Strain mapping at the nanoscale using precession electron diffraction in transmission electron microscope with off axis camera

International audiencePrecession electron diffraction is an efficient technique to measure strain in nanostructures by precessing the electron beam, while maintaining a few nanometre probe size. Here, we show that an advanced diffraction pattern treatment allows reproducible and precise strain measurements to be obtained using a default 512 x 512 DigiSTAR off-axis camera both in advanced or non-corrected transmission electron microscopes. This treatment consists in both projective geometry correction of diffraction pattern distortions and strain Delaunay triangulation based analysis. Precision in the strain measurement is improved and reached 2.7 x 10(-4) with a probe size approaching 4.2 nm in diameter. This method is applied to the study of the strain state in InGaAs quantum-well (QW) devices elaborated on Si substrate. Results show that the GaAs/Si mismatch does not induce in-plane strain fluctuations in the InGaAs QW region. (C) 2014 AIP Publishing LLC

Practical aspects of strain measurement in thin SiGe layers by (004) dark-field electron holography in Lorentz mode

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Existence of a bicontinuous zone in microemulsion systems

The interpretation of self-diffusion and conductivity studies shows the existence of a zone within the isotropic microemulsion domain, where the aqueous and oily phase are both continuous. The boundary of this zone is strongly but not uniquely related to the water volume fraction of the system.L'interprétation conjointe d'expériences d'auto-diffusion et de conductivité montre qu'il existe, dans le domaine isotrope des microémulsions, une zone à caractère continu aussi bien pour la partie huileuse que la partie aqueuse. Sa délimitation est liée de manière importante, mais non unique, à la fraction volumique d'eau du système

Alternate dissociation of the screw dislocations in a (001) buried small-angle twist boundary in silicon

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Control of the morphology transition for the growth of cubic GaN-AlN nanostructures

The Stransky–Krastanow growth mode of strained layers which gives rise to a morphology transition from two-dimensional layer to three-dimensional islands is studied in details for the cubic gallium nitride on cubic aluminum nitride ~GaN/AlN! system grown by molecular beam epitaxy. Besides the lattice parameter mismatch which governs this transition, we evidence the importance of two other parameters, namely the substrate temperature and the III/V flux ratio. Tuning each of these two parameters enables to control the strain relaxation mechanism of a GaN deposited onto AlN, leading to the growth of either quantum wells or quantum dots

Quantitative analysis of HOLZ line splitting in CBED patterns of epitaxially strained layers

International audienceA SiGe layer epitaxially grown on a silicon substrate is experimentally studied by convergent beam electron diffraction (CBED) experiments and used as a test sample to analyse the higher-order Laue zones (HOLZ) line splitting. The influence of surface strain relaxation on the broadening of HOLZ lines is confirmed. The quantitative fit of the observed HOLZ line profiles is successfully achieved using a formalism particularly well-adapted to the case of a -dependent crystal potential ( being the zone axis). This formalism, based on a time-dependent perturbation theory approach, proves to be much more efficient than a classical Howie–Whelan approach, to reproduce the complex HOLZ lines profile in this heavily strained test sample

Structural and optical properties of CdTe/MnTe tilted superlattices grown on vicinal surfaces

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