12 out of the 16 elements of a Mueller matrix, which can be completed by symmetry considerations for non-depolarizing samples [2]. This allows extraction of the true circular dichroism not overlaid by possible anisotropy effects from the sample. For an ultimate quantitative evaluation of the circular dichroism a series of measurements for samples with varying layer thickness is necessary. Furthermore, for determination of the true dissymmetry factor, which is the absorbance normalized circular dichroism, a correction for reflection losses due to the thin film nature of the samples is required [3]. [1] Schulz, Balzer, Scheunemann, Arteaga, Lützen, Meskers, Schiek. Adv. Funct. Mater. 29 (2019) 1900684. [2] Arteaga, Ossikovski. JOSA A 36 (2019) 416. [3] Schulz, Zablocki, Abdullaeva, Brück, Balzer, Lützen, Arteaga, Schiek. Nat. Commun. 9 (2018) 2413.

Authors : Coline Bretz, Andrea Vaccaro
Affiliations : LS Instruments AG

Resume : There is significant research interest in the field of soft matter that focuses on studying slow relaxation processes in systems that are close to a phase transition or are dynamically arrested. Yoghurt, gelatin and various food additives are example of such systems. In some cases, accessing dynamic properties in time scales of seconds or even minutes is crucial. One method that allows for studying slowly relaxing systems is to perform many DLS measurements, to obtain time averaged correlation functions. Between each measurement the sample is rotated such that a different speckle is observed. The results are then averaged to provide the ensemble average [1]. Additionally, when working with concentrated samples, the suppression of multiple scattering is required to obtain meaningful results. This is achieved through the 3D modulated cross-correlation technique [2,3], where two temporally separated light scattering experiments are performed at the same scattering vector on the same sample volume in order to extract only the single scattering information common to both. In this work, we present modulated 3D static and dynamic light scattering (SLS and DLS) measurements on Polystyrene particles suspended in a gel matrix. Using a sample goniometer, we rotate the sample to record a subsection of the configuration phase space. We then average over many sub-ensembles to capture the full phase space. We demonstrate that to follow such systems undergoing dynamical relaxation, as well as to study dynamically arrested samples, modulated 3D cross-correlation combined with a sample goniometer is a perfectly suited experimental tool that can record information otherwise not accessible. [1] K. N. Pham, S. U. Egelhaaf, A. Moussaı̈d, and P. N. Pusey, “Ensemble-averaging in dynamic light scattering by an echo technique”, Rev. Sci. Instrum. 75, 2419 (2004). [2] Patent EP2365313 A1 [3] Ian D. Block and Frank Scheffold, “Modulated 3D cross-correlation light scattering: Improving turbid sample characterization”, Rev. Sci. Instrum. 81, 123107 (2010).

15:45 Coffee Break    
Q.VII. Advanced nanoscale characterisation of material and devices I : O.Durand, L. Lombez
Authors : G. Delie*(1), I. Shlyakhov(1), K. Iakoubovskii(1), V. Afanasiev(1)
Affiliations : (1)Department of Physics and Astronomy, University of Leuven, B-3001 Leuven, Belgium; * lead presenter

Resume : Optical spectroscopy represents one of the primary methods to characterize electron states in mono- and few-layer (ML & FL) two-dimensional (2D) materials. It enables quality control of the 2D material during growth and processing, e.g., upon ambient exposure or layer transfer. However, when covering the few-ML film by another material to form heterojunctions or metallic contacts, observation of the 2D film optical spectra becomes problematic. We will show that the optical spectra of a 1 ML MOCVD-grown WS2 can still be observed by measuring transient photocurrent spectra in a Si/SiO2/WS2 capacitor even upon evaporation of a relatively thick (10-20 nm) metal layer overlayer. The photoconductivity (PC) signal arises in this case due to separation of electron-hole pairs optically generated in WS2 with subsequent trapping and detrapping at the interface with the underlying oxide. Characteristic excitonic peaks (A, B, C) observed in the optical spectra are reproduced in the PC spectra taken from unmetallized (air-exposed) 1ML WS2 and after evaporation of a 15-nm thick Al overlayer indicating that the 2D film is not modified. By contrast, evaporation of 15-nm Au or Cu results in attenuation of the PC signal and almost complete disappearance of the A exciton peak. Similar observations have also been made on MoS2 films (1.5-3.5 ML thick) indicating the PC method to be a viable technique in assessing the processing-induced changes in the ML-thin semiconductor.

Authors : Hamidreza Esmaielpour*(1), Daniel Suchet(2), Laurent Lombez(1)(3), Amaury Delamarre(4), Soline Boyer-Richard(5), Alain Le Corre(5), Olivier Durand(5), and Jean-François Guillemoles(1)(3)
Affiliations : (1) Institut Photovoltaique d’Ile de France (IPVF), 18 boulevard Thomas Gobert, 91120 Palaiseau, France; (2) Ecole Polytechnique, Institut Photovoltaïque d’Ile-de-France UMR 9006, 18 boulevard Thomas Gobert, 91120 Palaiseau, France; (3) CNRS-Institut Photovoltaique d’Ile de France (IPVF), UMR 9006, 18 boulevard Thomas Gobert, 91120 Palaiseau, France; (4) Centre for Nanoscience and Nanotechnology (C2N), CNRS, University Paris-Sud/Paris-Saclay, 10 boulevard Thomas Gobert, 91120 Palaiseau, France; (5) Univ Rennes, INSA Rennes, CNRS, Institut FOTON – UMR 6082, Rennes, France

Resume : Hyperspectral luminescence imaging technique is an optical measurement, which can spatially and spectrally resolved photoluminescence (PL) spectrum emitted from semiconductors. This is a powerful technique to map the surface of semiconductors and to investigate electrical and optical properties of photo-generated carriers in the system. The information about emitting particles, such as temperature and quasi-Fermi level splitting, can be extracted via fitting their PL spectrum with the generalized Planck’s law. However, in nanostructure materials, such as quantum wells (QWs), the fitting analysis can be challenging, especially at high excitation powers when the influence of band filling and discrete energy levels are not negligible. Therefore, it is required a careful analysis of emitted PL spectra considering complexities imposed by quantum confinements in such structures. Here, we present our results in hyperspectral imaging of InGaAs quantum well (QW) structures and fitting their full PL spectra with the Generalized Planck’s law. We have extracted temperature and quasi-Fermi level splitting of photo-generated carriers at various lattice temperatures and excitation powers. Via this information we have determined the strength of hot carrier thermalization and Seebeck effects in the QW structures. Moreover, we will present our advancements in extraction of absorption coefficients and linewidth broadenings from multiple transitions in the samples.

Authors : Mailis Lounasvuori*, Tristan Petit
Affiliations : Helmholtz-Zentrum Berlin für Materialien und Energie, Institute for Nanospectroscopy, Albert-Einstein-Str. 15, 12489 Berlin, Germany

Resume : Here we present an electrochemical infrared microspectroscopy setup operated in attenuated total reflectance (ATR) mode using microstructured Si wafers [1, 2] as the internal reflection element (IRE). Electrochemical infrared microspectroscopy is a powerful tool for probing the electrode-solution interface with a micrometre spatial resolution. Most operando measurements of electrochemical systems are conducted in thin-layer cells with inherently high solution resistance [3, 4], an issue which is avoided by choosing the ATR mode. Si is compatible with standard photolithography techniques, allowing the deposition of thin film electrodes of different geometries on the flat surface of the wafer. We show that the low-cost microstructured Si wafers used here enable lateral mapping of the sample over hundreds of micrometres, paving way for this technique to be used to investigate electrochemical processes occurring on microelectrode arrays for example. A proof of concept of IR mapping performed on a patterned Au thin film deposited onto the Si wafer will be presented. Operando measurements at the Au thin film electrode in 0.1 M sulphuric acid electrolyte will also be demonstrated. [1] Schumacher et al., Appl. Spectrosc. 2010, 64, 1022−1027. [2] Morhart et al., Anal. Chem. 2017, 89, 11818-11824 [3] J.-T. Li et al., Electrochimica Acta 2007, 52, 5725–5732 [4] K. Tu et al., J. Phys. Chem. C 2016, 120, 23640−23647

Authors : Burkovsky, R. G.* (1), Lityagin, G. A. (1), Kniazeva, M. A (1), Gao, R. (2), Dasgupta, A. (2), Andronikova, D. A. (3).
Affiliations : (1) Peter the Great Saint-Petersburg Polytechnic University, Russia (2) University of California, Berkeley, USA (3) Ioffe Institute, Russia

Resume : Functionality of thin films often depends on phase transitions, which either occur during device operation or reside nearby in the space of thermodynamic variables, thereby maximizing the essential characteristics. Characterizing the critical dynamics, associated with the transition in films was always challenging, especially the dynamics of inhomogeneous order parameters, which are described by finite wavevectors and can be probed only by short-wavelength radiation scattering. Practically important example are antiferroelectric (AFE) films, where the transition is related to inhomogeneous (staggered) dipole arrangement. We report on the first measurements of critical diffuse scattering (DS) in PbZrO3 AFE epitaxial thin films. The sample heterostructures PbZrO3 (100 nm)/SrRuO3 (20 nm)/SrTiO3 were grown by pulsed laser deposition at UC Berkeley. The measurements were performed at ID03 beamline of the ESRF. Using grazing-incidence setup we were able recording the critical DS distributions in the large regions of the Brillouin zone and tracing the temperature dependence of the signal. The results rule out the possibility of first- to second-order change of the transition character, suggested by recent studies, and point out towards near-interface structural heterogeneity as the origin of observed differences in phase transition scenarios in the film and bulk forms.

