Interaction of Pd-Er alloys with silicon

In situ resistivity measurements together with MeV ⁴He ⁺ backscattering, x-ray diffraction, barrier height measurements, and Auger electron spectroscopy combined with Ar sputtering have been used to investigate the interaction of silicon with alloys of rare-earth and near-noble metals with annealing at temperatures up to 650°C. Alloys of Pd-Er with three different compositions have been prepared by dual electron-gun coevaporation on both n- and p-type silicon and Pd/Er bilayers have been deposited on SiO₂. The results show that as-deposited these alloys are amorphous and the initial stages of the reaction with silicon upon annealing is controlled by the metal-metal interaction as well as the metal-silicon interaction. The Er-rich alloy (Pd₁₅Er_{8 5}) segregates Er to the silicon interface and forms Pd ₂Er₅. The segregated Er reacts with silicon producing ErSi₂. For the Pd-rich alloy (Pd₆₅Er ₃₅) the excess Pd is segregated at the silicon surface forming Pd₂Si. The near 50-50 alloy forms PdEr and a slightly higher temperature is necessary to promote the reaction with silicon to form the silicide of the excess component.