Investigate on Structure and Optical Properties of ZnO Nanostructures Grown on a-GaN/r-Sapphire

ZnO nanostructures were directly grown on a-GaN/r-sapphire with different growth time via aqueous method. Structural and optical properties of the nanostructures were investigated by using a variety of techniques including X-ray diffraction (XRD), scan electron microscope (SEM), room-temperature photoluminescence (PL), and Raman scattering. The results showed the growth mechanism of ZnO nanostructures grown on a-GaN is Volmer-Weber (VW) mode, which is due to the high interfacial free-energy between a-plane ZnO and GaN. Meanwhile, compressive strains were revealed to exist by the optical characterizations. And the strengths were found to reduce with increasing growth time.