Materials for energy and environmentC
Solid state ionics: thin films for energy and information applications
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Solid ionic and mixed ionic-electronic conductors are the key functional materials for electrochemical devices such as batteries, fuel cells and resistive memories. Integration of thin films into small and light-weight energy conversion and harvesting devices or in memory logics is becoming increasingly important. Mass and charge transport in thin film materials, at their interfaces, and structuring of new device concepts are focused.
Decreasing the volume of ionic conductors to the nanoscale has contributed to new electrochemical devices that can be integrated with Si-microfabrication processes. These comprise fast ionic conducting electrolytes for micro-fuel cells and batteries for energy harvesting or redox-reaction based resistive memories as new information logics. Both of them demand understanding of enhanced reaction and transport kinetics as well as novel processing/integration strategies for downscaling the individual devices and integrated units. Besides, both microscopic and large scale applications require solid state ionic or mixed ionic-electronic conducting thin films as constituents in electrochemical cells. Therefore, the main objective of this symposium is to address the use of thin films and engineering of their structure-property relations for potential electrochemical devices, including fundamental understanding of the "trivial" and “non-trivial” size effects on materials properties arising from the high density of homo- and heterojunctions such as space charges or strain.
The secondary objective of the symposium is consolidation of the knowledge on engineering of metastable films, complex heterostructures or strained interfaces are motivating new strategies to increase ionic or mixed conducting transport on the nano-scale. This part comprises of the following directions to gain understanding in:
(a) the role of mass and charge transport at interfaces and space charges to non-linear transport for solid oxide fuel cells/electrolyzers, batteries and resistive random access memories based on oxides.
(b) “chemo- and electro-mechanics” at the strained interfaces arising from the interaction of point defects and their influence of the performance of the electrolytes and electrodes upon up- and down-scaling of the devices;
(c) the role of the band structure and electronic/ionic carriers on the catalytic activity, electrode kinetics, and transport in model electrode thin film systems as well as in realistic devices.
(d) interface stability and charge storage in ionic conductors for improvement of charge/discharge rates of batteries.
(e) the fundamental and the practical issues of the highly non-equilibrium charge and material transfer under ultra-high electric fields taking place in redox-oxide films for resistive switches. Discrimination between the dominating theories of switching: “filament model vs. space charge model at interfaces”.
(f) novel characterization structural and composition characterization techniques for interfaces and surfaces at different length scales, including in-situ techniques.
(g) atomistic calculations at different levels as well as phenomenological modelling as a tool for understanding of the transport and reactivity in solid state ionic devices.
Papers are solicited on the following topics:
- Thin film processing of ionic and mixed conductors for energy and information applications
- Defect chemistry and phase stability of solid ionic and mixed conducting thin films
- Interfacially controlled materials, hierarchically ordered structures and interpenetrating networks
- Strain-point defect interaction in ionic and/or electronic conducting thin films “chemo-mechanics”
- Model electrode thin film structures for energy conversion and information storage
- Theory: “ab-inito calculations” and simulations
- Characterization methods with a special focus on in-situ, space-resolved and nano-analysis methods
- Micro-devices and components based on mass and charge transport, also integrated on Si-chip technology
- Innovative micro-structering routes to integrate functional thin films for energy and information devices, new array designs
- Applications for solid state ionic materials: materials applied in solid oxide fuel cells, batteries and resistive random access memory devices
List of invited speakers (confirmed):
- N. Balke, Oak Ridge Labs, USA
- M. Burriel, Imperial College, UK
- W. Chueh, Stanford, USA
- R. Dittmann, FZ Jülich, Germany
- R. Dedryvere, Université de Pau et des Pays de l’Adour, France
- J. Fleig, TU Vienna, Austria
- G. Gregori, MPI Stuttgart, Germany
- X. Guo, Huazhong University Wuhan, China
- C. Korte, FZ Jülich, Germany
- C. Marchiori, IBM Rüschlikon, Switzerland
- M. Martin, RWTH Aachen, Germany
- R. Meyer, Rambus Inc., USA
- D. Mueller, Stanford University, USA
- N. H. Perry, International Institute for Carbon-Neutral Energy Research (WPI-I2CNER) Japan &
Massachusetts Institute of Technology, USA
- F.B. Prinz, Stanford, USA
- P. Simon, Université Paul Sabatier, France
- H. Tuller, MIT, USA
- B Yildiz, MIT, USA
Jennifer L.M. Rupp
Phone: +41 44 633 04 51
Fax: +41 44 633 12 49
Phone: + 43 3842 402 4805
Fax: +43 3842 402 4802
Roger A. De Souza
Institute of Physical Chemistry
RWTH Aachen University
Phone: +49 241 80 94739
Fax: +49 241 80 92128
Department of Materials and Interfaces
Weizmann Institute of Science
Erik M. Kelder
Faculty of Applied Sciences
Delft University of Technology
2628 BL Delft
Phone: +31 15 278 3262
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Authors : An, J, Park, JS, Koh, AL, Lee, HB, Jung, HJ, Schoonman, J, Sinclair, R, Gur, TM, Prinz, FB
Affiliations : Stanford University
Resume : This talk will describe atomic scale structures of grain boundaries in oxide ion conductors. In particular, we report experimental observations of oxide-ion vacancy concentrations near symmetric tilt grain-boundaries of YSZ bi-crystal using aberration-corrected TEM. We observed significant oxygen deficiency due to segregation of oxide-ion vacancies near the grain-boundary core with half-width < 0.6 nm. Electron energy loss spectroscopy measurements with scanning TEM indicated increased oxide-ion vacancy concentration at the grain boundary core. Oxide-ion density distribution near grain boundaries simulated by molecular dynamics corroborated well with experimental results. This talk will summarize a recently published paper in Scientific Reports: Volume: 3, Article Number: 2680, DOI: 10.1038/srep02680, Published: SEP 17 2013
Authors : George F. Harrington, Andrea Cavallaro, Stephen J. Skinner, David W. McComb, John A. Kilner
Affiliations : 1) Department of Materials, Imperial College London, London, UK 2) Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio, USA
Resume : Strain effects in YSZ thin films have been a topic of controversy lately with reports of enhancements and reductions in the oxygen ion conductivity compared to bulk ranging over several orders of magnitude [1,2]. Variations in fabrication, processing and measurement techniques employed may be potential causes for this disparity in the literature, as well as an ambiguity in the charge carrier when measuring the transport properties of such systems electrically . We have fabricated highly textured YSZ thin films oriented in the (111) direction onto MgO and sapphire, and the (100) direction onto MgO, LAO and NGO using pulsed laser deposition (PLD). This allows the effect of lattice mismatch to be isolated while keeping the less well defined properties consistent. The films correspond to a range of lattice mismatches from 4.5% tensile to 18% compressive, and have been grown at a number of thicknesses in order to investigate interfacial effects. Impedance spectroscopy combined with isotope tracer diffusion will be shown to directly and unambiguously measure the oxygen ion transport properties in these films. This allows compositional, micro- and nano-structural variations observed in the film interfaces using HR-TEM to be associated with changes in the conduction properties. We will present evidence to show that a regular dislocation network at YSZ/substrate interfaces does not in fact drastically alter the conduction properties despite being linked to enhanced conduction properties previously [1, 4]. 1. Sillassen, M., et al., Adv. Funct. Mater., 2010. 20(13): p. 2071-2076. 2. Gerstl, M., et al., Phys. Chem. Chem. Phys., 2013. 15: p. 1097 - 1107. 3. Kim, H.-R., et al., Phys. Chem. Chem. Phys., 2011. 13(13): p. 6133-6137. 4. Korte, C., et al., Monatsh. Chem., 2009. 140(9): p. 1069-1080.
Authors : M.-H. Chambrier, I. Kehal, G. Mignardi, X. Flandre, V. Thoréton, A. Rolle ,S. Estradé, J.-F. Blach, C. Pirovano, S. Daviero-Minaud, R. N. Vannier
Affiliations : Univ Lille Nord de France, F-59000 Lille, France ; CNRS, UMR 8181, F-59650 Villeneuve d'Ascq, France; ENSCL, UCCS, F-59652 Villeneuve d'Ascq, France; UArtois, UCCS, F-62300 Lens, France; LENS,MIND-In2UB, Electronics Department, Universitat de Barcelona (UB),Mart'i Franqu's 1, Barcelona 08028, Spain
Resume : In the energetic concern, Solid Oxide Fuel Cells (SOFC) could be an interesting alternative to produce energy. The heart of these electrochemical cells is based upon the assembly of porous electrodes and dense electrolyte. This study was devoted to the promising electrode material Ca3Co4O9 (CCO) and the effect of the shaping of the electrodes and SOFC cells, on the electrochemical properties. To study the effect of a dense CCO layer at the interface between the dense CGO pellet and the CCO porous layer, a dense thin film was deposited on both sides of dense CGO pellets by Pulsed Laser Deposition (PLD). For this purpose, a 1 inch in diameter CCO PLD target, sintered at 900?C was used. As the electrochemical characterizations required symmetrical cells with defined surface-electrode layer, the CGO pellets were packed in a gold sheet fixed to a heat plate using silver on one side, and with a 10 mm in diameter hole, one the other side. Thin film deposition was carried out at temperature of 720?C, under a pressure of 10-1 mbar and with a laser frequency of 2Hz. All films were deposited for 9000 pulses to give more or less the same nominal thickness. The X-ray diffraction characterizations were performed using a 9 kW rotating anode in rasing mode for the precise characterization of thin films. In order to estimate the thickness, ellispometry measurements crossed with TEM observation have been done. TEM samples were prepared by Focused Ion Beam using the lift-out technique. Interestingly, as revealed by impedance spectroscopy the resistance of polarization of the sample with an interfacial dense layer was half that of sample without any interfacial layer.
Authors : Kiyong Ahn, Hyungchul Kim, Ho-Il Ji, Jongsup Hong, Kyung Joong Yoon, Ji-Won Son, Byung-Kook Kim and Jong-Ho Lee
Affiliations : High-Temperature Energy Materials Research Center, Korea Institute of Science and Technology Seoul 136-791, Republic of Korea
Resume : Micro-solid oxide fuel cells (μ-SOFCs) have received great attention as novel power sources for mobile applications because of their many intriguing properties. Electrode polarization is usually thought to be a main contributor to the performance losses of μ-SOFC, especially in relation to sluggish kinetics in cathode reactions. There is still a lack of basic understanding of the physicochemical properties of thin film cathodes. Thus far, most studies on the thin film cathodes have dealt with the measurement of their surface exchange coefficients (kchem) rather than the bulk diffusion properties (Dchem), because the surface exchange reaction is thought to be a main rate determining step in thin-film cathode. The very intricate measurement of the bulk diffusion coefficient due to its limited diffusion length is another reason for the lack of bulk diffusion studies on thin film cathodes. In a real μ-SOFC system, however, oxygen diffusion kinetics becomes very important for cathode reactions because of the extremely complex cathode structure. Hence, the transport properties of thin film cathodes should be thoroughly investigated and clarified to provide a substantial contribution on the development of a high performance cathode. Here we present our recent experimental and calculating works to make the proper interpretation of oxygen transport properties in thin film cathodes LaSrCoO3-δ (LSC), and we believe that this study can provide an actual insight into the proper implementation of thin film cathodes for high-performance μ-SOFCs.
