Catalyst/dopant-free growth of ZnO nanobelts with different optical properties from nanowires grown via a catalyst-assisted method

The paper reported a simple but effective gold catalyst-tailored chemical vapour deposition (CVD) method to grow ZnO nanowires and nanobelts with different photoluminescence (PL) behaviours. ZnO nanowires along the c-axis were synthesized via a gold catalyst-assisted CVD method through the conventional vapour-liquid-solid (VLS) mechanism. But, ZnO nanobelts grew along the a-axis enclosed with {0110} and {0001} base planes without using any catalyst or dopant through the vapour-solid (VS) mechanism. The nanowires and nanobelts were proved to be of different optical quality, which was related with their growth process. Besides the different origin of the near-band-gap emission at room temperature, laser emission was only observed from ZnO nanobelts while the nanowires show anomalous photoluminescence behaviour under higher excitation density.