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A B C D E F G H I J K L M N O P Q R S T U V W X Y

E-MRS Spring 2012 - Symposium X

Quantitative Microscopy of Energy Materials

Over the past decade, instrumental innovations and improvements (like the commercialization ofaberration-corrected electron optics) have boosted the capabilities of imaging and analysing at thenanoscale. Consequently, electron microscopy and related techniques are nowadays widely applied tocharacterize the micro and nanostructure of all kinds of materials. Driven by restricted naturalresources, so-called energy materials, i.e., materials used for energy generation, transmission, andstorage are gaining increasing importance. Being mostly operated under conditions that have a stronginfluence on their microstructure and properties, microdiagnostics and failure analyses are of highscientific and industrial relevance. This symposium will focus on the quantification of the microstructureevolution in such devices, using advanced electron microscopy and other microdiagnostics techniques,and the relationship between microstructure, properties, and efficiency.

Scope

Microstructure-property relations of complex materials commonly used in energy systems form the basisof the targeted applications. Being often subjected to harsh conditions upon operation, microstructure

modification and interactions between materials have to be monitored. Based on such microstructurecharacterization, a fundamental understanding of processes can be developed, being highly relevant fortechnological applications and the optimization of materials properties. Microstructure characterization,down to the nano scale, did significantly profit from the dramatic improvement of electron-opticalimaging and nano analyses over the past decade. The introduction of aberration correction, improveddetectors, enhanced site-specific preparation routes, as well as the exploitation of 3D techniques, haslead to truly advanced and quantitative imaging, diffraction, and spectroscopic analyses with electrons.Electron microscopy has become quantitative, e.g., it has rather become a method to analyse andmeasure quantitatively important microstructure parameters and materials properties. Now that thesechallenging nano-characterization tools are becoming more and more available in academia andindustry, their application in the various fields of materials science and life science is to be addressednext. In parallel, complementary methods for micro and nanocharacterization covering different lengthscales (such as X-ray and neutron diffraction) as well as surface characterization techniques like AFM,SEM will be addressed to gain a comprehensive picture of micro-nanostructure evolution. It is the

intention of this symposium to invite contributions, which will show current applications of suchadvanced techniques to the microcharacterization of materials for energy. This will help to bridge thegap between microdiagnostics methodology and practical applications to materials of economic andecologic importance. Special emphasis will be put on the influence of microstructure evolution on systemproperties, and in particular on the efficiency of energy conversion, transportation, and storage. In thiscontext, the symposium will cover the following topics:

Microdiagnostics: Advanced quantitative electron microscopy (EM) methods strategies and applications: EBSD,scanning-transmission EM for atomically resolved imaging and analytics, emerging in situ techniques(including environmental TEM and SEM), aberration-corrected EM, potential mapping using electrontomography, electron holography, nano-beam diffraction, electron nano-spectroscopic techniques forlocal bonding and elemental mapping, quantification by multiscale modelling Methods of physical failure localization: lock-in thermography, scanning acoustic microscopy, X-ray

diagnostics (tomography) Site-specific sample preparation using innovative ion-beam or laser-based approaches Quantitative microstructure analysis: grain size, coarsening effect, growth mechanisms, radiationdamages, thin film strains and defects, interfaces Crystal-phase identification (XRD, neutron diffraction, XAS, etc.)

Energy materials: Materials for solid-oxide fuel cells including purity issues, ceramic-metal interactions, and metallicinterconnects as well as for polymer electrolyte membranes Thin film PV cells, organic PV cells, materials for high-efficiency PV systems, back reflectors,substrates, transparent conductive oxides, packaging, nanowires Metals and alloys for high temperature utilization, catalysts, thermoelectric materials Separators & active materials for energy-storage Degradation: relation between microstructure, ageing and efficiency Diffusion and interdiffusion: interfaces, doping, and implantation Phase formation and/or transformation: effect of external parameters on phase transformation, relatedto property modifications

Hot topics to be covered by the symposium

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Following the two-pronged scope, the scientific sessions (including a poster session) will be dedicated tomethodological and microanalysis application subjects.Topics will include: Methods of failure analysis: lock-in thermography, scanning acoustic microscopy Site-specific sample preparation: focused ion beam, laser-based methods Microstructure imaging and chemical analysis: scanning-transmission electron microscopy(STEM), in situ electron microscopy, electron tomography, diffraction, e.g. for local strain analyses,aberration-correction and high-throughput EM, electron-beam techniques to map local bonding andelemental distributions, chemical analyses (EDXS, EELS, EFTEM) Solid oxide fuel cells(SOFC): Anode and cathode microstructure evolution, poisoning, pollutantspecies, metallic interconnect conductivity, protective layers Photovoltaic devices: thin film PV cells, organic PV, high efficiency systems, back reflectors,substrates, transparent conductive oxides, packaging, nanowires Polymer electrolyte membranes(PEM): water transport, membrane microstructure, chargetransfer, catalysts Metals and alloys in energy systems: corrosion, creep, mechanical wear, high temperatureutilisation, radiation damage, supported catalysts, thermoelectric materials Energy storage systems: Storage capacity and stability (during hydrogen absorption anddesorption), separators, active materials, corrosion, passivation

Conference Proceedings

Paper submissionis now possiblevia the JMS Online Manuscript Submission website:https://www.editorialmanager.com/jmsc/

Please note that this will NOT be A CONFERENCE PROCEEDING IN THE CLASSICAL SENSE!Allsubmitted paperswill be reviewed by the Guest Editors according to USUAL J Mater Scistandards.

Anything looking like a conference proceedingswill be automatically refused.ONLY FULL ORIGINAL ARCHIVAL PAPERS AND REVIEW PAPERS WILL BE CONSIDERED.

Anything that is not original will be automatically rejected.

Please, complete your submission prior to May 12and select: Special: Energy Materials &Thermoelectrics as an article type.

List of invited speakers

Rik Brydson (U Leeds)Miran Ceh (ISJ Ljubljana)Rafal E Dunin-Borkowski (FZ Jlich)Frank Dimroth (Fraunhofer ISE)Thomas Klassen (HZG)Laurent Legras (EDF)David McComb (Imperial)Paul Midgley (U Cambridge)Robin Schublin (CRPP-EPFL)Dries Van Gestel (Imec)Nestor Zaluzek (ANL)Stefan Zaefferer (MPI Dsseldorf)

Sponsors:



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Symposium organizers

Acha Hessler-WyserCentre Interdisciplinaire de Microscopie ElectroniqueEcole Polytechnique Fdrale de LausanneBat MXC 134, Station 12CH-1015 Lausanne, SwitzerlandPhone: +41 21 693 4830Fax: +41 21 693 [email protected]

Thomas HcheFraunhofer Institute for Mechanics of Materials IWMWalter-Hlse-Strae 1, D-06120 Halle, GermanyPhone: +49 345 5589 197Fax: +49 345 5589 [email protected]

Wolfgang JgerInstitute for Materials ScienceChristian-Albrechts-University KielD-24143 Kiel, Germany

Phone: +49 431 880 6177Fax: +49 431 880 [email protected]

Hugo BenderImecKapeldreef 75B-3001 Leuven, BelgiumPhone: +32 16 281304Fax: +32 16 28 [email protected]

A B C D E F G H I J K L M N O P Q R S T U V W X Y

European Materials Research Society23 Rue du Loess - BP 20 - 67037 Strasbourg Cedex 02 - France - Phone:+33-(0)3 88 10 63 72 - Fax:+33-(0)3 88 10 62 93 - emrs@emrs-

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PROGRAM VIEW : 2012 SpringMY PROGRAM : 2012 Spring

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Advanced microscopy: 3D and in situ: Thomas Hche

09:00 Quantitative Electron TomographyAuthors : Paul Midgley

Affiliations : University of Cambridge, Department of Materials Science andMetallurgy, Cambridge, U.K.Resume : The challenge to find new materials to help solve the worldsgrowing energy problems is one of the most important we face. To meetthat challenge, electron microscopy can play a key role in elucidating theproperty-microstructure relationships of these often complex materials.Electron tomography allows the microstructure of such materials to bestudied in three dimensions and at a high spatial resolution revealing keyinformation that can otherwise be obscured. Over recent years, electrontomography has developed into a powerful tool for materials science andwith the implementation of novel imaging modes has enabled not justmorphology to be seen in 3D but also composition, electrostatic potentialsand defects. Alongside such hardware and technique development, therehas been a rapid development of novel visualization software and

reconstruction algorithms. Importantly, as many of these materials arebeam sensitive, much of the software progress has been aimed at achievingreconstructions with minimal artefacts from limited data sets (and thuslimited electron dose). In this presentation, I will show a number ofexamples related to energy materials that illustrate the quantitative natureof electron tomography and how high fidelity reconstructions are possiblefrom very few images. Recent progress in atomic resolution tomography willalso be discussed.