Authors : L.-S. Unger1, M. Meffert2, C. Niedrig1, H. Störmer2, W. Menesklou1, S. F. Wagner1, D. Gerthsen2, E. Ivers-Tiffée1
Affiliations : 1) Institut für Werkstoffe der Elektrotechnik (IWE), Karlsruher Institut für Technologie (KIT), 76131 Karlsruhe/Germany 2) Laboratorium für Elektronenmikroskopie (LEM), Karlsruher Institut für Technologie (KIT), 76131 Karlsruhe/Germany firstname.lastname@example.org
Resume : In an oxygen-permeation membrane oxygen transport occurs due to a partial pressure (pO2) gradient applied across the dense mixed-conducting membrane. (Ba0.5Sr0.5)(Co0.8Fe0.2)O3-δ (BSCF) is a very promising candidate for such a membrane as its cubic phase, which can be stabilized by suitable doping strategies, exhibits excellent oxygen permeation properties. Electrical conductivity relaxation measurements as a function of pO2 yield information on the oxygen transport parameters (surface exchange coefficient kδ, diffusion coefficient Dδ). Using a closed YSZ oxygen pump setup facilitates measurements under varying atmospheres (pO2 = 10-5 1 bar). As kδ values significantly decrease at lower pO2, the membrane performance can be enhanced by improving the low-pO2 oxygen surface excorporation reaction. Such an enhancement can be achieved, e.g., by applying a nanostructured oxide functional surface layer. A nanoporous (La0.6Sr0.4)CoO3-δ (LSC) coating is an interesting method as not only the surface enlargement leads to an increased overall kδ but, moreover, the occurrence of hetero-interfaces could considerably contribute to the oxygen surface exchange. With the help of a combined electrochemical and transmission electron microscopy analysis the influence of such a surface activation of BSCF was investigated. Both the aspect of hetero-interfaces as well as possible interface reactions between the dense BSCF membrane and the nanoporous LSC functional layer are addressed.
Authors : A.U. Abuova1, T.M. Inerbaev1, A.T. Akilbekov1, Yu. A. Mastrikov2,3, E. A. Kotomin2,4
Affiliations : 1 L.N. Gumilyov Eurasian National University,Mirzoyan str.2, Astana, Kazakhstan 2 Institute of Solid State Physics, University of Latvia, Kengaraga str. 8, Riga, Latvia 3 Materials Science and Engineering Dept., University of Maryland, College Park, USA 4 Max Planck Institute for Solid State Research, Heisenbergstr.1, Stuttgart, Germany
Resume : Metallic silver is a potential component for the SOFC cathode operated at less than 800°C because of its good catalytic activity, high electrical conductivity, and relatively low cost. Different methods have been used to prepare functionalized composite cathodes with improved electrochemical performance and long term stability at reduced operating temperature.  In addition, even far below its melting point, silver is relatively mobile. Therefore, these concerns should be addressed prior to a long-term application of silver-based cathodes in SOFCs. To overcome this problem Zhou et. al. presented (La0.8Sr0.2)0.95Ag0.05MnO3-δ as a high performance intermediate temperature cathode material, in which the contained Ag functions as an effective catalyst through an intercalation/deintercalation mechanism.  Under cathodic polarization, Ag moves out of cathode to be deposited as small nanoclusters of Ag metal, leaving the remaining (La0.8Sr0.2)0.95MnO3-δ as a catalyst carrier. The Ag nanoclusters which are 515 nm are very active and stable in catalyzing the cathode reaction even at a reduced temperature. Under anodic polarization, the Ag moves back into the deficient sites of the LSM. This permits an easy regeneration method to restore Ag nanoclusters which may become degraded over time by fusing together, thereby losing the activity. We present results of ab initio calculations of Ag adsorption on the LMO  polar surface. The most energetically favourable adsorption sites on both MnO2- and LaO-terminations have been determined. Electron charge transfer between the adsorbate and the adsorbent has been analyzed. Optimized interatomic distances have been measured. . S. Uhlenbruck, F. Tietz, V. Haanappel, D. Sebold, H.P. Buchkremer, and D. Stover, Journal of Solid State Electrochemistry 8 (2004) 923-927.  W. Zhou, Z. Shao, F. Liang, Z.-G. Chen, Z. Zhu, W. Jin, and N. Xu, Journal of Materials Chemistry 21 15343-15351.
Authors : B.Bouadjemi*1, S.Bentata1, T. Lantri1, W.Benstaali1, A.Zitouni1 and A.Abbad2
Affiliations : 1 Laboratory of Technology and Solid Properties, 2Signals and Systems laboratory, LSS, Faculty of Sciences and Technology, Abdelhamid Ibn Badis Mostaganem University, BO 227, 27000 Algeria E-mail: email@example.com
Resume : We have investigated the electronic and magnetic properties of the cubic praseodymium oxides perovskites PrMnO3 were calculated using the density functional theory (DFT) with both generalized gradient approximation (GGA) and GGA+U approaches, where U is on-site Coulomb interaction correction. The results show a half-metallic ferromagnetic ground state for PrMnO3 in GGA+U approche, while semi-metallic ferromagnetic character is observed in GGA. The results obtained, make the cubic PrMnO3 a promising condidate for application in spintronics. Keywords : Electronic properties, Transition Metal, Magnetic moment, DFT, half- metallic  A.S. Verma, A. Kumar. Journal of Alloys and Compounds,541(2012) 210.  P. Blaha, K. Schwars, G.K H.madsen, D. Kvasnicka,and J. Luitz, WIEN2K,an Augmented Plane WaveRLocal Orbitals Program for Calculating Crystal Properties (Technische Universita « tWien,Austria,2001).  B.Bouadjemi*, S.Bentata, A.Abbad, W. Benstaali, B. Bouhafs,Solid State Communications168(2013)6-10.
Authors : B.Bouadjemi*1, S.Bentata1, T. Lantri1, W.Benstaali1and A. Zitouni1
Affiliations : 1 Laboratory of Technology and Solid Properties, Faculty of Sciences and Technology, Abdelhamid Ibn Badis Mostaganem University, BO 227, 27000 Algeria E-mail: firstname.lastname@example.org
Resume : The structural, electronic and magnetic properties of double perovskite Ba2MnMoO6 are studied by using the first-principales method of the full potential linear augmented plane waves plus the local orbitals (FP-LAPW+l0) within the local spin density (LSDA) and the generalized gradient approximation (GGA) approximations, in order to take into account the strong on-site coulomb interaction that means we included the Hubbard correlation terms : LSDA+U and GGA+U approaches. Our structural calculations are in agreement with the experimental and orders theoretical results which show that compound crystallizes in the cubic space group Fm-3m (a=7.91Å) .The calculated density of state presented in this study identifies the metallic behavior due to dominant Mn spin-up and Mo spin-down contributions. Keywords : Electronic structure, Double perovskite, First-principales, Ba2MnMoO6, coulomb interaction
Authors : S.Benatmane*1, B.Bouhafs1, B. Bouadjemi 2 and S. Bentata 2
Affiliations : 1Department of physics Faculty of sciences Djillali Liabes University of Sidi Bel-Abbes, 22000, Algeria 2Laboratory of Technology and Solid Properties,Faculty of Sciences and Technology, BP227 Abdelhamid Ibn Badis University, Mostaganem (27000) Algeria Email*1: email@example.com
Resume : The TiO2 has been recently used to realize high-temperature ferromagnetic semiconductors. In fact, it has been widely used for a long time as white pigment and sunscreen because of its whiteness, high refractive index, and excellent optical properties. However, its electronic structures and the related properties have not been satisfactorily understood. Here, we use Tran and Blahas modified Becke-Johnson (TB-mBJ) exchange potential (plus a local density approximation correlation potential) within the density functional theory to investigate electronic structures and optical properties of rutile and anatase TiO2. Our comparative calculations show that the energy gaps obtained from mBJ method agree better with the experimental results than that obtained from local density approximation (LDA) and generalized gradient approximation (GGA), in contrast with substantially overestimated values from many-body perturbation (GW) calculations. As for optical dielectric functions (both real and imaginary parts), refractive index, and extinction coefficients as functions of photon energy, our mBJ calculated results are in excellent agreement with the experimental curves. Our further analysis reveals that these excellent improvements are achieved because mBJ potential describes accurately the energy levels of Ti 3d states. These results should be helpful to understand the high temperature ferromagnetism in doped TiO2. This approach can be used as a standard to understand electronic structures and the related properties of such materials as TiO2. Titanium dioxide films have wide applications because of their useful electrical and optical properties, such as high refractive index, high dielectric constant, and excellent transmittance in the visible and near infrared range. Especially, the high refractive index and low absorption coefficient make them suitable for optical coatings. Therefore, many studies on the preparation of TiO2 films by various deposition procedures have been carried out [1-2]. For the preparation of optical coatings, such as TiO2 films, reactive sputtering is very useful technique because of the possibility to produce coatings with high optical quality and a good homogeneity. However, in the case of TiO2 film grown using the sputter method, the film properties, including the stoichiometry, microstructure, and optical characteristics are strongly dependent on growth parameters such as the substrate temperature and the gas composition in the sputtering atmosphere. The rutile and anatase structures are the most important phases for TiO2. Their structural, electric, and optical properties have been experimentally measured with various methods [3-6] and their electronic structures and optical properties have been theoretically investigated in terms of popular density functional- theory (DFT) approaches. [7-10] It is obvious that the electronic structures need to be accurately calculated because they are the starting point for first-principles calculations of other physical and chemical properties. Nevertheless, their energy gaps, like those of other semiconductors and insulators, are underestimated by local density approximation (LDA) and generalized gradient approximation (GGA)[8-9;11;12] in comparison with the experimental values.[4-5] Thus, further approximations, such as scissors approximations, are required to modify the gaps to make the calculated results comparable with the experimental results In this work, we use Tran and Blahas modified BeckeJohnson (TB-mBJ) exchange potential (plus LDA correlation potential) [13-14] within the density functional theory to investigate the optical properties of rutile and anatase TiO2. Key words: DFT / FP-LAPW / GGA / LDA / the TiO2 /the mBJ and optical properties References  H. K. Jang, S. W. Whangbo, H. B. Kim, Y. S. Lee, I. W. Lyo and C. N. Whang, J. Vac. Sci. Technol. A 18, 917 (2000).  J. D. Park and T. S. Oh, J. Korean Phys. Soc. 37, 1072 (2000).  Matsumoto Y, Murakami M, Shono T, Hasegawa T, Fukumura T, Kawasaki M, Ahmet P, Chikyow T, Koshihara S Y and Koinuma H 2001 Science 291 854  Cardona M and Harbeke G 1965 Phys. Rev. 137 A1467  Tang H, Levy F, Berger H and Schmid P E 1995 Phys. Rev. B 52 7771  Lin L B, Mot S D and Lin D L 1993 J. Phys. Chem. Solids 54 907  Hohenberg P and Kohn W 1964 Phys. Rev. 136 B864  del Sole R and Girlanda R 1993 Phys. Rev. B 48 11789  Thilagam A, Simpson D J and Gerson A R 2011 J. Phys.: Condens. Matter 23 025901  Kang W and Hybertsen M S 2010 Phys. Rev. B 82 085203  Perdew J P and Wang Y 1992 Phys. Rev. B 45 13244  Perdew J P, Burke K and Ernzerhof M 1996 Phys. Rev. Lett. 77 3865  Tran F and Blaha P 2009 Phys. Rev. Lett. 102 226401  Koller D, Tran F and Blaha P 2011 Phys. Rev. B 83195134
Authors : D. Taharchaouche1, F. Mechachti1, A. Djebaili1*
Affiliations : 1 Laboratory of chemistry and environmental chemistry L.C.C.E - University of Batna- Algeria
Resume : Ab-initio calculations, carried out with different basis sets, for the static longitudinal linear polarizability, αL, and second order hyperpolarizability, γL, of small doubly charged polyacetylene (PA) chains, are presented. The polarizabilities were calculated using the HartreeFock (HF) method while the electron correlation effects were included through the second-order MøllerPlesset perturbation theory (MP2). Positively and negatively charged bipolarons were studied. The results obtained for positive and negative chains show that the ionization state effect decreases more rapidly, as the chain length is increased, for αL than for γL. Or both types of charged chains, the incorporation of the electron correlation increase the αL, and γL values, as compared to the HF values. A comparison between the results obtained using the standard 6-31G basis set and augmented versions of this set, obtained by the addition of diffuse and polarization functions, shows that 6-31G basis set does not provide a good description of the negative chains studied here and that the addition of extra diffuse functions on the basis set is needed in order to obtain reliable estimates for polarizabilities, specially for γL. Key words : polarizabilities; hyperpolarisability; polyacetylene; bipolarons; correlation effects.
