Growth of Zn thin films based on electric field by thermal evaporation method and effect of oxidation time on physical properties of ZnO nanorods

摘要

Zinc oxide (ZnO) nanorods (NRs) were obtained by oxidation of Zn thin layers, prepared by thermal evaporation method under electric field, at different times of 2.5, 5, 7.5 and 10 h. The crystal structure of samples was investigated using X-ray diffraction (XRD) measurement, which showed samples had a wurtzite hexagonal structure. In addition, field emission scanning electron microscopy (FESEM) indicated that with an increase in the oxidation time, the NRs diameter increased too. Elemental analysis of samples was performed using energy-dispersive X-ray spectroscopy (EDX) which clearly confirmed the presence of Zn and O with an atomic ratio of 1:1. Further, Raman spectra of samples verified wurtzite hexagonal phase due to high- and low-frequency vibration of E2 modes at room temperature and showed that with an increase in the oxidation time, the lattice defects decreased whereas crystal quality of samples increased. Optical properties of samples were determined by UV spectroscopy and demonstrated that when the oxidation time was added, the band gap energy of ZnO NRs decreased, which was attributed to the increase in crystallite size.