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09:30 Nanometric Defects in Metals in Transmission Electron MicroscopyAuthors : Robin Schaeublin (1), Brigitte Dcamps (2)Affiliations : (1) Ecole Polytechnique Fdrale de Lausanne (EPFL), Centre deRecherches en Physique des Plasmas, Association Euratom-Confdration Suisse,5232 Villigen PSI, Switzerland; (2) Centre de Spectromtrie Nuclaire et de

Spectromtrie de Masse (CSNSM), CNRS-IN2P3-Univ. Paris-Sud 11, UMR 8609, Bt.108, 91405 Orsay, FranceResume : Conventional transmission electron microscopy including in situdeformation experiments is revisited in order to refine methods for theidentification of nanometric defects in metals and their interaction withdislocations. Nanometric crystal defects play an important role as theyinfluence, generally in a detrimental way, physical properties and inparticular mechanical properties of metals designed for aggressiveenvironments such as high irradiation fields or high heat loads. For instance,radiation induced damage in metals strongly degrades mechanicalproperties, rendering the material stronger but brittle. Indeed, these defectsare obstacles to mobile dislocations, vector of plasticity. It is thus critical tofully characterize them, ideally with transmission electron microscopy. Thedifficulty in using TEM to identify the nature and size of such defects resides

in their small size, close to the resolution of CTEM. TEM image simulationsare deployed to explore limits and possible ways to improve on spatialresolution and contrast on e.g. dislocation loops or stacking fault tetrahedra.Examples of in situ straining experiments of Cu and Fe showing the

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interaction of mobile dislocations with nanometric defects are given. Resultsobtained in Fe are compared to molecular dynamics simulation. Besides, itappears that some image formation mechanisms, using diffraction contrast,are still unclear. We present here the case of energy filtered images ofthreading dislocations that exhibit a top bottom asymetry with increasingenergy loss, and also three dimensional defects in pure Fe and Fe(Cr) thatexhibit anomalous contrast behaviour in weak beam dark field under gcondition while it is normal under bright field condition.

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10:00 Coffee break

10:30 NiO reduction studied by environmental transmission electron microscopyAuthors : Q. Jeangros (1), T.W. Hansen (2), J.B. Wagner (2), C.D. Damsgaard (2),R.E. Dunin-Borkowski (3), C. Hbert (1), J. Van Herle (4), A. Hessler-Wyser (1)Affiliations : (1) Interdisciplinary Centre for Electron Microscopy, EPFL, CH-1015Lausanne, Switzerland; (2) Center for Electron Nanoscopy, Technical University ofDenmark, DK-2800 Lyngby, Denmark; (3) Ernst Ruska-Centre, Jlich ResearchCentre, D-52425 Jlich, Germany; (4) Laboratory for Industrial Energy Systems,EPFL, CH-1015 Lausanne, SwitzerlandResume : Nickel oxide reduction and subsequent Ni behavior under H2atmosphere is of practical importance in the field of solid oxide fuel cells(SOFC) as it determines the structure of the anode electron conductorduring operation. Despite extensive coverage in literature, somediscrepancies remain, notably regarding NiO reduction kinetics andstructural evolution. In situ reduction of an industrial NiO powder from JTBaker is performed under 1.3 mbar of H2 (2 mlN/min) in a differentiallypumped FEI Titan 80-300 environmental transmission electron microscope(ETEM). Images, diffraction patterns and electron energy loss spectra(EELS) are acquired at different temperatures to monitor the structural andchemical evolution of the system. High-resolution ETEM is also performedduring similar experiments. EELS analysis illustrates that reduction firstproceeds quickly at temperatures below 400C up to a reduced fraction ofabout 0.6, until the reaction is slowed down by water created uponreduction. Ni nucleation on NiO is observed to be either epitaxial in thinareas or randomly oriented in thicker regions. The growth of Ni crystallitescreates pores within NiO grains to accommodate the volume shrinkageassociated with reduction. Densification is then observed at temperatureshigher than 550C: pores created at lower temperatures disappear and Nigrains coarsen. This reorganization of Ni is detrimental to both theconnectivity of the Ni catalyst and to the redox stability of the SOFC.

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10:45 Resolving deformation in carbon nanotubes in contact with metal islands atthe atomic levelAuthors : X. Ke, S. Turner, S. Bals, C. Bittencourt, G. Van TendelooAffiliations : EMAT, University of Antwerp, BelgiumResume : The high contact resistance between the carbon nanotubes(CNTs) and metal leads is one main concern in integration of CNTs intodevices. The diameters of the CNTs, the quality of the CNTs and different

contact materials are all considered to influence the contact. Therefore, wefocus on the study of the interface between CNTs and various contactmaterials from structural point of view. CNTs deposited with Au, Pd, Rh andTi are studied by aberration-corrected high resolution transmission electronmicroscopy (AC-HRTEM). Au, Pd and Rh form discreet nanoparticles on multi-walled CNTs, whereas Ti forms continuous film wetting completely theCNTs. More interestingly, 3D electron tomography of the structure has foundout that the graphitic layers in direct contact with Au nanoparticles aredeformed to a certain degree. The deformation degree depends not only onthe contact metal, but also on the diameters of CNTs. Examples will be givenfor different metals and different size CNTs. By using AC-HRTEM at 80kv inorder to reduce knock-on damage to the CNTs, the deformation of thegraphitic layers can be investigated at atomic resolution. The displacementof the carbon atoms from their perfect position can be further quantified and

related to the strain which is believed to be induced by the contact to metal.AC-STEM-EELS is performed in deformed CNT layers to look for thedifferences in electronic states. The study may help optimizing the systemforming CNT-metal contacts for devices.

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Electron Backscatter Diffraction, Atomic Force Microscopy, X-ray Absorption

Spectroscopy, X-ray Diffraction: Hugo Bender

11:00 Quantitative characterization of deformation and transformationmicrostructures of advanced steels using electron diffraction techniques in

the SEMAuthors : S. Zaefferer, N.N. Elhami, C. Tasan, P. Konijnenberg, F. RamAffiliations : Max-Planck-Institute for Iron Research, Department of MicrostructurePhysics, 40237 Duesseldorf, GermanyResume : The scanning electron microscope offers powerful diffractiontechniques which allow the quantitative characterization of defects ofcrystalline materials. These techniques are electron backscatter diffraction(EBSD), electron channelling contrast imaging (ECCI) and Kossel diffraction.EBSD has become a popular method to obtain microstructural images andlocal texture of materials with a spatial resolution of 50 to 100 nm. Newanalysis methods for EBSD patterns and orientation data allow deeperinsight into materials: The measurement of orientation gradients enables thequantitative description of the density of geometrically necessarydislocations (GND), the detailed evaluation of diffraction band profiles givesaccess to the total dislocation density, in-situ deformation experiments allow

understanding of interaction of boundaries and dislocations. 3-dimensionalEBSD based on serial sectioning enables the detailed description of thecrystallography of grain boundaries. The ECCI technique makes it possible toobserve dislocations and stacking faults directly with a similar (but weaker)contrast as in dark field TEM but on bulk samples. This allows, for example,characterization of slip systems, quantification of dislocation and nanotwindensities and observation of dislocation evolution during deformationexperiments. The smallest features observable with this technique are in theorder of 10 to 20 nm.

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11:30 Intermetallic growth in Al-Fe system studied by time resolved X-raytomography combined with FIB/SEM/TEMAuthors : Guillaume Pasche, Acha Hessler-Wyser, Robin Schublin, Ccile HbertAffiliations : Centre Interdisciplinaire de Microscopie Electronique, EcolePolytechnique Fdrale de Lausanne, CH-1015 Lausanne, SwitzerlandResume : The formation of Fe-Al intermetallics is known as taking animportant part in the wear process of steel tools used for aluminiuminjection moulding. Rapid formation of intermetallic phases with highbrittleness coupled to different mechanical movements and thermal cyclinglead to a precocious wear of a specific part of the tool called shot sleeve.Studying their formation gives precious information how to limit intermetallicgrowth and subsequently the shot sleeve wear. A liquid metal immersionfacility (LMIF) is used for diffusion couple investigation. Scanning electronmicroscopy (SEM) techniques are used to assess kinetics and morphology inintermetallics growth process. A quantitative method shows that the growthof the two principal intermetallic phases (Fe4Al13 and Fe2Al5) is dictated byspecies diffusion. A tongue-like structure of the Fe2Al5 is observed andtransition layer of the FeAl phase around the tongue is identified for the firsttime in the Fe-Al system at 973 K through electron back scattered diffraction(EBSD), 3D Focused Ion Beam tomography (3D FIB) and TransmissionElectron Microscopy (TEM). Further investigation through in situ X-Raytomography gives a more complete understanding of growth/dissolutioncompetition of the intermetallic compounds in providing a continuousobservation of the interface during the reaction.

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11:45 Nanoscale electrical characterization of polymer/carbon nanotubes blendsfor organic photovoltaic applicationsAuthors : Simon Desbief (1), Olivier Douhret (1), Nomie Hergu (2), MathieuSurin (1), Philippe Dubois (2), Roberto Lazzaroni (1), Philippe Leclre (1)Affiliations : (1) Laboratory for Chemistry for Novel Materials; (2) Laboratory ofPolymeric and Composite Materials Center of Innovation and Research in Materials

and Polymers (CIRMAP), University of Mons, UMONS / Materia Nova, Place du Parc20, 7000 Mons, BelgiumResume : In the growing field of molecular electronics, devices containingcarbon nanotubes (CNTs) are extensively studied. In this context, the

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control of the morphological properties, and the understanding of theelectrical properties at the nanometer scale are essential. The use of theAFM (Atomic Force Microscopy) permits to have access to the localmorphological properties. Besides this technique, the recently introducedPeak-Force TUNA (PFTUNA) constitutes a powerful imaging mode allying theadvantages of the Tapping Mode AFM (spatial resolution below 10 nm) andof C-AFM (current sensitivity of 100 fA). In this work, we characterizemorphological and electrical properties of blends made of CNT and a p-typesemiconducting polymer, the regio-regular poly-3-hexylthiophene (P3HT),deposited on a glass substrate patterned with ITO (Indium Tin Oxide). TheP3HT is a very good candidate for the fabrication of organic photovoltaicdevices thanks to its good carrier mobility and its absorption spectra. TheCNTs present good conduction properties, and their size is ideal for buildingconduction paths in organic devices. The combination of C-AFM and PFTUNAprovides valuable information on the electrical properties of the hybrids,showing a high resolution contrast attributed to the local properties of theconjugated materials and therefore contributes to a better understanding ofthe links between the morphological properties and the global electricalperformances of the devices.

