ELASTIC STRAIN DETERMINATION IN SEMICONDUCTOR EPITAXIAL LAYERS BY HREM

A new technique that is independent of image contrast and robust to th e presence of experimental noise is presented to analyze strains from high resolution electron microscopy (HREM) lattice images. This approa ch involves the analysis of the cumulative sum of deviations (CUSUM) i n lattice-fringe spacings from a target value. The effects of surface roughness at an interface, and surface relaxation due to transmission electron microscope (TEM) sample preparation are discussed. The CUSUM method was applied to two simulated and two experimental HREM images o f semiconductor strained layer structures in [1(1) over bar0$] zone ax is projection. The CUSUM technique was able to accurately reproduce th e strain profiles from the simulated and experimental images in all ca ses studied except for the component of the strain in the slip directi on (e(xx)) of an edge dislocation in a simulated image. In this case, the strain field near the core appeared hemispherical rather than lobe d as expected. Copyright (C) 1996 Elsevier Science Ltd.