Hidden hydrogen in as-grown ZnO

An O-H stretching line at 3326.3 cm(-1) was previously assigned to a shallow donor that is introduced into ZnO by H. This infrared line has been found to appear in as-grown ZnO samples when they are annealed near 400 degreesC without an external source of H, showing that there is an H-containing defect in commercially available ZnO that is not seen by infrared spectroscopy that can be converted into a shallow donor. The interstitial H-2 molecule in ZnO is suggested as a candidate for the hidden H species. (C) 2004 American Institute of Physics.