Authors : Lipin Chen(1), Gabriel loget(2), Mahdi Alqahtani(3), Christophe Levallois(1), Antoine Létoublon(1), Julie Stervinou(1), Rozenn Piron(1), Soline Boyer-Richard(1), Laurent Pedesseau(1), Yoan Léger(1), Jean-Marc Jancu(1), Tony Rohel(1), Rozenn Bernard(1), Nicolas Bertru(1), Bruno Fabre(2), Jiang Wu(3), Ivan P. Parkin(4), Charles Cornet(1)
Affiliations : (1) Univ Rennes, INSA Rennes, CNRS, Institut FOTON – UMR 6082, F-35000 Rennes, France; (2) Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes)-UMR 6226, F-35000 Rennes, France; (3) Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom; (4) Department of Chemistry, University College London, London WC1H 0AJ, United Kingdom

Resume : Solar water splitting converting the solar energy into green hydrogen fuel is one significant milestone on the road to a sustainable energy future and has driven many researches in the past years [1]. III-V/Si tandem material combining the good optical properties of III-V semiconductor with the low cost of Si substrate is considered as one kind of promising material for efficient water splitting reactions [2-3]. In this work, we demonstrate a new photoelectrode material GaPSb/Si for solar water splitting. The band structure of GaPSb alloy are determined by combining experimental absorption measurements with tight binding (TB) theoretical calculations, which shows good bandgap and appropriate band alignment for water splitting. Besides, the PEC characterizations were made on GaPSb/Si sample, which show very good PEC performances. The GaPSb/Si tandem material is thus a potential candidate for low-cost high-efficiency solar water splitting. References: [1] A. J. Bard and M. A. Fox, “Artificial photosynthesis: solar splitting of water to hydrogen and oxygen”, Accounts of Chemical Research, 28(3), 1995. [2] I. Lucci et al., “A Stress-Free and Textured GaP Template on Silicon for Solar Water Splitting”, Advanced Functional Materials, 28(30):1801585, 2018. [3] M. Alqahtani et al., “Photoelectrochemical water oxidation of GaP(1− x)Sbx with a direct band gap of 1.65 eV for full spectrum solar energy harvesting”, Sustainable Energy & Fuels 3, 2019.

Poster Session Symposium Q : O.Durand, T.Kiwa
Authors : Naoufel Khemiri, D. Abdelkader, M. Kanzari
Affiliations : Université Tunis El Manar, Institut Préparatoire aux Etudes d’Ingénieurs El Manar, Campus Universitaire Farhat Hached, B.P 244, Tunis 2092, Tunisie. Université Tunis El Manar, Ecole Nationale d’Ingénieurs de Tunis, Laboratoire de Photovoltaïque et Matériaux Semi-conducteurs, B.P 37, 1002,Le Belvédère Tunis, Tunisie. Université de Tunis, IPEITunis Montfleury, Laboratoire de Photovoltaïques et Matériaux Semi-conducteurs-ENIT

Resume : Tin antimony sulfide Sn-Sb-S (TAS) thin films were deposited on glass and Si substrates using vacuum evaporation technique. Spectroscopic ellipsometry (SE) is a non-destructive method that we used to study the optical properties of the films. The SE measured data were analyzed by considering double layer optical model for all the samples, with the two Tauc-Lorentz oscillators and Gaussian dispersion relations. From the ellipsometric study, we extracted the thickness, absorption coefficient, band gap energy, refractive index and extinction coefficient of all samples. All the films exhibited high absorption coefficient a in the visible range (>105 cm-1). The values of the band gap energy Eg of Sn-Sb-S thin films deposited on glass varied from 1.13 to 1.48 eV. For the samples deposited on silicon, the band gap energy Eg varied from 1.44 to 1.72 eV. The spectral dependencies of the refractive index and the extinction coefficient of Sn-Sb-S thin films were determined and analyzed.

Authors : Zakaniaina Rajaofara1-2, Erwan Capitaine2, Philippe Leproux2, Hideaki Kano3, Philippe Thomas1 ,Tomokatsu Hayakawa4, E. Roginskii5-6, M. Smirnov5, Vincent Couderc2, Jean-René Duclère1,
Affiliations : 1: Institut de Recherche sur les Céramiques, UMR 7315 CNRS-Université de Limoges, Centre Européen de la Céramique, 12, rue Atlantis, 87068 Limoges Cedex, France ; 2: Institut XLIM, UMR 7252 CNRS – Université de Limoges, 123, Avenue Albert Thomas, 87060 Limoges Cedex, France ; 3: Department of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan ; 4: Field of Advanced Ceramics, Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Gokiso, Showa, Nagoya 466-8555, Japan ; 5: Faculty of Physics, St Petersburg State University, Petrodvoretz, 194508 St. Petersburg, Russia ; 6: Ioffe Institute, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia.

Resume : In this work, we report the extraction of the real part of the third order nonlinear optical susceptibility of a c-cut paratellurite (TeO2-α) single crystal using the detected intensity of the nonresonant background (NRB) in multiplex Coherent Anti-Stokes Raman Scattering (M-CARS) measurements. Using fused silica and SF57 as nonlinear reference materials, we particularly show that the pure electronic contribution of the third order nonlinear susceptibility can be obtained alone without significant impact of the vibrational response, provided some precautions in the selected frequency range. The results are then confronted with the data obtained by Duclère et al. from Z-scan experiments. The (a,b) in-plane modulation of the nonlinear refractive index of TeO2-α is finally evaluated.

Authors : Z. Labadi (a), Z. E. Horvath (a), Z. Zolnai (a), M. Fried (a,b)
Affiliations : (a) Institute of Technical Physics and Materials Science (MFA), Centre for Energy Research, P.O. Box 49, H-1525 Budapest, Hungary (b) Institute of Microelectronics and Technology, Óbuda University, Tavaszmezo u. 17, H-1084 Budapest, Hungary

Resume : Electrochromism is defined as the ability of a material to change its optical state in response to an applied DC voltage. Tungsten and Molybdenum oxides are widely studied for this application purpose, however little attention is paid for their mixed oxides. Thin films of Tungsten and Molybdenum mixed oxides were prepared by reactive DC magnetron sputtering using combinatorial technique (i.e. simultaneous sputtering from different targets). Samples were made with different composition as well as with different morphologies (i.e. superlattice type and amorphous mixed oxide type samples.) The deposited films were characterized by Spectroscopic Ellipsometry, SEM and TEM microscopy for morphology and amorphous content. Furthermore electrochromic coloration efficiency and response times were studied in electrolyte cells using propylene carbonate – lithium perchlorate electrolyte. Correlation between the sputtering parameters (oxygen pressure, power), layer morphology and electrochromic properties is studied for establishing enhanced composition-dependent electrochromic performance. Authors acknowledge the funding of Hungarian National Science Fund OTKA NN131269 and K129009

Authors : I. Stepanova, O. Petrova, G. Korolev, M. Guslistov, M. Zykova, I. Avetissov
Affiliations : D. Mendeleev University of Chemical Technology of Russia

Resume : The ferroelectric crystalline phase Bi2GeO5 has spontaneous polarization value comparable to BaTiO3 ceramics. To date, most researchers consider this phase to be metastable so it can be hardly synthesized by conventional crystal growth methods. We offer a new look at the phase formation in the Bi-Ge-O system, which considers Bi2GeO5 as an oxygen-deficient phase and makes it easy to synthesize from non-stoichiometric compositions. The Bi2GeO5 single phase has been successfully synthesized from Bi2O3-Bi-GeO2 batch when Bi oxide has been partially replaced by metallic Bi to form an oxygen deficiency. The crystallization was made both in solid phase and from melts at different temperatures. The structure of the formed crystal phases have been investigated by XRD. It was found that both the melt temperature rise and metallic Bi amount increase led to the formation of Bi2GeO5 single phase. The optimal initial batch compositions and crystallization conditions to produce a single Bi2GeO5 crystal phase has also been found. The research was supported by Russian Science Foundation by the grant 19-79-10003.

