退火处理对ZnS薄膜的结构和光学性质的影响

在200 ℃下利用激光沉积技术分别在玻璃和Si(100)上沉积制备了ZnS薄膜,并在300,400,500 ℃下退火1 h。用X射线衍射(XRD)仪、紫外/可见光/近红外分光光度计、台阶仪和原子力显微镜(AFM)分别对不同衬底上样品的特征进行了观察。结果表明,玻璃上的ZnS薄膜只在28.5°附近存在着(111)方向的高度取向生长。在可见光范围内透射率为60%~90%。计算显示薄膜的光学带隙在3.46~3.53 eV之间,其小于体材料带隙的原因在于硫元素的缺失。根据光学带隙判断薄膜是单晶立方结构的β-ZnS。Si(100)上生长的是多晶ZnS薄膜:500 ℃下退火后,表面也比未退火表面更加平整致密,变化规律与ZnS/glass的类似。说明高温下退火可以有效地促进晶粒的结合并改善薄膜质量。

Influences of Annealing Treatment on Structure and Optical Properties of ZnS Films

ZnS films were prepared on glass and p-Si(100) substrates by pulse laser deposition at 200 ℃ temperature. Annealing treatment was conducted at 300,400 and 500 ℃. XRD spectra,ultraviolet-visible spectra, Alpha-step surface profiler and atomic force microscopy(AFM) was used to observe the characteristics of ZnS/glass and ZnS/Si(100).The results showed that highly oriented films are prepared with only one sharp XRD peak at 2θ=28.5°corresponding to β-ZnS (111) crystalline orientation on glass substrates. The UV-Vis absorption showed that the films deposited on glass have a good transmission over 60% in visible region. The calculation of optical band gap ranged from 3.46~3.53 eV that can be ascribed to sulphur deficiency. The images from AFM showed that annealed treatment at 500 ℃ can increase the grain size and improve the quality of ZnS films on Si(100), making the film surface become more smooth and compact than that of as-grown films at 200 ℃.