Thin film characterisation of chromium disilicide

Abstract

The ambiguous binding energy (BE) shift of the Cr 2p3/2 peak of chromium disilicide with respect to the one of pure Cr metal in the X-ray photoelectron spectroscopy (XPS) has meant difficulties in practice for silicide determination. In the present study, with the aid of an interconnected ultrahigh vacuum (UHV) system for silicide fabrication and characterisation, high purity Cr–Si thin films with thickness around 100nm and well-controlled chemistry were produced. The characteristics with respect to chemical composition and phase identity were determined by means of XPS and X-ray diffraction (XRD). The experimental results were also compared with predictions using thermodynamic effective heat of formation (EHF) model. Whilst the BE positions of the core-level Cr 2p3/2 peak of Cr and CrSi2 are close to each other, larger shifts are determined for their corresponding L3M23M23 Auger transitions. By establishing a chemical-state plot, or the so-called Wagner plot, it is illustrated that the core-level shift caused by the initial-state effects is basically compensated by the one owing to the final-state effects, resulting in a small negative BE shift of the Cr 2p3/2 peak from metallic state to disilicide state. The valence band spectra were also investigated and correlated to the core-level spectra.