Cu掺杂ZnO薄膜的光学性质

采用射频反应磁控溅射方法,在Si(100)和石英基片上使用双靶溅射的方法制备了Cu掺杂ZnO薄膜。利用X射线衍射、透射光谱和光致发光光谱分析了薄膜的晶体结构及光学性质,并与密度泛函理论计算的结果进行了对比。研究结果显示:Cu掺杂ZnO薄膜均具有高的c轴择优取向,无Cu及其氧化物相关相析出,掺杂对晶格参数的影响较小,与理论计算结果一致。Cu掺杂显著改变了ZnO薄膜在近紫外及可见光波段的吸收特性,其光学带隙随着Cu掺杂量的增加有所减小,带隙宽度的变化趋势与理论结果有着很好的一致性。Cu掺杂显著降低了ZnO薄膜的发光效率,具有明显的发光猝灭作用,但并不影响光致发光的发光峰位。说明Cu掺杂导致的吸收特性的改变可能与杂质能级有关,这与能带结构计算发现的Cu-3d电子态位于价带顶附近的禁带中是一致的。

Optical Properties of Cu-doped Thin ZnO Films

Cu-doped ZnO films grown on Si (001) wafers and quartz substrates were prepared with a radio-frequency reactive magnetron sputtering method. X-ray diffraction, transmittance spectra, photoluminescence spectra, and calculation based on the density functional theory are used to analysis the crystal structure, optical properties, and band structure. All the Zn1-xCuxO films are highly (001) textured without any precipitated phase, and Cu dopants hardly change the c parameter of ZnO. In the transmittance spectra, there is ob-vious abnormal absorbability in near ultraviolet and visible area. Being consist with the calculation, the band gap of Zn1-xCuxO films decrease with the increasing Cu concentration. Significant reduction of the PL efficiency caused by Cu dopants is seen in PL spectra. The emission in near ultraviolet and visible area is found moves with increasing the Cu concentration, while the location of the main emission peak doesn't move. It is believed that the absorbability and the emission in near ultraviolet and visible area is related to the impurity levels caused by Cu dopants. And the calculation results that the Cu-3d states lie the entry of the forbidden band confirming our standpoint. We hope this study will be helpful for the understanding of optical properties of Cu-doped thin ZnO films.