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

Journal Article · Wed Sep 07 00:00:00 EDT 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4962202· OSTI ID:22598818

Mori, Daichi; Kawai, Kentaro; Morita, Mizuho; Arima, Kenta ^[1]; Oka, Hiroshi; Hosoi, Takuji; Watanabe, Heiji ^[2]; Crumlin, Ethan J.; Liu, Zhi ^[3]

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1. Department of Precision Science and Technology, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871 (Japan)
2. Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871 (Japan)
3. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

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, 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.

• OSTI ID: 22598818
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 9 Vol. 120; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ADSORPTION
AIR
CATIONS
ELECTRONS
FILMS
GERMANATES
GERMANIUM OXIDES
HUMIDITY
HYDROXIDES
IRRADIATION
LAYERS
SEMICONDUCTOR DIODES
SEMICONDUCTOR MATERIALS
SILICA
SILICON OXIDES
WATER
X RADIATION
X-RAY PHOTOELECTRON SPECTROSCOPY