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12:00 Characterization of Electrical Surface Properties by Electrostatic ForceMicroscopy: Modeling Resolution and Sensitivity

Authors : Markus Ratzke, Jrgen ReifAffiliations : Lehrstuhl fr Experimentalphysik II, BTU Cottbus, IHP/BTU JointLab,Konrad-Wachsmann-Allee 1, 03046 Cottbus, GermanyResume : Today's highly integrated semiconductor technology requires amapping of surface properties with resolution in the nanometer range, withparticular emphasis on electrical features such as surface potential and near-surface capacitance, these parameters giving access to the material'selectronic properties. For photovoltaic applications, local recombinationactivities are of interest. To obtain such information, non-destructiveexperimental methods are of particular advantage, which do not requirecomplicated, invasive sample preparation, thus allowing investigations ofpristine surfaces. Non-contact scanning probe techniques, generally, providea tool for such investigations. "Scanning Kelvin Probe Microscopy" and"Scanning Capacitance Microscopy" have been demonstrated to be very well

suited for a QUALITATIVE estimate of surface electronic structure. However,for a QUANTITATIVE assessment, fundamental aspects of these experimentshave to be clarified. Most important hereby will be the specific knowledge ofthe relation between quantity of interest and measured signal, determinedby an appropriate transfer function. We will derive such a transfer function,based on both numerical simulations and analytical modeling. We estimatethe resolution and sensitivity of the experimental techniques, thusaddressing potential ways for a reliable quantitative signal recovery. Ourquasi analytical models allow, indeed, a simple deconvolution of the rawdata, making Electrostatic Force Microscopy an even more useful tool.

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12:15 Lunch

Fuel Cells: Acha Hessler-Wyser

14:15 Effect of interfaces on the ionic conductivity of SOFC materialsAuthors : David W. McCombAffiliations : Dept of Materials Science and Engineering, The Ohio State University,Columbus, OH, 43210, U.S.A.Resume : The search for new strategies to enhance the oxide ionicconductivity in oxide materials is an active field of research. Such materialsare needed for application in a new generation of more efficient and durablesolid state electrochemical devices such as reduced-temperature Solid OxideFuel Cells (SOFCs). There have been numerous reports in the literature ofsignificantly enhanced ionic conductivity in multilayer heterostructures

formed from ionic conductors and insulators. There have also been anumber of reports suggesting that these enhancements are due to electronicrather than ionic conductivity. In this invited contribution I will discussrecent results obtained in collaboration with colleagues in Spain, the UK and

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the USA from three different multilayer structures. Using scanningtransmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray (EDX) analysis wehave probed the structure, composition and bonding with high spatialresolution in order to relate the interfacial structure and chemistry to theobserved conductivity.

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14:45 Relating nanostructures of yttria-stabilized-zirconia thin films to theirproton conductivityAuthors : Julia Martynczuk(1), Meike V. F. Schlupp(1), Barbara Scherrer(1), DieterStender(2), Ren Tlke(1), Anna Evans(1), Michel Prestat(1), Ludwig J. Gauckler(1)Affiliations : (1) Nonmetallic Inorganic Materials, Department of Materials, ETHZurich, CH-8093 Zurich, Switzerland (2) General Energy Research Department, PaulScherrer Institute, CH-5232 Villigen-PSI, SwitzerlandResume : Zirconia-based thin films are potential electrolyte membranes inmicro-solid oxide fuel cells [1]. Below 400C, the electrical conductivity ofsome yttria-stabilized-zirconia (YSZ) thin films deviates from the well-knownoxygen ion conductivity and an enhanced conductivity at room temperatureas high as normally at 400C can be observed. In this study, we investigatethe reason for this behavior using advanced electron microscopy with atomicresolution for the evolution of the different nanostructures of the YSZ filmsdepending on the deposition technique and conditions. Films made by spray

pyrolysis, aerosol-assisted chemical-vapor deposition and pulsed laserdeposition [2-4] were investigated resulting in either porous thin films withequiaxed grains or dense films with columnar nanostructures. Cross-sectional views of the thin films were prepared by site-specific samplepreparation using a focused ion beam technique. Scanning transmissionelectron microscopy (STEM), aberration-corrected EM, chemical analyses(EDXS), and nano-beam diffraction were used to gain a comprehensivepicture of the nanostructure evolution. The rather high electrical conductivityat low temperatures is attributed to proton conduction of chemisorbed andphysisorbed water in open porosity of the thin films. 1. A. Evans et al., J.Power Sources (2009). 2. B. Scherrer et al., Adv. Funct. Mater. (2011). 3.M. V. F. Schlupp et al., J. Power Sources (2011). 4. S. Heiroth et al., J. Eur.Ceram. Soc. (2010).

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15:00 Microstructure influence on ohmic resistance and transport properties ofporous SOFC electrodes and electrolysis diaphragmsAuthors : Lorenz Holzer (1) Thomas Hocker (1) Lukas Keller (1) Daniel Wiedenmann(2) Bernard Grobety (2) Boris Iwanschitz (3) Michel Prestat (4) Beat Munch (5)Affiliations : (1) ZHAW, Zurich University of Applied Sciences, Winterthur,Switzerland; (2) Uni Fribourg, Geoscience Department, Fribourg, Switzerland; (3)Hexis SA, Winterthur, Switzerland; (4) ETH Zurich, Institute for nonmetallic inorganicmaterials NIM, Zurich, Switzerland; (5) EMPA Materials Science and Technology,Duebendorf, SwitzerlandResume : High resolution tomography in combination with dedicated imagemodelling techniques allow for a better understanding which morphologicalfeatures are actually dominating the transport properties of porous andcomposite materials (e.g. conductivity). Investigations are undertaken inSOFC electrodes (Ni-YSZ and Ni-CGO anodes, LSC cathodes) and in porous

diaphragms of electrolysis cells. A new method is presented which enablesto describe quantitatively the effect of bottle necks (i.e. constrictivity). Datais presented which indicates that constrictivity has a higher impact on themacroscipic transport properties than the geometric tortuosity. Usingmeasured constrictivity, tortuosity and phase volume fractions, the transportproperties (i.e. conductivity) can be predicted based on the parameterswhich are entirely extracted from tomography. In this way quantitativemicroscopy can be used directly for the determination of macroscopicmaterials properties.

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15:15 Opportunities and Limits of SEM/EDS Analyses for Polymer Electrolyte FuelCellsAuthors : H. Echsler, C. Korte, D. Stolten

Affiliations : Forschungszentrum Jlich GmbH, IEK-3, D-52425 Jlich, GermanyResume : Besides various other factors, Polymer Electrolyte Fuel Cells relyon the ion conductivity in both the membrane and the gas diffusionelectrodes (GDE), respectively. Especially in the latter case the micro- oreven nanostructure of the component or the amount and the distribution of

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the ion conducting polymer, in most cases Nafion, is of special interest forthe properties and performance of the cell. Within the last decade greatprogress has been achieved in the field of SEM / EDX analyses with regardto maximum possible resolution and variability of the materials to beinvestigated. Now it is possible to visualize structures down to thenanometer scale, as they are prevailing in the GDE, not only with TEM butalso with SEM. Nevertheless, the detection and quantification of lightelements and especially F, which is a major constituent of Nafion via EDX,is still a challenge. Beam damage of the polymers or vaporisation of e.g. F isunavoidable which makes its quantification at least for small spots or areasinaccurately. In the present work insight is given to amount of F-loss due tothe beam damage in respect to the investigated excitation volume orduration of the measurement. A routine is presented for correction of themeasured values of the F-content and its limitations will be discussed withregard to the effect of the microstructure on the properties and performanceof the cell.

