Investigation of metal-induced crystallization in amorphous Ge/crystalline Al bilayers by Auger microanalysis and selected-area depth profiling

Abstract

The diffusion processes and accompanying microstructural changes occurring in amorphous Ge (a-Ge)/crystalline Al bilayers upon annealing have been investigated by using a combined approach of Auger microanalysis, selected-area depth profiling (SA-DPR), scanning electron microscopy (SEM) and X-ray diffraction. Upon annealing at 150°C for 10 min, the partially crystallized Al/a-Ge (with the Al layer at the top) and a-Ge/Al (with the a-Ge layer at the top) specimens show reacted and un reacted regions with a lateral size of ∼1 -2 μm at their surfaces. SA-DPR at the location of unreacted regions at the surface shows that at such locations the original Al/a-Ge (or a-Ge/Al) bilayer structure is almost preserved. On the other hand, depth profiling at the location of reacted regions shows that at such locations the original a-Ge sublayer had fully crystallized and contains 10-20 at.% Al, and that in the original Al sublayer, crystalline Ge (c-Ge) had formed at the Al grain boundaries (GBs). These observations could be explained in consequence of the initiation of crystallization of a-Ge at the Al GBs followed by the nucleation of crystallization at the a-Ge/Al interface, as supported by thermodynamic calculations of interface energetics. Copyright © 2008 John Wiley & Sons, Ltd.