Fabrication and characterisation of high quality ZnO thin films by reactive electron beam evaporation technique

High quality zinc oxide thin films have been deposited on silicon substrates by reactive e-beam evaporation in an oxygen environment. The effect of the growth temperature and air annealing on the structural, optical and electrical properties has been investigated. X-ray diffraction measurements have shown that ZnO films are highly c-axis-oriented and that the linewidth of the (002) peak is sensitive to the variation of substrate temperature. The optimum growth temperature has been observed at 300 °C. Raman spectroscopy has been found to be an efficient tool to evaluate the residual stress in the as-grown ZnO films from the position of the E2 (high) mode. On the other hand, the vanishing of the 574 cm−1. Raman feature after annealing has been explained as due to an increase of grain size and the reduction of O-vacancy and Zn interstitial. The SEM images have shown that the surfaces of the electron beam evaporated ZnO became smoother for the growth temperatures higher than 300 °C. The optical transmittance is the highest at 300 °C and has been increased after annealing in air showing an improvement of the optical quality. Finally, the maximum electrical resistivity has been found at 300 °C, which explains its relation with the crystal quality and increased from 5.8×10−2 Ω cm to reach an approximate value of 109 Ω cm after annealing at 750 °C.