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15:30 Coffee break

Materials for Energy Systems: Acha Hessler-Wyser

16:00 On the help of microscopies in the understanding of degradationmechanisms observed on materials in Pressurized Water ReactorAuthors : Laurent LEGRASAffiliations : EDF R&D MAI, FranceResume : Even if temperature, pressure and chemistry of the cooling waterare not very high and aggressive, materials used in Pressurized WaterReactor (PWR) are exposed to different degradation mechanisms. Some ofthese materials (internal components, vessel,..) are also exposed toirradiation leading to more complex degradation mechanisms. One of themain goal of the research programs launch in that field is to developphysical modelling of the mechanism down to the atomic scale. Suchapproach need a clear description and understanding of the degradation

mechanism at the same scale. This talk will aim at illustrating the benefit ofmicroscopy (TEM, atom probe, dual beam microscopes, EBSD,...) up to thevery new promising possibilities of monochromated and aberrationscorrected TEM. A specific focus will be done on four different degradationmechanism : irradiation aging, fatigue corrosion, stress corrosion crackingand corrosion of stainless steel. 1- Irradiation aging : In the internalstructures of the PWR vessel are made of stainless steel. Irradiation inducescontinuously punctual defects (vacancies and interstitials) which can beeliminated on sink (surfaces, grain boundaries, dislocations). Interstitialscan aggregate forming disk shape i.e. dislocations loops or segregate ongrain boundaries. Vacancies could lead to the formation of cavities orbubbles when combining with gas diffusion, or to reverse flux of specieswhen segregating on boundaries. The kinetics and the quantification ofthese phenomena are performed using TEM and (tomographic) atom probe

and are used as key data for the understanding of mechanisms and formodelling live time extension of actual PWR. 2- Fatigue corrosion : Specificareas of primary circuit in PWR reactor can be affected by thermal fatigue.Recent TEM studies on fatigue crack tips clearly showed that the effect ofcorrosion is combined to the fatigue solicitation and thus that it have to betaken into account. 3D images using FIB are now used as a first step tounderstand and quantify this coupled effect. 3- Stress corrosion cracking(SCC): Strain gradients and preferential sites of intergranular SCC initiationappeared recently to be correlated. Combining complex strain on specimenpre-mapped by EBSD and pre-covered by gold microgrids and the possibilityof extracting TEM thin foils on a precise location using dual beam offer apromising possibility to understand fracture mechanism ahead crack tips.Actual TEM studies using EFTEM, EELS & EDX of such specimen are trying tounderstand the stability of oxides films at the cracks tips as a function of

crystallographic orientation and strain degree. 4- Corrosion SCC andcorrosion behaviour are controlled by the properties of the oxides films. Thewell known duplex structure of the oxides is still suffering of someuncertainties such as on the very first step of their growth and theircrystallographic structure. These two questions are currently under

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investigation up to the atomic scale on very short exposure time usingmonochromated and aberrations corrected electron microscope TITAN.HRTEM and Astar software developed by Nanomegas and E. Rauch is usedto study crystallographic relationship between metal and oxide as wellEFTEM and HREELS to study the local chemistry of the oxide.

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16:30 Designing Semiconductor Photocatalyst/ Metal Cocatalyst Composites forWater Splitting.Authors : N.S. Hondow, Y-H. Chou, K. Sader, Y. Chimoupara, R. Mitchell, R.E.Douthwaite and R.BrydsonAffiliations : Institute for Materials Research, SPEME, University of Leeds, U.K.;Department of Chemistry, University of York, U.K.Resume : One potential method for the conversion of solar into storableenergy is the use of semiconductors (so called photocatalysts) whichmediate the decomposition of water to hydrogen and oxygen. Oxidesemiconductors are a common choice due to their corrosion resistance andthe possibility of engineering their band gaps via doping. Howeverapplication of these materials is currently limited because of a low overallefficiency, due to absorption being confined to the UV periphery of the solarspectrum, rapid electron-hole recombination, and potentially poor surfacechemistry. To overcome the latter two problems cocatalysts, such as Pt,RuO2 and NiO, are intentionally added to the surface of the photocatalyst to

act as electron traps and hydrogen evolution sites, thus increasing activity.In this paper we detail a structural investigation of the semiconductorsNiTa2O6 and InTaO4 decorated with nickel/nickel oxide core shell cocatalystnanoparticles, similar to those presented in the literature and draw somegeneral conclusions about the design and stability of such co-catalysts. Wealso discuss the possibilities for creating macroporous photonic band gapstructures from photocatalysts to enhance their overall efficiency.

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17:00 Structural and chemical investigations of the oxides formed on 316L alloy inPWR environmentAuthors : R. Soulas (1), L. Legras (1), M. Cheynet (2), T. Neisius (3), Y. Brechet (4)Affiliations : (1) EDF R&D, 77250 Moret-Sur-Loing, France; (2) INP Grenoble CNRSUJF, SIMAP, F-38402 St Martin Dheres, France; (3) Universit Paul Czanne, F-13397 Marseille, France; (4) SIMaP INP Grenoble, F-38402 Saint MartindHegraveres, FranceResume : To improve the durability of PWR primary circuits with respect tostress corrosion cracking, understanding of oxidation mechanisms is crucial.316L alloy composing vessel internals and primary circuits is in contact withPWR environment. This leads to the formation of an oxide with a doublelayer (an inner part composed with a chromium enriched oxide and an outerpart composed with magnetite) in which cracks may be initiated in presenceof stress with or without irradiation. It appears, today, that oxidationmechanisms are achieved during the first exposure minutes to the oxidizingenvironment. It is, thus, essential to describe precisely the morphology, thestructure and the chemistry of the oxides forming the protective layers.Thanks to a special oxidation loop allowing exposure times ranging fromminutes to few hours, it is possible to study the first steps of oxidation. Toavoid averaging effects resulting from crystallographic features, FIB thin

foils are taken out from grains with different orientations ([111], [110]),after different oxidation times (1 minutes, 2 minutes, 10 minutes, 1 hour, 5hours and 24 hours). TEM observations are carried out using either aTecnai20F (image, diffraction and EFTEM), a Titan 80-300 kV with objectivelens corrector (HRTEM) or a Titan 80-300 kV with monochromator and probelens corrector (HR-EELS and STEM). These observations provide preciseinformation at the nanometer scale concerning the chemistry (elementalquantification, elemental electronic structure), the microstructure of oxidelayers (using ASTAR simulation) and the epitaxial relation between the inneroxide layer and the metal. Macroscopic observations using XPS, Ramanspectroscopy and GIDRX are performed in parallel to confirm and generalizemicroscopic conclusions about oxide formation. The amorphous chromiumenriched passive layer initially present at the surface of the specimen assoon as air exposition, begins to crystallize as oxidation in primary water

occurs. ASTAR simulations from aberrations corrected HRTEM imagesshowed that the Cr rich inner oxide layer evolves from nano-grains tomonocrystalline grain. The unique cristal of fcc spinel AB2O4 oxide has aclose epitaxial relationship with the sublying metal grain. A double network

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of misfit dislocation is observed at the metal/oxide interface. Edgedislocations with burger of [220] and [202] are localized every seven atomicplanes of the metal compensating the 16% of misfit between oxide andmetal lattice parameters. The outer layer is formed of well shapedcrystallites of magnetite. The fine electronic structure obtained using HR-EELS are also confident with the spinel AB2O4.

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17:15 Radiation induced structural and magnetic changes in Fe-Cr alloysAuthors : A. Idhil (1), C.N. Borca (1), A.-C. Uldry (1), D. Grolimund (1), C. Hebert(2), M. Samaras (3)Affiliations : (1) Paul Scherrer Institute, CH-5232 Villigen, Switzerland; (2) colePolytechnique Fdrale de Lausanne, CH-1015 Lausanne, Switzerland; (3)SwitzerlandResume : We investigate irradiation damage mechanisms and changes inmicrostructure upon ion-beam implantation of the model Fe1-xCrx alloys,with x up to 20%. Fe+-beam implantation simulates the effect of neutronirradiation with respect to formation and evolution of atomic displacementcascades. Using EXAFS and micro-XRD techniques we could investigate thechanges in atomic structure leading to formation of displacement cascadeswhich affect the fundamental mechanical properties of these materials.Additionally, the influence of irradiation on the elemental magnetic momentshas been investigated using XMCD. We observed that the implantation

temperature has the biggest impact on the atomic and magnetic structuresof the model Fe1-xCrx alloys. These experiments not only bring insight intothe material structure, but also enable a robust modeling tool to bedeveloped.

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17:30 Structure determination and chemical analyses in complex tungstatesmaterialsAuthors : L. Patout (1), T. Renovato dos Santos (1,2), A.L. Lopez-Moriyama (1,2),C. Pereira de Souza (2), M. Arab (1), Ch. Leroux(1)Affiliations : (1) IM2NP UMR CNRS 6242 Universit Sud Toulon Var, BP20132,83957 La Garde Cedex, France; (2) Universidade Federal do Rio Grande do Norte,DEQ/PPGEQ/LTRC, Campus Universitrio, Lagoa Nova, 59072-970, Natal, BrasilResume : It is possible to produce syngas (CO and H2) from natural gas inpresence of catalysts. The reform of natural gas CH4, followed by anadequate filtering, is an alternative for the hydrogen production. However,due to the high stability of methane it is necessary to develop new hightemperature materials. We developed chemical routes to synthesizenanostructured materials based on tungstate of rare earths elements. Wefocused on cerium and strontium based tungstates. Only SrWO4 and Ce2(WO4)3 have known structures. We tentatively synthesised ceriumtungstate with Ce4+ and obtained mixed powder of a new phase withstoichiometry CeW2O8 , and Ce2(WO4)3. The space group of this newphase is determined by means of various quantitative electron diffraction,among them microdiffraction. Microdiffraction patterns of high symmetryzone axes reveal the Bravais lattice, the presence of glide mirrors andhelicoidal axis. Precession experiments are also envisaged. First resultsindicate this new phase is orthorhombic. Stoichiometric SrWO4 as well aspowders with excess of W or Sr were synthesized in order to determine if

Sr1 W1 O4 may exist. The EDS analyses of these compounds revealeda failure of commercial EDS software in the relative quantification of Sr andW. The ternary tungstates with Sr and Ce exhibit unexpected tetragonalscheelite structures, as the few ternary tungstate found in the literature aremonoclinic. This work was supported by the CAPES -COFECUB and ARCUS-BRAZIL funds.

