Effect of Annealing Temperature on Morphology and Electrical Property of Hydrothermally-Grown ZnO Nanorods/-Si Heterojunction Diodes.

In this study, ZnO nanorods (NRs) were synthesized using the hydrothermal method, and the effects of annealing temperature (150 °C-600 °C) on morphology, crystallinity, defects states of the NRs, and electrical property of the -type ZnO NRs/-type Si heterojunction diodes were investigated. No appreciable changes in the morphology and crystal structure of the ZnO NRs were observed with increasing annealing temperature up to 450 °C. As the temperature increased to 600 °C, the average length and diameter of the NRs decreased due to the partial melting and sintering in the NRs. From the X-ray photoelectron spectroscopy (XPS) results, the concentration of internal oxygen vacancies decreased with increasing annealing temperature to 450 °C due to thermal diffusion of oxygen vacancies to the surface. The electrical conductivity of the NRs increased to 450 °C, which was attributed to the increased crystallinity and low defects concentration (oxygen vacancy) in the NRs. Conversely, the electrical conductivity degraded at 600 °C due to the decreased effective contact area.