Zn掺杂SnS薄膜的表征及光学特性

Deposition and Optic Property Characterization of Zn-Doped SnS Films

真空共蒸发制备掺Zn(2%,4%(质量比))的SnS薄膜。研究热处理对Zn掺杂SnS薄膜的结构、表面形貌、化学组分及光学特性的影响。实验给出2%掺Zn薄膜经300℃,40 min热处理后,得到正交晶系的SnS多晶薄膜。掺Zn可一定程度抑制薄膜中S的损失,使薄膜体内Sn∶S元素化学计量得到改善,从未掺Zn的Sn∶S比为1.90∶1降到1.38∶1(2%)及1.36∶1(4%)。掺Zn后SnS薄膜的吸收边都发生红移,光吸收系数高达105cm-1。未掺Zn薄膜的直接光学带隙1.95 eV,掺Zn是1.375 eV(2%)和1.379 eV(4%)。Sn和S在薄膜中分别呈+2和-2价态,Zn以间隙和替位两种状态存在。

The Zn-doped SnS films were deposited by vacuum co-evaporation on glass substrate. The influencing growth factors, including the Zn content, ratio of Sn, Zn and S evaporation rates, annealing temperature and time, and de- position rate, were evaluated. The microstructures, stoichiometries, and optic properties of the Zn-doped SnS films were characterized with X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy （SEM）. The re- sults show that Zn-doping significantly affects the microstructures and optic properties. For example, after annealing at 300 ~C for 40 min. doping with 2% （wt） of Zn significantly inhabits S loss.The stoichiometries of the orthorhombic structured polycrystalline SnS changed from Sn： S = 1.9： 1 of the control sample to 1.38 ： 1 of the 2 % Zn-doped one, and 1.36： 1 of the 4% Zn-doped one, respectively. Besides, Zn-doping results in a red-shift of the absorption edge and an increase of light absorption coefficient up to 10s cm- 1. Zn-doping narrows the direct optical gap from 1.95 eV of the control sample to 1.375 eV, and 1.379 eV of the SnS films doped with 2% and 4 % of Zn, respectively. Sn2 ~ and S2- were found to co- exist in the SnS films, and interstitial and substitution states of the Zn atoms were observed.