Authors : Yong Jun Kim,Yong-Hwan Cho, and Han-Ki Kim
Affiliations : School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Republic of Korea

Resume : We investigated the enhanced indium tin oxide(ITO)/Ag/Polytetrafluoroethylene(PTFE) tri-layer through the improved wettability between the oxide layer and metal layer by the oxygen plasma treatment. Using a successive multi-cathode magnetron sputtering system, the ITO/Ag/PTFE tri-layer electrode with the fixed thickness (50nm/9nm/40nm) was prepared on a colorless polyimide substrate. The oxygen plasma treatment was conducted with increasing treatment time at fixed power of 20 W. The structural and morphological properties of the oxide layer were analyzed by a contact angle, scanning electron microscopy(SEM), X-ray photoelectron spectroscopy, and atomic force microscopy. The improved wettability of oxide layer showed a lower pinhole size of the thin Ag layer on the oxide layer through the SEM analysis. As these result, the oxygen plasma treated ITO/Ag/PTFE tri-layer electrode had a higher optical transmittance of 87.4% at visible region wavelength(550nm) and lower sheet resistance of 13.5 Ohm/square than untreated ITO/Ag/PTFE due to oxygen plasma treatment effect.

Authors : Yong-Hwan Cho, Yong Jun Kim, and Han-Ki Kim*
Affiliations : School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066, Seobu-ro, Jangan-gu, Suwon-si, Gyeonggi-do, 16419, Republic of Korea

Resume : As an essential part of a transparent electrode for highly flexible electronic devices, Oxide/polymer composite and the sandwich structure transparent electrode of oxide-polymer hybrid/metal/hybrid(OPHMH) structure have been proposed. Amorphous oxide embedded in polytetrafluoroethylene(PTFE) was fabricated on flexible substrates using a continuous magnetron sputtering system with RF and DC simultaneously. Oxide/polymer composite layer showed that the higher the amount of PTFE in oxide/PTFE composite, the higher the water contact angle and flexibility. As part of our commitment to uniform deposition of the sandwich structure, plasma and ion beam pre-treatment effects were also investigated in order to control surface energy and wettability. This pre-treatment resulted in surface activation and hydrophilicity improvement of both oxide and polymer, and uniform thin film deposition was possible. Due to the stable structure of tri-layer interfaces, we could demonstrate that the OPHMH structure with a hydrophobic surface ensures high flexibility and optical properties in the visible wavelength region (400 ~ 800 nm), and low sheet resistance applicable to highly flexible electronic devices.

Authors : Laurent PEDESSEAU (1), Debdipto ACHARYA (1), Boubacar TRAORE (1), Mikael KEPENEKIAN (2), George VOLONAKIS (2), Jean-Christophe BLANCON (3), Sergei TRETIAK (4), Aditya MOHITE (3), Claudine KATAN (2), and Jacky EVEN (1)
Affiliations : (1) FOTON Institute – INSA Rennes, France; (2) ISCR, France; (3) Rice Univ., USA; (4) LANL, USA

Resume : FOTON Institute - INSA Rennes is part of the DROP-IT1 consortium. DROP-IT aims at combining optoelectronics and photonics in a single flexible drop-on demand inkjet technology platform by means of exploiting the potential of lead-free perovskite materials. A survey of lead-free perovskite materials performed by the perovskite team in Rennes will be presented based on the literature2,3. The simulation team has developed in addition density functional theory (DFT) simulations of perovskite lead free materials and a DFT methodology based on to extract band alignments and dielectric mismatch between perovskite materials and hole and electron transporting layers in thin film device architectures4,5. This project has received funding from the European Union’s Horizon 2020 research and innovation Programme under the grant agreement No 862656. The information and views set out in the abstracts and presentations are those of the authors and do not necessarily reflect the official opinion of the European Union. Neither the European Union institutions and bodies nor any person acting on their behalf may be held responsible for the use which may be made of the information contained herein. References: (1) DROPIT (accessed Jan 13, 2020). (2) Volonakis, G.; Filip, M. R.; Haghighirad, A. A.; Sakai, N.; Wenger, B.; Snaith, H. J.; Giustino, F. Lead-Free Halide Double Perovskites via Heterovalent Substitution of Noble Metals. J. Phys. Chem. Lett. 2016, 7 (7), 1254–1259. (3) Volonakis, G.; Haghighirad, A. A.; Milot, R. L.; Sio, W. H.; Filip, M. R.; Wenger, B.; Johnston, M. B.; Herz, L. M.; Snaith, H. J.; Giustino, F. Cs2InAgCl6: A New Lead-Free Halide Double Perovskite with Direct Band Gap. J. Phys. Chem. Lett. 2017, 8 (4), 772–778. (4) Traore, B.; Pedesseau, L.; Blancon, J.-C.; Tretiak, S.; Mohite, A. D.; Even, J.; Katan, C.; Kepenekian, M. Importance of Vacancies and Doping in Hole Transporting Nickel Oxide Interface with Halide Perovskites. ACS Appl. Mater. Interfaces 2020. (5) Canicoba, N. D.; Zagni, N.; Liu, F.; McCuistian, G.; Fernando, K.; Bellezza, H.; Traoré, B.; Rogel, R.; Tsai, H.; Le Brizoual, L.; et al. Halide Perovskite High-k Field Effect Transistors with Dynamically Reconfigurable Ambipolarity. ACS Materials Lett. 2019, 1 (6), 633–640.

Authors : Jaeyong Kim, Harim Oh, Minseok Seo, Junho Lee, Gijoon Bae, Chanhee Kim, and Myeongkyu Lee
Affiliations : Department of Materials Science and Engineering Yonsei University of Korea

Resume : Broadband light absorbers are highly desirable in numerous applications including solar-energy harvesting, thermo-photovoltaics, sensing and imaging, photodetectors, and thermal emitters. Metal-insulator-metal (MIM) layers has attracted enormous interest as a lithography-free and scalable structure for realizing planar super absorbers. However, typical MIM cavity exhibits a narrow absorption band, and efforts have thus been made to increase the absorption bandwidth. This study demonstrates that near-perfect absorption over a broad spectral range can be obtained from the MIM structure by using thermally evaporated Ag and Au thin films. A 55-nm-thick SiO2 spacer sandwiched between a 10-nm Ag top layer and a 100-nm Al back reflector exhibits absorption > 95% in the visible range of 400-700 nm. The broad absorption band shifts to a near-infrared range of 650-1000 nm by replacing the top layer with a 10-nm-thick Au film and increasing the SiO2 spacer thickness to 115 nm. The experimental results are supported by finite-difference time-domain (FDTD) simulation. The large absorption bandwidth is attributed to the lossy nature of the top metallic layer combined with the resonant absorption of the MIM cavity.

Authors : Louise P. Ryan, Melissa M. McCarthy, Shane O’Brien, Mircea Modreanu, Ian M. Povey
Affiliations : Tyndall National Institute, University College Cork, Cork, Ireland

Resume : Organometallic halide perovskite solar cells have gained considerable interest in recent times due to their rapidly improving power conversion efficiencies. However, as with all technology the cost of ownership is key to its take up and viability, thus despite perovskite solar cells approaching the Shockley Queisser efficiency limit for a single junction device it cannot compete with established silicon technology. As a consequence, perovskite technology is shifting towards multi-junction solar cells where differing absorber layers respond to different spectral regions and hence negate this limitation. Such a development does come with complications, one issue is the standard transparent conducting oxide (TCO) currently employed is indium-tin oxide (ITO). Although ITO has ideal electrical and optical properties the material is deposited using sputtering methods and high temperatures (>400oC) heat treatments. Such a fabrication methodology is not compatible with thermal budget restrictions necessary to fabricate heterojunction devices, as a result an alternative material or methodology is required. Here we examine atomic layer deposition, an industry compatible large area low temperature growth technique, to grow ZnO and its doped variants as TCO layers. The materials properties were characterised and optimised. Finally, perovskite solar cells were fabricated in a P-I-N configuration and compared to the current state of the art devices.

