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Electronic Properties of Post-transition Metal Oxide Semiconductor Surfaces

Chapter
Part of the Springer Series in Materials Science book series (SSMATERIALS, volume 149)

Abstract

Metal oxides such as ZnO, Ga2O3, CdO, In2O3, and SnO2 exhibit high degree of transparency to visible light while supporting high levels electrical conductivity. The causes of the conductivity and the role played by the surface are current topics of research. This chapter presents a systematic study of the electronic structure and electrical properties of these post-transition metal oxides (PTMO) using a combination of X-ray photoelectron spectroscopy, angle-resolved photoelectron spectroscopy, Hall effect, infrared reflectivity, and optical absorption spectroscopy measurements. Evidence of surface electron accumulation in these PTMO is presented. It is found that for CdO and In2O3, electron accumulation is observed even in the absence of extremely high doping levels. The results also indicate that despite the strong tendency to exhibit surface electron accumulation, these materials can also exhibit an electron depletion layer under the appropriate surface stoichiometry conditions or when certain anions are adsorbed. The proclivity towards surface electron accumulation shown by the PTMOs is discussed in terms of bulk band structure, surface states, and the position of their band edges in an absolute energy scale. The electronic properties of thin films and bulk crystals of the PTMO surfaces also provide information vital for the interpretation of conductivity measurements of PTMO nanostructures, which are often dominated by surface effects.

Keywords

Fermi Level Electron Accumulation Charge Neutrality Level Electron Depletion Surface Fermi Level 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

The following people are gratefully acknowledged for fruitful collaborations on determining the surface electronic properties of PTMOs: P. H. Jefferson, J. Zúniga-Peréz, V. Muñoz-Sanjosé, Ch. Y. Wang, V. Cimalla, O. Ambacher, A. Bourlange, D. J. Payne, K. H. L. Zhang, R. G. Egdell, M. W. Allen, S. M. Durbin, N. Peng, W. M. Linhart, G. R. Bell, I. Maskery, L. F. J. Piper, K. E. Smith, E. D. L. Rienks, M. Fuglsang Jensen, Ph. Hofmann, F. Fuchs, A. Schleife, J. Furthmüller, and F. Bechstedt. The Engineering and Physical Sciences Research Council, UK, is acknowledged for funding a Career Acceleration Fellowship for TDV (Grant no. EP/G004447/1).

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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • T. D. Veal
    • 1
  • P. D. C. King
    • 1
  • C. F. McConville
    • 1
  1. 1.Department of PhysicsUniversity of WarwickCoventryUK

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