Study of Erbium Oxidation by XPS and UPS

X-ray and UV photoelectron spectroscopy (XPS and UPS were used for studying the oxidation of Er films deposited on Ta substrate under ultra-high vacuum.Oxidation has been carried out at room temperatue with an oxygen pressure of 2x10-5 mbar.Erbium exposition to oxygen produces ; Er2O3 and a hydoxide.Subjecting the sample to a post annealing treatment at 750 °C dissociates the hydroxide and produces additional Er2O3.UPS and XPS valence band gives evidence that the formed oxide is Er2O3.