Bath Temperature Effect on c-axis Preferred Orientations and Band Gap of Semiconductor ZnO Thin Films

Abstract

Semiconductor ZnO thin films were deposited via chemical bath deposition technique (CBD) on glass substrates at varying temperatures (75°C-90°C). Influence of bath temperature on c-axis preferred orientations of ZnO thin films were examined. X-ray diffraction (XRD) results proved that thin films deposited at 80°C and 85°C bath temperature have a preferred orientation towards (011) peak. The preferred orientation changed towards (010) peak when the bath temperature increased to 90°C. Field Emission Scanning Electron Microscope (FESEM) images proved that ZnO thin film structure was formed by flower-like nanorods. In the thin films produced at 80°C and 85°C, the alignment of the nanorods was vertical, while in the films produced at 90°C, the nanorods mostly formed horizontally. These FESEM images also proved that the preferential orientation has changed from (011) to (010). Effects of bath temperature on band gap of semiconductor ZnO thin films were investigated by UV-Visible Spectrophotometer. ZnO thin films band gap value increased to 3.37 eV as the bath temperature increased to 85°C. When the bath temperature increased to 90°C the band gap value strongly decreased to 3.24 eV.