Rhodium and silicon system: II. Rhodium silicide formation

Detailed characterizations of rhodium/silicon films prepared by co-deposition using magnetron sputtering have been carried out on silicon substrates at room temperature up to 900 °C. The properties of the films were investigated using XPS/UPS, XRD, SIMS, SEM and AFM techniques. It should be emphasized that XPS/UPS measurements are carried out without breaking the vacuum to avoid any contamination of the film. Up to 500 °C an interdiffusion between the oxidized silicon wafer and the deposited Rh/Si film occurred leading to hole formation in the entire film at 900 °C. Diffraction patterns for the compounds Rh₂Si, Rh₅Si₃, RhSi and Rh₃Si₄ were measured. Upon annealing the covalent character is increased and for the samples forming the compound RhSi the valence band structure is markedly changed. Depth profiling (XPS and SIMS) reveals a stable composition in the bulk of the film. For these measurements the silicon-rich alloy in the interfacial layer is probably an effect of sputtering, by implanting the Rh atoms into the silicon substrate. A previously reported negative shift for the compound Rh₅Si₃ could be connected to the sample preparation, as sputtering of the surface is reducing the silicon content and inducing a glassy state. For the first phase Rh₂Si formed on the rhodium-rich side the shift in binding energy is unclear, for all the other compounds encountered in this work a positive shift relative to pure rhodium was found.