Interrelationship of interdiffusion and microstructure in thin-film systems

Simultaneous fitting of independently measured sputter-depth profiles of intensities of Auger electrons or photoelectrons from different Auger transitions (AES) or core levels (XPS) is shown to increase the reliability of the thus determined concentration-depth profiles in diffusion-annealed thin film systems, as compared to the usually applied single profile fitting. In this context an extension of the Mixing-Roughness-Information depth (MRI) model is presented, which includes the concentration dependence of the MRI parameters for mixing and information depth, as well as of the backscattering correction factor and the sputter rate. The thus proposed procedure is applicable for diffusion lengths as small as a few nanometre and was applied to determine the concentration dependent self-diffusion coefficients from measured AES and XPS sputter-depth profiles recorded from diffusion-annealed amorphous Si/polycrystalline Ge bilayers.