Self-doping of cadmium stannate in the inverse spinel structure

Using first-principles total energy calculations, we have studied self-doping in the ternary transparent conducting oxide, Cd2SnO4. Formation of the CdO and SnO2 binaries limits ale inverse spinel CdSnO4 phase into a narrow region in the atomic chemical potential (mu) space. This suggests that mu(Sn) is not independent of mu(Cd), so a Cd-rich growth or annealing condition also implies Sn-rich, and vice versa. We found that the widely accepted intrinsic donors such as oxygen vacancy and cadmium interstitial are not responsible for the observed conductivity in Cd2SnO4: both require too much energy to form. In addition, the oxygen vacancy is rather deep. We show instead that the Sn-on-Cd antisite defect is the most probable donor responsible for the n typeness under Cd-rich conditions. (C) 2002 American Institute of Physics.