Hydrogen Adsorption on Ga2O3 Surface: A Combined Experimental and Computational Study

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• 作者：Yun-xiang Pan ; Donghai Mei ; Chang-jun Liu ; Qingfeng Ge
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：May 26, 2011
• 年：2011
• 卷：115
• 期：20
• 页码：10140-10146
• 全文大小：909K
• 年卷期：v.115,no.20(May 26, 2011)
• ISSN：1932-7455

文摘

In the present work, hydrogen adsorption on the Ga₂O₃ surfaces was investigated using Fourier transform infrared spectroscopy (FTIR) measurements and periodic density functional theory (DFT) calculations. Both the FTIR and DFT studies suggest that H₂ dissociates on the Ga₂O₃ surfaces, producing OH and GaH species. The FTIR bands at 3730, 3700, 3630, and 3600 cm^鈥? are attributed to the vibration of the OH species whereas those at 2070 and 1990 cm^鈥? to the GaH species. The structures of the species detected in experiments are established through a comparison with the DFT calculated stretching frequencies. The O atom of the experimentally detected OH species is believed to originate from the three-coordinated surface O atom. However, the H adatom that binds the coordinately unsaturated Ga atom results in the experimentally detected GaH species. Dissociative adsorption of H₂ on the perfect Ga₂O₃ surface, with the formation of both OH and GaH species, is endothermic and has an energy barrier of 0.90 eV. In contrast, dissociative adsorption of H₂ on the defective Ga₂O₃ surface with oxygen vacancies, which mainly produces GaH species, is exothermic, with an energy barrier of 0.61 eV. Accordingly, presence of the oxygen vacancies promotes H₂ dissociation and production of GaH species on the Ga₂O₃ surfaces. Higher temperatures are expected to favor oxygen vacancy creation on the Ga₂O₃ surfaces and thereby benefit the production of GaH species. This analysis is consistent with the FTIR results that the bands assigned to GaH species become stronger at higher temperatures.