Synthesis of ZnO nanowalls on A1₂O₃ (0001) by catalyst-free metalorganic chemical vapor deposition

We report the synthesis of epitaxially aligned ZnO nanowalls on Al ₂O₃ (0001) by metalorganic chemical vapor deposition without using any metal catalyst. ZnO nanowalls of 60-150 nm thickness are uniformly assembled on the substrate. A small amount of ZnO nanowires additionally grow and are coupled with the ZnO nanowalls. Interestingly, the crystals in the ZnO nanowalls are aligned in both the out-of- and in-plane direction. A strong UV emission at around 380 nm, observed in a room temperature photoluminescence spectrum, indicates excellent optical quality of the ZnO nanowalls.