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Functional Metal Oxide Nanostructures pp 127–145Cite as

Electronic Properties of Post-transition Metal Oxide Semiconductor Surfaces

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Part of the book series: Springer Series in Materials Science ((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.

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Notes

  1. 1.

    While this picture may be complicated somewhat by many-body effects within the surface space-charge region, as will be discussed later in this chapter, it still provides a correct qualitative and indeed semi-quantitative picture of the surface space-charge characteristics of a given material.

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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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Authors and Affiliations

  1. Department of Physics, University of Warwick, Coventry, CV4 7AL, UK

    T. D. Veal, P. D. C. King & C. F. McConville

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  1. T. D. Veal
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  2. P. D. C. King
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  3. C. F. McConville
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Correspondence to T. D. Veal .

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Editors and Affiliations

  1. , Dept. Materials Science & Engineering, University of California, Berkeley, Berkeley, 94270-1760, California, USA

    Junqiao Wu

  2. , Energy Storage & Conversion Materials, GE Global Research, Research Circle 1, Niskayuna, 12309, New York, USA

    Jinbo Cao

  3. , Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, 11973, New York, USA

    Wei-Qiang Han

  4. , Materials Department, University of California, Santa Barbara, Santa Barbara, 93106-5050, New York, USA

    Anderson Janotti

  5. , Almaden Research Center, IBM Research Division, Harry Road 650, San Jose, 95120-6099, New York, USA

    Ho-Cheol Kim

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Veal, T.D., King, P.D.C., McConville, C.F. (2012). Electronic Properties of Post-transition Metal Oxide Semiconductor Surfaces. In: Wu, J., Cao, J., Han, WQ., Janotti, A., Kim, HC. (eds) Functional Metal Oxide Nanostructures. Springer Series in Materials Science, vol 149. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-9931-3_6

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