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17:45 TEM analysis of nanoporous Ptn+-CeOx catalyst on CNTsAuthors : V. Potin (1)*, S. Bruyre (1), V. Matoln (2), I. Matolnov (2), M.Vorokhta (2), and S. Bourgeois (1)Affiliations : (1) I.C.B. - Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR5209 CNRS - Universit de Bourgogne, 21078 Dijon CEDEX, France; (2) CharlesUniversity, Faculty of Mathematics and Physics, Department of Surface and Plasma

ScienceResume : In this study we report TEM study of carbon nanotubes coatingby Pt-CeO2 catalyst by using simultaneous magnetron sputtering ofplatinum and cerium oxide. This technique permits to prepare oxide layerscontinuously doped with Pt atoms during the growth. The Pt doped

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sputtered cerium oxide films contain high concentration of cationic platinumPt2+ and Pt4+ (nearly 100%) which opens the way for using such systemsas highly active thin film catalysts. Different samples were investigated, withdifferent Pt content. Platinum and cerium were deposited simultaneously byrf-magnetron sputtering on multiwall carbon nanotubes (MWCNT) depositedby sedimentation on silicon substrate or grown perpendicularly to the siliconwafer by the chemical vapor deposition technique. SEM and STEMexperiments reveal the high porosity of the deposited layers. Studies ofHRTEM images indicate the presence of CeO2 crystallized nanoparticles.Pt4+ cations are in substitution positions of the face centered cubic lattice ofcerium oxide, as Ce4+1-x Pt4+xO2. Moreover, in the case of MWCNTdeposited by sedimentation, STEM images show that the deposition isinhomogeneous, as one face is more exposed to the deposited species. WithEDX experiments performed in STEM mode, the Ce/Pt ratio was studied infunction of the deposit localization. EELS experiments were also performedto study the evolution of Ce4+/Ce3+ ratio. This research is supported byANR within IMAGINOXE project (ANR-11-JS10-001).

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18:00 Tungsten carbide identification in a re-deposited layer on an ASDEXUpgrade divertor tileAuthors : M. Rasinski (1), M. Balden (2), M. Mayer (2), R. Neu (2), T. Pociski (1),M. Lewandowska (1), K.J. Kurzydlowski (1)

Affiliations : ASDEX Upgrade Team (1) Warsaw University of Technology; Faculty ofMaterial Science and Engineering Woloska 141, 02-507, Poland, (2) Max-Planck-Institut fr Plasmaphysik, Euratom Association, Boltzmannstrae 2, D-85748Garching, GermanyResume : Erosion and redeposition of plasma-facing materials is one of themost important issues in fusion devices and therefore is an area of interestfor many research groups. However, the structure and composition of re-deposited layers as well as the mechanism and condition of their formationare not fully described and understood yet. In the present study, structureand phase composition of the deposited layer (500 - 1000 nm in thickness),which grew during the 2007 campaign on a tile from the inner strike pointregion in the ASDEX Upgrade divertor, were examined. High resolutionscanning transmission electron microscopy (HR STEM) combined with localnano-diffraction technique have been used to identify the deposits phase

composition, supported by energy-dispersive X-ray spectroscopy (EDX) andelectron energy loss spectroscopy (EELS). In the deposited layer two typesof tungsten carbide (WC1-x and W2C) were identified. The phasecomposition results from the layer deposited in the divertor were comparedwith those obtained from amorphous carbon thin films doped with differenttungsten concentration which were subjected to annealing at differenttemperatures. Such specimens can be considered as model system for there-deposit creation on the divertor. The correlation between the phasecomposition of the model system layers and the real deposit from thedivertor provides information about local conditions during the creation ofthe deposits.

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PROGRAM VIEW : 2012 Spring

MY PROGRAM : 2012 Spring

Symposium : X


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Photovoltaics: Wolfgang Jger

08:30 Electron energy-loss spectroscopy of dopant concentration profiles andoptical absorption in thin film silicon solar cells

Authors : Rafal E. Dunin-Borkowski, Martial Duchamp, Chris B. Boothroyd, M. SergioMoreno, Bas B. Van Aken, Wim J. SoppeAffiliations : Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons,Peter Grnberg Insititute, Forschungszentrum Jlich, D-52425 Jlich, Germany;Centro Atmico Bariloche, 8400 S. C. de Bariloche, Argentina; ECN Solar Energy,P.O. Box 1, NL-1755 ZG Petten, The NetherlandsResume : We use electron energy-loss spectroscopy (EELS) to study thinfilm silicon solar cells on plastic, glass and metallic substrates prepared fortransmission electron microscopy (TEM) using focused ion beam milling. Fora solar cell in which an intrinsic amorphous silicon layer is sandwichedbetween 10-nm-thick n-doped and p-doped amorphous silicon layers, weuse core loss EELS to measure the boron concentration quantitatively andcompare our measurements with real space ab initio multiple scatteringcalculations. For a sample that contains 200-nm-thick i-SiC, p+-SiC and

p++-SiC layers sandwiched between back (ZnO/Ag) and front (ITO) contactlayers, we use monochromated EELS to correlate changes in plasmonenergy with measurements of boron concentration made using secondaryion mass spectrometry. We discuss whether the observed changes inplasmon energy across the device can be related directly to the boronconcentration in the doped layers. We also assess whether monochromatedEELS can be used to map plasmon absorption in Ag reflector layerssputtered onto rough ZnO with a spatial resolution of better than 10 nm.The correlation of such measurements with the microcrystalline structure ofthe layers, including variations in composition at grain boundaries, isimportant for understanding the origin of parasitic optical absorption, whichdecreases the photo-generated current.

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09:00 Microscopy study of thin-film polycrystalline silicon solar cells, were optical

electrical and structural material characterization, in the sub micron range,meets each otherAuthors : D. Van Gestel, J. Deckers, I. Gordon, J. PoortmansAffiliations : IMEC vzw, Kapeldreef 75, B-3001 Leuven, BelgiumResume : Thin-film polycrystalline-silicon (pc-Si) solar cells with a grainsize in the order of 1-100 micron could substantially lower the price ofphotovoltaic (PV) energy. Similar to bulk silicon PV there is a need tocombine electrical optical and structural characterization to support R&D.However because many properties of pc-Si material are one or more orderssmaller then for bulk Si, advanced new and or improved characterizationtechniques are needed. In this contribution we will discuss and show theusefulness of different quantitative characterization methods throughout thewhole pc-Si solar cell production process. The pc-Si material was made byepitaxial thickening of a seed layer. Structural properties were measured

with electron back scattered diffraction (EBSD), transmission and scanningelectron microscopy (TEM,SEM), defect etch, atomic force microscopy(AFM), X-ray diffraction (XRD) and Raman microscopy. For electricalcharacterization mainly current-voltage (IV) measurement, electron beam

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induced current (EBIC) measurement and scanning spreading resistantmicroscopy (SSRM) were used. Transmission-reflection and quantumefficiency measurements were applied to study optical properties whereasphotoluminescence (PL), secondary ion mass spectroscopy (SIMS) and totalX-ray reflection measurements (TXRF) were used to monitor contaminationissues. All these methods were successfully combined to study the influenceof different variations throughout the whole solar cell processing.

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09:30 Evolution of surface roughness and grain size in the transition fromamorphous to microcrystalline silicon thin films growthAuthors : E. Farsari, A.G. Kalampounias, N. Spiliopoulos, E. Amanatides, D. MatarasAffiliations : Plasma Technology Lab., Dpt. of Chemical Engineering, University ofPatras Patra GR26504, GreeceResume : Hydrogenated microcrystalline silicon is a mixed phase materialconsisting of micro- and nano-crystallites embedded in an amorphousmatrix. This material has attracted great scientific interest due to itsapplication in thin film transistors and solar cells. The physical,morphological and chemical properties of the material, determined by thedeposition conditions, affect the final performance of the optoelectronicdevices. Several microscopic techniques such as TEM, STM, AFM, KPFM,SNOM have been used in order to examine the morphological, electronic andoptoelectonic properties of microcrystalline Si:H thin films. The purpose of

this work is to use conventional and conductive AFM for the characterizationof Si:H films deposited near the transition to a-Si:H growth. The materialsdeposited under such conditions present the best performance whenincorporated to the devices. The samples were deposited by Silane-Hydrogen glow discharges at different experimental conditions in order tocross the transition from amorphous to microcrystalline growth. Thetopography of the samples was examined by AFM measurements and thevariation of the surface roughness was calculated. The estimation of thecrystallinity and the distribution of crystallites size were achieved byconductive AFM under ambient conditions, while oxidation effects were alsoexamined. The above mentioned results are compared with FESEM andRaman Spectroscopy measurements and the observed differences arediscussed.

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09:45 EFTEM studies of Si nanowire networks in SiO2 for thin film PV cellsAuthors : B. Liedke (1), A. Mcklich (1), K.-H. Heinig (1), B. Schmidt (1), D.Friedrich (1), U. Keles (2), C. Bulutay (2)Affiliations : (1) Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden,Germany; (2) Bilkent University, Physics Department, 06800 Bilkent, Ankara, TurkeyResume : Si based nanostructures became in the last years a promisingmaterial for the PV cells. The quantum confinement effect of Sinanostructures allows for band gap engineering by size manipulation whichcan be used for optimization sun light absorption. Here, we consider SiOxlayers deposited by magnetron sputtering. By subsequent rapid thermalprocessing, SiOx decays by spinodal decomposition into a network of Sinanowires (NWs) in SiO2. To get images of the morphology of Si NWs inSiO2 it is not sufficient to use mass contrast or lattice plane imaging. The Siand SiO2 phases can only be distinguished by energy filtering of the

transmitted electrons (EFTEM). Here, the relative energy shifts of theplasmonic valence band resonances of Si and SiO2 are used. HR-EFTEMtechniques are applied to study morphology and crystallinity of the Si NWnetworks fabricated from different metastable SiOx. To facilitateunderstanding of the TEM images, details of decomposition are studied usingkinetic Monte-Carlo (KMC) simulations. For the EFTEM images, density-density correlations are calculated to determine the structure size of NWnetwork, which are then compared with the 3D morphologies provided byKMC. Combining EFTEM with KMC allows us to predict and control theaverage size of the NWs. Former studies and our electronic structurecalculations provide a guideline for band gap optimization of Si NWnetworks, thus paving the way to band gap engineering via control of themean NW diameter.

