Search results for "high resolution electron microscopy"

1986

High resolution electron microscopy of liquid crystalline polymers

1990

Les images de microscopie electronique a haute resolution des polymeres cristaux liquides calamitiques [CO−CH(R)−CO 2 −(CH 2 ) 6 −OPh−N:N−PhO−(CH 2 ) 6 −O] n (R=CH 2 −CH=CH 2 , (CH 2 ) 6 −O−Ph N=N−Ph−CN) et discotique poly (hexadecanedioate de triphenylene) sont simulees sur ordinateur et comparees avec les structures obtenues a partir des resultats experimentaux de diffraction electronique. Une theorie est developpee pour expliquer le bon accord observe

Structural properties of GaN quantum dots

2006

The strain state and the deformation profile of GaN quantum dots embedded in AlN have been measured by high resolution electron microscopy, medium energy ion scattering and grazing incidence X-ray diffraction. The results are compared with theoretical calculations, allowing one to conclude that GaN quantum dots experience a non biaxial strain which drastically decreases when going from the basal plane up to the apex of the dots. We also demonstrate that AlN is distorted in the surroundings of the dots, which provides the driving force for vertical correlation of GaN dots when the AlN spacer between successive planes is thin enough.

Growth, structural and optical properties of GaN/AlN and GaN/GaInN nanowire heterostructures

2012

Abstract After discussing the GaN NW nucleation issue, we will present the structural properties of axial and radial (i.e. core/shell) GaN/AlN NW heterostructures and adress the issue of critical thickness during the growth of such heterostructures. Next, we will present the growth of InGaN NWs on a GaN NW base. It will be shown that the morphology and structural properties of the InGaN NW sections depend on the In content: for high In content a flat top is observed and plastic relaxation is occuring, with mismatch dislocations formed at the InGaN/GaN interface. By contrast, for In content below 25% InGaN NWs exhibit a pencil-like shape assigned to a purely elastic strain relaxation process…

The fingerprint of Te-rich and stoichiometric Bi2Te3 nanowires by Raman spectroscopy

2016

We unambiguously show that the signature of Te-rich bismuth telluride is the appearance of three new peaks in the Raman spectra of Bi2Te3, located at 88, 117 and 137 cm−1 . For this purpose, we have grown stoichiometric Bi2Te3 nanowires as well as Te-rich nanowires. The absence of these peaks in stoichiometric nanowires, even in those with the smallest diameter, shows that they are not related to confinement effects or the lack of inversion symmetry, as stated in the literature, but to the existence of Te clusters. These Te clusters have been found in nonstoichiometric samples by high resolution electron microscopy, while they are absent in stoichiometric samples. The Raman spectra of the l…

1991

The sanidic polyamide [NM-Ph(CO 2 R) 3 (CO 2 Me)-NMCO-Ph(OR) 2 CO] n (R=C 12 H 25 ) is studied. It is shown that this polymer has a biaxial structure with quasi 2-D long range translational correlations. The correlations in one direction are limited by the length of the molecule. The oriented regions are separated by regions in which the molecules are less oriented