Comprehensive study of the interstitial hydrogen donor in SnO2

The nature of interstitial hydrogen in ${\mathrm{SnO}}_{2}$ has been inferred by a combined study of first-principles theory and infrared absorption, near band edge absorption, and photoluminescence spectroscopy. The earlier interpretation of a center with an $\mathrm{O}--\mathrm{H}$ stretch mode at 3156 ${\mathrm{cm}}^{\ensuremath{-}1}$ as interstitial hydrogen is confirmed. Uniaxial stress experiments on the 3156 ${\mathrm{cm}}^{\ensuremath{-}1}$ mode reveal that the interstitial hydrogen atom is located in the open $c$ channel of the rutile ${\mathrm{SnO}}_{2}$ structure. Migration along the $c$ axis of the crystals occurs via low barrier hydrogen jumps of around 0.57 eV to symmetrically equivalent nearest-neighbor positions. Combinational vibrations of the $\mathrm{O}--\mathrm{H}$ stretch mode with the out-of-$ab$-plane and in-$ab$-plane wag modes at about 4014 and 4332 ${\mathrm{cm}}^{\ensuremath{-}1}$ have been identified. Free carrier absorption and excitonic properties of the defect demonstrate that ${\mathrm{H}}_{i}$ forms an effective shallow-donor-like state similar to the well-characterized F, Cl, and Sb $n$-type dopants in this material.