Abstract
The mechanical properties of zinc oxide epitaxial layers grown on a - and c -axis sapphire have been studied by spherical nanoindentation and cross-sectional transmission electron microscopy. As-grown threading dislocations, which are characteristic of epitaxial material, combined with the presence of the much harder, underlying substrate are found to have a significant effect on the mechanical behavior of ZnO epilayers as compared to bulk material. Epilayer material is found to be significantly harder than its bulk counterpart. For a -axis epilayers, analysis of load-unload data yields a hardness of 6.6±1.2 GPa, and 5.75±0.8 GPa for c -axis layers. We attribute this increased hardness to strain compensation via the presence of as-grown defects. These defects inhibit the slip mechanism responsible for relative softness of bulk single crystals. The absence of pop-in events from analyzed continuous-load nanoindentation data is further evidence for strain compensation by native defects within the epilayers. Large variations in the spread of collected data are indicative of inhomegenity in the epilayers.
| Original language | English |
|---|---|
| Article number | 203105 |
| Pages (from-to) | 1-3 |
| Number of pages | 3 |
| Journal | Applied Physics Letters |
| Volume | 86 |
| Issue number | 20 |
| DOIs | |
| Publication status | Published - 16 May 2005 |