Authors : S. Bitam1, F. Mechachti2, A. Djebaili2
Affiliations : 1 Laboratory of Physical chemistry- University of Media- Algeria 2 Laboratory of chemistry and environmental chemistry L.C.C.E - University of Batna- Algeria
Resume : Our work has allowed us to clarify the relations structures / properties and the isomerization reactions of polyacetylene. As regards the relations structures / properties, our results are: 1- The study of the conduction properties of polyacetylene doped with iodine gas at saturation as a function of various parameters regulating morphology and density of the material was optimized. In particular we have shown that the two key parameters governing the electrical conductivity of the polymer are the density and the fibrillar structure of polyacetylene. 2- The comparison of samples prepared horizontally and vertically gave a conductivity of greater than ~ 45 % for those deposited vertically, thereby reflecting the difference in morphology of the two types of film.. 3- The study of the ohmic conductivity of undoped and thermally isomerized samples showed a very different behavior depending on whether the polyacetylene film is deposited horizontally or vertically, thus confirming the different morphologies of the analyzed films. With regard to isomerization reactions of polyacetylene, our results are: i- The study of the thermal isomerization Cis / Trans of undoped polyacetylene by differential thermal analysis allowed us to calculate the activation energy of the reaction Ea=31kcal/M, as well as the pre-exponential factor A = 2.3*1013 /s regardless of the type of polymer considered (deposited vertically or horizontally). ii- The kinetic studies by DSC showed that the isomerization reaction was neither of order 1, nor of a simple order. iii- An additional study of the thermal isomerization was carried out by Raman backscattering . This study allowed us in particular to establish a new original method for the determination of the isomeric composition of samples of polyacetylene. Also a relation for connecting the laser power to the induced temperature at the impact level was proposed. Finally, the kinetics of isomerization approaches the order 2/3. Note that the activation energy and the pre-exponential factor of the isomerization reaction determined by this method are different from those obtained by DSC.
Authors : N. Abdelmalek1, F. Djeffal1, T. Bentrcia and M. Meguellati2
Affiliations : LEA, Department of Electronics, University of Batna, Batna 05000, Algeria. E-mail: firstname.lastname@example.org, email@example.com, Tel/Fax: 0021333805494
Resume : The Gate All Around GAA MOSFETs have emerged as excellent devices to provide the electrostatic integrity needed to scale down transistors to minimal channel lengths, and allowing a continuous progress in digital and analog applications. Employing this design for chemical and environment monitoring applications becomes more beneficial if the device is made in vertical cylindrical recrystallized silicon due to highly flexible process integration options. In this paper, a numerical investigation of a new pH-ISFET design, called the Junctionless Gate All Around Ion-sensitive field-effect transistor with oxide kernel (pH-JGAAISFET), is proposed, investigated and expected to improve the fabrication process and the sensitivity behavior for pH-ISFET sensor-based applications. The numerical investigation has been used to propose a new sensitivity performance and predict the device behavior. The comparison of device architectures shows that the proposed sensor exhibits a superior performance with respect to the conventional ISFET in term of electrical performances. The obtained results make the proposed sensor a promising candidate for low cost monitoring and high performance pH sensing applications.
Authors : G. Kaptagai1, T.M. Inerbaev1, A.T.Akilbekov1, Yu.A. Mastrikov2,3, E.A. Kotomin2,4
Affiliations : 1 L.N. Gumilyov Eurasian National University, Mirzoyan str. 2, Astana, Kazakhstan 2 Institute of Solid State Physics, University of Latvia, Kengaraga str. 8, Riga, Latvia 3 Materials Science and Engineering Dept., University of Maryland, College Park, USA 4 Max Plank Institute for Solid State Research, Heisenberg str. 1, Stuttgart, Germany
Resume : Water interaction with fluorine-doped Co3O4 (100) and (111) surfaces Electrochemical water splitting has attracted substantial interest in the recent years as a key process in hydrogen production from sunlight and other sources of electricity. Recent experimental studies have demonstrated that Co3O4 is high-promising anode material for electrochemical water splitting due to its high catalytic activity in the oxygen evolution reaction (OER) . In this context, understanding the interaction of Co3O4 surfaces with water is an essential preliminary step that can help to shed light on the atomic scale reaction mechanisms. Our attention is focused on investigation of Co3O4 (100) and (111) surfaces which are the most abundantly presented in Co3O4 nanoparticles . Density functional method is applied to describe thermodynamics of electrocatalytic water splitting on the Co3O4 (100) and (111) surfaces. We calculated free energy changes along the reaction pathway using the computational standard hydrogen electrode (SHE) allowing us to replace a proton and an electron with half a hydrogen molecule at U = 0 V vs SHE. The analysis performed for the free energies is at standard conditions (pH = 0, T = 298.15 K) and U = 0. Using accurate DFT+U calculations, we shown that water adsorbs dissociatively on Co3O4 on the (100) and intactly on the (111) surfaces. From the computed free-energy changes along the OER, we found that the (100) surface is catalytically inactive while (111) surface demonstrates some electrocatalytic activity on its threefold coordinated surface cobalt ions. In this case free energy changes along the OER is the same to corresponding value for the most stable termination of (110) Co3O4 surface. Fluorine doping of Co3O4 nanoparticles drastically changes their interaction with water. In our investigations solvent effects are generally expected to be small for neutral species, the neglect of the water environment is a rather drastic approximation, for which the main justifications are that it provides a qualitative description of experimentally observed trends, and it is the first step toward more complete treatments that include the solvent.  I. C. Man, H.-Y. Su, F. Calle-Vallejo, H. A. Hansen, J. I. Martínez, N. G. Inoglu, J. Kitchin, T. F. Jaramillo, J. K. Nørskov, and J. Rossmeisl, ChemCatChem (2011) 3, 1159 1165.  F. Zasada, W. Piskorz, S. Cristol, J.-F. Paul, A. Kotarba, and Z. Sojka, J. Phys. Chem. C (2010), 114, 2224522253.
Authors : Yu. A. Mastrikov1,2, E. A. Kotomin1,3, R. Merkle3, M. M. Kuklja2, and J. Maier3
Affiliations : 1Institute of Solid State Physics, University of Latvia, Kengaraga str. 8, Riga, Latvia; 2 Materials Science and Engineering Dept., University of Maryland, College Park, USA; 3Max Planck Institute for Solid State Research, Heisenbergstr.1, Stuttgart, Germany;
Resume : ABO3-type perovskite solid solutions with a large oxygen deficiency exhibit a perceptible ionic conductivity, leading to their use as electrolytes ((La,Sr)(Ga,Mg)O3-) or materials for oxygen permeation membranes and solid oxide fuel cell cathodes ((La,Sr,Ba)(Mn,Fe,Co)O3-) . The oxygen migration occurs by the vacancy mechanism with the migration through a "critical triangle" formed by one B- and two A site cations, as the bottleneck . Oxygen ionic conductivity is not only important for transport though the cathode material, it also affects the surface chemistry. The formation and migration energies of oxygen vacancies were found to be major factors determining the surface oxygen reduction rate . We analyze these two quantities for a series of complex (La,Sr)(Co,Fe)O3- (LSCF) perovskites by means of first principles DFT calculations . The atomic relaxation, electron charge redistribution and energies of the transition states for oxygen ion migration are obtained and differences with Ba1-xSrxCo1-yFeyO3- (BSCF) perovskites  (which exhibit considerably lower migration barriers) are discussed in detail, with special emphasis on the vacancy formation and migration at the surface. . M. Kuklja et.al. Phys. Chem. Chem. Phys. 15, 5443 (2013).  Yu.A. Mastrikov et.al. Phys. Chem. Chem. Phys. 15, 911 (2013)  R. Merkle et. al. J Electrochem.Soc. 159, B 219 (2012).
Authors : Wolfgang Preis
Affiliations : Chair of Physical Chemistry, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben, Austria
Resume : The reduction of oxygen at mixed ionic-electronic conducting SOFC cathodes, e.g. La0.6Sr0.4CoO3-d, is mainly determined by the oxygen exchange reaction at the surface, including pores, as well as the transport of oxygen ions through the thin cathode layer. The kinetics of these processes can be described by means of the surface exchange coefficient and the ionic conductivity. Impedance spectroscopy represents a powerful tool for the investigation of the polarization mechanism. A square grain model has been developed in order to simulate impedance spectra of porous cathodes under OCV conditions by application of a finite element approach. The grains and pores of the thin cathode layer may be squares of equal side length (0.1 - 1 µm), while the grain boundaries as well as the interface between the grains of the cathode and a homogeneous electrolyte may consist of thin slabs with a width of 0.5 nm. The simulated impedance spectra can be interpreted reasonably well in terms of a Gerischer element. An additional semicircular arc is found at high frequencies, which corresponds to the charge transfer resistance (double layer capacitance) of the interface between the cathode and the electrolyte as well as current constriction effects. The surface exchange coefficient and ionic conductivities of bulk and grain boundaries have been varied systematically. The effect of the ionic grain boundary conductivity on impedance spectra of thin porous cathode layers will be presented in detail.
Authors : A. Welzl, T. M. Huber, E. Navickas, A. K. Opitz, H. Hutter, J. Fleig
Affiliations : Vienna University of Technology Institute of Chemical Technologies and Analytics Research Division Electrochemistry
Resume : Sr-doped lanthanum manganite (LSM) is the most used cathode material in solid oxide fuel cells (SOFC). Nevertheless, many aspects of the oxygen reduction at LSM are not completely understood. Even though ionic conductivity of LSM is low, oxygen reduction not only occurs at the three phase boundary via a surface path but also at the LSM surface and thus via a bulk path. By applying a dc-bias to LSM electrodes, their oxygen chemical potential is changing and thus surface kinetics as well as bulk transport kinetics can be modified. In combination with oxygen partial pressure changes, which also affect the defect chemistry of LSM, the contribution and individual relevance of interfacial and transport kinetics can be investigated at elevated temperatures. In this contribution, current-voltage and impedance studies are performed on LSM microelectrodes with variation of electrode geometry, dc-bias, oxygen partial pressure and temperature. These experiments provide information on the current voltage characteristics of different kinetic steps, allow separation of reaction pathways and enable identification of rate limiting steps. Moreover 18O incorporation upon cathodic bias is used to visualize the electrochemically active zones of the different reaction pathways and their changing contributions for microelectrodes under different measurement conditions.
Authors : Heon Jae Jeong, Jun Woo Kim, Ho Jean Jeong, Kiho Bae, Joon Hyung Shim
Affiliations : School of Mechanical Engineering, Korea University, Seoul, Korea
Resume : For use of solid oxide fuel cells (SOFC) in small and mobile applications, methanol or ethanol has attracted attentions as an alternative fuel source instead of hydrogen. In operation of SOFCs at intermediate temperatures under 500C, bimetallic Pt-Ru catalyst has been known as the most effective for oxidation of alcohol fuels. Various methods have been attempted for the deposition of bimetallic catalysts. Among them, atomic layer deposition (ALD) has been successfully utilized to synthesize high-performance catalysts for fuel cells. ALD can achieve uniform coating of metal layers in thickness of several atomic layers or a few nanometers on meso-porous substrates due to its self-limited chemical reaction per each precursor cycle. This characteristic of the ALD process enables to maximize surface area of the deposited metal layer in minimized volume, which is advantageous especially in manufacturing of core-shell catalysts with precious shell metals including Pt and Ru. In this study, ALD Ru was deposited onto porous Pt and Ni substrates as anodes of Gd0.1Ce0.9O2-δ (GDC)-based SOFCs. Both methanol and eathanol were tested as fuels and performance was examined in terms of maximum voltage, power output, and electrochemical impedance under 500C. To evaluate chemical stability or resistance to carbon coking, surface composition of the ALD Ru-Pt and -Ni catalysts was measured by using x-ray photoelectron spectroscopy (XPS) before and after the fuel cell testing. As a result, the SOFCs with ALD Ru-Pt or ALD Ru-Ni outperform ones with pure Pt demonstrating power output enhanced by at least one order compared to pure Pt-SOFCs with significantly improved long-term stability.
Authors : Jolita Sakaliuniene, Brigita Abakeviciene, Kestas Slapikas, Sigitas Tamulevicius
Affiliations : Institute of Materials Science of Kaunas University of Technology, Savanorių av. 271, LT-50131 Kaunas, Lithuania
Resume : Platinum is an interesting material due to its unique properties such as high melting point, good chemical resistance and catalytic behavior. Consequently it is used as potential electrode for micro-Solid Oxide Fuel Cells. In the present research the microstructure, porosity as well as conductivity of thin (d~200 nm) platinum electrodes deposited on silicon/silicon oxide substrates and yttria stabilized zirconia films were varied by using different working pressure in the chamber during platinum sputter-deposition process. To obtain good platinum adhesion on silicon/silicon oxide substrate, titanium thin layer (d~20nm) was used as an adhesion and a diffusion barrier layer. Structure of platinum electrodes was analyzed using grazing incidence X-ray diffraction, morphology - by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The ImageJ processing program was used to evaluate the porosity of the Pt thin film from the SEM images. Electrical properties of platinum films were measured using the four-point probe method. Thermal treatment at different annealing temperatures (from 500 to 800C) was applied. It was observed that higher working pressure in the chamber results in denser and smoother platinum films, and correspondingly lower working pressure allows to produce porous platinum thin films without any thermal treatment. Thermal treatment results show that pores start to compose after 15 minutes annealing in 600C in air.
Authors : F. Baiutti1, G. Logvenov1, G. Gregori1, Y. Wang2, Z. Chen2, W. Sigle2, P.A. van Aken2, J. Maier1
Affiliations : 1 Max Planck Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany; 2 Stuttgart Center for Electron Microscopy, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
Resume : Knowledge about charge and ion redistribution is essential to understanding interface effects occurring in many functional oxides. In this contribution, the electrical transport properties of a model system based on hetero-structures of strontium delta-doped lanthanum cuprate (La2CuO4) are considered. Thanks to the unique capabilities of the layer-by-layer oxide molecular beam epitaxy (MBE) technique, that allows the control of the structural composition down to the single atomic layer, we fabricated epitaxial multilayered (La,Sr)2CuO4 structures, in which atomic layers of SrO were precisely inserted in the parent La2CuO4 lattice structure. Remarkably, although both La2CuO4 and SrO single layers do not exhibit superconducting properties, the resulting hetero-structures (obtained by varying the spacing between the La2CuO4 and SrO layers) are high-Tc superconductors with a maximum Tc ≈ 40 K. In order to rationalize this exciting finding and determine the relevance of cation intermixing at the interface, electrical transport data are discussed together with structural information, the latter being obtained from X-ray diffraction (XRD), atomic-column-resolved high-angle annular dark-field (HAADF) imaging in combination with energy-dispersive X-ray spectroscopy (EDXS) and electron energy-loss spectroscopy (EELS) in a spherical aberration-corrected scanning transmission electron microscope.
Authors : Mareike V. Hohmann, Andreas Klein
Affiliations : Technische Universität Darmstadt, Institut für Materialwissenschaft, Fachgebiet Oberflächenforschung, Jovanka-Bontschits-Strasse 2, 64287 Darmstadt, Germany
Resume : The application of transparent conductive oxides in most electronic devices requires a good knowledge of their electrical properties such as conductivity, but also carrier mobility. In addition, oxygen exchange plays a crucial role for post-deposition treatments and the functionality of devices. In order to elucidate the relation between electrical properties and oxygen equilibration a system for in situ Hall effect and electrical conductivity measurements of oxide thin films has been set up, giving the opportunity for temperature dependent measurements in controlled atmosphere. The use of the setup is exemplified with differently doped In2O3 thin films, which are deposited by magnetron sputtering onto quartz glass substrates. The amount of Sn doping, the oxygen pressure during film deposition and during temperature treatment is varied. The results indicate that oxygen equilibration is not the only factor which affects the electrical properties, but also other long term processes. Reversible segregation of Sn to grain boundaries is one possible mechanism contributing to the long term processes.
Authors : A.P. Bakhtinov (1), V.M. Vodopyanov (1), Z.R. Kudrynskyi (1), Z.D. Kovalyuk (1), V.V. Netyaga (1), O.S. Lytvyn (2)
Affiliations : (1) Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Chernivtsi Department, str. I. Vilde 5, 58001 Chernivtsi, Ukraine, (e-mail: kudrynskyi [at] gmail.com); (2) Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, pr. Nauky 4, 03028 Kyiv, Ukraine.
Resume : The p-GaSe(RbNO3) and n-InSe(RbNO3) nanocomposite materials were prepared by inserting ionic salt RbNO3 from the liquid phase between the layers of the layered crystals. We have obtained self-organized structures that consist of a layered matrix and arrays of nanorings and nanowires formed from solid ionic salt RbNO3 nanocrystals on the atomically smooth van der Waals (0001) surfaces of layered semiconductor crystals. Atomic force microscopy, infrared spectroscopy, X-ray diffraction and impedance spectroscopy are used to characterize morphology, chemical composition, structural and electrical properties of the grown materials. We observed electric field-induced changes in the complex impedance by a factor of 10^5-10^8 in the frequency range 10^-1-10^6 Hz at T=300K for solid state RbNO3/n-InOx/n-InSe nanostructures with structurally abrupt interfaces when a few volts voltage was applied. Under an applied gate voltage the nanometer-thick electric double layers (nanogap capacitors with a large capacitance) consisting of Rb+ ions and electrons accumulated on the surface of n+-InOx nanoscale layers with a high electron density were formed. In this work, we study the role of structural properties (such as ionic nanocrystals size and density, pyramidal defect density on the (0001) layered crystals surface) on the electron/ionic carriers transport in the anisotropic structures. Our results suggest that these nanostructures are promising for energy and information applications.
Authors : Young Seon Lee, Jun Young Choi, Sang Yeol Lee
Affiliations : Department of Electronic Engineering, Cheongju University, Cheongju, Chungbuk 360-764, Republic of Korea; Department of Electrical Engineering, Korea University, Seoul, 136-703, Republic of Korea; Department of Semiconductor Engineering, Cheongju University, Cheongju, Chungbuk 360-764, Republic of Korea
Resume : Low-emissivity glasses for high transparency in visible range and low emissivity in IR range were investigated. The multilayers have been fabricated and consisted of two outer oxide layers and a middle layer of Ag as a metal layer. Oxide layers were formed by dc sputtering and metal layers were formed by evaporator at room temperature. In-Si-O (ISO) film was used as oxide layer. The ISO/Ag/ISO coatings were analyzed using transmittance, atomic force microscope (AFM), X-ray diffraction (XRD) and Hall effect measurement. The OMO multilayer structure was designed to investigate the effect of Ag layer thickness on the optical and electrical property. The results revealed that the optical and electrical properties are closely related with Ag layer thickness.
Authors : Moo Yeol Bae, Jun Young Choi, and Sang Yeol Lee
Affiliations : Department of Semiconductor Engineering, Cheongju University, Cheongju, Chungbuk 360-764, Republic of Korea; Department of Electrical Engineering, Korea University, Seoul 136-701, Republic of Korea; Department of Semiconductor Engineering, Cheongju University, Cheongju, Chungbuk 360-764, Republic of Korea
Resume : In the high oil price age, building is the country's total energy consumption by 22.3% and the glass takes up most of the energy loss of building. Therefore, in order to prevent loss of heat, development of Low-E glass is underway and it is already commercially available. Low-E glass having an oxide-metal-oxide structure has a low emissivity, it transmits visible light area and block makes the IR area, because of reduces heat loss. Oxide-Metal-Oxide on the glass as a SIZO-Ag-SIZO Multilayer was constructed. Silicon indium zinc oxide (SIZO) were deposited by RF-sputter method and Ag by the DC-sputter of change in thickness was deposited. By measuring the transmittance of multilayer depending on the thickness of Ag, optical properties were compared. By changing the thickness of the deposited Ag, optical properties were different. It is possible to optimize the thickness of the Ag indicating the high transmittance of visible light area and low transmittance of IR area for low cost applications.
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Resistive Switching in Metal Oxides : Prof. R. Dittmann and Prof. X. Guo
Authors : R. Meyer
Affiliations : -
Resume : With planar NAND Flash memory technologies approaching its physical limits, the semiconductor memory industry is looking into non-silicon alternatives with the potential to compete with and eventually replace the main stream technology. Over the last decade several memory technologies based on a resistance change effect, commonly referred to as resistive RAM, have been developed. Prominent examples are Magnetic RAM (MRAM, STT-MRAM), Phase Change Memory (PCM), Conductive Bridge Memory (CBRAM), and oxide based RRAM. Oxide based RRAM cells comprise of one or more functional oxide layers. The resistance change is based on an electric field driven redistribution of oxygen vacancies within the layers causing a variation of the electrical conductivity. Even though there are similarities in the operation compared to solid oxide fuel cells and batteries, high electric fields, self-heating, interface effects, and the lack of knowledge of the material properties on the nanoscale are key challenges in indentifying underlying mechanisms and improving the performance of oxide RRAM devices. The tunnel RRAM is one example of an oxide based RRAM. The device is formed by a two layer structure comprising of a thin ZrO2 tunnel oxide layer and a conductive perovskite layer, which is typically a manganate. The tunnel RRAM is characterized by a uniform rather than a local change in conductivity, which allows describing the behavior using 1D models. The resistive memory effect is achieved by exchanging oxygen vacancies between the conductive layer and the tunnel barrier. In the presentation, we will review the device functionality and the current state of understanding of the device physics. Opportunities and challenges regarding device modeling and optimization as well as requirements for emerging memory technologies to be able to make the transition from lab to product will be discussed.
