Abstract
A novel method for detecting and measuring the static atomic displacements from the perfect crystal sites existing in some alloys is investigated. The method uses the influence of the channelling of an electron beam on the ratio of the numbers of characteristic X-rays emitted by two atoms which are displaced differently with respect to the average lattice planes. Calculations taking into account the delocalization of the ionizing events and the atoms' thermal vibrations show that displacements smaller than 0·01 nm should be detectable. This is confirmed by an experimental STEM study of thin In0.53Ga0.47As epitaxial layers, where the arsenic atoms are shown to be displaced from the perfect crystal sites more than are the indium and gallium atoms.