Optical investigations of multi-dimensional ZnO hybrid structures

The authors report on the optical properties of multi-dimensional ZnO hybrid structures, consisting of film (2D)/nanorods (1D)/sapphire substrate (2D), grown by metalorganic chemical vapor deposition (MOCVD). Photoluminescence investigations reveal that the sample with top layer grown at a decreased growth temperature of 240 °C and increased reactor pressure of 5 Torr exhibits superior emission properties. The presence of strong E₂^high optical phonon mode at 438.5 cm^{- 1} in the visible micro-Raman spectra demonstrates the wurtzite nature of ZnO. Although the ultraviolet Raman scattering measurements of the hybrid structures reveal the presence of in-plane tensile stress in the top ZnO layer, the sample with the improved emission performance shows the release of tensile stress.