Authors : M. Martin, L. Nagarajan, J. Brendt, M. Liu
Affiliations : Institute of Physical Chemistry, RWTH Aachen University, Germany
Resume : Ionic and electronic transport in functional oxide materials is of great relevance for applications in the fields of energy and data storage, e.g. solid oxide fuel cells (oxygen ion conductivity), oxygen permeation membranes (ambipolar diffusion of oxygen), or data storage materials (electronic and/or ionic conductivity). In this contribution our recent work on highly non-stoichiometric thin film oxides will be discussed with special emphasis on amorphous, highly non-stoichiometric oxides. In amorphous solids structural disorder can lead to an insulatormetal transition on account of Anderson localization, i.e. the electronic states below the mobility edge are localized. If the Fermi energy passes through the mobility edge the material changes from an electronic insulator to a metal. In addition, large deviations from the ideal stoichiometry of an oxide, that is, high defect concentrations, provide a high concentration of electronic defects (self-doping). We will consider examples of highly disordered oxides that were prepared by pulsed laser deposition and discuss their electronic conductivities and their application in resistive memory devices.
Authors : R. Dittmann
Affiliations : Peter Grünberg Institute (PGI 7), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
Resume : Although there exists a general consensus that bipolar resistive switching in transition metal oxides is in most cases connected with a redox-process, the details of the underlying physical mechanism are only poorly understood up to now. One of the obstacles for its further elucidation is that the net changes of structure, stoichiometry and valence state during electroforming and switching are very small and occur primarily at the electrode interface ore within nanoscale filaments. In this talk, we will present an overview over the current state of experimental verification of the proposed switching models. For epitaxial SrTiO3 thin film devices, by the combination of scanning force microscopy with photoelectron spectromicroscopy and X-ray absorption spectroscopy, we were able to prove that electroforming goes along with a homogeneous as well a local formation of oxygen vacancies. Moreover, significant changes are detected in the chemical state as well as in the relative stoichiometry of the cation sublattice during electroforming demonstrating the formation of new phases. By performing hard X-ray photoelectron spectroscopy, we could experimentally prove that resistive switching in Pt/Ti/PCMO/SRO/STO devices is based on a redox-process, which mainly happens on the Ti side. The different resistance states are determined by to the amount of fully oxidized Ti-ions in the stack, implying a reversible redox-reaction at the interface, that governs the formation and shortening of an insulating tunnel barrier.
Authors : S. Brivio, G. Tallarida, E. Cianci and S. Spiga
Affiliations : Laboratorio MDM, IMM-CNR, via C. Olivetti 2, 20864 Agrate Brianza (MB), Italy
Resume : In most resistive switching (RS) devices, the commutation of resistance among diverse states is explained in terms of formation and rupture of conductive filaments (CFs) made of ionic species inside a Metal-Oxide-Metal stack. The filamentary-type of operation leads to important implications for downscaling capabilities as well as for operation variability, reasons why a clear understanding of the evolution of the CF shape during formation and rupture processes is a decisive issue. In the present work the tip of a Conductive Atomic Force Microscopy (CAFM) is employed as a mobile electrode on a HfO2/TiN RS structure. First we recognize that in the initial state the conduction is localized in nanometric paths activated by defects sited near the HfO2/TiN interface. The defective paths develop into CFs when a sufficiently high voltage is applied to the structure, reducing the resistance of a RS device. We demonstrate that CFs can be disrupted, closing a RS cycle and restoring a high resistance state. The AFM tip is also used to address single CFs and to study how the operation over one filament influences the neighboring ones. Finally we propose a comprehensive picture of the evolution of CF shape during formation and rupture: rather than a group of nearly parallel and independent CFs, a network of conductive branches ramifies from the defects that activate the conduction in the initial state. This work is partially supported by Fondazione Cariplo (MORE Project n?2009-2711).
Authors : F. Messerschmitt, M. Kubicek, S. Schweiger, J.L.M. Rupp
Affiliations : Electrochemical Materials, ETH Zurich
Resume : Redox-based metal oxide resistive switching offers new perspectives towards replacement of classic transistor based memories. Despite the promises of fast non-volatile ns-switching and high package density there is a lack of studies in which carrier contributions (ionic vs. electronic) are systematically varied for an oxide solid solution. Sr(Ti,Fe)O3 is a well-studied model material for which the band gap can be altered by 1.5eV. In this study, cross-bar memory arrays of the model system Pt|Sr(Tix,Fe1-x)O3|Pt were fabricated and discussed towards carrier contributions to kinetics and switching mechanism. First, we classically analyze switching kinetics via cyclovoltametry and pulsed experiments. Independent on doping hysteretic bipolar I-V profiles were recorded; a decrease of the low resistance state (LRS) with reduction of sweep rate is observed. Unfortunately, pure diffusion kinetics via Randles Sevcik equation cannot be extracted for such redox-based systems in metastable state. Hence, chronoamperometry (CA) measurements to analyze diffusion kinetics and to understand equilibrium vs. non equilibrium transport processes are suggested to the field. Exemplarily, time constants of 200-400s at 1-3V (till stable currents establish) are measured via CA. Through an extension of the classic Cottrell equation we determine bias-dependent diffusion constants of 2x10-19-9x10-20m2/s for 6-2MV/m. Further, humidification effects on the devices` programming voltage and LRS are discussed.
Authors : Nina Balke, Stephen Jesse, Sergei Kalinin
Affiliations : Center for Nanophase Materials Sciences Oak Ridge National Laboratory
Resume : Ionic currents determine the functionality of various devices for energy and information applications, such as Li-ion batteries, fuel cells, or memristor-type applications. To understand device limitations and to draw a roadmap to optimize device properties, the ionic flow has to be studied on relevant length scales of grain sizes, structural defects, and local inhomogeneities, i.e. over tens of nanometers. Knowledge of the interplay between the ionic flow, material properties, and microstructure can be used to optimize the device properties, for example to maximize energy density, increase charging/discharging rates, and improve cycling life for Li-ion batteries for applications in electric vehicles and aerospace. Scanning Probe Microscopy (SPM) is a universal tool to study electromechanical effects in oxide materials. While used extensively to investigate the piezoelectric effect in ferroelectric materials, SPM was used in various ways to study ionic transport in oxides in recent years. Ionic transport in these systems can be studied through the interplay of materials volume changes and ionic concentration and the interaction of near-surface charges and the SPM tip. In this talk, we want to give an overview over what has been achieved in the fields of Li-ion batteries, Li-air batteries, fuel cells, and electrochemical supercapacitors using SPM-based techniques. We will focus on SPM signal generation and data interpretation and provide numerical and analytical models to support various scenarios. The goal is to show the possibilities of SPM-based methods to study ionic transport in various material systems with an unmatched lateral resolution and highlight the interplay between ionic transport and microstructure. Support was provided by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division, Scientific User Facilities Division, and by the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center.
Theory : Prof. M. Martin and Dr. R. DeSouza
Authors : Bilge Yildiz, Lixin Sun, Dario Marrochelli, Yue Fan
Affiliations : Laboratory for Electrochemical Interfaces, Department of Nuclear Science and Engineering, Massachusetts Institute of Technology 24-210, 77 Massachusetts Avenue, Cambridge 02139, USA
Resume : Enhancement of ionic conductivity in thin films or multilayers of oxide materials, i.e. doped zirconia and ceria, has sparked great interest in the search for fast ion conducting structures for fuel cells as well as for red-ox based resistive memories. The enhancement in ionic conductivity in such structures could be attributed to elastic strain arising from the lattice mismatch at the interface. However, this assumes that the interface between two materials is perfectly coherent, while in most cases dislocations are observed, and these dislocations relax the interfacial elastic strain. The strain field and the electrostatic field that arises from the dislocations can also impact the defect stability, distribution and mobility in these materials; and yet, the role of dislocation on the ionic conductivity is not consistently reported in the literature nor is it clearly understood. The aim of our work is to quantitatively assess the dislocation's influence on the ionic conductivity in fluorite and perovskite oxides, exemplified by doped CeO2 and SrTiO3, respectively. Edge dislocations in in these materials are studied by atomistic simulations combining the Monte Carlo, Molecular Dynamics and Nudge Elastic Band calculations. Asymmetric distribution profiles of dopant cations and oxygen vacancies are found as a result of the strain field of the dislocation, and the diffusion kinetics along and across the dislocations is found to depend on the structure and composition.
Authors : E.A. Kotomin, M.M. Kuklja, D. Fuks, Yu. A. Mastrikov, J. Maier
Affiliations : Max Planck Institute for Solid State Research, Stuttgart, Germany; Institute for Solid State Physics, University of Latvia, Riga, Latvia; Materials Science and Eng. Dept., University of Maryland, College Park, MD, USA; Dept Materials Engineering, Ben Gurion University of the Negev, Israel
Resume : Among advanced materials for clean energy, oxygen-deficient mixed conducting perovskites BSCF and LSCF are considered as promising materials for cathodes in solid oxide fuel cells (SOFC) and oxygen permeation membranes. BSCF exhibits the best oxygen exchange performance amongst similar materials, which can be related to its mixed electronic and ionic conductivity. In particular, its high oxygen vacancy concentration and low diffusion activation barrier contribute to the fast oxygen reduction kinetics. However, it exhibits a tendency to decompose at intermediate temperatures into a mixture of cubic and hexagonal perovskite phases which is detrimental for its use. In order to understand a mechanism of this unwanted process, first principles quantum mechanical calculations of BSCF and LSCF with different oxygen deficiency were performed and possible decomposition scenarios studied. It was shown that formation energies of oxygen vacancies in the cubic and hexagonal phases of BSCF differ considerably not only in absolute values, but also in their variation with the actual oxygen non-stoichiometry. In fact, it is a large oxygen non-stoichiometry that makes the cubic phase more stable than the hexagonal one. LSCF is shown to be much more stable with respect to such a phase transformation. The first principles calculations are accompanied with the thermodynamic analysis of the conditions under which the cubic phase is stable. M. Kuklja, E.Kotomin, R. Merkle, PCCP 15, 5443 (2013).
