退火对MOCVD法生长ZnO薄膜性能的影响

Influence of Annealing on ZnO Thin Films Grown on Silicon Substrate by MOCVD

采用MOCVD方法在(001)Si衬底上生长ZnO薄膜,并在空气中800℃退火1h。生长及退火样品的XRD图谱均显示了较强的(002)ZnO衍射峰,表明ZnO薄膜为c轴高取向生长。光电子能谱(XPS)分析显示,退火后ZnO薄膜从富Zn生长变为富O生长。在样品的室温PL谱中,观察到未退火样品的紫外发射峰的中心为3.28eV,并观察到退火样品位于3.30eV的自由激子发射峰和位于3.23eV的施主-受主对的复合发光峰。实验结果表明,退火后ZnO薄膜的晶体质量得到提高。

ZnO thin films were deposited on (001) Si substrate by metal-organic chemical vapor deposition (MOCVD). Thermal annealing was performed at 800 ℃ in air for 1 hour. The X-ray diffraction patterns of the samples show sharp diffraction peaks for ZnO (002), which indicates that the films are highly c-axis oriented. X-ray photoemission spectra (XPS) were used to confirm the stoichiometry of ZnO film. From the statistical results of XPS spectra, we could conclude that the atom ratio of O: Zn was 0. 93: 1 before annealing and 1. 04: 1 after annealing, which shows that ZnO film has changed from Zn-rich to O-rich after annealing. Two ultraviolet (UV) emission peaks were found clearly at 3. 30 eV and 3. 23 eV due to free exciton emission and donor to acceptor pair transition respectively in photoluminescence (PL) spectrum of annealed ZnO thin film. The comparison between ZnO films before annealing and after annealing indicates that the crystalline quality has been improved through annealing.