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Defects and the Origin of p-Type Conductivity in Cu2O: a First Principles Investigation

Michael J. Nolan 1Simon D. Elliott 

1. University College Cork, Tyndall National Institute (TYNDALL), Lee Maltings, Prospect Row, Cork, Ireland


The search is on for novel p-type transparent conducting oxide (TCO) materials, with Cu2O derived materials currently leading candidates. As part of the "Novel Advanced Transparent Conducting Oxides" (NATCO) project, we are using first principles density functional theory (DFT) to study the properties of Cu2O derived materials, with the aim of using the resulting band gap and computed effective hole masses to screen potential candidate p-type TCO materials. Before investigating TCO candidates, it is necessary to understand the properties of Cu2O, the origin of the electronic structure and the p-type character of Cu2O, which provide important insights for investigating more complex Cu2O derived materials. In this talk, we present DFT calculations of stoichiometric Cu2O and Cu2O with Cu and O vacancy defects. From these calculations, we find the following (i) the small band gap in Cu2O arises from the Cu-Cu interactions in Cu2O, (ii) Cu vacancies have a significantly smaller formation energy than O vacancies, (iii) at finite temperature and pressure, Cu vacancies will form spontaneously, while O vacancies have a much larger formation energy and will not dope Cu2O n-type or compensate holes (iv) neutral Cu vacancies are the origin of the p-type character of Cu2O, leading to the formation of hole states 0.2 eV above the valence band. The implications of these results for candidate TCO materials are discussed.


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Presentation: Oral at E-MRS Fall Meeting 2007, Symposium H, by Michael J. Nolan
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 12:47
Revised:   2009-06-07 00:44