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Oxide Interfaces : Prof. T. Ishihara and Dr. R. Merkle
Authors : Carsten Korte
Affiliations : Fuel Cell Laboratory, FZ Jülich, Germany
Resume : Ionic conduction and diffusion in micro-/nanoscaled materials differs significantly from bulk materials. This is due to the modified transport properties of solid-solid interfaces and surfaces. In this contribution a literature overview is given on experimental studies treating ionic transport in thin films and multilayers. By reviewing and comparing the data, the magnitudes of the observed interface effects can be classified, considering the total increase of the conductivity/diffusivity together with the layer thickness. The least effect can be found i) in case of transport along boundaries between extrinsic ionic conductors (and insulator). Mediocre effects can be measured for ii) transport along surfaces of extrinsic ionic conductors. The highest effects are reported for iii) transport along boundaries between intrinsic ionic conductors. The effects differ by about two orders of magnitude (1 : 101 : 102). The modified interface transport in category i) is most probably due to strain effects, misfit dislocations or disordered transition regions. Focussing on strain effects, an analytical model, based on a phenomenological description will be presented. A multilayer consisting of crystalline thin films with coherent interfaces and biaxial mechanical strain due to lattice misfit is assumed. The conjoined layers consist of columnar crystallites with constricted cross section, enabling strain relaxation by shear. Expressions for the total ionic transport relative to bulk transport and for the spatial extent of the strained interface regions as a function of the layer thickness are obtained. The model is used to describe experimental data from O2- conductivity and 18O diffusion studies as well as from XRD strain studies, performed on YSZ/rare earth metal oxide multilayers with systematically varied lattice misfit.
Authors : F.Gunkel, S. Wicklein, S. Hoffmann-Eifert, R. Dittmann, R. Waser
Affiliations : Forschungszentrum Jülich GmbH, Peter Gruenberg Institute 7 & JARA-FIT
Resume : The role of defects is a focus of the ongoing discussion about the electronic properties of the conducting interface between the two insulators LaAlO3 (LAO) and SrTiO3 (STO). In this study, the LAO/STO-interface is discussed from a defect chemical point of view. Utilizing conductance measurements in high temperature equilibrium with the surrounding atmosphere we discuss the conduction mechanism and defect-related charge compensation mechanisms at the LAO/STO interface. In particular, we will show that at high oxygen partial pressures Sr-vacancies are formed as a result of an unavoidable thermodynamic equilibrium process (Schottky-equilibrium). These acceptor-type defects reduce the electron density finally resulting in insulating interfaces. We furthermore investigated the transport properties of LAO/STO-bilayers. The interplay of cationic defects in the STO layer and electronic properties of the bilayer-interface is systematically analyzed by a growth-controlled variation of the cation-stoichiometry in the STO thin films. Resistance measurements and Hall measurements on various bilayer-samples reveal a stoichiometry-effect on both electron mobility and carrier density. The results indicate an enhancement of scattering processes in as-grown non-stoichiometric samples which is in line with an increased density of defects.
Authors : E. Eustache1,2,3, C. Douard2, P. Tilmant1,3, L. Morgenroth1,3, P. Rousse4l, T. Brousse2,3 and C. Lethien1,3
Affiliations : 1 Institut d'Electronique, de Microélectronique et de Nanotechnologie, CNRS UMR 85202 2 Institut des Matériaux Jean Rouxel, CNRS UMR 6502 France, 3 Réseau sur le Stockage Electrochimique de l'Energie (RS2E), CNRS FR 3459 4 Unité de Catalyse et de Chimie du Solide (UCCS), CNRS UMR 8181
Resume : To get autonomous smart microsystem, a miniaturized power source should be integrated. As the device is surface limited, the energy and power performances of commercially available planar microbatteries and micro-supercapacitors are not sufficient to reach this goal. To improve their performances while keeping constant the footprint area of such devices, a 3D topology is proposed. The silicon micropillars and microtubes fabricated by a top down approach allows to reach a high area enlargement factor (AEF). Energy density can be increased by one or two orders of magnitude compared to standard planar micro-devices, thus providing improved autonomy to the powered microsytems. Step conformal deposition of platinum (current collector) and TiO2 (negative electrode of the Li-ion microbattery) are performed on the 3D structures by Atomic Layer Deposition facility. With a 3D scaffold having an AEF close to 25 combined with a 150 nm thick TiO2, a surface capacity of 0.2 mAh/cm2 at C/10 is reported. A micro-supercapacitor electrode based on a thin manganese dioxide film is conformably grown by pulsed electrodeposition on the 3D topologies. A MnO2 film (275 nm thick) reaches 250 mF/cm? at 5 mV/s. The surface capacitance is drastically enhanced compared to a standard 2D electrode with a comparable thickness. This study shows promising AEF leading to high energy density while keeping enough spacing in the microstuctrures array to allow the deposition of the overlying layers.
Authors : H. Wardenga, M. V. Hohmann, A. Klein
Affiliations : Technische Universität Darmstadt, Institute of Materials Science, Surface Science Division, Jovanka-Bontschits-Straße 2, 64287 Darmstadt, Germany
Resume : In2O3 is an important transparent electrode material for solar cells. In order to obtain sufficiently high carrier concentrations, Sn-doping is widely used. Such films show electron mobilities of 30-40 cm2/Vs and have a high reflectivity in the infrared region of the light spectrum. While this is desirable for energy efficient (low-E) windows, it can cause noticeable reduction of the photocurrent of solar cells with semiconductor energy gaps around 1 eV. One way to prepare In2O3 films with high carrier mobility (up to 100 cm2/Vs) is vacuum annealing of films deposited at room temperature under the addition of H2O to the process gas. We have deposited such films using magnetron sputtering. The samples are analyzed in-situ using photoelectron spectroscopy, and ex-situ using X-ray diffraction, optical transmission and Hall-effect. Moreover, we present in-situ Hall-effect studies during vacuum annealing, revealing distinct dependence of carrier concentration and mobility with time at different annealing temperatures. For all annealing temperatures, the evolution with annealing time occurs in three steps, which occur faster with higher temperature. The strong changes of carrier concentration and mobility are related to the decomposition of the partially present hydroxide into oxide, crystallization and strain relaxation, as well as to H and O diffusion. It is suggested that H passivation of grain boundaries is the main origin of the high mobilities obtained with In2O3:H2O films.
Authors : G. Gregori, M.C. Göbel, F. Baiutti, E. Gilardi, G. Logvenov, J. Maier
Affiliations : Max Planck Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany
Resume : The ability of fabricating thin films and multilayered heterostructures with different microstructures by simply modifying the growing conditions or choosing different substrates has disclosed an exciting playground to (i) investigate how boundary effects (e.g. charge carriers redistribution and strain) impact the electrical transport properties and (ii) explore new solutions to improve conduction properties of materials. Over the last years, we have quantitatively investigated how (i) boundaries affect the charge carrier concentrations by comparing the conductivities of nanocrystalline and epitaxial thin films; (ii) how a charge carrier enrichment can be safely detected at the film/substrate interfaces and to which extent it can affect the transport properties of the film; (iii) how ion redistribution at interfaces of heterostructures can modifies the overall electrical properties of multilayered systems. In the present contribution, a series of fascinating examples will be illustrated, which emphasize the relevance of interface effects on the ionic and the electronic transport properties of the above mentioned situations.
Authors : George F. Harrington, Stephen J. Skinner, David W. McComb and John A. Kilner
Affiliations : 1) Department of Materials, Imperial College London, London, UK 2) Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio, USA
Resume : Cation segregation to the surface of materials for SOFC applications is known to impact on overall device performance and hence is of great interest both fundamentally and practically. Experimental studies focused on the transport properties of ion conductors when grown as strained thin films have recently attracted considerable interest, yet cation segregation is rarely considered. However, changes in the chemical composition cannot be neglected especially when the dimensions of the films approach those distances (tens of nanometers) over which cation segregation is expected to occur. In this work we have employed Low Energy Ion Scattering (LEIS) to study the (100) surface of CGO films on STO, YSZ and LAO substrates and the (111) surface grown on sapphire fabricated by pulsed laser deposition (PLD). We show that as-grown films show minimal segregation despite high temperatures used during fabrication (600 - 800?C), yet the surface composition varies drastically from the nominal bulk when heated post growth to temperatures associated with processing or conductivity measurements (800 - 1000?C). Furthermore we find that the strain induced on the films by the substrates, as measured by XRD, affects the extent of the surface segregation. After an 800?C anneal CGO films grown on STO are observed to have a surface Gd/Ce ratio of over 7 times that of the bulk composition whereas those grown on LAO show only a three-fold increase, with the CGO/YSZ system being the intermediate case. The effects of lattice strain on the driving force for dopant segregation will be discussed along with the composition profile as the film thicknesses are decreased to the length scales associated with the segregation effects.
Authors : Marchiori, C. Fompeyrine J.
Affiliations : IBM Research
Resume : During the last 10 years, the quest for a replacement gate dielectric in field effect transistors has been a powerful driver to investigate the deposition of ultra thin oxide thin films. Replacing SiO2 with HfO2 in transistors was a major breakthrough for the microelectronic industry and generated a lot of know-how. This knowledge is today cross-fertilizing research areas that are not limited to the search for a new gate dielectric. Controlling the interface between the oxide and silicon has for example always been a key issue. This specific research triggered the development of new deposition processes, enabling researchers to grow high quality, crystalline, complex oxide films onto silicon. Such functional oxides have physical properties that make them very attractive to perform functions that will be required in future Information and Communication Systems. Properties such as ferroelectricity, piezoelectricity or electro-optic activity is often tightly depending on the ionic character of these materials, on the structural details in the cationic or anionic sub lattice, etc. This presentation will deal with the opportunities and challenges to combine silicon microfabrication techniques with the capability to grow crystalline directly on silicon. It will in particular focus on the use of ferroelectric perovskites for photonic circuits in future systems, and how defect chemistries might play a crucial role.
Authors : Peter Velicsanyi, Andreas Nenning, Edvinas Navickas, Alexander K. Opitz, Herbert Hutter, Juergen Fleig
Affiliations : Vienna University of Technology, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria
Resume : In surface science ceria is a highly interesting material owing to its attractive catalytic surface activity and it was thus intensively investigated within the last decade. This high catalytic activity was recently demonstrated to be also very beneficial for the electrochemical H2 oxidation on Sm doped CeO2 electrodes with noble metal current collectors . For further improvement and understanding, analysis of the effect of (co-)doping on transport and surface kinetics is helpful. In the present study, model-type thin films of Gd doped and Gd/Mn co-doped ceria were investigated by means of impedance spectroscopy in humid H2 atmosphere. A novel measurement technique for microelectrodes with interdigitating Pt current collectors was employed. This method allows a separation of the different elementary processes contributing to the electrode impedance. After annealing at 650 °C in humid H2 atmosphere, the electronic conductivity of Gd-doped ceria is higher than that of the co-doped material. In terms of surface exchange rate, however, the Gd/Mn co-doped ceria shows the higher activity. In addition 18O tracer incorporation into Gd-doped ceria electrodes from a H2/H218O atmosphere was performed with and without cathodic polarization. The tracer distribution within the ceria thin film was subsequently analyzed by secondary ion mass spectrometry (SIMS) and correlated with the electrochemical results.  Chueh et al. Nat. Mat. 11 (2012), p.155
Authors : C. Niedrig, L.-S. Unger, S. F. Wagner, W. Menesklou, E. Ivers-Tiffée
Affiliations : Institut für Werkstoffe der Elektrotechnik (IWE), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe/Germany
Resume : For high-temperature energy applications, e.g., as solid oxide fuel cell cathodes or as dense ceramic oxygen-permeation membranes, mixed ionic-electronic conducting (MIEC) perovskites, namely of the composition (AxSr1-x)(CoyFe1-y)O3-delta (A = La, Ba, Pr), are promising candidates given their excellent oxygen-ionic and electronic transport properties. A high level of oxygen non-stoichiometry is an important prerequisite for a high performance; however, the structural stability of the oxide is also affected by oxygen deficiency. Changes in oxygen stoichiometry Δdelta were determined by coulometric titration experiments performed on selected state-of-the-art MIEC samples (BSCF, LSCF, PSCF) in a tubular zirconia oxygen pump setup. This setup facilitates precise oxygen partial pressure control in the entire range between pO2 = 10^-18 ... 1 bar between 700 °C and 900 °C. By monitoring the electric current necessary for pumping oxygen through the solid electrolyte into or out of the measurement chamber, the amount of oxygen transported and, thus, changes in oxygen stoichiometry can be determined with a high resolution. All experiments were performed on fine-grained powders to avoid kinetic influences resulting from non-equilibrium conditions. The Δdelta(pO2) behaviour was investigated for the above-mentioned high-performance MIEC oxides down to their low-pO2 stability limits which were similar for all compositions (< 10^-10 bar at temperatures of 700 900 °C).
