Oxidation of thin erbium and erbium silicide overlayers in contact with silicon oxide films thermally grown on silicon

Pure Er and co-evaporated Er and Si layers were deposited near room temperature in UHV on SiO2 films grown on Si(100) wafers and were subsequently annealed at increasing temperature up to 1153 K. The samples were characterized in situ by X-ray photoelectron spectroscopy following deposition and each annealing step. The co-evaporated samples were also post-examined by Rutherford backscattering spectroscopy after the final annealing. The results show that both the Er and the ErSix adlayers react readily with the SiO2 upon increasing temperature to give Er2O3, silicon suboxides and elemental silicon. The erbium oxide remains stable up to 1073 K and then transforms back to erbium silicide with a simultaneous loss of oxygen from the surface via the volatile SiO. This behavior is rationalized in terms of a number of solid phase reactions taking place in the overlayer.