Hydrogen donor in anataseTiO2

An IR absorption study of hydrogen-related defects in natural single-crystalline anatase ${\mathrm{TiO}}₂$ has been carried out. A complex with IR absorption lines at 3412 and $3417 {\mathrm{cm}}^{\ensuremath{-}1}$ is shown to act as a donor with ionization energy of tens of meV. The two lines are identified as stretching local vibrational modes of the O-H bonds of the donor in the neutral and positive charge states, respectively. The defect is unstable against annealing at approximately 300 ${}^{\ensuremath{\circ}}\mathrm{C}$ and a storage at room temperature on the time scale of a few weeks. These findings suggest that interstitial hydrogen is a plausible model of this defect.