Determination of the composition of Ultra-thin Ni-Si films on Si: constrained modeling of electron probe microanalysis and x-ray reflectivity data

The homogeneous bulk assumption used in traditional electron probe microanalysis (EPMA) can be applied for thin-layered systems with individual layers as thick as 50 nm provided the penetration depth of the lowest accelerating voltage exceeds the total film thickness. Analysis of an NIST Ni-Cr thin film standard on Si using the homogeneous model yielded certified compositions and application of the same model to ultra-thin Ni-Si layers on GaAs yielded their expected compositions. In cases where the same element is present in multiple layers or in the substrate as well as the film, the homogeneous assumption in EPMA alone is not sufficient to determine composition. By combining x-ray reflectivity (XRR) thickness and critical angle data and using an iterative approach, quantitative compositional data in EPMA can be achieved. This technique was utilized to determine the composition of Ni-Si ultra-thin films grown on silicon. The Ni-Si composition determined using this multi-instrumental technique matched that of Ni-Si films simultaneously deposited on GaAs. Copyright  2008 John Wiley & Sons, Ltd.