Authors : C. Niedrig, L. Willms, L.-S. Unger, W. Menesklou, S. F. Wagner, E. Ivers-Tiffée
Affiliations : Institut für Werkstoffe der Elektrotechnik (IWE), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe/Germany
Resume : The kinetics of oxygen transport is essential for an application of mixed ionic-electronic conducting (MIEC) oxides as solid oxide fuel cell (SOFC) cathodes, as high-temperature gas sensors or as oxygen-permeation membranes. The performance of the materials is determined by the chemical diffusion coefficient D and the surface exchange coefficient k. Commonly, D and k values are determined by electrical conductivity σ relaxation (ECR) using different gas mixtures. Here, however, a closed tubular zirconia oxygen pump  was used which facilitates precise control of oxygen partial pressure pO2 continuously within the entire range between 10^-18...1 bar at temperatures above 700 °C to determine D and k values for several MIEC oxides such as BSCF and LSCF . In this study we evaluate D and k values by numerical analysis (using MATLAB) of both pO2(t) and σ(t) with the focus on the influence of sample response behaviour, sample geometry, amplitude of pO2 steps (in the range from 10^-5...10^-1 bar), and setup-dependent flush times on the determinability and accuracy. This analysis tool was developed in order to identify a confidence region for (ideally) a set of both D and k values or (in the case of diffusion control) only a D value or (for surface control) only a k value. References  C. Niedrig et al., J. Electrochem. Soc. 160, F135 (2013)  C. Niedrig, H. J. M. Bouwmeester et al., manuscript in preparation
Authors : C. Niedrig, L. Wolff, L.-S. Unger, W. Menesklou, S. F. Wagner, E. Ivers-Tiffée
Affiliations : Institut für Werkstoffe der Elektrotechnik (IWE), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe/Germany
Resume : A high-temperature measurement setup was developed to deconvolute the electronic conductivity in mixed ionic-electronic conducting (MIEC) oxides at temperatures as high as 600 °C. We focus on (Ba0.5Sr0.5)(Co0.8Fe0.2)O3-δ (BSCF) which is a very promising candidate for an application as oxygen-permeation membranes due to its excellent permeation properties . Its conductivity mechanism as a function of temperature has, however, so far not been fully understood. Determination of the (p-type) electronic carrier concentration and mobility may contribute to this understanding. The very low Hall mobilities require frequency-selective measurements which we realized by lock-in technique. The setup includes an alumina high-temperature sample holder with which a 5-point contacted homogeneous sample can be inserted into an external magnetic field of variable flux density B (up to 700 mT), resulting in a Hall voltage perpendicular to both B and the electrical current I. Additionally, a sealed setup enables measurements in different gas atmospheres . By using BSCF thin-film samples chemically deposited onto NdGaO3 single-crystalline substrates  a satisfactory signal-to-noise ratio is ensured for the Hall voltage. References  J. Sunarso et al., J. Membrane Sci. 320,13 (2008)  R. Moos, W. Menesklou, K.H. Härdtl, Appl. Phys. A 61, 389 (1995)  K. Asano et al., Solid State Ionics (2013), submitted
Authors : Catalin Constantinescu (1), Valentin Ion (1), Simona Condurache-Bota (2), Petre Rotaru (3)
Affiliations : (1) INFLPR National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor bd., RO-077125, Bucharest, Romania; (2) "Dunarea de Jos" University, Faculty of Sciences; 111 Strada Domneasca St., RO-800201, Galati, Romania; (3) University of Craiova, Faculty of Physics, 13 A.I. Cuza St., Craiova RO-200585, Dolj, Romania;
Resume : Bismuth oxide has seen interest as a material for solid oxide fuel cells, since it is an ionic conductor, i.e. oxygen atoms move through it. Herein, we present results on bismuth oxide thin films grown by pulsed laser deposition and radiofrequency-assisted pulsed laser deposition, in oxygen atmosphere. The influence of the deposition parameters, i.e. laser wavelength, fluence, oxygen pressure, the use of an oxygen plasma, and substrate type and temperature, on the thin film structure and morphology, are discussed. A comparative study is presented here, on the advantages of using laser processing and micro-/nano structuring vs. other techniques, for applications in solid oxide fuel cells.
Authors : Jung- Hee Kim; Hae-Kyoung Kim; Hee Young Lee; Jai-Yeoul Lee
Affiliations : Yeungnam University
Resume : Li doped spinel, Ni1-xLixCo2O4, thin films were fabricated by sputtering and pulsed laser deposition. Thin films were grown on glass and c-sapphire single crystal substrates at various substrate temperatures and oxygen partial pressures. The effects of the processing parameters on the crystal structure, electrical and optical properties of Li- doped spinel thin films were analyzed by XRD, AFM, four point probe method, and UV spectrometer. As the doping concentration x increased, the electrical conductivity increased up to x=0.3. The optical transmittances increased with increasing substrate temperature up to 400℃. The thin films growth with strong (111) preferred orientations were observed on the sapphire substrates. Li doped Ni1-xLixCo2O4 spinel thin films with electrical conductivity of 60 S/cm and optical transmittance about 50% were fabricated with optimum processing parameters.
Authors : Malek Atyaoui, Ben Amor Sana,Wissem Dimassi, Brahim Bessaïs and Hatem Ezzaouia.
Affiliations : Laboratoire de Photovoltaïque, Centre de Recherche et des Technologies de lEnergie, PB: 95, Hammam Lif 2050, Tunisia
Resume : We report on the effects of substrate temperature (Ts) on the morphology and structural properties of Hydrogenated nanocrystalline silicon (nc-Si:H) thin films, grown by radio frequency Plasma Enhanced Chemical Vapor Deposition (PECVD) on silicon single crystal (1.0 0) using a gas mixture of silane (SiH4) and hydrogen (H2). Substrate temperature was varied from room temperature to 450 °C. Characterization of these films X-ray diffraction (XRD), Raman spectroscopy revealed that the crystallite size and at same time the volume fraction of crystallites in the films tends to decrease with increase in Ts. The Fourier transform infrared spectroscopic analysis (FTIR) showed at low temperature the hydrogen is incorporated in the nc-Si:H films in the mono-hydrogen (Si-H) bonding configuration. With increasing Ts the hydrogen bonding in nc-Si:H films shifts from mono-hydrogen (Si-H) to di-hydrogen (Si-H2) and (Si-H2)n. The hydrogen content in the nc-Si:H films decreases with increase in Ts. From The Atomic Force Microscopy (AFM), it was shown that the increase in Ts tends to increase the porosity and decrease the crystalline grain size. In order to more understand the effect of Ts on this structural change, Minority Carrier Lifetime (MCL) measurement show that only the films with a nanocrystalline silicon structure present an enhancement in MCL which could be related to a quantum size effect and to the SiH-related bonds
Authors : V. Silva1,2, P. Louro1,2, M. A Vieira1,2, M. Vieira1,2,3
Affiliations : 1Electronics Telecommunication and Computer Dept. ISEL, R. Conselheiro Emídio Navarro, 1949-014 Lisboa, Portugal Tel: +351 21 8317290, Fax: +351 21 8317114; 2 CTS-UNINOVA, Quinta da Torre, Monte da Caparica, 2829-516, Caparica, Portugal.; 3 DEE-FCT-UNL, Quinta da Torre, Monte da Caparica, 2829-516, Caparica, Portugal
Resume : The use of UV steady state illumination increases the spectral sensitivity of a double pin/pin photodiode beyond the visible spectrum. Increased sensitivity in the range of 400 nm-850 nm is experimentally demonstrated. Results show that the spectral current under UV front light irradiation (350 nm) increases with the background intensity in the 470nm-800nm range and decreases for low power wavelengths in the visible range. Under back irradiation the spectral current decreases for wavelengths higher than 550nm and strongly increases beneath them. Under front irradiation and low power intensity the gain is high and presents a well defined peak at 750 nm and strongly quenches in the visible range. As the power irradiation increases the peak shifts to the visible range and can be deconvoluted into two peaks one in the red range and another in the green range. In the blue range the gain is much lower showing the filtering properties of the device at different UV background intensities. Under back irradiation the gain is high in the violet/blue ranges and strongly quenches for higher wavelengths whatever the intensity of the background. Results show that, front background enhances the light-to-dark sensitivity of the medium, long and infrared wavelength channels and quench strongly the low wavelength, depending optical amplification on the background intensity. Back UV background enhances only the channel magnitude in short wavelength range and reducing it in the long ones.
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Mixed Conducting Perovskites I : Prof. W. Preis and Dr. M. Burriel
Authors : M. Burriel1,2, A.M. Saranya1, A. Morata1, H. Téllez2,3, Y. Chen4, N. Tsvetkov4, B. Yildiz4, A. Tarancón1 and John A. Kilner2,3
Affiliations : 1 Catalonia Institute for Energy Research (IREC), Department of Advanced Materials for Energy 2Department of Materials, Imperial College London, London, SW7 2AZ, UK 3International Institute for Carbon-Neutral Energy Research, Kyushu University 4Laboratory for Electrochemical Interfaces, Massachusetts Institute of Technology, US
Resume : In order to design novel optimized compositions with improved MIEC (Mixed Ionic Electronic Conducting) properties for IT-SOFC cathodes it is of high importance to: 1) acquire a better understanding of the oxygen incorporation, oxygen diffusion and surface reconstruction processes and 2) achieve fast screening of new materials and properties by fine tuning compositions. In this sense, low-energy ion scattering (LEIS) has emerged as a unique technique capable of quantifying the chemistry of the outermost surface with single-atomic-layer sensitivity. In addition, by combining LEIS with oxygen isotope exchange coupled with time-of-flight secondary ion mass spectrometry (ToF-SIMS) it has been possible to correlate exchange kinetics with chemical processes at materials atomic surfaces. Examples of the application of these ion beam analysis techniques for the characterization of epitaxial layered MIEC thin films will be presented, emphasizing the valuable and unique insight provided in the oxygen-incorporation and cation segregation processes. Moreover, by applying the Isotope Exchange Depth Profiling technique to a binary perovskite composition system generated by combinatorial PLD, spatially-resolved oxygen exchange and mass transport properties (k* and D*) have been obtained. This combinatorial approach to material synthesis and characterization has recently opened a new avenue on the generation of entire compositional diagrams in a single experiment.
