I thought this talk which is taking place this afternoon might be of interest.



Friday, January 15, 2010, 4:00 PM, ESB 1001
Professor Chris F. McConville
Department of Physics University of Warwick
“Oxides as Semiconductors”
Oxide semiconductors have enormous potential for new and innovative uses and may also improve existing device applications. The fact that some of these materials, such as indium tin oxide in a low quality form, have seen significant industrial use as transparent conductors has perhaps contributed to the belated recognition of their possibilities as semiconductors in their purer form. Here, the surface and bulk electronic properties of several epitaxially grown high-quality oxide semiconductors (In2O3, CdO, and ZnO) will be discussed. Optical, electrical and structural properties of the semiconducting oxide films will be presented, including data on the revision of the band gap of In2O3 from 3.7 eV to less than 3.0 eV. Both the valence band density of states and the surface electronic properties of the oxide semiconductors have been studied using high-resolution photoemission spectroscopy. A common property of these oxide semiconductors is found to be the presence of a surface electron accumulation layer, which is in marked contrast to the electron depletion generally observed at the surface of conventional compound semiconductors. Additionally, hydrogen is found to be a donor and 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 of these semiconducting oxides.