XPS study of Sol–Gel produced lanthanum oxide thin films

Abstract

La₂O₃ thin films were prepared by a sol–gel method and annealed in air and vacuum at various temperatures. The X-ray photoelectron spectroscopy (XPS) was used to investigate the properties and composition of films. The La 3d and O 1s spectra of films were analysed. It was shown that oxygen ions in La₂O₃ are in two states – O^2– anions connected with lanthanum, and oxygen in the (OH)^– group. The thermal transformation of lanthanum hydroxide to oxide process was triggered by thermal treatment at temperatures above 600 K. It was shown that after annealing thin films for longer time intervals in vacuum the intensity of O^2– component increases and the intensity of oxygen in (OH)^– decreases. The drop of oxygen in the (OH)^– group was attributed to dehydration process.