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10:00 Coffee break



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10:30 Material science for high-efficiency III-V solar cellsAuthors : F. Dimroth, T. Roesener, V. Klinger, R. Kellenbenz, A. WekkeliAffiliations : Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstrasse2, 79110 Freiburg, GermanyResume : III-V multi-junction solar cells are reaching the highestconversion efficiencies of sunlight into electricity. These solar cells consist ofcomplex layer structures which can contain up to 40 different layers.Excellent material quality and low dislocation density is a requirement for

these high efficiency devices. In 2009, Fraunhofer ISE reached for the firsttime an efficiency of 41.1 % under concentrated sunlight with ametamorphic (lattice mismatched) Ga0.35In0.65P/Ga0.83In0.17As cellstructure on Ge. Today, lattice-mismatched growth is used in many cellarchitectures including III-V solar cells on silicon and inverted metamorphicstructures. Understanding the origin and propagation of dislocations is animportant requirement for the development of these solar cells. Structuralanalysis of the layer stack by transmission electron microscopy helps tounderstand the formation and propagation of misfit and threadingdislocations in the metamorphic layers. But these techniques have to becombined with additional methods like high-resolution x-ray diffraction, EPDof threading dislocation densities, measurements of material hardness andsurface roughness to generate a full picture of suitable growth conditionsand materials. The presentation will give an insight into the essential

methods which support the development of todays highest efficiency solarcells.

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11:00 High Resolution Characterisation of CdCl2-treated CdTe Thin-film Solar CellsAuthors : Ali Abbas (1), Paul Rowley (2), Geoff West (1), John Walls (2), JakeBowers (2), Piotr Kaminski (2)Affiliations : (1) School of Materials; (2) CREST, School of Electronic, Electrical andSystems Engineering, Loughborough University, Leics. LE11 3TU, U.K.Resume : Cadmium Telluride (CdTe)-based photovoltaic devices represent apromising route towards the realisation of low cost thin film solar cells ofefficiencies above 16%. However, the current level of fundamentalunderstanding of key process routes towards optimised cells, such asimproved doping, cadmium chloride recrystallization and contacting issomewhat poor. In this paper, we present the results of a comprehensive

programme of high-resolution characterisation of CdTe solar cells, with afocus on the analysis of cadmium chloride (CdCl2) treatments and theobjective of gaining a deeper mechanistic understanding of their impacts oncell performance. A range of characterisation techniques, including EBSD(Electron Backscatter Diffraction) analysis, STEM (Scanning TransmissionElectron Microscopy) and electron nano-spectroscopic elemental mappingwere applied. Analysis of CdCl2-treated cells shows the presence of chlorinerich regions at the CdTe/CdS interface, along with an indication of chlorineand sulphur segregation at CdTe grain boundaries. Furthermore, in additionto significant grain refinement, an impact on the prevalence of intragranularstacking faults is indicated. The results of grain orientation mapping beforeand after treatment are also presented. Finally, the relevance of the work tothe construction of numerical models that aid the understanding offundamental aspects of cell function such as electron trapping and diffusion

are presented.

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11:15 Structure-property relationships in thin-film solar cells by electronmicroscopyAuthors : Daniel Abou-Ras (1), Sebastian Schmidt (1), Jaison Kavalakkatt (1),Melanie Nichterwitz (1), Hubert Schulz (2), Katja Tsyrulin (2), Frank Bauer (3),Christoph T. Koch (4), Bernhard Schaffer (5), Miroslava Schaffer (5)Affiliations : (1) Helmholtz-Zentrum Berlin fr Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany; (2) Carl Zeiss NTS GmbH, Carl-Zeiss-Strasse 56, 73447 Oberkochen, Germany; (3) Oxford Instruments GmbH,NanoAnalysis, Otto-von-Guericke-Ring 10, 65205 Wiesbaden, Germany, (4) Institutefor Experimental Physics , Ulm University, Albert-Einstein-Allee 11, 89081 Ulm,Germany, (5) SuperSTEM, STFC Daresbury Laboratories, Keckwick Lane, Warrington,WA4 4AD, U.K.Resume : Among all thin-film solar cells, those with polycrystalline Cu(In,Ga)Se2 absorber layers have shown the highest power-conversionefficiencies of currently more than 20 %. It is an essential issue of furtherimprovements of this kind of solar cells to relate microstructural properties

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of the Cu(In,Ga)Se2 thin films to the corresponding device performances.Optimizing the microstructure is key for power-conversion efficiencies of 21% and beyond. For this aim, electron microscopy provides various imagingand analysis techniques. Cross-section preparation, imaging, and alsoanalysis can all be performed by applying a focused ion beam (FIB)machine. However, the incongruent ion-beam sputtering of Cu(In,Ga)Se2leads to formation of agglomerates, which can be reduced substantially byuse of reactive gases. The introduction of XeF2 during FIB slicing resulted inexcellent images, in which the microstructures of most layers in the Cu(In,Ga)Se2 thin-film stack are visible, including the microstructure of the 20nm thin MoSe2 layer. Acquisition of high-quality two-dimensional and alsothree-dimensional electron backscatter diffraction (EBSD) data was possible.Combination of EBSD with energy-dispersive X-ray spectrometry providesmeans for unambiguous phase analysis, while the acquisition of EBSD,electron-beam-induced current, and cathodoluminescence measurements onidentical specimen positions give information on the electrical andoptoelectronic properties of grain boundaries in polycrystalline Cu(In,Ga)Se2layers. Electron holography measurements provide insight in potentialdistributions around structural defects, which, for grain boundaries, can berelated directly to a change in composition.

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Organic Photovoltaics: Hugo Bender

11:30 Investigation of aged organic solar cells stacks by cross-sectionaltransmission electron microscopy coupled with elemental analysisAuthors : P. Favia (1), E. Voroshazi (2), P. Heremans (1), H. Bender (1)Affiliations : (1) imec, Kapeldreef 75, B-3001 Leuven, Belgium; (2) KatholiekeUniversiteit, Arenberg Kasteelpark 10, ESAT, B-3001, Leuven, BelgiumResume : Polymer solar cells are of great interest as candidates for futurelow-cost and light-weight energy sources. One of the major reliabilityproblems of these devices is the thermal instability of the blend morphologycomposed of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acidmethyl ester (P3HT, PCBM). Phase segregation of the blend has beenextensively investigated by transmission electron microscopy (TEM) on free-standing films. In this study, we investigate in cross-section the morphologyreorganization of P3HT:PCBM layers confined between poly(3,4-ethylenedioxythiophene)poly- (styrenesulfonate)(PEDOT:PSS) and a metalelectrode similarly to solar cell devices. Combining TEM imaging of the layerstack with energy dispersive spectroscopy (EDS), we not only gain insightinto the vertical phase segregation process but also explore theinterdiffusion and adhesion in the layer stack. Over 100 C annealing leadsto the formation of elongated particles of ~ 300 nm height, which are mostlycomposed of carbon, signature of PCBM. Thinning of the neighboring areasindicates the direction of the diffusion. Interestingly, the metal cathoderemains conformal to these large aggregates and the particles protrudethrough the metal layer only after 300 h. Furthermore, we also show thecrystalline nature of these particles embedded in the amorphous matrix.Elemental analysis confirms that the diffusion of the electrode materials (In,Na and Yb) remains below the detection limit.

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12:00 Impact of thermal annealing on the morphology and interfacial compositionof bulk heterojunction organic solar cellsAuthors : P. G. Karagiannidis, N. Kalfagiannis, A. Laskarakis, D. Georgiou, C.Pitsalidis, S. LogothetidisAffiliations : Laboratory for Thin Films-Nanosystems and Nanometrology (LTFN),Physics Department, Aristotle University of Thessaloniki, GR-54124, Thessaloniki,GreeceResume : Nowadays, organic solar cells have attracted enormous interestdue to their great technological potential as a renewable energy source, theadvantage of high efficiency-to-cost ratio, the low weight and mechanicalflexibility of organic materials and the easy thin-film casting technology.Since the introduction of bulk heterojunction, a substantial progress in

organic solar cell performance has been achieved. Although a lot of researchhas been made at the efficiency race, the morphology evolution that definesthe device performance and lifetime is still under investigation. In this work,we have studied the effect of thermal annealing on the morphology and theinterfacial composition of poly(3-hexylthiophene) (P3HT): Phenyl-C61-

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butyric acid methyl ester (PCBM) blends. Lateral phase separation wasidentified by Atomic Force Microscopy and Optical Microscopy, and itsevolution with the duration of annealing and temperature from the nano- tothe micro-scale was quantified by the statistical parameters of surfaceroughness and the power spectral density. Spectroscopic Ellipsometry in theNIR-Vis-farUV spectral region revealed P3HT segregation at the top region ofthe films and PCBM accumulation at the bottom interface. This verticalphase separation, which is related to the difference in the surface energiesof the P3HT, PCBM and the substrate, was found to have a dramatic effecton the device performance.

