Structural and optical studies of ZnO films grown at low temperature

Epitaxial growth of monocrystalline ZnO thin films was achieved by reactive e-beam evaporation on glass substrates at low temperature. The influences of growth temperature and O2 pressure in the reaction chamber on the microstructural evolution of achieved ZnO films were studied. The results show that the microstructure of ZnO films is affected significantly by growth temperature, and the optimal growth temperature is between 300 °C and 350 °C. Highly c-axis oriented ZnO films with small line width (only 0.28 °) of (002) X-ray diffraction peak were obtained at growth temperature of 325 °C. Measurements of photoluminescence (PL) and photoluminescence excitation (PLE) were also carried out to demonstrate the optical transitions in the ZnO films. Although XRD analysis shows the crystalline structures of ZnO films grown under different O2 pressure do not change, the PLE spectra reveals that the absorption characteristic near the band edge is remarkably improved with the increase of oxygen content in the ZnO films.