Various defect studies of hydrothermally grown (00•1)-oriented ZnO crystals electrochemically doped with H were presented. The H content in the crystals was determined by nuclear reaction analysis and it was found that already 0.3at%H exists in chemically bound form in the virgin ZnO crystals. A single positron lifetime of 182ps was detected in the virgin crystals and attributed to saturated positron trapping at Zn vacancies surrounded by H atoms. It was demonstrated that a very high amount of H (up to ~30at%) could be introduced into the crystals by electrochemical doping. More than half of this amount was chemically bound, i.e., incorporated into the ZnO crystal lattice. This drastic increase of the H concentration was of marginal impact on the measured positron lifetime, whereas a contribution of positrons annihilated by electrons belonging to O–H bonds formed in the H doped crystal was found in coincidence Doppler broadening spectra. The formation of hexagonal shape pyramids on the surface of the H-doped crystals by optical microscopy was observed.

Defect Studies of ZnO Single Crystals Electrochemically Doped with Hydrogen. J.Čížek, N.Žaludová, M.Vlach, S.Daniš, J.Kuriplach, I.Procházka, G.Brauer, W.Anwand, D.Grambole, W.Skorupa, R.Gemma, R.Kirchheim, A.Pundt: Journal of Applied Physics, 2008, 103[5], 053508