Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 4: Focussed session: Transparent conductive oxides I (jointly with HL, DS)

O 4.1: Topical Talk

Monday, March 14, 2011, 11:15–11:45, WIL A317

Surface and Bulk Properties of Post-Transition Metal Oxide Semiconductors — Philip D.C. King, Sepehr Vasheghani Farahani, Tim D. Veal, and •Chris F. McConville — Department of Physics, University of Warwick, Coventry, CV4 7AL UK

Oxide semiconductors have become of great interest lately with enormous opportunities for new uses that will potentially improve existing materials and device applications. The fact that some of these materials, such indium tin oxide, in a relatively low quality form, have seen significant industrial use as transparent conductors has perhaps contributed to the belated recognition of the possibilities as semiconductors in their purer form. Here, the surface and bulk electronic properties of epitaxially grown high-quality oxide semiconductors (In₂O₃, CdO, and ZnO) will be discussed. Optical, electronic and structural properties of these semiconducting oxide films will be presented. The valence band density of states and the surface electronic properties of these oxide semiconductors have been studied using high-resolution photoemission spectroscopy and compared with theoretical band structure calculations. A common property of these oxide semiconductors is found to be the presence of a surface electron accumulation layer, in marked contrast to the electron depletion generally observed at the surfaces of conventional semiconductors. Additionally, hydrogen is found to be a donor and any native defects have a propensity to be donors in already n-type material. The origin of these phenomena will be discussed in terms of the band structure and intrinsic properties of these materials.