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Mori D., Oka H., Hosoi T., et al. 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. Journal of Applied Physics, 120, 9, 095306. https://doi.org/10.1063/1.4962202., The energy difference between the oxide and bulk peaks in X-ray photoelectron spectroscopy (XPS) spectra was investigated 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. This may be related to the reported negative shift of flat band voltages in metal-oxide-semiconductor diodes with an air-exposed GeO2 layer.

Very thin oxide films with a high electrical insulating performance have been grown by controlling preoxide growth using the ultraclean oxidation method. The current level through the ultraclean oxide is lower than that through the conventional dry oxide including thicker preoxide. The barrier height at the silicon‐oxide interface for electrons emission from silicon to oxide for the ultraclean oxide is little decreased as the thickness is thinner, while the barrier height for conventional dry oxide is drastically decreased. The growth rate of ultraclean oxide at 900 °C is governed by a simple parabolic law even in the range of 5–20 nm.

The authors demonstrate that Ge(100) surfaces containing metallic particles are etched anisotropically in water. This originates from the catalytic reduction of dissolved oxygen (O2) in water to water molecules (H2O) on the metallic particles, which is followed by the enhanced oxidation of Ge around the particles. The soluble nature of Ge oxide (GeO2) in water promotes the formation of inverted pyramidal etch pits composed of (111) microfacets. On the basis of the results, the authors propose strategies for avoiding unwanted surface roughening during the wet cleaning of Ge.

Very thin SiO2 films thermally grown on Si were annealed at a temperature of 950 or 1050 °C in the glow discharge of either an NH3 gas containing 4% CF4 or a pure NH3. From the chemical analysis of annealed films using Auger electron spectroscopy and x‐ray photoelectron spectroscopy, it is found that annealing has resulted in the formation of silicon nitride layer on the SiO2 surface and in the incorporation of bonded nitrogen into the SiO2 layer. It is also demonstrated that the surface nitride layer is formed primarily by the deposition of silicon nitride resulting from the reaction of fragments of NH3 with the silicon atoms produced by the plasma etching of the quartz tube wall by atomic hydrogen and fluorine.

Zirconium dioxide (ZrO2) films have been grown on Si(100), Si(111), and SiO2/Si substrates heated at the range from room temperature to 800 °C by vacuum evaporation. X‐ray diffraction and reflection high‐energy electron diffraction observations reveal the epitaxial growth of tetragonal ZrO2(200) films on Si(100) substrates at 800 °C. The epitaxial imperfection is caused by preferentially oriented tetragonal ZrO2(002) grains. The crystalline system of ZrO2 films depends on the substrate temperature. The crystalline perfection and the orientation of tetragonal ZrO2 films grown at 800 °C depend on the substrate orientation.

The interface‐state parameters near the band edge at the Si/SiO2 interface were measured using the MOS conductance method with the reflection technique, extending the frequency up to 100 MHz. The double peaks were observed in the conductance‐vs‐frequency curves. The decrease of the capture cross section toward the band edge was found due to the overlap of the double peaks. The new peak at higher frequencies suggests the existence of new interface states, which has been overlooked so far.

Thin films of ZrO2 vacuum‐deposited on Si(100) substrates were oxidized in dry O2 at 800 °C and then analyzed by infrared absorption and Auger electron spectroscopy. It was found that the SiO2 layer was formed at the ZrO2/Si interface. Mo/ZrO2/SiO2/p‐Si(100) metal‐insulator‐semiconductor diodes were electrically characterized. The static dielectric constant of the ZrO2 layer decreases from 21.1 e0 to about 15.5 e0 due to the crystallization of amorphous ZrO2 during the oxidation. The SiO2 layer formed at the ZrO2/Si interface was found to lower the leakage current through the dielectric film.

Single‐crystal AlN layers have been grown on Si substrates at ∼1200 °C using metalorganic chemical vapor deposition. The metal/AlN/Si MIS structures have been investigated by the MIS conductance method. It was found that the interface‐state density Nss and electron capture cross section σn in the depletion region are of the order of 1011 eV−1 cm−2 and 10−17 cm, respectively.