Hydrogen incorporation and diffusivity in plasma-exposed bulk ZnO

Hydrogen incorporation depths of >25 mum were obtained in bulk, single-crystal ZnO during exposure to H-2 plasmas for 0.5 h at 300 degreesC, producing an estimated diffusivity of similar to8x10(-10) cm(2)/V.s at this temperature. The activation energy for diffusion was 0.17+/-0.12 eV, indicating an interstitial mechanism. Subsequent annealing at 500-600 degreesC was sufficient to evolve all of the hydrogen out of the ZnO, at least to the sensitivity of secondary ion mass spectrometry (<5x10(15) cm(-3)). The thermal stability of hydrogen retention is slightly greater when the hydrogen is incorporated by direct implantation relative to plasma exposure, due to trapping at residual damage in the former case. (C) 2003 American Institute of Physics.