Hydrogen incorporation, diffusivity and evolution in bulk ZnO

Abstract

Hydrogen is readily incorporated into bulk, single-crystal ZnO during exposure to plasmas at moderate (100-300°C) temperatures. Incorporation depths of >25 μm were obtained in 0.5 h at 300°C, producing a diffusivity of ∼8 × 10-10 cm2/Vs at this temperature. The activation energy for diffusion is 0.17 ± 0.12 eV, indicating an interstitial mechanism. Subsequent annealing at 500-600 °C is sufficient to evolve all of the hydrogen out of the ZnO, at least to the sensitivity of Secondary Ion Mass Spectrometry (< 5 × 1015 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. © 2003 Elsevier Ltd. All rights reserved.