氧分压对Mg掺杂ZnO薄膜结晶质量和光学特性的影响

利用脉冲激光沉积技术,通过改变沉积过程中的氧气压力,在蓝宝石(0001)基片上制备了一系列ZnMgO合金.通过X射线衍射、反射和透射光谱以及室温和变温荧光光谱,对薄膜的结构和光学性能进行了系统地表征,分析了工作气压对ZnMgO合金薄膜的结晶质量及光学特性的影响.研究结果表明:随着沉积环境中氧气压力的增大,ZnMgO薄膜的结晶质量下降,富氧环境下,与蓝宝石晶格平行的ZnO晶粒的出现是导致薄膜结晶质量下降的主要原因;相对于本征ZnO,不同氧气环境下沉积的ZnMgO薄膜的紫外荧光峰均出现了不同程度的蓝移.随着工 关键词： ZnO Mg掺杂 脉冲激光沉积 薄膜生长 光学特性

Influence of oxygen partial pressure on the crystal quality and optical properties of Mg-doped ZnO films

Zn_1-xMg_<i>xO films have been deposited on Al₂O₃(0001) substrates at different oxygen pressures by using pulsed laser deposition method. The influence of oxygen pressure on the crystal quality and optical properties of the films is studied with X-ray diffraction (XRD), transmittance spectra, and photoluminescence (PL). It is found that the crystal quality of the films lowers with increasing of oxygen pressure from 10^-4Pa to 10 Pa. At the pressure of 10^-4 Pa, the epitaxial relationship between the film and sapphire substrate is determined to be ZnMgO (0001)// Al₂O₃(0001),ZnMgO 1 0]//Al₂O₃ 2 0]. In the oxygen rich environment, however, another epitaxial relationship, ZnMgO (0001)//Al₂O₃(0001) and ZnMgO 1 0]//Al₂O₃ 1 0], is also present in the films, which is suggested to be responsible for the decline of the crystal quality. Compared with pure ZnO films, the UV peak of Zn_1-xMg_<i>xO alloys shows red-shift from 3.374 to 3.332 eV with increasing oxygen working pressure increasing from 10^-4 Pa up to 10 Pa. The difference in red-shifts can be attributed to the decrease of Mg content in the films resulting from the variation of oxygen pressure. A broad UV PL spectrum was observed at 10 K in the films deposited under different pressures and can be decomposed into two recombination processes of excitons, corresponding to the bound and the localized exciton luminescence, respectively. The binding energy of bound excitons in the ZnMgO films is larger than that in pure ZnO and has an increasing trend with increasing oxygen pressure.