Zinc Oxide Nanowires Prepared by Oblique Angle Deposition Method


This paper presents a detailed study of the oblique deposition effect on the morphology, structure and optical properties of ZnO nanowires (NWs) prepared by the deposition of zinc metallic films on glass substrates at different angles (0, 50 and 70°) and then oxidized in air at 650°C. Highly transparent ZnO thin films were successfully prepared by the oblique angle deposition (OAD) technique on glass substrates at room temperature. Atomic force microscopy (AFM) results show that the sample obliquely deposited presented greater roughness as compared with normally deposited ZnO NWs (Ө=0). Optical measurements showed a sharp absorption edge, near 380 nm, in both normal and oblique films. When the oblique angle increased, the absorption edge of spectra demonstrated a red shift with a direct band gap (3.11eV). Scanning electron microscopy (SEM) results show that the OAD led to the formation of bent columnar ZnO NWs. These NWs were inclined from the substrate normal in a direction opposite to the incident vapor beam. Due to the OAD technique, surface diffusion enhanced the self-shadowing effect. When oblique Zn thin film was later oxidized in air at 650°C for a longer time, the ZnO NWs had a needle-like structure, as was clearly shown by SEM images obtained.