Origin of electron accumulation in In2O3

We have used ARPES at low photon energy to directly image a quantized two-dimensional electron gas at the surface of In2O3(111). The microscopic origin of these electrons is shown to be oxygen vacancies, acting as doubly ionized shallow donors, localized at the surface.

  Zhang et al., Phys. Rev. Lett. 110, 056803 (2013).

Angle-resolved photoemission spectroscopy at low photon energy reveals the presence of a two-dimensional electron gas at the surface of In2O3(111). Quantized subband states arise within a confining potential well associated with surface electron accumulation. Coupled Poisson-Schrödinger calculations suggest that downward band bending for the conduction band must be much bigger than band bending in the valence band. Surface oxygen vacancies acting as doubly ionized shallow donors are shown to provide the free electrons within this accumulation layer. Identification of the origin of electron accumulation in transparent oxides has significant implications in the realization of devices based on these compounds.

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Microscopic Origin of Electron Accumulation in In2O3
K.H.L. Zhang, R.G. Egdell, F. Offi, S. Iacobucci, L. Petaccia, S. Gorovikov, P.D.C. King,
Phys. Rev. Lett. 110, 056803 (2013).
doi: 10.1103/PhysRevLett.110.056803

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