Depth resolved investigations of defects and their evolution upon interdiffusion were carried out on Al/Ge thin film bilayers, using concurrent measurements of positron beam based Doppler broadening lineshape and secondary ion mass spectrometry profiles. Measurements were made of the as-grown films and of films annealed at various temperatures between 370 and 670K. Secondary ion mass spectrometry studies established the occurrence of extensive intermixing of the Al and Ge layers above 370K. It was found that there was asymmetrical diffusion across the interface, with Ge being the predominant diffusing species. The intermixed Al/Ge region formed in the near-surface layers of the sample annealed at 670K showed Ge precipitation, as confirmed by electron microscopy and secondary ion mass spectrometry imaging. Analysis of the Doppler broadening lineshape variation, together with the secondary ion mass spectrometry concentration profiles, indicated an increased production of small vacancy clusters at the Al/Ge interface, around 520K; brought about by the enhanced diffusion of Ge. The interfacial vacancy structure was deduced to be a tri-vacancy cluster.

Study of Interdiffusion and Defect Evolution in Thin-Film Al/Ge Bilayers using SIMS and Positron Beam. G.Raghavan, G.Venugopal Rao, G.Amarendra, A.K.Tyagi, B.Viswanathan: Applied Surface Science, 2001, 178[1-4], 75-82