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Title: Comparative study of GeO 2/Ge and SiO 2/Si structures on anomalous charging of oxide films upon water adsorption revealed by ambient-pressure X-ray photoelectron spectroscopy

The energy difference between the oxide and bulk peaks in X-ray photoelectron spectroscopy (XPS) spectra was investigated in this paper for both GeO 2/Ge and SiO 2/Si structures with thickness-controlled water films. This was achieved by obtaining XPS spectra at various values of relative humidity (RH) of up to ~15%. The increase in the energy shift is more significant for thermal GeO 2 on Ge than for thermal SiO 2 on Si above ~10 -4% RH, which is due to the larger amount of water molecules that infiltrate into the GeO 2 film to form hydroxyls. Analyzing the origins of this energy shift, we propose that the positive charging of a partially hydroxylated GeO 2 film, which is unrelated to X-ray irradiation, causes the larger energy shift for GeO 2/Ge than for SiO 2/Si. A possible microscopic mechanism of this intrinsic positive charging is the emission of electrons from adsorbed water species in the suboxide layer of the GeO 2 film to the Ge bulk, leaving immobile cations or positively charged states in the oxide. Finally, this may be related to the reported negative shift of flat band voltages in metal-oxide-semiconductor diodes with an air-exposed GeO 2 layer.
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  1. Osaka Univ. (Japan). Graduate School of Engineering. Dept. of Precision Science and Technology
  2. Osaka Univ. (Japan). Graduate School of Engineering. Dept. of Material and Life Science
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source
Publication Date:
Grant/Contract Number:
AC02-05CH11231; JP24686020; JP26630026; JP16K14133
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 120; Journal Issue: 9; Journal ID: ISSN 0021-8979
American Institute of Physics (AIP)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Japan Society for the Promotion of Science (JSPS) (Japan); Murata Science Foundation (Japan); Mikiya Science and Technology Foundation (Japan)
Country of Publication:
United States
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Germanium; Elemental semiconductors; Water vapor; X-ray photoelectron spectroscopy; Adsorption
OSTI Identifier: