Point defects and related properties of highly co-doped bixbyite In₂O₃

The method of co-doping has been employed to achieve and study the influence of high defect populations in bixbyite In₂O₃. Substantial metastable Sn-doping levels can be achieved in nanocrystalline In₂O₃ with associated co-doping by oxygen interstitials. The resulting electrical properties, diffraction data (X-ray and neutron), and EXAFS studies support the presence of 2: 1 Sn-oxygen interstitial point defect clusters. Upon reduction, some of these clusters can be reduced to liberate donors and generate charge carriers. Extensive Cd/Sn co-substitution for indium in In₂O₃ has been achieved in equilibrium solid solutions. This self-compensated (isovalent) and relatively size-matched substitution reveals a tendency for off-stoichiometry in favor of donors, resulting in "self-doped" behavior irrespective of oxygen partial pressure. Ramifications of bixbyite defect structure for transparent electrode applications are discussed.