Effect of Deposition Time on Nanostructure ZnO Thin Films Synthesized by Modified Thermal Evaporation Technique

The aim of this work is to deposit nanostructure zinc oxide (ZnO) thin films by thermal evaporation system with modified source-substrate orientation. At first, the zinc films have been deposited on bare glass substrate with chamber pressure of 0.04 Torr, source temperature of 700 degrees C and various deposition times of 1, 5, 30 min. The prepared zinc film is annealed at 500 degrees C for 2 hours. The structural, optical, and surface morphological properties of ZnO films have been investigated by X-ray diffraction analysis, ultraviolet/visible and photoluminescence spectrophotometer, and scanning electron microscopic respectively. All ZnO films have showed high crystallinity with hexagonal wurtzite structure. The nanofibers, nanoflakes and nanospikes like structures are confirmed by SEM images with different deposition times. The average length and diameter of nanospikes are 1.98 mu m and 113 nm respectively. The optical band gap of prepared ZnO films is decreased from 3.26 to 3.09 eV with increase of the deposition time, which can enhance the excitation of ZnO films by the near visible light. The different properties of ZnO films have been investigated and correlated with deposition time.