The thin-film formation of rhodium silicides

The interaction of rhodium thin films with single-crystal substrates of silicon leads to the formation of four silicides. RhSi forms by diffusion-controlled kinetics at temperatures of about 350 °C with an activation energy of 1.9 eV. For long annealing times one observes the layered formation of Rh2Si at the RhSi-Rh interface. At higher temperatures, in the vicinity of 825 °C, Rh4Si5 forms in the same way as IrSi3: it grows as islands with no measured composition gradient through the thickness of the films. Between 925 and 950 °C Rh 4Si5 transforms to Rh3Si4. Oxidation experiments provide useful information about the stability of the Si-rich phases, Rh4Si5 and Rh3Si4, and their mode of formation. The large number of silicides, four, formed in a single metal-silicon system provides the opportunity to examine various modes of thin-film interactions. Some striking differences in behavior in the otherwise similar systems, Ir-Si and Rh-Si, are briefly discussed.