Mg掺杂ZnO薄膜的结构和光致发光性能的变化

为深入了解ZnMgO合金薄膜的结构与发光性能的关系,采用ZnO和MgO粉末球磨、冷压成型后再高温烧结的方式制靶,在石英基底上室温射频磁控溅射制备了Mg含量0%～8% (原子数分数) 的ZnMgO薄膜,然后于400 ℃空气退火。采用X射线衍射仪表征薄膜的晶体结构,场发射扫描电子显微镜及附带的X射线能谱仪(EDS)观测薄膜颗粒形貌和化学成分,荧光分光光度计测试光致发光(PL)谱。结果发现:ZnMgO合金膜为纤锌矿hcp结构的固溶体,随Mg含量增加,形貌由近似圆形变为圆形和无规则多边形混合型,原因是(002)晶厚失去主导且长大速率被(101)和(110)超过;PL谱出现一个强的紫光峰(390～393 nm)和一个微弱的近红外峰(758～765 nm);随Mg含量的增加,紫光峰位先蓝移后红移,近红外峰位则发生红移;400 ℃空气退火后,所有峰位红移,强度显著增大。对退火处理前后出现的紫光峰和近红外峰的来源和变化规律进行了机制探讨。

Variations in Structure and Photoluminescence Properties of Mg-Doped ZnO Thin Films

In order to further understand the relationship between the structure and luminescence properties of ZnMgO alloy thin films, the targets for films were prepared by ball milling ZnO and MgO powders, cold pressing, and high temperature sintering. ZnMgO thin films of Mg content ranging from 0% to 8% (atomic number fraction) were prepared by RF magnetron sputtering on quartz substrates at room temperature and annealed at 400 ℃ in air atmosphere afterwards. The crystal structure of the film was characterized by X-ray diffractometer, the morphology and chemical composition of the particles were observed by field emission scanning electron microscope and the X-ray energy dispersive spectrometer (EDS), the photoluminescence (PL) spectra were measured by fluorescence spectrophotometer. ZnMgO thin film is found to be a solid solution with wurtzite hcp structure. With the increase of Mg content, the morphology changes from approximately round to round and random polygon mixture, which is attributed to the grain thickness of (002) losing its dominance and its growth rate exceeded by (101) and (110). The PL spectrum shows a strong violet peak (390～393 nm) and a weak near infrared (NIR) peak (758～765 nm). With the increase of Mg content, the location of violet peak first blueshifts and then redshifts, while the NIR peak redshifts. All peak positions redshift and the intensity increase significantly after annealing at 400 ℃. The generation and variation mechanism for the violet and NIR peaks before and after annealing are discussed.