Abstract
Hydrogen has been found to be an important source of n-type conductivity in the transparent conducting oxide SnO2. We have studied the properties of H in SnO2 single crystals with infrared spectroscopy. When H or D is introduced into SnO2 by annealing in an H2 or D2 ambient at elevated temperature, several O-H and O-D vibrational lines are produced along with the low-frequency absorption that is characteristic of free carriers. To probe the relationship between H and the free carriers it introduces, the thermal stability of the free carrier absorption, and its relationship to the thermal stabilities of the O-H lines have been examined. Two H-related donors are found, one that is stable at room temperature on a time scale of weeks and a second that is stable up to 600ºC. These electrically active defects are found to interact with other O-H centers and can be converted from one to another by thermal treatments. The vibrational modes have been found to have distinctive polarization properties that provide an important test of microscopic defect models for the several O-H and (O-H)2 centers that we have observed.