Authors : Alexander K. Opitz (1), Markus Kubicek (1,2), Stefanie Huber (1), Tobias Huber (1), Andreas Nenning (1), Edvinas Navickas (1), Gerald Holzlechner (1), Herbert Hutter (1), and Jürgen Fleig (1)
Affiliations : (1) Vienna University of Technology, Institute of Chemical Technologies and Analytics, Getreidemarkt 9/164-EC, 1060 Vienna, Austria; (2) ETH Zurich, Department of Materials, Electrochemical Materials, Schafmattstraße 30, 8093 Zurich, Switzerland
Resume : Recently, model-type thin film electrodes were demonstrated to be powerful tools for investigation of solid state electrochemical systems. One of their major advantages is that electrochemically active zones are relatively easy accessible by surface analytical methods. Oxygen incorporation zones, for example, can be visualized by polarization-driven 18O tracer incorporation in combination with time-of-flight secondary ion mass spectrometry analysis. In the present contribution, application of this technique to a number of different electrode materials is discussed. By 18O incorporation at Pt electrodes two different reaction pathways could be identified at high cathodic polarization. A successful separation of different oxygen reduction pathways was also possible for La0.8Sr0.2MnO3-δ (LSM) electrodes. Under lower polarization a surface path with oxygen incorporation at the three-phase boundary is found to dominate, whereas at higher cathodic polarization a bulk path becomes more pronounced. Measurements on La0.6Sr0.4CoO3-δ (LSC) and La0.6Sr0.4FeO3-δ (LSF) in 18O2 illustrate the limitations of the tracer incorporation method in case of very high electrochemical activity (LSC) and due to polarization-induced changes of the electrodes electronic conductivity (LSF). Finally, reaction zones of cathodic water reduction at SrTi0.7Fe0.3O3-δ (STF) electrodes were investigated in a H2/H218O atmosphere and results are compared with electrochemical impedance measurements on this system.
Authors : Tatsumi Ishihara, Young-Wan Ju, Shintaro Ida
Affiliations : International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka, Japan; Department of Applied Chemistry, Faculty of Engineering, Kyushu University, Fukuoka, Japan
Resume : Solid oxide fuel cells (SOFCs) have been attracting much interest as alternative energy conversion system for next generation. At present, improvement of long term stability is strongly required for SOFC and one reason for decrease in power density could be assigned to the sintering of porous anode, Up to now, three phase boundary is considered as the active site for anode. In this study, we applied La(Sr)Fe(Mn)O3 film as a dense anode for low temperature SOFCs. Dense La(Sr)Fe(Mn)O3-δ (LSFM) nano-film anode is introduced between a NiFe metallic support and LaGaO3 based oxide electrolyte. It was found that the cell using LSFM thin film anode exhibits much improved power density comparing with that of cell with a simple porous Ni-Fe anode. The maximum power density of the cell having LSFM film is approximately 3.0 W/cm2 at 973 K. The improved power density is mainly originated from enhanced anodic properties. Furthermore, the dense LSFM thin film anode is effective for increasing fuel utilization of Ni-Fe metallic anode supported cell. This suggests that two phase boundary (anode and gas phase) is also highly active for anodic reaction. The cell stably shows high power density over reasonably long period. This could be explained by the low dependency of anodic overpotential of LSFM on fuel concentration. Consequently, this study reveals that two phase boundary of LSFM/gas phase is highly effective for high energy conversion efficiency of SOFC.
Authors : Xin Guo
Affiliations : Laboratory of Solid State Ionics, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, P.R. China
Resume : Owing to their wide applications in oxygen sensors, multi-layer ceramic capacitors (MLCC), positive temperature coefficient resistors (PTCR), etc., doped SrTiO3 and BaTiO3 are one of the most important electroceramics. Perovskite structure can tolerate high concentrations of defects, for example, oxygen vacancies, electrons and holes, without changing its structure. Defect reactions and reaction parameters of SrTiO3 and BaTiO3, published in literatures, over the doping range from acceptor to donor, temperature range from room temperature to >1500 K and oxygen partial pressure range of 10^-23 to 1 bar are summarized in this work, and a Windowsbased DefectChemCal program is developed. With the program, we can calculate the defect concentrations and the electrical properties of acceptor and donor-doped SrTiO3 and BaTiO3, and the validity of the program is demonstrated by comparing the calculation results and experimental results.
Authors : S. Adams, R. Prasada Rao, M.H. Chen, H.M. Chen
Affiliations : National University of Singapore, Department of Materials Science and Engineering, Singapore
Resume : Rechargeable all-solid-state lithium batteries are attractive power sources for small scale applications and electrochemically stable Li+ fast ion conductors (FIC) can help to widen their application field. Identifying stable fast ion conductors is thus the key to building practical solid-state batteries. Among the most promising compounds with high ionic conductivities are the thiophosphate-based solid electrolytes. Our studies shed light on the role of disorder in the immobile sublattice as a crucial factor for maximizing their conductivity. This is exemplified both for argyrodite-type halide-doped thiophosphates Li6PS5X (where the S2-/X- disorder for X = Cl, Br opens up local paths for Li+ motion), Li7P3S11, Li9+xGexP2-xS12 (LGPS, where local P/Ge disorder limits the packing density) and isostructural compounds in comparison to a series of known and newly designed thiophosphates. Ab initio structure optimisations and bond-valence based atomistic simulations highlight the role of free volume for fast ion transport and the effect of the chemical sulfur-bonding on the structural and electrochemical stability of the compounds. To reduce the synthesis costs of the thiophosphate solid electrolytes, we designed low temperature or no heating routes for their preparation. Electrochemical impedance studies and the performance of these solid electrolytes in all solid state Li-ion and Li-sulfur batteries (reaching theoretical capacity) will be presented.
Authors : T. M. Huber (1), A. K. Opitz (1), M. Kubicek (1), A. Welzl (1), G. Holzlechner (1), E. Navickas (1), Y. Chen (2), H. Hutter (1), B. Yildiz (2), J. Fleig (1)
Affiliations : (1) Vienna University of Technology Institute of Chemical Technologies and Analytics Research Division Electrochemistry, (2) MIT Department of Nuclear Science and Engineering Laboratory for Electrochemical Interfaces
Resume : Sr-doped lanthanum manganite (LSM) is a widely used cathode material in commercially produced solid oxide fuel cells (SOFC). Despite being a poor ion conductor, LSM electrodes may reduce oxygen via different pathways: a path which includes surface diffusion of oxygen species (surface path) and a path based on oxygen bulk diffusion (bulk path). Separation of effective reaction rates on LSM cathodes into contributions of each path is experimentally highly non-trivial. Accordingly, a detailed knowledge of the rate limiting steps and their dependence on experimental parameters is still missing. In this contribution several methods are employed to identify, quantifying and modify the oxygen reduction paths of (La0.8Sr0.2)MnO3 and (La0.8Sr0.2)0.95MnO3 thin film model electrodes: (i) LSM films on strontium titanium oxide (STO) and yttria-stabilized zirconia (YSZ) with different microstructures, from epitaxially growth to columnar textured, were investigated by 18O tracer diffusion. Numerical analysis allowed separating surface exchange and bulk diffusion properties of both, grains and grain boundaries. (ii) Impedance spectroscopy was used to measure polarization resistances and capacitive effects of micro-patterned and macroscopic thin film, dense LSM microelectrodes. Three phase boundary length and exposed surface areas were varied. (iii) Field driven 18O incorporation and subsequent SIMS analysis revealed quantitative information on the contributions of both reaction paths.
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Cation Conductors : Dr. H. Tellez and Dr. A. Opitz
Authors : Yoshitaka Aoki, Etsushi Tsuji, Hiroki Habazaki
Affiliations : YA; ET; HH; Faculty of Engineering, Hokkaido University YA; JST, PRESTO
Resume : Novel thin film fuel cell based on the 100 nm-thick electrolyte of amorphous ZrP2.5Ox, working at 400C, was demonstrated. The hydrogen permeable membrane fuel cell (HMFC) using a Pd foil as a nonporous solid anode was fabricated. Ni interlayer of several hundreds nm thickness was introduced between the Pd anode and the ZrP2.5Ox electrolyte in order to suppress the deterioration of the electrolyte nanofilm by the deformation of the Pd anode during hydrogen absorption. In the ZrP2.5Ox electrolyte the transport number of proton was unity at 400C as determined by an EMF measurement. The modification of the Ni anode surface by an ultrathin Pt or Pd layer effectively decreased the anode/electrolyte interfacial polarization. Consequently, the HMFC revealed the OCV of 1.0 V and the maximum power density of 20 mW cm-2 at 400 degree C.
Authors : Aline Fluri, Daniele Pergolesi, Thomas Lippert, Alexander Wokaun
Affiliations : Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
Resume : Y-doped barium zirconate (BZY) is a proton conductor with good chemical stability and high protonic conductivity. It is a promising candidate as an electrolyte for solid oxide fuel cells in the intermediate temperature range (400-700 °C), and therefore a possible alternative to oxygen ion conductors. It has been shown that BZY with compressive stress results in larger bulk activation energies for proton migration. By extrapolation, it is expected that tensile lattice distortions may lower the activation energy leading to larger proton conductivities at lower temperatures. However, up to date no experimental evidence has been reported on this effect of tensile stress. For this work, pulsed laser deposition is used for the fabrication of higly textured BZY thin films. Epitaxial thin films free of high angle grain boundaries have been grown with the fully relaxed crystalline structure, in compressive and in tensile stress. In our deposition chamber two in situ diagnostics, i.e. Reflective High Energy Electron Diffraction (RHEED) and a Multi-beam Optical Stress Sensor (MOSS) are combined for the first time. This combination allows an understanding of the connection between the growth mechanism and the stress generation/evolution during film growth. X-ray diffraction (XRD) is employed to characterize the crystalline structure, while electrical characterisations will be performed and correlated to the stress state and the growth mechanism, as revealed by MOSS, XRD, and RHEED.
Carbon Conductors : Dr. M. Bokova
Authors : P. Huang, P.L. Taberna, and P. Simon
Affiliations : Université Paul Sabatier, CIRIMAT UMR CNRS 5085, 118 route de Narbonne, 31062 Toulouse, France
Resume : Electrical Double Layer Capacitors (EDLCs), also known as supercapacitors, are electrochemical energy storage devices for high power delivery or energy harvesting applications . EDLCs store charge through the reversible adsorption of ions from an electrolyte onto high surface area carbons, thus charging the double layer capacitance. Large-size ECs are already used today for power supply and energy harvesting in various applications such as aeronautics, tramways, HEVs ( ) . The recent boom in multifunction portable electronic equipment and the increasing need for wireless sensor networks for the development of smart environments has raised the problem of developing sufficiently compact or flexible energy storage. Designing efficient, miniaturized energy-storage devices that can achieve high energy delivery or harvesting at high discharge rates with a lifetime that matches or exceeds that of the machine being powered remains a challenge. Integrating the storage element as close as possible to the electronic circuit (directly on a chip) is another challenge. This talk will present an overview of the results obtained using carbons in micro-supercapacitors. We will show results obtained using exohedral and microporous carbons, as well as bulk carbon films in micro-devices prepared from different methods. The performance achieved to date addresses the need for microscale energy storage in numerous areas where electrolytic capacitors cannot provide sufficient volumetric energy density, such as nomad electronics, wireless sensor networks, biomedical implants, active radiofrequency identification (RFID) tags and embedded microsensors. References  P. Simon and Y. Gogotsi, Nature Materials, 7 (2008) 845-854.