Behavior of ultrathin layers of Co on Si and Ge systems

Photoelectron spectroscopic study of the interaction of Co with Ge surface is reported for the first time. The behavior of ultrathin layers of Co on Ge(100) has been compared with that on Si(100) surfaces based on ultraviolet and X-ray photoelectron spectroscopic studies (UPS and XPS). Formation of silicides and germanides take place upon depositing Co on clean Si(100) and Ge(100) surfaces, respectively, at room temperature. The Co 2p transition is observed at a slightly higher binding energy in the case of silicide (778.7 ± 0.2eV) compared to that of the germanide (778.1 ± 0.2eV). Upon annealing the Co covered surfaces, the Co atoms diffuse into the bulk and the onset temperature of inward diffusion is low in Ge (∼ 150°C) compared to that in Si (∼ 350°C). Co-deposition of Co and Ge on clean Ge(100) surface at room temperature leads to the formation of a mixture of different germanide phases.