低温硫化制备ZnS薄膜的物理性质研究

采用磁控溅射方法先在玻璃衬底上室温下沉积Zn金属薄膜，接着先后在200和400 ℃温度下的硫蒸气和氩气流中进行退火，生长出 ZnS 薄膜。薄膜样品的微观结构、物相结构、表面形貌和光学性质分别采用正电子湮没技术 (PAT)、X射线衍射仪 (XRD)、扫描电子显微镜 (SEM)和紫外-可见分光光度计进行表征。该ZnS薄膜在可见光范围具有约80%的高透光率，随着硫化时间的增加，其带隙由3.55 增加到3.57 eV，S/Zn原子比从0.54上升至0.89，薄膜质量明显得到改善，相对于以前报道的真空封装硫化所制备的ZnS薄膜，硫过量问题得到了较好解决。此外，慢正电子湮没多普勒展宽谱对硫化前后薄膜样品中膜层结构缺陷研究表明，硫化后薄膜的S参数明显增大，生成的ZnS 薄膜结构缺陷浓度高于Zn薄膜。

Physical Properties of ZnS Thin Films Prepared by Low-temperature Sulfidation

In the article, Zn thin films were deposited on the glass substrates at room temperature by magnetron sputtering from a zinc target. And ZnS thin films were prepared by annealing Zn thin films in sulfur vapor and Ar gas at 200 and 400 ℃. The microstructure defects, crystallizations, surface morphology and optical properties of the samples were analyzed by PAT(positron annihilation technique), XRD(X-ray diffraction), SEM(scanning electron microscopy) and UV-VIS spectrophotometer. The resultant ZnS thin films exhibited a high optical transmittance of about 80% in the visible region. With the increase of sulfidation time, the band-gap value was increased from 3.55 to 3.57 eV, and the S/Zn atomic ratio was enhanced from 0.54 to 0.89, implying an obvious improvement of ZnS film quality. This demonstrated that the excess-sulfur problem in the ZnS films was well solved compared with those samples prepared by sulfidation in the vacuum-sealed quartz-glass ampoules. Besides, the structural defects of the thin films before and after sulfidation were investigated by positron annihilation Doppler broadening measurements. It was found that the S parameter of the samples after sulfidaton was greater than that before sulfidation, implying the higher structural defect concentration for the former.