Water-Adsorbed Ultrathin GeO 2 /Ge and SiO 2 /Si Structure Studied In Situ by Near-Ambient-Pressure X-ray Photoelectron Spectroscopy

Abstract

We carried out near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) measurements of water-adsorbed ultrathin GeO 2 films on Ge substrates, and the results were compared with those for SiO 2 films on Si. We obtained NAP-XPS spectra at relative humidity (RH) values of up to 〜 15 % and showed that the GeO 2 / Ge structures attract more water molecules than the SiO 2 / Si structures at RH above 〜 10 − 4 % . This is probably because water molecules infiltrate the GeO 2 films to form hydroxyls. Then we revealed positive charging of the water-adsorbed SiO 2 films by their interaction with X-rays. For the water-adsorbed GeO 2 films, we observed greater positive charging of the films, of which origin is discussed.