Hydrogen absorption and diffusivity in ZnO single crystals

• Published in: Journal of alloys and compounds 2013-12, Vol.580, p.S51-S54
• Main Authors: Čížek, J., Lukáč, F., Vlček, M., Melikhova, O., Traeger, F., Rogalla, D., Becker, H.-W.
• Format: Article
• Language: English
• Subjects: Channels; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystals; Deformation and plasticity (including yield, ductility, and superplasticity); Diffusion; Diffusion in solids; Diffusion rate; Electrical resistivity; Exact sciences and technology; Hydrogen; Hydrogen storage; Materials science; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Nuclear reaction analysis; Physics; Single crystals; Specific surface; Surface treatments; Transport properties of condensed matter (nonelectronic); Wurtzite; Zinc oxide; ZnO
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.02.075

► Hydrothermally grown ZnO crystals were electrochemically doped with hydrogen. ► Depth profile of hydrogen concentration introduced into the crystal was determined. ► Hydrogen loading created sub-surface region with high hydrogen concentration. ► Hydrogen-induced plastic deformation causes specific surface modification. ► Hydrogen diffusion in ZnO is faster in the c-direction than in the a-direction. ZnO single crystals electrochemically charged with hydrogen were characterized. The concentration of hydrogen introduced into the crystals was determined by nuclear reaction analysis and was found to be in a reasonable agreement with the value estimated from the Faraday’s law. Moreover, a sub-surface layer with very high concentration of hydrogen and very high density of open-volume defects was formed by plastic deformation caused by hydrogen-induced stress. Specific surface modification caused by hydrogen-induced slip in the c-direction was observed on hydrogen loaded crystals. Hydrogen diffusion coefficient in ZnO was estimated by in situ electrical resistivity measurement. It was found that hydrogen diffusion in the c-direction is faster than in the a-direction most probably due to open channels existing in the wurtzite structure along the c-axis.