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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

Abstract

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.

Authors:
 [1];  [2];  [2];  [1];  [1];  [3];  [3];  [2]; ORCiD logo [1]
  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:
Research Org.:
Osaka Univ. (Japan); 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)
OSTI Identifier:
1377479
Grant/Contract Number:
AC02-05CH11231; JP24686020; JP26630026; JP16K14133
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 120; Journal Issue: 9; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Germanium; Elemental semiconductors; Water vapor; X-ray photoelectron spectroscopy; Adsorption

Citation Formats

Mori, Daichi, Oka, Hiroshi, Hosoi, Takuji, Kawai, Kentaro, Morita, Mizuho, Crumlin, Ethan J., Liu, Zhi, Watanabe, Heiji, and Arima, Kenta. Comparative study of GeO2/Ge and SiO2/Si structures on anomalous charging of oxide films upon water adsorption revealed by ambient-pressure X-ray photoelectron spectroscopy. United States: N. p., 2016. Web. doi:10.1063/1.4962202.
Mori, Daichi, Oka, Hiroshi, Hosoi, Takuji, Kawai, Kentaro, Morita, Mizuho, Crumlin, Ethan J., Liu, Zhi, Watanabe, Heiji, & Arima, Kenta. Comparative study of GeO2/Ge and SiO2/Si structures on anomalous charging of oxide films upon water adsorption revealed by ambient-pressure X-ray photoelectron spectroscopy. United States. doi:10.1063/1.4962202.
Mori, Daichi, Oka, Hiroshi, Hosoi, Takuji, Kawai, Kentaro, Morita, Mizuho, Crumlin, Ethan J., Liu, Zhi, Watanabe, Heiji, and Arima, Kenta. 2016. "Comparative study of GeO2/Ge and SiO2/Si structures on anomalous charging of oxide films upon water adsorption revealed by ambient-pressure X-ray photoelectron spectroscopy". United States. doi:10.1063/1.4962202. https://www.osti.gov/servlets/purl/1377479.
@article{osti_1377479,
title = {Comparative study of GeO2/Ge and SiO2/Si structures on anomalous charging of oxide films upon water adsorption revealed by ambient-pressure X-ray photoelectron spectroscopy},
author = {Mori, Daichi and Oka, Hiroshi and Hosoi, Takuji and Kawai, Kentaro and Morita, Mizuho and Crumlin, Ethan J. and Liu, Zhi and Watanabe, Heiji and Arima, Kenta},
abstractNote = {The energy difference between the oxide and bulk peaks in X-ray photoelectron spectroscopy (XPS) spectra was investigated in this paper for both GeO2/Ge and SiO2/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 GeO2 on Ge than for thermal SiO2 on Si above ~10-4% RH, which is due to the larger amount of water molecules that infiltrate into the GeO2 film to form hydroxyls. Analyzing the origins of this energy shift, we propose that the positive charging of a partially hydroxylated GeO2 film, which is unrelated to X-ray irradiation, causes the larger energy shift for GeO2/Ge than for SiO2/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 GeO2 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 GeO2 layer.},
doi = {10.1063/1.4962202},
journal = {Journal of Applied Physics},
number = 9,
volume = 120,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
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  • The energy difference between the oxide and bulk peaks in X-ray photoelectron spectroscopy (XPS) spectra was investigated for both GeO{sub 2}/Ge and SiO{sub 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{sub 2} on Ge than for thermal SiO{sub 2} on Si above ∼10{sup −4}% RH, which is due to the larger amount of water molecules that infiltrate into the GeO{sub 2} film to form hydroxyls. Analyzing the origins of this energy shift,more » we propose that the positive charging of a partially hydroxylated GeO{sub 2} film, which is unrelated to X-ray irradiation, causes the larger energy shift for GeO{sub 2}/Ge than for SiO{sub 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{sub 2} film to the Ge bulk, leaving immobile cations or positively charged states in the oxide. This may be related to the reported negative shift of flat band voltages in metal-oxide-semiconductor diodes with an air-exposed GeO{sub 2} layer.« less
  • The adsorption of water on KBr thin films evaporated onto SiO2 was investigated as a function of relative humidity (RH) by ambient pressure X-ray photoelectron spectroscopy. At 30percent RH adsorbed water reaches a coverage of approximately one monolayer. As the humidity continues to increase, the coverage of water remains constant or increases very slowly until 60percent RH, followed by a rapid increase up to 100percent RH. At low RH a significant number of the Br atoms are lost due to irradiation damage. With increasing humidity solvation increases ion mobility and gives rise to a partial recovery of the Br/K ratio.more » Above 60percent RH the increase of the Br/K ratio accelerates. Above the deliquescence point (85percent RH), the thickness of the water layer continues to increase and reaches more than three layers near saturation. The enhancement of the Br/K ratio at this stage is roughly a factor 2.3 on a 0.5 nm KBr film, indicating a strong preferential segregation of Br ions to the surface of the thin saline solution on SiO2.« less
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  • The oxidation behavior of NiAl(100) by molecular oxygen and water vapor under a near-ambient pressure of 0.2 Torr is monitored using ambient-pressure X-ray photoelectron spectroscopy. O 2 exposure leads to the selective oxidation of Al at temperatures ranging from 40 to 500 °C. By contrast, H 2O exposure results in the selective oxidation of Al at 40 and 200 °C, and increasing the oxidation temperature above 300 °C leads to simultaneous formation of both Al and Ni oxides. Furthermore, these results demonstrate that the O 2 oxidation forms a nearly stoichiometric Al 2O 3 structure that provides improved protection tomore » the metallic substrate by barring the outward diffusion of metals. By contrast, the H 2O oxidation results in the formation of a defective oxide layer that allows outward diffusion of Ni at elevated temperatures for simultaneous NiO formation.« less