Authors : Andreea Costas, Camelia Florica, Nicoleta Preda, Nicoleta Apostol, Andrei Kuncser, Andrei Nitescu, Mihaela Beregoi, Cristina Popa, Gabriel Socol, Victor Diculescu and Ionut Enculescu
Affiliations : 1 National Institute of Material Physics, 405A Atomistilor, 077125, Magurele, Romania 2 National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, 077125, Magurele, Romania

Resume : Metal oxide nanowires have focused the interest of the scientific community due to their potential applications in fields such as photocatalysis, photodetectors, sensors, nanoscale electronics, etc. In the last years, great effort was made towards the preparation of metal oxide core-shell nanowire arrays with advanced functionalities provided by the radial heterojunction formed between the two metal oxides. Zinc oxide is a n-type semiconductor with a wide band gap, whereas copper oxide is a p-type metal oxide semiconductor with a narrow indirect band gap. By aligning these two metal oxide into a core-shell heterostructure, a p-n staggered gap heterojunction is achieved between the two semiconductors promoting a good control of the charge carrier generation at the interface. Thus, ZnO-CuO core-shell nanowire arrays were synthesized using two dry methods, thermal oxidation in air and magnetron sputtering. Morphological, structural, optical, compositional, surface chemistry, electrical and photocatalitycal properties of the ZnO-CuO nanowire arrays were investigated. An optimum copper oxide shell thickness was found for which the degradation of methylene blue under UV illumination was improved due to the heterojunction formed between the ZnO and CuO. Also, single ZnO-CuO core-shell nanowires were contacted using lithographic and thin film deposition techniques for applications in UV photodetectors.

Authors : Alina Cismaru*, Martino Aldrigo, Sergiu Iordanescu, Mircea Dragoman, Catalin Parvulescu
Affiliations : National Institute for Research and Development in Microtechnologies (IMT), Erou Iancu Nicolae Street 126A, 077190, Voluntari (Ilfov), Romania.

Resume : In this paper, a simple and efficient approach is presented for the design in CST of a 10 GHz metamaterial based resonator used for high sensitive chemical sensor. The sensor was designed and fabricated as CPW line deposited on front side of high-resistivity Si/SiO2 substrate by incorporating four metamaterial Split Ring Resonator (SRR) on back side and covered in the center area with a thin film sensing MoS2 material. The simulation results demonstrate a very good quality factor of about 2000 for the MoS2 based metamaterial resonator being very useful for sensing applications. The proposed configuration is applied for chemical discrimination as NO2 gas sensing. A thin-film of MoS2 was deposited on the resonator using a pristine MoS2 nanoflake solution supplied by Graphene Supermaket. The response of the sensor have been study by passing different concentrations of NO2 gas through the gas chamber. The S-parameters have been measured as a function of frequency using a Vector Network Analyzer (VNA) for the MoS2 based resonator in air (without gas flow inside the chamber) and with gas flow into the chamber at different concentrations. In the literature was demonstrated that upon NO2 adsorption, the MoS2 based sensor resistance decreases. The change of the MoS2 based sensor resistance for different NO2 gas concentrations demonstrates a frequency of resonance shift of about 100 MHz resulting in a high sensitivity NO2 gas sensor. Acknoledgements; We are grateful for financial support of H2020 project NANOPOLY

Authors : Minseok Seo, Harim Oh, Jaeyong Kim, Joonho Lee, Kijun Bae, Chanhee Kim Myeongkyu Lee
Affiliations : Yonsei Univerisity

Resume : The mechanochromic active device can measure stress or strain exerted by human body and exhibit visual warning signs when they are highly stressed or strained. These characteristic make the device be readily exploited for the applications where real-time interactivity is more required than unilateral information delivery, such as sports industry or medical application. Most of the mechanochromic researches are focusing on photonic crystal structure because the period of the photonic crystal can be easily changed by the tension and photonic crystal can show vivid color. However, photonic crystal is difficult to make uniform color distribution on large area and has highly angle-dependence property. Instead of photonic crystal structure, we fabricate the stretchable metal-insulator-metal planar cavity structure by using PDMS as substrate and insulator. Depending on the strain, the thickness of PDMS insulator layer is decreased and the MIM cavity resonance peak can be easily shifted. Also,compared with photonic crystal structure, this device has low angle-dependence property because the thickness of PDMS insulator layer is very thin. Consequently, we make mechanochromic active device using MIM planar cavity structure and tested on the human body for real-time interactivity application.

Authors : N.Kornienko , A.Naumenko, V.Gubanov, L.Kulikov, O.Kolomys
Affiliations : Taras Shevchenko National University of Kyiv, 64/13 Volodymyrs’ka Str., 01601, Kyiv, Ukraine; Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, 3, Krzhizhanovsky Str., 03142, Kyiv, Ukraine; V.E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine, 41 pr. Nauki, 03028, Kyiv, Ukraine

Resume : Our research is based on two major scientific and technical problems: 1) the use of unique physicochemical properties of two-dimensional (2D) structures of graphene, BN and transition metals dichalcogenides of (TMD) MeX2, where Me - metals of IV, V and VI groups (Ti- Hf, V-Ta, Mo, W), and X = S, Se, Te, as well as 2) enhancing their capabilities during intercalation by impurity atoms and molecules. The results of a detailed study of the Raman spectra of natural MoS2 microcrystal (MC) powder and synthesized graphene-like 2H-MoS2 nanoparticles (NP) with additives 0.5 and 1 wt% of carbon excited by 488 nm and 632.8 nm laser radiation are highlighted here. A detailed numerical analysis of the shape of the observed D and G Raman bands, including their decomposition into spectral components, as well as comparison with the reference spectra of the detonation nanodiamonds of ~ 5 nm, is carried out. This revealed the formation of graphite and diamond-like nanostructures in MoS2 NC and their existence in molybdenite MC. Significant effect of 632.8 nm laser radiation that is in resonance with 2H-MoS2 excitons on synthesis and ordering of diamond and graphite-like structures was established for the first time

Authors : V. Ion1, N.D. Scarisoneanu1, N. Enea1, F. Craciun2, R. Birjega1 and M. Dinescu1
Affiliations : 1 National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor St, Magurele, Romania 2 CNR-ISC, Istituto Dei Sistemi Complessi, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy

Resume : The properties of BCT-BZT system can be controlled by varying the Ba/Ca and Zr/Ti ratios, the amount of (Ca2+) in A-site and (Ti4+) in B-site being the key of tuning different functionalities of these materials. The phase diagram of (x(Ba0.7Ca0.3TiO3)-(1 − x)(BaZr0.2Ti0.8O3) system exhibit a morphotropic phase boundary (MPB) point in which the tetragonal and rhombohedral ferroelectric phases meet the paraelectric cubic phase. The structural phase diagram of BCTZ as a function of temperature is still under debate, the existence of an additional orthorhombic phase between rhombohedral and tetragonal ones being notices in some studies, but can be summarized as follows: for x ≤ 0.3 and x>0.8 a single phase transition is observed from R-phase to the high-temperature prototype cubic Pm3m structure (x ≤ 0.3) and from T to the C-phase for x>0.8. Between those limits, a multiple phase transitions through a R-T-C phase has been observed. In the present work we report the experimental values of transition temperature between R-T-C phases for the epitaxial thin films of BCTZ with x=0.45, 0.50, 0.55, obtained by spectrometric ellipsometry technique. Epitaxial thin films of (x(Ba0.7Ca0.3TiO3)-(1 − x)(BaZr0.2Ti0.8O3) were growth on SrTiO3, GdScO3 substrates by Pulsed Laser Deposition method. The structural properties of thin films were investigated by X -ray diffraction.The optical properties of BCTZ have been investigated in the 25-1000 C range of temperature.

Authors : Andrii A. Voznyi, Hervé Roussel, Odette Chaix-Pluchery, Anikin Mikhail and Jean-Luc Deschanvres
Affiliations : Institute of Engineering, Univ. Grenoble Alpes, CNRS, Grenoble, INP LMGP, F-38000 Grenoble, France

Resume : VO2 polymorphs, such as VO2(B) and VO2(M), have a broad range of application in informational technology. The former is promising for lithium-ion batteries, while the later showed promise in ultrafast optical switchers and smart windows, mainly due to the reversible metal-insulator transition phenomena. In our work, we investigate the thermally-induced phase recrystallization from VO2(B) to VO2(M) by thermal vacuum annealing of initial VO2(B) thin films obtained by aerosol assisted CVD. According to the annealing conditions (temperature, time) highly textured and homogeneous VO2(M) layers with sharp and reversible metal-insulator phase transition (resistance ratio ΔR = (R30 °C – R90 °C)/R90 °C of around 10^4) were obtained. Phase recrystallization was confirmed by X-Ray diffraction (XRD), Raman spectroscopy (RS) and electrical measurements. In-situ XRD and in-situ RS measurements are deployed to study the phase transformation mechanism in vanadium dioxide system.

Authors : Y. Hoshi 1, S. Hayashida 1, K. Watanabe 2, T. Taniguchi 2, and K. Sawano 1
Affiliations : 1 Tokyo City University, 2 National Institute for Materials Science

Resume : A semiconducting molybdenum ditelluride (MoTe2) monolayer, which is atomically-thin layered materials, has been attracting considerable attentions for development of various opto-electronic devices since it has a direct bandgap around 1.1 eV applicable to optical communications and exhibits an extraordinarily large exciton binding energy of several hundred meV owing to strong electron-hole confinement. However, the MoTe2 crystal has a critical disadvantage of formation of the surface decomposition-induced cluster defects and Te vacancies during thermal treatment even at low temperature of 200 ̊C. On the other hands, atomically-thin layered materials encapsulated by hexagonal boron nitride (hBN) are considered promising structures for enhancement of electrical and optical device performances. In this study, we investigated effects of thermal treatment on the crystal quality in the mechanically-exfoliated MoTe2 monolayer encapsulated by hBN using steady-state photoluminescence measurements, demonstrating suppression of desorption of Mo and Te atoms owing to existence of hBN capping layer. It was furthermore found that residues remained at the interfaces between hBN and MoTe2 for the as-fabricated samples, and the thermal treatment was effective for removal of the residues at the interfaces. These results indicate that combination of hBN encapsulation and thermal treatment is promising for realization of high-performance MoTe2-based opto-electronic devices.

Authors : Sung-Hoon Hong; Byoungsu Ko
Affiliations : Electronics and Telecommunications Research Institute (ETRI), Republic of Korea

Resume : Metamaterials is the artificially engineered materials which can tailor the properties depend on its structures. Recently, it has been greatly attractive for anticounterfeit applications due to its unique properties. In this study, we present metamaterial based broadband perfect absorbers in NIR wavelength for multiple, broadband NIR absorber fabrication. The NIR perfect absorbers were fabricated with high lossy metals. The it shows the complex, multiple absorption properties in NIR wavelength, and it can be tailored by the kind of materials, thickness, and nanostructures of perfect absorbers. The nanostructures of metamaterials were fabricated by nanoimprinting process on flexible substrate for industrial applications.

Authors : Wansleben,M.(1), Zech,C.(2), Streeck, C.*(2), Weser,J.(2), Genzel,C. (1), Beckhoff, B.(2) & Mainz,R.(1)
Affiliations : (1) HZB, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany (2) PTB, Physikalisch-Technische Bundesanstalt, X-ray Spectrometry, Germany

Resume : Liquid-metal jet X-ray sources promise to deliver high photon fluxes, which are unprecedented for laboratory based X-ray sources, because the regenerating liquid-metal anode is less sensitive to damage caused by an increased electron beam power density. For some quantitative X-ray analysis techniques, knowledge of the absolute photon flux is needed. However, a precise experimental determination of the photon flux of high-performance X-ray sources is challenging, because a direct measurement results in significant dead time losses in the detector or could even harm the detector. Indirect determinations rely on data base values of attenuation or scattering cross sections leading to large uncertainties. In this study we present an experimental determination of the photon flux of a liquid-metal jet X-ray source by means of elastic and inelastic photon scattering. Our approach allows for referencing the unpolarised output radiation of the liquid-metal jet X-ray source to polarized synchrotron radiation in a simple setup. Absolute photon fluxes per solid angle are presented with a detailed uncertainty budget for the characteristic emission lines of Ga Ka and In Ka for two different acceleration voltages of the X-ray source. (DOI: 10.1039/c9ja00127a)

Authors : Abdelkrim FEDALA, Ines LACHEBI, Mohamed KECHOUANE
Affiliations : USTHB, Faculté de Physique, Laboratoire de physique des matériaux, Equipe Couches Minces et Semiconducteurs, B.P. 32, El Alia, 16111 Bab-ezzouar, Algers, ALGERIA

Resume : The aluminum nanoparticles (Al-NPs) are obtained by thermal evaporation on heated substrates at 500°C. The mean diameter of Al-NPs is controlled by the evaporated aluminum amount. The equivalent film thickness is varied from 4 to 20 nm. The used substrates are Quartz glass and crystalline silicon wafer oriented (100). For the characterization we used the Scanning Electron Microscopy to define the morphological properties and the optical transmission technique to define optical absorbance spectral. The Al-NPs diameter distribution reveals two kinds of population types : small and thick ones. For the aluminum evaporated amount with an equivalent film thickness less than 8 nm only the small population has been observed with a mean diameter around 20nm. The optical absorbance spectrum reveals a band absorption due to the Localized Surface Plasmon Resonance. The LSPR absorption band is closely linked to the nanoparticle's morphological properties. The position of the LSPR band varied from 274 to 355 cm-1.

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Q.VII. Advanced nanoscale characterisation of material and devices II : O.Durand, T.Kiwa
Authors : Shimizu, T.*(1,2), Mimura, T.(2), Tashiro,Y.(2), Sakata O.(1), & Funakubo H.(2)
Affiliations : (1)National Institute for Materials Science, Japan (2)Tokyo Institute of Technology, Japan

Resume : The HfO2-based ferroelectric materials have gathered much attention due to their excellent compatibility with state-of-the-art semiconductor technology because the HfO2-based materials are employed as alternate gate dielectrics for field-effect transistors. The ferroelectricity in HfO2 is considered to originate from the metastable orthorhombic structure. On the other hand, it has been scarcely reported that the ferroelectric phase transition of HfO2 ferroelectric materials because most polycrystalline HfO2-based ferroelectric film transforms into the most stable monoclinic phase upon heating. We have developed the epitaxial film of HfO2 ferroelectric materials by substituting Y and investigated the fundamental properties of the materials. In this study, we investigate the phase transition of HfO2-based ferroelectric materials with epitaxial film by means of X-ray diffraction including synchrotron X-ray source. In addition, we also study the phase formation of the orthorhombic ferroelectric phase in epitaxial film. As a result, the tetragonal phase stabilized at high temperature transition to the orthorhombic phase during the cooling process.

Authors : Shintaro Yasui1, Sou Yasuhara1, Takashi Teranishi2, Osami Sakata3 and Mitsuru Itoh1
Affiliations : 1Tokyo Institute of Technology; 2Okayama University; 3NIMS/SPring-8

Resume : Li ion battery is one of suitable energy storage in our life, such as mobile electronic devices and electric vehicles. For delightful and convenient existence, high speed charging and long battery life are very important. Charging time of smart phone is too long, which is about 5 hours for full-charge from empty state. Generally, 0.2C is used for charging current, otherwise battery capacity is reduced under higher C-rate (higher charging speed). This is because SEI layer, which is decomposed materials of electrolyte, LiF and organic solvent etc., is deposited on active cathode and anode materials. In this paper, we have achieved to obtain the ultrahigh speed charging and very tough cycling properties in LiCoO2 cathode thin film battery decorated with ferroelectric BaTiO3.[1] The important point is the blocking of creating SEI on cathode surface. In details, we have investigated interface reaction between cathode and electrolyte using epitaxial thin film battery. We have tried to insert artificial SEI of high dielectric constant materials, BaTiO3, on the cathode LiCoO2 epitaxial thin film. The high rate performance and cyclability are enhanced by existence of triple phase interface, cathode LiCoO2 – electrolyte LiPF6 (EC:DEC)– dot BaTiO3. The key point of this effect is that high dielectric constant material is better. [1] S. Yasuhara, S. Yasui et al., Nano Lett. 19 (2019)1688.

Authors : C. Ossig, C. Strelow, A. Schropp, J. Garrevoet, G. Falkenberg, E. Avancini, R. Carron, A. N. Tiwari, C. G. Schroer, A. Mews, T. Kipp, M. E. Stuckelberger
Affiliations : Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany and University of Hamburg, Hamburg, Germany; University of Hamburg, Hamburg, Germany; Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany; Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany; Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany; Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland; Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland; Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland; Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany and University of Hamburg, Hamburg, Germany; University of Hamburg, Hamburg, Germany; University of Hamburg, Hamburg, Germany; Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany

Resume : Polycrystalline thin film solar cells suffer from a laterally inhomogeneous grain structure, which may cause spatial variations of their electronic properties. For an improvement of the conversion efficiency, a better understanding of the limiting defects at sub-grain-size resolution is required. Therefore, we seek to correlate the electrical properties with the structure, composition, and deposition conditions. While measurement methods such as laser- or electron-beam induced current offer spatially resolved electrical information, they are not compatible with simultaneous non-destructive and high-sensitivity measurements of the composition and structure. Synchrotron-based multi-modal measurements using scanning X-ray microscopy enable the simultaneous measurement of several relevant aspects: with a spatial resolution on the nanoscale, hard X-ray ptychography maps the structure; X-ray fluorescence (XRF) gives insight into the elemental composition; and X-ray beam induced current (XBIC) and X-ray excited optical luminescence (XEOL) test the electrical and optical properties. For the first time, we have combined all these modalities in simultaneous measurements of a Cu(In,Ga)Se2 solar cell. Hence, we have been able to perform a point-by-point correlation of the electrical and optical solar cell performance with the structure and composition. In this contribution, we will report on these correlations with a focus on grain boundaries and voids in Cu(In,Ga)Se2.

