Sources of Electrical Conductivity in ${\mathrm{SnO}}_2$

${\mathrm{SnO}}_2$ is widely used as a transparent conductor and sensor material. Better understanding and control of its conductivity would enhance its performance in existing applications and enable new ones, such as in light emitters. Using density functional theory, we show that the conventional attribution of $n$-type conductivity to intrinsic point defects is incorrect. Unintentional incorporation of hydrogen provides a consistent explanation of experimental observations. Most importantly, we find that ${\mathrm{SnO}}_2$ offers excellent prospects for $p$-type doping by incorporation of acceptors on the Sn site. Specific strategies for optimizing acceptor incorporation are presented.

Figure 1

Calculated formation energies of (a) intrinsic donor-type defects and (b) impurities in ${\mathrm{SnO}}_2$, as a function of the Fermi level (referenced to the valence-band maximum), for Sn-rich conditions.

Figure 2

Local structural configurations of (a) $V_{\mathrm{O}}^{2+}$, (b) ${\mathrm{Sn}}_i^{4+}$, (c) ${\mathrm{H}}_i^{+}$, and (d) ${\mathrm{H}}_{\mathrm{O}}^{+}$ in ${\mathrm{SnO}}_2$.