Effects of thermal annealing on ZnO films grown by plasma enhanced chemical vapour deposition from Zn(C2H5)2 and CO2 gas mixtures

To improve ZnO thin film quality, the ZnO thin films grown on silicon (100) by plasma enhanced chemical vapour deposition from Zn(C2H5)2 and CO2 gas mixtures at a low temperature of 120 deg. C are annealed in an oxygen ambient at temperature ranging from 600 deg. C to 1000 deg. C. X-ray diffraction spectra indicate that ZnO films possess a polycrystalline hexagonal wurtzite structure. Atomic force microscopy results show an increase of ZnO grain size with the increase of annealing temperature. The photoluminescence is closely related to the annealing temperature. The free exciton binding energy deduced from the temperature-dependent PL spectra is about 59 meV for the ZnO film annealed at 900 deg. C, suggesting that the film quality can be improved by annealing process