Contribution a l'etude des proprietes de transport a basse temperature dans les semiconducteurs amorphes du groupe IV : application au systeme Six Sn1-x

SIGLECNRS T 60145 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Modeling Dislocation Contrasts Obtained by Accurate-Electron Channeling Contrast Imaging for Characterizing Deformation Mechanisms in Bulk Materials

Electron Channeling Contrast Imaging (ECCI) is becoming a powerful tool in materials science for characterizing deformation defects. Dislocations observed by ECCI in scanning electron microscope exhibit several features depending on the crystal orientation relative to the incident beam (white/black line on a dark/bright background). In order to bring new insights concerning these contrasts, we report an original theoretical approach based on the dynamical diffraction theory. Our calculations led, for the first time, to an explicit formulation of the back-scattered intensity as a function of various physical and practical parameters governing the experiment. Intensity profiles are modeled for dislocations parallel to the sample surface for different channeling conditions. All theoretical predictions are consistent with experimental results

Accurate electron channeling contrast analysis of a low angle sub-grain boundary

International audienceHigh resolution selected area channeling pattern (HR-SACP) assisted accurate electron channeling contrast imaging (A-ECCI) was used to unambiguously characterize the structure of a low angle grain boundary in an interstitial-free-steel. The boundary dislocations were characterized using TEM-style contrast analysis. The boundary was determined to be tilt in nature with a misorientation angle of 0.13 degrees consistent with the HR-SACP measurements. The results were verified using high accuracy electron backscatter diffraction (EBSD), confirming the approach as a discriminating tool for assessing low angle boundaries

Etude de la morphologie de couches minces de BGaN épitaxiées par MOVPE sur substrat template AlN

International audienceUne nouvelle classe de matériaux à base de GaN est apparue ces dernières années. La réalisation de sources optiques compactes à base de ces alliages pouvant émettre dans la gamme des courtes longueurs d’onde ( bleu et UV) ouvre la voie vers de nombreuses applications. Cependant l’épitaxie de ces matériaux est rendue difficile à cause du désaccord paramétrique entre les couches déposées et les substrats existants. L’incorporation de bore dans GaN permet de réduire le désaccord entre le nouvel alliage obtenu BGaN et le pseudo - substrat d’AlN. Les propriétés de ces matériaux dépendent fortement de la qualité des couches déposées. Aussi, ce travail présente une étude de la morphologie d'échantillons de BGaN de différentes compositions de bore fabriqués par MOVPE. Cette étude morphologique est réalisée via la microscopie à force atomique (AFM) et la microscopie électronique à balayage (MEB). Elle montre une évolution de l'état de surface en fonction de la composition de bore

Experimental study of optical and electrical properties of ZnO nano composites electrodeposited on n-porous silicon substrate for photovoltaic applications

ZnO films deposited on silicon porous substrates (PS) were prepared by electro-deposition anodization on n type (100) silicon wafer. This ZnO/PS structure combines substrates having specific structural and optical properties (IR emission), with nano-composites of ZnO potentially interesting due to their functional properties (UV emission) to be integrated as constitutive elements of devices in various optoelectronic applications mainly in blue light emitters. With this combined structure, the blue shift in the PL peak is possible and easy to obtain (467nm). The vibration modes of PS and ZnO films on PS substrates (ZnO /PS) were investigated by infrared (FTIR) measurements and their behaviors were analyzed and discussed by considering the structural properties characterized by X-ray diffraction (DRX) and scanning electronic microscopy (MEB)

Influence of precursor solution volume on the optical properties of spray deposited ZnO films

International audienceIn this contribution we present the optical properties of ZnO films prepared by spray pyrolysis on glass substrate growth at 350°C with various precursor solution volumes. Optical characterization of ZnO films was carried out by transmittance measurement. The optical transmittance spectrum for the film deposited at low precursor solution volume exhibits high transparency with a decrease when the precursor solution volume increases. It is found that the optical band gap decreases from 3.30 to 3.27 eV and the optical constants increase with the increase of the thickness of the films attributed to the increase in lattice defects

A Dislocation-Scale Characterization of the Evolution of Deformation Microstructures around Nanoindentation Imprints in a TiAl Alloy

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Non resonant Raman scattering and photoluminescence in ZnO nano-pyramidals

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Sn-doped ZnO thin films deposited by spray pyrolysis technique: Preparation and optical sudies

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