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We present an experimental study of asymmetric wafer deformation for 3C-SiC layers grown on deliberately misorientated silicon substrates. An asymmetric curvature has been observed both on (100) and (111) oriented layers. In this work we focus on the (100) oriented samples. The curvature of the wafers is studied as a function of wafer thickness and offcut angle. We look for the correlations between the observed asymmetric strain relaxation and the layer morphology and microstructure. We claim that different defect pattern, measured along  and [1-10] direction can be at the origin of almost complete relaxation of mismatch strain along the offcut direction.
A systematic distortion in high-angle annular dark-field scanning
transmission electron microscope (HAADF-STEM) images, which may be caused
by residual electrical interference, has been evaluated. Strain mapping,
using the geometric phase methodology, has been applied to images acquired
in an aberration-corrected STEM. This allows this distortion to be removed
and so quantitative analysis of HAADF-STEM images was enabled. The
distortion is quantified by applying this technique to structurally
perfect and strain-free material. As an example, the correction is used to
analyse an InAs/GaAs dot-in-quantum well heterostructure grown by
molecular beam epitaxy. The result is a quantitative measure of internal
strain on an atomic scale. The measured internal strain field of the
heterostructure can be interpreted as being due to variations of indium
concentration in the quantum dot.
An investigation of 1–5 nm in diameter indium rich clusters in MOCVD InxGa1-xN/GaN quantum well is carried out. To this end, quantitative High Resolution Transmission Electron Microscopy (HRTEM) is coupled with the Finite Element Method (FEM) for the calculation of thin foil relaxation and for image simulation. The measurement of the tetragonal distortion from HRTEM images is a useful tool for the determination of chemical composition in heterostructures. However, for a correct interpretation of the measured lattice distortion on HRTEM images, one needs to take into account the strain averaging across TEM sample and inhomogeneous relaxation of the sample. As a first step, 3D FEM simulation of the relaxation process as a function of the position of indium rich cluster relative to the foil surface is performed. Next, the calculated 3D displacement field is used to simulate the HRTEM images. The results clearly show that the magnitude of the strain field depends on the cluster position. It is concluded that the HRTEM images of indium rich clusters can differ even for the same indium content due to different positions of the clusters.
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