X-ray Photoelectron Spectroscopy Study of Indium Tin Mixed Oxides on the Surface of Silicate Glass

Abstract

Indium tin oxide (ITO) films grown on silicate glass substrates have been characterized by X-ray photoelectron spectroscopy (XPS). Valence band and core level XPS spectra have been used for qualitative and quantitative elemental analysis of the films before and after Ar+ ion etching to a depth of ~50 nm. It has been found that the densest (best quality) oxide layer was produced on the surface of sample M3, prepared at a lower pressure in comparison with the other samples and a higher discharge voltage in the magnetron plasma. Sample M2 and, to a lesser extent, sample M1 have been shown to contain constituent elements of the silicate glass substrate (Si, Al, Na, K, Ca, Mg, Fe, S, O, and C), which was due to the loose structure (poor quality) of the indium tin oxide coating on the substrate. The surface layer of the as-prepared samples contained mostly In3+ and Sn2+ ions bonded not only to oxygens of the In2O3 and SnO oxides but also to the oxygens of impurity hydroxyl and carbonate groups. Ar+ ion etching of the sample surface led to the removal of the impurities. As a result, there were mostly In3+ and Sn2+ ions bonded to oxygen in In2O3 and SnO.