The Growth and Optical Properties of ZnO Nanowalls

Nanowalls are novel nanostructures whose networked morphology holds potential for applications such as solar cells and gas sensors. The realization of such nanowall-based devices depends directly on a comprehensive understanding of the nanowall growth, namely, its competition with nanowire growth and the role of seed particles. We induced a morphological evolution from nanowires to nanowalls by increasing source flux during vapor transport and condensation growth. Nanowall growth kinetics indicates that their morphological dominance was driven by a time-dependent curvature of the nanowall growth facet. Nanowalls have excellent crystalline quality and strong near-band-edge luminescence and were found to grow by a combination of Au- and nonassisted mechanisms, resulting in Au nanoparticles within 300 nm of the substrate whose positions were associated with the origin of green luminescence. These results imply that the growth mechanism causes nanoscale structural variations, which in turn locally affect the optical properties of nanowalls.