High temperature electrodeposition of ZnSe

ZnSe is a good candidate both for photovoltaic applications and laser techn ology 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(I V) ions in the molten CaCl2-NaCl mixture at 550 degrees C. The first step of this study concerns the electrochemical behavior of the d ifferent Zn(II) and Se(IV) starting compounds involved in the process as we ll as SnO2. A thermodynamical diagram was established indicating the stabil ity ranges of these species depending on potential and melt acidity. Deposits were successfully obtained using a potentiostatic method at severa l potential values. Transparent, yellow, adherent and homogeneous films wer e 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 p hases 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.