Direct determination of defocus, thickness and composition from high-resolution electron microscopy lattice images of group-IV semiconductors

摘要

A quantitative method for determination of defocus △f and local thickness t from high-resolution electron microscopy lattice images of wedge shaped Si, Ge and SixGe_(1-x) samples in [100], [110] and [111] projections is proposed, which also allowa a restriction-free determination of local compositions x at coherent Si/SixGe_(1-x) interfaces. The method relies on the analytically derived depndence of the first-order linear and non-linear image Fourier coefficients J_1 and J-2 on △f, t and x. by plotting J-1 versus J_2 for varying t, ellipses with defocus-and composition specific geometry are obtained. By reconstructing the appropriate ellipse for image regions of constant composition, △f and t can be determined independently. At in terfaces, local compositions x can be determined by utilizing a systematic " rotation" of the ellipses with varying composition.