Correlation between luminescent properties and growth conditions for ZnO films grown on Si(100) by sputtering technique

We report the effects of the growth condition on emission properties of ZnO films grown on Si (100) by rf magnetron sputtering. With increasing the O2/Ar+O2 ratio in the growing ambient, the visible emission in the room-temperature photoluminescence spectra (PL) was drastically suppressed without sacrificing the intensity of exciton-related emission at ultraviolet region. This tendency was estimated to be due to the reduction in intrinsic defects such as the oxygen vacancies and zinc interstitials in the film with an improvement of the film stoichiometry in oxygen rich condition, indicating that the visible emission of ZnO may originate from oxygen vacancy or zinc interstitial related defects. An additional violet emission peaked at about 401 nm (3.09 eV) was also observed in the low temperature PL (LTPL) spectra of the ZnO films grown under oxygen-rich conditions and this violet emission peak was gradually weakened as the growth temperature increases from 400 °C to 700 °C, and ultimately, disappeared at 800 °C. From the above observation, it is deduced that this emission band has a close relation with the intrinsic defects related to an oxygen-rich condition, and the dependence of this emission on growth temperature can be due to an improvement of the film stoichiometry by an oxygen out-diffusion at high growth temperature.