アンモニア-アルカリ性水溶液からのCdTe電析に及ぼす電解液組成の影響

抄録

Electrodeposition of CdTe from a variety of CdSO₄-TeO₂-NH_3-(NH₄)₂SO₄ aqueous solutions was studied to determine optimum conditions for crystalline CdTe deposition. The deposit obtained from an electrolyte whose Cd (II)/Te (IV) concentration ratio was 1, showed an amorphous structure and tellurium-rich composition. Polycrystalline CdTe was obtained by partial oxidation of Te (IV) to Te (VI) in the solution, suppressing Te deposition, and by a decreasing the total ammonia concentration, accelerating Cd deposition. In electrodeposition at a cathode potential of -0.80V vs SHE and a total ammonia concentration of 5kmolm^-3, polycrystalline CdTe was obtained at a Cd (II)/Te (IV) concentration ratio of 25 to 4. Particularly at a Cd (II)/Te (IV) concentration ratio of 3, the deposit showed high crystallinity, although Cd codposition was observed. Increasing the cathodic potential from -0.80V to -0.70V vs SHE and keeping the Cd (II)/Te (IV) concentration ratio at 3, suppressed Cd codposition. These results suggest that a polycrystalline CdTe single phase is obtained by controlling the cathodic potential and the Cd (II)/Te (IV) concentration ratio of the ammonia-alkaline solution, in which TeO₂ solubility is higher than that in acidic solution.