Water Growth on GeO2/Ge(100) Stack and Its Effect on the Electronic Properties of GeO2

作者：Mura Atsushi; Hideshima Iori; Liu Zhi; Hosoi Takuji; Watanabe Heiji; Arima Kenta^*

来源：Journal of Physical Chemistry C, 2013, 117(1): 165-171.

DOI：10.1021/jp304331c

Water growth on GeO2 films on a Ge(100) substrate and their effect on the electronic properties of GeO2 films are investigated using ambient-pressure X-ray photoelectron spectroscopy at relative humidity (RH) values from 0% to approximately 45%. Water adsorbs at low RI-Is and continues to grow gradually up to similar to 1% RH, probably forming hydroxyls. Water grows rapidly above 1% RH, indicative of the formation of a molecular water film. The molecular water film formed reaches more than one monolayer in thickness at 10% RH. We show that the energy separation between Ge4+ and Ge0+ signals in Ge3d spectra increases with RH until it reaches 1%. In addition, the collapse of an initial abrupt GeO2/Ge interface is demonstrated in this humidity range, indicating that water molecules in the gas phase infiltrate into the permeable GeO2 film, and water-related species accumulate at the GeO2/Ge interface. We propose that water-related species emit electrons to the Ge bulk and positive charges are created in GeO2 close to the GeO2/Ge interface, which is the origin of the specific features of Ge3d spectra. These positive charges are likely to be the cause of the reported negative shift of the flatband voltage in metal-oxide-semiconductor (Ge) capacitors with air-exposed GeO2.

• 出版日期2013-1-10