Authors : Zakaniaina Rajaofara, Philippe Leproux, Marc Dussauze, Vincent Rodriguez, Lara Karam, Jean-René Duclère, and Vincent Couderc
Affiliations : IRCER – University of Limoges ; XLIM – University of Limoges ; ISM – University of Bordeaux ; ISM – University of Bordeaux ; ISM – University of Bordeaux ; IRCER – University of Limoges ; XLIM – University of Limoges

Resume : We demonstrate, for the first time to our knowledge, a correlative 2D mapping of the second and third order nonlinear susceptibilities of a thermally poled borophosphate niobium glass. The experiment is conducted by means of ultrabroadband multiplex coherent anti-Stokes scattering (M-CARS) setup. By means of the latter, we already reported previously the measurement of the third order susceptibility of a paratellurite single crystal. This work represents a step further in regards to this previous work, by extending it to a fast and large scale imaging technique of the second and third order susceptibilities of a microstructured niobium borophosphate glass on which a thermal poling process was conducted. Thermal poling process consisted of the application of a static electric field in a micrometer scale under an eleveted temperature using microstructured anode electrodes. The nonlinear imaging results highlight a second harmonic generation and a decrease of the third order nonlinear susceptibility in the areas of the glass where a static electric field is written and where a density change occurs. These results are in total agreement with Marc Dussauze et al. previous works on the very exact same sample. This allows us to conclude that M-CARS is a suitable technique for a fast investigation of the third order nonlinearity of glasses and is also compatible with the second harmonic imaging process without any significant change in the setup. That bimodal investigation is useful in the field of material science for samples with complex structures.

Authors : Laurent PEDESSEAU (1), Tal BINYAMIN (2), Sergei REMENNIK (2), Amal SAWAHREH (2), Lioz ETGAR (2) and Jacky EVEN (1)
Affiliations : (1) FOTON Institute – INSA Rennes, France; (2) The Hebrew University of Jerusalem, Israel

Resume : Nowadays, mixed cation perovskites1,2 are one of the most efficient light harvesters in perovskite solar cells. The mixed cation perovskites are used mainly in their “bulk” form in the solar cell. However, confined perovskite nanostructures have been recently synthesized and seemed to be a promising route to efficient optoelectronic devices, taking advantage of the superior bulk properties of metal lead halide perovskite as well as the nanoscale properties. Recently, mixing two inorganic cations in the same Nanoparticles (NPs) was reported3,4. Indeed, Rb was incorporated into Cs-based NPs, forming all inorganic mixed cation perovskite NPs. A detailed structural study of mixed inorganic cation lead halide perovskite NPs at the atomic level is presented. We focused our investigations on mixed cation perovskite NPs having an RbxCs(1−x)PbBr3 composition5 (with x = 0, 0.2, 0.4, 0.6, and 0.8). A High-angle annular dark-field (HAADF) detector was used to obtain NPs imaging with atomic resolution. Density Functional Theory (DFT) calculations help understanding the role of Rb atoms into the stability of such NPs at various Rb concentrations. This work was supported within the framework of the Israeli−French scientific cooperation (Joint Research Projects 2019−2021 entitled ALLPOA (From Atomic Level to Layered Perovskite for Optoelectronic Applications)) by the Ministry of Science & Technology of the State of Israel (MOST) and France’s Centre National de la Recherche Scientifique (CNRS). References: (1) Saliba, M.; Matsui, T.; Domanski, K.; Seo, J.-Y.; Ummadisingu, A.; Zakeeruddin, S. M.; Correa-Baena, J.-P.; Tress, W. R.; Abate, A.; Hagfeldt, A.; et al. Incorporation of Rubidium Cations into Perovskite Solar Cells Improves Photovoltaic Performance. Science 2016, 354 (6309), 206–209. (2) Yi, C.; Luo, J.; Meloni, S.; Boziki, A.; Ashari-Astani, N.; Grätzel, C.; Zakeeruddin, S. M.; Röthlisberger, U.; Grätzel, M. Entropic Stabilization of Mixed A-Cation ABX3 Metal Halide Perovskites for High Performance Perovskite Solar Cells. Energy Environ. Sci. 2016, 9 (2), 656–662. (3) Amgar, D.; Binyamin, T.; Uvarov, V.; Etgar, L. Near Ultra-Violet to Mid-Visible Band Gap Tuning of Mixed Cation RbxCs1−xPbX3 (X = Cl or Br) Perovskite Nanoparticles. Nanoscale 2018, 10 (13), 6060–6068. (4) Baek, S.; Kim, S.; Noh, J. Y.; Heo, J. H.; Im, S. H.; Hong, K.-H.; Kim, S.-W. Development of Mixed-Cation CsxRb1–XPbX3 Perovskite Quantum Dots and Their Full-Color Film with High Stability and Wide Color Gamut. Advanced Optical Materials 2018, 6 (15), 1800295. (5) Binyamin, T.; Pedesseau, L.; Remennik, S.; Sawahreh, A.; Even, J.; Etgar, L. Fully Inorganic Mixed Cation Lead Halide Perovskite Nanoparticles: A Study at the Atomic Level. Chem. Mater. 2019.

Authors : Cosmin Romanitan [1,2], Irina Bratosin [1,2], Dana Culita [3], Eugenia Tanasa [1,4], Simona Somacescu [3]
Affiliations : [1] National Institute for Research and Development in Microtechnology (IMT-Bucharest), 126A Erou Iancu Nicolae Street, 077190, Voluntari, Romania. [2] Faculty of Physics, University of Bucharest, 405 Atomistilor Street, 077125, Magurele, Romania. [3] Ilie Murgulescu’ Institute of Physical Chemistry, Romanian Academy, 202, Splaiul Independentei, Bucharest, 060021, Romania. [4] 3Faculty of Applied Sciences, Politehnica University of Bucharest, 313 Splaiul Independentei, Bucharest, 060042, Romania.

Resume : The microstructural parameters of electrode materials strongly influence the storage mechanisms and, besides, the overall performances of supercapacitors. Furthermore, the internal strain governs the stability during the long term cycling, and the strain engineering approach is lately a valuable method for development of energy storage electrodes. In this context, non-destructive characterization by X-ray based methods represents a necessity for both understanding the storage mechanisms and further progresses in this field. Starting from porous silicon substrate with high internal area obtained at different current densities and etching times, nanocomposite materials were fabricated through a polymer electrochemical deposition followed by thermal treatment partial carbonization, obtaining finally interconnected graphene-silicon nanofibrils networks. Analyzing the shape and of width of the diffuse scattering were obtained information regarding the pore morphology. Thus, it was found that the diffuse scattering is broadened after graphitization and consequently the decreasing of the crystallite sizes is connected with increasing of the internal strain, leading to an inherent emergence of grain boundaries in the PS lattice. Testing the new electrodes in a standard PVA-H 2 SO 4 electrolyte we observed a significant improvement of the specific capacitance after polymerization, accompanied by slight improvement of capacity retention, probably given by the increased lattice value.

Authors : Bi-Hsuan Lin1*, Yu-Hao Wu1, Chien-Yu Lee1, Bo-Yi Chen1, Gung-Chian Yin1, Shao-Chin Tseng1, Shih-Hung Chang1, Mau-Tsu Tang1
Affiliations : 1National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan

Resume : X-ray excited optical luminescence (XEOL) and Time-resolved XEOL (TR-XEOL) have been developed successfully for the 23A X-ray nanoprobe beamline located at the Taiwan Photon Source (TPS). The advantages of the TR-XEOL include not only a nano-focused X-ray beam (<60 nm) with excellent spatial resolution, but also a streak camera that can simultaneously record the light-emitting spectrum and decay lifetime. Especially, the operating TR-XEOL in the hybrid bunch mode also can provide a high enough X-ray photon flux because the electron beam current reaches 500 mA and long time span (30 ps ~ 220 ns) can facilitate temporal domain measurements. Using XEOL and TR-XEOL to study optical properties of the light-emitting materials, such as MgZnO/ZnO MQWs, InGaN/GaN MQWs, and perovskite CsPbBr3, will be reported.

Authors : Minchao Qin, Kinfai Tse, Tsz-Ki Lau, Yuhao Li, Chun-Jen Su, Guang Yang, Jiehuan Chen, Junyi Zhu, U-Ser Jeng, Gang Li, Hongzheng Chen, and Xinhui Lu*
Affiliations : The Chinese University of Hong Kong; National Synchrotron Radiation Research Center; The Hong Kong Polytechnic University; Zhejiang University

Resume : Mixed perovskites have achieved substantial successes in boosting solar cell efficiency, but the complicated perovskite crystal formation pathway remains mysterious. In our work, the detailed crystallization process of mixed perovskites (FA0.83MA0.17Pb(I0.83Br0.17)3) during spin-coating is revealed by synchrotron-based in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements, and three phase-formation stages are identified: I) precursor solution; II) hexagonal δ-phase (2H); and III) complex phases including hexagonal polytypes (4H, 6H), MAI–PbI2–DMSO intermediate phases, and perovskite α-phase. The correlated device performance and ex situ characterizations suggest the existence of an “annealing window” covering the duration of stage II. The spin-coated film should be annealed within the annealing window to avoid the formation of hexagonal polytypes during the perovskite crystallization process, thus achieving a good device performance. Remarkably, the crystallization pathway can be manipulated by incorporating Cs+ ions in mixed perovskites. Combined with density functional theory calculations, the perovskite system with sufficient Cs+ will bypass the formation of secondary phases in stage III by promoting the formation of α-phase both kinetically and thermodynamically, thereby significantly extending the annealing window. This study provides underlying reasons of the time sensitivity of fabricating mixed-perovskite devices and insightful guidelines for manipulating the perovskite crystallization pathways toward higher performance.

