Infrared absorption on a complex comprising three equivalent hydrogen atoms in ZnO

Abstract

A hydrogen-related defect in ZnO which causes two broad IR absorption bands at 3303 and $3321 {\mathrm{cm}}^{\ensuremath{-}1}$ is studied by means of infrared absorption spectroscopy and first-principles theory. In deuterated samples, the defect reveals two sharp absorption lines at 2466 and $2488 {\mathrm{cm}}^{\ensuremath{-}1}$ accompanied by weaker sidebands at 2462 and $2480 {\mathrm{cm}}^{\ensuremath{-}1}$. Isotope substitution experiments with varying concentrations of H and D together with polarization-sensitive measurements strongly suggest that these IR absorption lines are due to stretch local vibrational modes of a defect comprising three equivalent hydrogen atoms. The zinc vacancy decorated by three hydrogen atoms, ${V}_{\mathrm{Zn}}{\mathrm{H}}_{3}$, and ammonia trapped at the zinc vacancy, $({\mathrm{NH}}_{3}){}_{\mathrm{Zn}}$, are discussed as a possible origin for the complex.