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

A hydrogen-related defect in ZnO which causes two broad IR absorption bands at 3303 and 3321 cm(-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 cm(-1) accompanied by weaker sidebands at 2462 and 2480 cm(-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, VZnH3, and ammonia trapped at the zinc vacancy, (NH3)(Zn), are discussed as a possible origin for the complex.