Metal-rich Pd-silicide formation in thin-film interactions

Phase formation of metal-rich Pd silicides was studied in palladium–amorphous-silicon thin-film interactions by means of 4He+-ion backscattering, Auger spectrometry, electron microprobe, and x-ray diffractometry. In the initial stage of compound formation, where both unreacted Si and Pd layers ar present, the Pd2Si phase has been observed. At increasing annealing temperature in SiO2/Si(a)/Pd systems, where the metal-film thickness was larger than that of amorphous-Si film, phases richer and richer in metal have been detected, following exactly the phase diagram reported in literature. The Pd-richest phase was identified as Pd4Si and is stable up to 650 °C in the presence of unreacted Pd. A crystallographic characterization of this new thin-film end phase was performed on the basis of a triclinic unit cell.