Transmission electron microscopy studies of displacement cascades in Cu₃Au

Abstract

Displacement cascades produced in ordered Cu₃Au by the impact of Cu+ions of energy 5–100 keV are studied using the method described in Part I. It is found that each incident ion of energy ≳ 10 keV creates, at the core of the resulting displacement cascade, a zone of reduced long-range order which can be imaged in the electron microscope. The sizes of displacement cascades in Cu₃Au are well described by the analytical theory of Sigmund and co-workers. The best evidence for this comes from a comparison of experimental and theoretical image contrast profiles at an ion energy of 10 keV, when reasonably direct physical arguments can be used to link experimental and theoretical parameters. At ion energies ≳ 30 keV many of the disordered zones develop extrusions, and the formation of some discrete sub-cascades is observed. The various mechanisms which might give rise to the disordering are discussed.