Study Of Preparing The ZnS Thin Films By Chemical Bath Deposition

Zinc sulphide(ZnS) is an important â…¡-â…¥ semiconducting material with a wide direct band gap of from 3.6 to 3.8ev.It is of great importance in the optoelectronic application.Chemical bath deposition(CBD) that is used to prepare ZnS thin films is negligible in our country,There are only few units to study it.The method produces good qulity polycrystalline or uncrystalline semiconductor films with simple and effective technology over a large area at a low cost and low temperature, at the same time,the request of vacuum is not high.However, the repetition of deposition is not very good and homogeneous precipitation can reach the substrate and form the film.The thesis studied various influencing factors during preparing ZnS thin films using chemical bath deposition by the numbers,Combining the study of growth mechanism, optimum solution concentrations and deposition conditions were put forward.Experiment was carried out with N2H4 system,the surfaces, compositions,structures, transmission,reflectivity, band gap,extinction coefficient, refractive index of ZnS thin films were observed and measured by optical microscope,scanning electron microscopy,X-ray diffraction,nkd thin-film analysis and measurement system when solution concentrations, deposition temperature and time were changed.1. The influence of concentrations.The studies were carried out when the concentrations of NH3, Sc(NH₂)₂,ZnSO₄ and N₂H₄ were changed,respectively.Results are shown: When concentration of NH3 is not larger than 1.5M,good leveling and transmission(larger than 95% in medium and long wave),high band gap(3.81ev), uncrystalline ZnS films could be prepared. Increasing the concentration of Sc(NH₂)₂ could improve hydrolysis of NH3,produce of S^2- and increase the transmission of short wave of ZnS films.At the beginning,increasing the concentration of ZnSO₄ was beneficial that Zn²⁺ reached the substrate and entered into the film, deposition speed of film chould be improved, When the concentration of ZnSO₄ was increased furtherly, Zn²⁺ tended to enter into the solution,instead of substrate which made deposition speed of film reduce.At the same time, the concentration of ZnSO₄ influenced the...