The electronic effects of H atoms at interstitial sites in ZnO were investigated by

high-resolution electron energy loss spectroscopy. A reversible doping was

achieved by exposing single crystalline (00•¯1)-oriented ZnO substrates to atomic

hydrogen. At low temperatures, interstitial H atoms form shallow donor states. At

sufficiently high temperatures, the electrons were excited into the conduction band.

Electron energy loss spectroscopy was used to demonstrate the presence of

plasmons resulting from this finite density of charge carriers in the conduction

band. Above 100K, a strong, plasmon-induced broadening of the quasi-elastic peak

in the high-resolution electron energy loss spectroscopic data was observed. The

analysis of the temperature dependence yielded a donor level ionization energy of

25meV.

Ionization Energies of Shallow Donor States in ZnO Created by Reversible

Formation and Depletion of H Interstitials. H.Qiu, B.Meyer, Y.Wang, C.Wöll:

Physical Review Letters, 2008, 101[23], 236401