12:30 Lunch break    
Q.IX. Current trends in Raman spectroscopy : J.Even, G.E. JELLISON
Authors : Agnès Tempez, Ophélie Lancry, Andrey Krayev and Marc Chaigneau
Affiliations : HORIBA Scientific

Resume : 2D transition metal dichalcogenides (TMDCs) materials are considered of very high potential semiconductors for future nanosized electronic and optoelectronic devices. An information-rich nanoscale characterization technique is required to qualify these materials and assist in the deployment of 2D material-based applications. Scanning Probe Microscopy (SPM) is a powerful technique to image physical properties of 2D materials, such as topography, conductivity or other electrical properties. Combining SPM and Raman in a single instrumentation is extremely powerful as it makes imaging of both chemical and physical properties possible. As Raman is diffraction limited, only plasmon enhanced Raman and photoluminescence spectroscopies yield correlated electrical and chemical information down to the nanoscale. In this talk, we will report on Tip-Enhanced Photoluminescence (TEPL) and Tip-Enhanced Raman spectroscopy (TERS) data obtained on single crystal WS2 and WSe2 flakes directly grown on SiO2/Si. TEPL and TERS images will be correlated with contact potential difference and capacitance maps as results of Kelvin force probe microscopy acquisition. In addition, we will show the sensitivity of electronic properties (related to Fermi level and charge accumulation) upon light illumination. Beside these semiconductor/dielectric (SiO2) interfaces, probing TMCD/metal interfaces is also essential to integrate TMCDs in 2D or 3D complex structures of devices. We will show results from WS2 on silver and WSe2 and MoS2 on gold. Such transferred surfaces exhibit nanoscale inhomogeneities observed in correlated CPD and Raman maps. Finally, TEPL together with AFM topography data on a lateral single layer WS2/WSxSe1-x/WSe2 heterostructure grown on SiO2/Si will be presented: nanoscale PL response variations are observed beyond the smooth nano-resolution topography.

Authors : Jayeong Kim, Seokhyun Yoon; Tomke E. Glier, Benjamin Grimm-Lebsanft, Sören Buchenau, Melissa Teubner, Florian Biebl, Michael Rübhausen; Nam-Jung Kim, Heehun Kim, Dongha Yoo, Gyu-Chul Yi
Affiliations : Department of Physics, Ewha Womans University, Seoul, Korea; Institut für Nanostrukturforschung, Center for Free Electron Laser Science (CFEL), Universität Hamburg, Germany; Department of Physics and Astronomy, Institute of Applied Physics, and Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul, Korea

Resume : Raman spectroscopy is an effective tool to study many properties without damaging the material. In general, the Raman signal is very small, and one of the methods to amplify the signal intensity is surface enhanced Raman scattering (SERS). SERS is a good amplification technique that enables single molecule detection, so much research has been done for decades. However, the chemical enhancement mechanism, which is one of the two enhancing mechanisms of SERS, is not completely understood. Since there is a limit to the signal enhancement by using electromagnetic enhancement only, the research of chemical enhancement mechanism can provide further clues to enhance the signal. In this study, we present results of chemical enhancement due to charge transfer transition to an excitonic state. First, we investigated the chemical contribution of the SERS effect of 4-mercaptopyridine (4-Mpy) molecules deposited on zinc oxide nanostructure substrates by resonance Raman scattering. The excitation energy is given from 1.7eV to 5.7eV, which covers all possible resonance contributions between the molecules and the substrate. We observed that the Raman intensities of 4-Mpy peaks at 5.14 eV in the UV region is about 20 times larger than that in the visible region. We contend that one of the reasons for the large amplification in this UV region is a charge transfer transition to the excitonic state and provide evidence of it. Furthermore, the comparison with GaN substrates without excitonic state at room temperature ensures the effect of the excitonic state on chemical SERS. Our results provide information regarding the role of charge transfer transition from the molecule HOMO to the excitonic state in SERS that can lead controllable enhancement of Raman signal.

Authors : Eunji Ko, Jayeong Kim, Yukyung Shin, Myunghwa Kim, Seokhyun Yoon*
Affiliations : Department of Physics, Ewha Womans University, Seoul, 03760, Korea; Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Korea

Resume : There have been large number of theoretical and experimental studies of surface-enhanced Raman spectroscopy (SERS) over the last few decades. Unlike electromagnetic enhancement by surface plasmon resonance when using metallic substrate, chemical enhancement is responsible for selective enhancement of Raman response of different analyte molecules adsorbed on the same substrate materials. In this study, we use non-metallic substrates to clarify less studied effect of chemical enhancement in SERS. Rhodamine 6G (R6G) molecules are adsorbed on different structures of tungsten disulfide such as plane, flake and nanoflower. We estimate both electromagnetic enhancement by structure and chemical enhancement of R6G, by comparing finite-difference time-domain (FDTD) calculations to our Raman experimental results. We then discuss the contribution of both enhancement and crucial factors for attaining large enhancement factors. Based on our theoretical and experimental results, we suggest optimization conditions for SERS.

Authors : Yan Busby, Jackob Hübner, Denis Spitzer
Affiliations : NS3E Laboratory, French-German research Institue of Saint-Louis (ISL) 5, rue du Général Cassagnou, BP 70034, 68301, SAINT-LOUIS, Cedex, France

Resume : Spray flash evaporation (SFE) is a rapid and versatile technology to crystallize organic nanomaterials. This SFE processing was originally developed in the NS3E Laboratory about ten years ago and basically consists in injecting a pressurized hot liquid solution (10

Authors : I. Kochylas, V. Gianneta, V. Likodimos, S. Gardelis, P. Falaras, A. G. Nassiopoulou
Affiliations : National and Kapodistrian University of Athens, Department of Physics, Section of Condensed Matter Physics, Panepistimiopolis, 15784, Greece; NCSR Demokritos, Institute of Nanoscience and Nanotechnology (INN), 15341 Agia Paraskevi, Athens, Greece; National and Kapodistrian University of Athens, Department of Physics, Section of Condensed Matter Physics, Panepistimiopolis, 15784, Greece; National and Kapodistrian University of Athens, Department of Physics, Section of Condensed Matter Physics, Panepistimiopolis, 15784, Greece; NCSR Demokritos, Institute of Nanoscience and Nanotechnology (INN), 15341 Agia Paraskevi, Athens, Greece; NCSR Demokritos, Institute of Nanoscience and Nanotechnology (INN), 15341 Agia Paraskevi, Athens, Greece

Resume : Surface-Enhanced Raman Scattering (SERS) constitutes a powerful tool for sensitive detection down to the level of a single molecule that has been used in many areas such as chemical and biological analysis. In this study, we developed highly sensitive SERS substrates of high surface area, consisting of silicon nanowires (SiNWs) decorated with Ag nanostructures by a facile single-step Metal Assisted Chemical Etching (MACE) process. One-step MACE was performed on p-type Si substrates (5-6 Ωcm) by immersion in AgNO3/HF aqueous solutions resulting in the formation of SiNWs decorated by Ag dendrites. We used two alternative fabrication routes: in the first approach the silver dendrites that formed during SiNWs’ growth were removed in HNO3 aqueous solution. By re-immersion in the initial AgNO3/HF aqueous solution, Ag nanoparticle aggregates were deposited in a controllable way mainly at the SiNWs tips. In the second approach, we used directly the composite structure produced by MACE by adjusting the growth time to achieve the desired density of Ag nanostructures. SERS evaluation was performed using Rhodamine 6G as probe analyte at 514 nm, ensuring near-plasmonic resonance as the reflection measurements demonstrated. Substrates fabricated by the first approach enabled R6G detection down to 10^-16 M, whereas using the second approach the detection limit was markedly improved down to 10^-18 M. Enhancement factors exceeding 10^12 were calculated, demonstrating very high SERS sensitivities for analytic applications.