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12:15 Solution-processed LiF for work function tuning in organic solar cellsAuthors : Taner Aytun, Ayse Turak, Iain Baikie, Grzegorz Halek, and Cleva W. Ow-YangAffiliations : Sabanci University, Max Planck Institute for Metals Research, KPTechnology, Ltd.Resume : The indium-tin-oxide/active layer interface is critical to theperformance of organic solar cell devices. Though PEDOT:PSS is widely usedas an interlayer, poor energy level matching with the active polymer blendcan lead to poor long term performance. The possibility of tailoring the workfunction to match the energy level of the active organic layer is of greatinterest in the fabrication of organic devices to form barrier-free Ohmic

contacts, where the work function no longer controls device performance. Inthis study, submonolayer films of LiF nanoparticles are deposited on theelectrode surface with the assistance of polymeric micelle reactors that alsoenable particle deposition with controlled nanoscale surface coverage.Scanning Kelvin probe microscopy is used to determine the global averagesurface work function of the LiF/ITO bilayer. The results reveal a workfunction tunable with nanoparticle coverage with higher values than that ofbare indium tin oxide (ITO). As thermally evaporated LiF typically lowers thesurface work function, the tunable behavior of the solution-processed LiFnanoparticles on ITO is attributed to a lateral depolarization effect, with theeffective dipole direction switching as full surface coverage is obtained.Incorporation of the solution-processed bilayer electrodes into aconventional P3HT:PCBM device shows significant improvement in deviceperformance, especially when used in combination with a PEDOT:PSS layer.

The results indicate that interface energy level engineering is an essentialtool for future device optimization requirements.

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12:30 Lunch

14:15 Microstructure imaging and chemical analysis of photoactive thin films oncarbon tube biohybrids by HR SEM and FT-IR spectroscopyAuthors : O. Kysil (1), V. Frolov (2), I. Tomylko (1), O. Ivanyuta (1), E. Buzaneva(1), U. Ritter (3), P. Scharff (3)Affiliations : (1) National Taras Shevchenko University of Kyiv, 01601 Kyiv,Ukraine; (2) Paramed Company, 03187 Kyiv, Ukraine; (3) TU Ilmenau, Institut frChemie und Biotechnology, 98684 Ilmenau, Germany

Resume : The investigation is aimed to develop architectures models, tobiodesign and to test microstructure, chemical content of photoactive in UV-visible range thin films on carbon single-, multiwall tubes integrated bybiomolecules that control optical properties of the films. Selectedbiomolecules (cysteine and phenylalanine) non-covalently interact with thehydroxyl and oxygen surface groups of carbon tubes to form filmmicrostructure, chemical content and their photoactivity in UV-visible rangefor PV cells. HR SEM images and elemental mapping are taken to visualizethe organized film microstructures from the biomolecules and carbon tubesduring drying of their suspensions on silicon surface. FT-IR spectroscopy isused for chemical analysis and characterization of the interactions betweentubes and biomolecules during the film microstructure organization. The filmmicrostructures were also characterized by optical absorbance in 200-650nm wavelength range and photoluminescence spectra for the laser

illumination (337, 420 nm). The experimental results confirm the developedmodel for donor-acceptor pair organization in photoactive biohybrids carbonnanotubes networks into the films. The concept of these microstructure andelemental mapping influence on an optical activity in different ranges of thethin film PV cells is based on developed model for photoresponse of

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biohybrids materials on carbon nanotube that has bond with modified bybiomolecule ends and/or walls carbon nanotube.

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14:30 Study of the microstructure of inkjet printed P3HT:PCBM blend forphotovoltaic applicationsAuthors : Immacolata Angelica Grimaldi (1,2), Rosita Diana (1), Pasquale Morvillo(1), Fausta Loffredo (1), Fulvia Villani (1)Affiliations : (1) ENEA, UTTP-NANO,Piazzale Enrico Fermi 1, 80055 Portici (Naples),

Italy; (2) Department of Physics Science, University of Naples Federico II, PiazzaleTecchio 80125, Naples, ItalyResume : Recently, great interest has been devoted to cost-effectivealternative energy sources such as organic solar cells due to the low cost offabrication, the mechanical flexibility and the versatility of chemicalstructure and ease of processing. As concerning this last point, thepossibility of organic materials processing by solutions at low temperaturesmakes them employable for fabricating printed solar cells by using inkjetprinting technology. The most exploited active material for photovoltaicdevices is the regioregular poly(3-hexylthiophene) (P3HT), p-typeconjugated polymer, blended with [6,6]-phenyl-C61-butyric acid methylester (PCBM), n-type material. In the present work, we studied the influenceof the chemico-physical properties of the solvents on the morphology of theactive layer through optical and morphological (AFM, SEM) analyses. The

micostructure of the photoactive material was optimized by combining themixing ratios of the solvents and the printing parameters (drop emissionfrequency, drops overlapping degree, substrate temperature) thusimproving the electrical performances of the organic solar cells.

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14:45 Understanding the morphology of the active layer in organic solar cells: ATEM based approachAuthors : Kulpreet Singh Virdi, Alaa Abdellah, Markus Dblinger, Paolo Lugli,Giuseppe Scarpa, Christina ScheuAffiliations : Department of Chemistry, Ludwig-Maximilians-Universitt Mnchen,Germany; Institute for Nanoelectronics, Department of Electrical Engineering andInformation Technology, Technische Universitt Mnchen, GermanyResume : The increasing push for cleaner energy sources has fuelledresearch in the direction of photovoltaics and other light harvesting devices.Conventionally, the harvesting of solar energy has been dominated bysilicon based photovoltaic devices. However recently fully organic solar cellscomprising of an active layer of organic materials have acquired thespotlight. These organic solar cells offer exciting prospects because of theireconomical fabrication and easy integration into circuitry. Despite a variedchoice of materials available for active layer, [6,6]-phenyl-C61 butyricmethyl ester (PCBM) and poly(3-hexylthiophene) (P3HT) have been used asacceptor and donor respectively. It has been widely reported in literaturethat annealing improves the device performance, though the mechanism ofmicrostructure evolution due to annealing is not yet fully understood. Wehave investigated fully organic solar cells fabricated using spray coatingtechnology using transmission electron microscopy (TEM), selected areaelectron diffraction (SAED), scanning transmission electron microscopy(STEM) and energy dispersive X-ray spectroscopy (EDS). Results indicate

the annealed active layer to comprise of a highly crystalline PCBM layerwidely varying in thickness and a P3HT rich layer uniform in thickness.These results do comply with some recent reports postulating diffusion ofPCBM into P3HT during annealing, however further work is necessary tostrengthen the theory for better understanding of such device interfaces.

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15:00 Microstructural aspects of transition metal oxide p-type doping of organicsemiconductorsAuthors : L. Dieterle (1,2), K. Schultheiss (1,2), M. Pfannmller (3), D. Donhauser(1,2), M. Krger (1,2), R.R. Schrder (2,3), W. Kowalsky (1,2)Affiliations : (1) Institut fr Hochfrequenztechnik, Technische UniversittBraunschweig, Germany; (2) InnovationLab GmbH, Heidelberg, Germany; (3)CellNetworks, Universitt Heidelberg, Germany

Resume : Electrochemical doping is essential to overcome limitations inorganic semiconductors devices imposed by low intrinsic conductivity andhigh charge injection barriers at the contacts. Materials with very deep lyingHOMO-levels like 4,4'-Bis(N-carbazolyl)-1,1'-biphenyl (CBP) can be p-typedoped with transition metal oxides, e.g., MoO3. CBP or other wide bandgap

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materials are commonly used in organic light emitting diodes (OLEDs).However, dopant activation meaning the relation between charge carrierdensity and MoO3 doping concentration is in the range of 1-2 %.Therefore, high doping ratios, which can exceed 10 mol %, are often appliedfor doping CBP. To find the origin of this effect, the microstructure of MoO3-doped CBP organic thin films was studied by transmission electronmicroscopy, electron spectroscopic imaging (ESI) and electron tomography.Instead of homogenously dispersed MoO3 dopants, MoO3 forms amorphousagglomerates. Electron tomography revealed the filament-like nature ofthese agglomerates, which are preferentially oriented along the growthdirection of the thin film. Because charge carriers in organic thin films arenormally localized at single molecules, it can be expected from our resultsthat charge transfer occurs at the interface of CBP and the MoO3 nano-filaments. First results on co-evaporated CBP/MoO3-films on cooledsubstrates show homogeneously dispersed MoO3 without agglomerationindicating a possibility to enhance the low doping efficiency.

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15:15 Coffee break

Poster session: Acha Hessler-Wyser, Thomas Hche, Hugo Bender, WolfgangJger

16:00 Cross-Section STEM Study of Bonding Concepts for Solar CellsAuthors : D. Hussler (1), M. Kurttepeli (1), S. Essig (2), K. Derendorf (2), F.Dimroth (2), W. Jger (1)Affiliations : (1) Microanalysis of Materials, Christian-Albrechts-University Kiel,24143 Kiel, Germany; (2) Fraunhofer Institute for Solar Energy Systems ISE, 79110Freiburg, GermanyResume : Crystalline silicon based multi-junction solar cells are a promisingway to circumvent the conversion efficiency limits of conventional single-junction photovoltaic cells. In GaInP/GaAs/Si multi-junction solar cells, thevisible and near infrared wavelength range of the solar spectrum isconverted more efficiently when compared to solar cells produced

conventionally. As a decisive step of the technology a bonding process isaimed in which a GaInP/GaAs sub-cell is contacted with a Si substrate. Theinterface between GaAs and Si is of great importance for the total efficiencyof this multi-junction cell. Cross-section TEM samples are prepared from twotypes of GaInP/GaAs/Si multi-junction solar cell specimens. In order toinvestigate the bonding concepts, between the GaAs middle-cell and the Sibottom-cell, in the vicinity of the bonding interface, elemental distributionshave been analyzed using STEM / EDXS and pictured using spectra andelemental maps. With the help of HRTEM micrographs an amorphous layerhas been detected in the samples and gauged with high accuracy.

