Surface and interface XPS characterization of the oxide layer grown on antimony under UV laser irradiation

Abstract

Abstract The ultraviolet light from an ArF excimer laser (photon energy = 6.4 eV) strongly stimulates in the air the kinetics of the superficial oxidation of crystals or evaporated films of antimony. The characteristics of X-ray photoelectron spectroscopy (XPS) have been exploited to characterize both the nature and the structure of the oxide layer grown on antimony under ultraviolet irradiation. A stoichiometry close to Sb 2 O 3 is deduced from the ratio of the intensities of the Sb 3d and O 1s XPS signals, and from the chemical shift measured on the Sb 3d lines upon oxidation. Since the oxidation of a film evaporated on a quartz microbalance shows a linear increase of the oxygen uptake versus the number of exposures to the pulsed laser beam, the pure exponential decrease of the relative intensity of the Sb 4d signal from the substrate during the growth indicates a layer-by-layer growth and the presence of a sharp interface between the substrate and the overlayer. These results yield values for the rate of oxidation with the same absolute precision as this one on the electronic mean free path of the Sb 3d and Sb 4d photoelectrons.