Authors : Trang Thi Thu Nguyen(1), Yejin Kim(1), Seokhyun Yoon(1), Hye Ri Jung(1), William Jo(1), Won Seok Woo(2), Chang Won Ahn(2), Shinuk Cho(2), Ill Won Kim(2), Maryam Bari(3), Zuo-Guang(3)
Affiliations : 1;Department of Physics, Ewha Womans University, Seoul 03760, Korea 2;Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44919, Korea 3;Department of Chemistry, Simon Fraser University, Burnaby, Canada

Resume : Over the years, many studies on photovoltaic absorber materials have been conducted to improve the efficiency of photovoltaic devices. However, there are many challenging issues to overcome for the solar cell materials research ensuring longer lifetime of the cell and better chemical stability for practical application, for example. In particular, for organic-inorganic hybrid perovskite materials, the role and characteristics of organic cations that remain unclear. In this study, we focus on understanding the fundamental structural properties.One of the remarkable features of organic-inorganic hybrid perovskite is that it has different phases as the temperature varies. For example, CH3NH3PbBr3 shows a phase transition from cubic to tetragonal structure at ~235K and CH3NH3PbCl3 shows similar phase transition at ~179K. We measured temperature-dependent Raman spectra in single crystalline MAPbBr3 and MAPbCl3 samples and observed abrupt changes in spectra from both samples at the phase transition temperatures. Our results show that contributions to the phase transition in each atomic/molecular vibration are different but there are common features existing for different compounds. We show that Raman scattering spectroscopy is a very effective way for studying structural phase transitions in complex materials.

15:45 Coffee break    
Q.X. Advanced nanoscale characterisation of material and devices III : O.Durand, T.Kiwa
Authors : D. J. Rogers1, V. E. Sandana1, P. Bove1, F. H. Teherani1
Affiliations : 1Nanovation, 8 route de Chevreuse, 78117 Châteaufort, France

Resume : The epitaxial layers that constitute the active regions in many electronic/photonic devices are often grown on substrates which are not ideal for integration/use in the targeted end-application. For instance, growth substrates can be too expensive or bring undesired constraints such as poor thermal/electrical conductivity, rigidity, opacity, etc etc. For these reasons lift-off of the active epilayers from the growth substrate, and their subsequent transfer/bonding to alternative substrates, has become a very widespread practice. One of the most elegant approaches to this transfer challenge is a technique called Epitaxial Lift-Off (ELO). In ELO a sacrificial underlayer (which also serves as a crystalline template) is employed so as to release the active epilayers from the growth substrate. The release is performed using a preferential chemical etch/dissolution of the sacrificial layer. A key advantage of this approach is that the released epilayer presents a pristine underside which is suitable for direct/fusion bonding to a substrate of choice (irrespective of crystallographic or thermal expansion mismatches). In practise, however, only a very limited set of substrates, epilayers and sacrificial layers have proven amenable to ELO and many epitaxial material combinations must resort to more complicated/destructive/elaborate approaches such as laser lift-off or smart cut. In this talk we will reveal a novel approach which has the potential to significantly extend the portfolio of materials that can be transferred to alternative substrates using ELO.

Authors : Yu-Hao Wu 2,1, Bi-Hsuan Lin 1*, Xiao-Yun Li 1, Wei-Rein Liu 1, Chih-Hao Lee 2, Mau-Tsu Tang 1,2 and Wen-Feng Hsieh 3
Affiliations : 1. National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan 2. Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan 3. Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan *

Resume : The X-ray excited optical luminescence (XEOL) and time-resolved X-ray excited optical luminescence (TR-XEOL) at 23A X-ray Nanorpobe (XNP) beamline of the Taiwan Photon Source (TPS) were applied to investigate the emission properties of the non-polar a-plane ZnO and MgZnO epi-films. Similar to our previous study[1], not only the intensity of near-band-edge (NBE) of a-MgZnO dramatically enhanced more than 10 times after using nano-focused beam irradiation, but also appeared an anomalous emission at 325nm, which was not observed in a-ZnO epi-films. We attribute that the high peak power density of the X-ray nanobeam may give rise to the anomalous excitation relative to the Mg energy states. The luminescence dynamic processes of the two samples were performed by TR-XEOL operating in the hybrid bunch mode, which provided the advantages that high enough X-ray photon flux as well as longer time interval (30 ps ~ 220 ns). The decay lifetime of a-MgZnO decreased gradually with the X-ray irradiation time. The detailed experimental processes will be reported. References: [1] Bi-Hsuan Lin, Yu-Hao Wu, Tai-Sing Wu, Yung-Chi Wu, Xiao-Yun Li, Wei-Rein Liu, Mau-Tsu Tang, and Wen-Feng Hsieh, Appl. Phys. Lett. 115, 171903 (2019).

Authors : Sung-Hoon Hong
Affiliations : Electronics and Telecommunications Research Institute (ETRI), Republic of Korea

Resume : Metamaterials is the artificially engineered materials which can tailor the properties depend on its structures. Recently, it has been greatly attractive for high performance ICT device such as super lens, holography, photonic integrated circuits, energy harvesting, sensor device, display device and so on. In this study, we present metamaterial based broadband perfect absorbers in visible wavelength for highly reflective, vivid color filter fabrication. The broadband perfect absorbers were fabricated with high lossy metals and coupled nanocrystals. The reflective color of metamaterial were tailored by the kind of materials, thickness, and nanostructures of perfect absorbers. The nanostructures of metamaterials were fabricated by nanoimprinting process for industrial applications. It also demonstrated on the flexible substrate for flexible display applications.

Authors : Kriukova, I.S.*(1,2), Samokhvalov, P.S.(2), Mochalov, K.E.(3), & Nabiev, I.R.(1)
Affiliations : (1) Laboratoire de Recherche en Nanosciences, LRN-EA4682, Université de Reims Champagne-Ardenne, 51100 Reims, France; (2) National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 115409 Moscow, Russia; (3) Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia;

Resume : Fluorescent semiconductor nanocrystals are extremely promising and actively investigated materials that have various potential optoelectronic, photovoltaic, and biomedical applications. The optical and physico-chemical properties of the nanocrystals can be controlled not only by varying their shapes and sizes, but also by synthesizing complex core/multishell particles with controllable energy structure of the nanocrystals. The core/multishell nanocrystals with a fluorescence quantum yield reaching 100% have been designed, and the importance of the structure–optical properties correlation in these materials has been demonstrated. Raman spectroscopy has been proven to be one of the best approaches to the quality control of core/shell nanomaterials. Here, we have synthesized the extended series of CdSe(core)/multishell quantum dots (QDs) with different thicknesses and compositions of the shells and investigated them using the Raman spectroscopy technique. The CdSe Raman scattering bands characteristic of the longitudinal optical phonon of the cores, as well as the bands related to the vibrational states of different layers of the CdS, ZnS, and CdSe shells of the QDs, have been recorded and analyzed. The Raman spectroscopy approach to the quality control of the synthesized core/multishell nanomaterials is proposed.

Authors : D. K. Gorai, T. K. Kundu
Affiliations : Indian Institute of Technology Kharagpur, Kharagpur, WB, India-721302

Resume : Graphitic carbon nitride (g-C3N4) shows excellent possibility to enhance its visible-light photocatalytic performance by tuning its electronic and optical properties as well as bandgap via Li and P codoping. The Li and P codoped g-C3N4 is synthesized by the polymerization of melamine, lithium carbonate, and ammonium phosphate at elevated temperature and characterized the obtained sample. After Li and P codoping, the photocatalytic performance of g-C3N4 for rhodamine B (RhB) and methyl blue (MB) degradation increases by increasing visible light absorption and decreasing the band gap compared to the pristine g-C3N4. Theoretical results show that after codoping with Li and P, there is more strong delocalized HOMO and LUMO state and the reactive sites, which facilitate the migration of photogenerated charge carriers and hence enhanced the photocatalytic performance compared to the pristine g-C3N4. keywords: Graphitic carbon nitride, codoping, Photocatalysis, rhodamine B, methyl blue, HOMO-LUMO

17:45 Concluding remarks Symposium Q    
18:30 AWARD CEREMONY followed by SOCIAL EVENT    
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Symposium organizers
Gerald E. JELLISONMaterials Science and Technology Division - Oak Ridge National Laboratory

1 Bethel Valley Road Oak Ridge, TN 37831 USA

+865 576 7309
Mircea MODREANU (Main)Tyndall National Institute-University College Cork

Lee Maltings, Dyke Parade, Cork, Ireland

+353 21 4904267
Olivier DURANDUniversité Européenne de Bretagne - FOTON-OHM - UMR-CNRS 6082

INSA de Rennes, 20, avenue des Buttes de Coësmes - CS 70 839, 35708 Rennes, France

+33 (0) 2 23 23 86 28
Toshihiko KIWAOkayama University

3-1-1 Tsushima-naka, Kita-ku, Okayama, 700-8530 Japan

+ 81 (86) 251 8130