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16:00 Microstructural studies of fluorine-implanted titanium aluminides forenhanced environmental durabilityAuthors : Rossen A. Yankov (1)*, Andreas Kolitsch (1), Johannes von Borany (1),Frans Munnik (1), Arndt Mcklich (1), Alexander Alexewicz (2), Hartmut Bracht (2),Harald Rsner (2), Alexander Donchev (3), Michael Schtze (3)Affiliations : (1) Institute of Ion Beam Physics and materials Research, Helmholtz-Zentrum Dresden-Rossendorf e.V,. POB 510119, 01314 Dresden, Germany; (2)Institute of Materials Physics, University of Muenster, Wilhelm-Klemm-Str. 10, D-48149 Muenster; (3) Karl-Winnacker-Institut, High-Temperature Materilas,DECHEMA e.V., Theodor-Heuss-Allee 25, D-60486 Frankfurt am Main, GermanyResume : Titanium aluminides based on the gamma-phase (gamma-TiAl)are promising materials for advanced power generation, aerospace andautomobile applications. Oxidation-resistance problems, however, limit themaximal service temperature of these alloys to about 700C. A significantimprovement in environmental durability of gamma-TiAl up to 1050C canbe achieved by ion-implanting fluorine into the alloy subsurface relying onthe so-called halogen effect. In this work, characterization of the

microstructure of F-implanted gamma-TiAl has been undertaken using cross-sectional transmission electron microscopy in conjunction with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy.Preliminary studies by elastic recoil detection analysis have revealed

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anomalously broad, high-concentration (up to 70 at. %) F profiles of eitherGaussian or plateau-like shape extending to much larger depths than thosepredicted by theory. It has been found that the F profiles are not associatedwith standard F diffusion, but rather result from a complexamorphiztation/phase-transition process, which occurs via the implantzone/substrate interface progressing toward the bulk. The final F distributionis implantation-temperature dependent, with higher temperatures causingpartial dynamic self-annealing of the amorphized material and profileshrinkage. The analyses have been helpful in understanding the behavior ofthe F-implanted TiAl from both a basic scientific and a technologicalstandpoint.

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16:00 FIB-SEM and HRTEM investigations of microstructure of chalcogenide filmsAuthors : R. Brinia, G. Schmerberb. M. Kanzaria, B. RezigaAffiliations : (1) Laboratoire de Photovoltaque et Matriaux Semiconducteurs(LPMS), Ecole Nationale d'Ingenieurs de Tunis (ENIT), 1002 Tunis, Tunisia; (2)Institut de Physique et Chimie des Matriaux Strasbourg (IPCMS), UMR 7504 CNRS-UDS, 67034 Strasbourg, France.Resume : We investigate the microstructure of CuAlS2 thin films depositedon Silicon (111). The polycristaline films with different preferred grainorientations are grown by thermal evaporation from powder of synthesisdeposited inelemental sources. The CuAlS2 film was analyzed using focused

ion beam-scanning electron microscopy (FIB-SEM), and HRTEM. FIB-SEMcross-sectioned images revealed that the irregular-shaped particles wereembedded in the film and that the surface region and the bulk arestructurally similar, with no ordered defect chalcopyrite structure observed.However, their composition is slightly different, indicating that they can havedifferent point defect physics. Microstructure properties of the films was witha transmission electron microscope. (112) textured films show sharpcontrasts at the grain boundaries, whereas grain boundaries in (220/204)textured films give only very weak contrasts indicating a preferentialpopulation of electronically rather inactive grain boundaries. Nonchalcopyriteordering of the metal atoms in CuAlS2 is observed by TEM, which isidentified as CuAu-type ordering. Sharp spots in electron diffraction patternsreveal the ordered Cu and Al atom planes alternating along the [001]direction over a long range. High-resolution electron microscopy confirms

this ordering. The CuAu-ordered structure coexists with the chalcopyriteordered structure, in agreement with theoretical prediction. This papershows that dual beam FIB-SEM seems to be an easy, less time consumingand useful method to characterize the cross-sectioned particles of CuAlS2films

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16:00 Quantitative study of structure factors at large reciprocal vectors usingconvergent beam electron diffraction: Application to anharmonicity of thethermal motion in Mg2SiAuthors : Kjetil Valset (1), Oystein Prytz (1), Vidar Hansen (2), Johan Tafto (1)Affiliations : (1) Department of Physics, University of Oslo, P.O. Box 1048, N-0316Oslo, Norway; (2) Faculty of Science and Technology, University of Stavanger, 4036Stavanger, NorwayResume : A wide angle convergent beam electron diffraction technique is

used to determine structure factors with high accuracy from nanoscalevolumes. With this technique the electron probe is focused on a nanometersized area, and many reflections with large reciprocal vectors aresimultaneously at the Bragg position. We demonstrate the power of thetechnique by studying the anharmonic thermal motion of atoms in thepromising thermoelectric material Mg2Si. As reported previously fromneutron and x-ray diffraction on different crystals with the fluorite structure,we observe anharmonic motion of the Mg atoms in their tetrahedralenvironment. We conclude that the Mg atoms at room temperature vibratearound positions displaced 4.50 0.14 pm from the center of the tetrahedron[1]. [1] K.Valset, J.Taft?. Wu and Y. Zhu, Physical Review B 84, 22031(R)(2011) Supported by the Norwegian Research Council through theNANOMAT program.

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16:00 Structure-property correlation of DyBa2Cu3O7-(DyBCO) coatedconductors with critical currents exceeding 1000 A/cmAuthors : Z. Aabdin, M. Drrschnabel, O. Eibl

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Affiliations : Institute of Applied Physics, Auf der Morgenstelle 10, D-72076Tbingen, Germany.Resume : DyBCO thin films are deposited on metallic tapes yielding CoatedConductors (CCs) which are second generation superconducting wires forthe magnet and energy technology. The most significant property of the CCis the critical current density, high critical current densities can only beobtained by biaxially-textured DyBCO and require effective pinning ofmagnetic flux lines by the nanostructure. Therefore, TEM with its resolutioncapabilities is required for analyzing the nanostructure for structure-propertycorrelation. Inclined Substrate Deposition (ISD) yields biaxially-texturedbuffer layers on randomly oriented polycrystalline substrates suitable forlong length CCs. DyBCO films were grown on biaxially-textured MgO bufferlayers deposited on Hastelloy substrates. Typical critical current densitieswere 2.1 MA cm-2 at 77 K in self-field, yielding a record total critical currentof about 1000 A/cm for 5 m thick films. Different to other technologies thecritical current density does not decrease with increasing film thicknesswhen ISD is used. Cross-section imaging and electron diffraction in the TEMwas used to quantify the biaxial-texture of the MgO films, the facetorientation, and the DyBCO texture. The DyBCO grain size was about 250-650 nm, only small-angle grain boundaries appeared over the completeDyBCO film thickness (up to 5 m). A detailed analysis of the microstructurewill be summarized and a growth model for the DyBCO film will bepresented.

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16:00 Metal nanoparticles studied by SEM in transmission modeAuthors : Ulrich Herr, Balati KuerbanjiangAffiliations : Institute of Micro- and Nanomaterials, Ulm University, 89081 Ulm,GermanyResume : Metallic nanoparticles are of interest for various applications, e.g.for the concentration of light (plasmonics) or in magnetic data storageapplications. Since many properties depend sensitively on the size of theparticles, a precise characterization of the particle size distribution ismandatory. A standard technique frequently used is electron microscopy.Scanning electron microscopy is often preferred due to the low effort forsample preparation. However, artefacts such as apparently larger size ofparticles may occur due to electron scattering effects. These artefacts can

be reduced by using thin support structures, like those used in TEMinvestigations. Using a specially designed sample holder, it is possible to usetransmitted electrons to generate an image in a conventional SEM withoutfurther modification. We compare the images and size distributions obtainedby the standard technique, and in transmission mode. We find a pronouncedreduction of the particles sizes measured in transmission mode, togetherwith an improved resolution as demonstrated by resolving individualnanoparticles inside agglomerates.

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16:00 The effect of phase transformation on the thermal expansion property inAl/ZrW2O8 compositesAuthors : Yi Wu, HaoWei Wang, Zhe Chen, MingLiang Wang, Naiheng MaAffiliations : State Key Laboratory of Metal Matrix Composites, Shanghai Jiao TongUniversity, Shanghai 200240, Peoples Republic of China

Resume : This paper studied the effect of phase transformation on thethermal expansion property in Al/ZrW2O8 composites. The Al/ZrW2O8composites of low thermal expansion were fabricated by a squeeze castingmethod. However, the coefficient of thermal expansion (CTE) of as-madecomposites was discovered sharply increased at around 130 degree C. The X-

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EMRS 2012