The effect of growth parameters and post-processing on the optical properties of ZnO thin films

ZnO thin films with perfect c-axis were deposited on silicon substrates in pulsed laser deposition system.The photoluminescence(PL) spectra of the thin film fabricated under different oxygen partial pressures(10-3pa,10-2pa,10-1Pa,1Pa,10Pa) and different substrate temperatures(250℃～600℃) have been examined.Wecan find that oxygen partial pressure and substrate temperature have important influence on the optical properties of ZnO thin films.As to get ZnO thin films with strong UV emission,these two parameters should be considered comprehensively.In a word,the higher the substrate temperature is,the higher the oxygen partial pressure is.The following studies indicate that defects and impurities bounded electron states were produced under higher substrate temperature or after annealing.The bounded electron states leads to the lattice relaxation and multi-phonons related nonradiative recombination of electrons which hence reduced the DL emission of ZnO thin films.