Two-dimensional ZnO:Al nanosheets and nanowalls obtained by Al2O3-assisted carbothermal evaporation

Free-standing, two-dimensional ZnO nanosheets and branched honeycomb-like nanowalls have been grown together with one-dimensional nanothreads on gold covered a-plane sapphire and GaN templates on silicon substrates using Al2O3 assisted carbothermal evaporation of ZnO. In X-ray diffraction 2Θ−ω scans two orientations, ZnO(0001) and ZnO(10-11), of the two-dimensional nanosheets were detected. Temperature dependent cathodoluminescence shows bound exciton and donor-acceptor pair recombinations with a linewidth of 2.1 meV at 10 K. We show that the formation of the novel Al-doped ZnO nanostructures is due a vapor-liquid-solid mechanism.