ZnSe is a good candidate both for photovoltaic applications and laser technology because of its large band gap. High temperature electrodeposition was chosen to prepare thin layers of ZnSe on substrates made of a glass plate covered with tin oxyde, using the simultaneous reduction of Zn(Ⅱ) and Se(Ⅳ) ions in the molten CaCl2-NaCl mixture at 550°C.
The first step of this study concerns the electrochemical behavior of the different Zn(Ⅱ) and Se(Ⅳ) starting compounds involved in the process as well as SnO2. A thermodynamical diagram was established indicating the stability ranges of these species depending on potential and melt acidity.
Deposits were successfully obtained using a potentiostatic method at several potential values. Transparent, yellow, adherent and homogeneous films were prepared with a thickness equal to 3.5 micrometer. The atomic composition measured by X-Ray fluorescence analysis gives a ratio Se/Zn equal to 1.06 and the X-Ray diagrams show the peaks characteristic of the two different phases of ZnSe (hexagonal and cubic) and of CaCl2. The width of these peaks is characteristic of very good crystallinity of the electrodeposited films showing that post heat treatment is not required.