Valence-band density of states and surface electron accumulation in epitaxial SnO2 films

Abstract

The surface band bending and electronic properties of SnO2(101) films grown on r-sapphire by plasma-assisted molecular beam epitaxy have been studied by Fourier-transform infrared spectroscopy (FTIR), x-ray photoemission spectroscopy (XPS), Hall effect, and electrochemical capacitance-voltage measurements. The XPS results were correlated with density functional theory calculation of the partial density of states in the valence-band and semicore levels. Good agreement was found between theory and experiment with a small offset of the Sn 4d levels. Homogeneous Sb-doped SnO2 films allowed for the calculation of the bulk Fermi level with respect to the conduction-band minimum within the k⋅p carrier statistics model. The band bending and carrier concentration as a function of depth were obtained from the capacitance-voltage characteristics and model space charge calculations of the Mott-Schottky plots at the surface of Sb-doped SnO2 films. It was quantitatively demonstrated that SnO2 films have downward band bending and surface electron accumulation. The surface band bending, unoccupied donor surface-state density, and width of the accumulation region all decrease with increasing Sb concentration.

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Vasheghani Farahani, S. K., Veal, T. D., Mudd, J. J., Scanlon, D. O., Watson, G. W., Bierwagen, O., et al. (2014). Valence-band density of states and surface electron accumulation in epitaxial SnO2 films. 90(15). https://doi.org//10.1103/PhysRevB.90.155413
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CC BY 3.0 Unported