OXIDATION OF THIN ERBIUM AND ERBIUM SILICIDE OVERLAYERS IN CONTACT WITH SILICON-OXIDE FILMS THERMALLY GROWS ON SILICON

Pure Er and co-evaporated Er and Si layers were deposited near room te mperature in UHV on SiO2 films grown on Si(l00) wafers and were subseq uently annealed at increasing temperature up to 1153 K. The samples we re characterized in situ by X-ray photoelectron spectroscopy following deposition and each annealing step. The co-evaporated samples were al so past-examined by Rutherford backscattering spectroscopy after the f inal annealing. The results show that both the Er and the ErSix adlaye rs react readily with the SiO2 upon increasing temperature to give Er2 O3 silicon suboxides and elemental silicon. The erbium oxide remains s table up to 1073 K and then transforms back to erbium silicide with a simultaneous loss of oxygen from the surface via the volatile SiO. Thi s behavior is rationalized in terms of a number of solid phase reactio ns taking place in the overlayer.