Electrochemical quartz crystal microbalance study of the electrodeposition mechanisms of Cu2-xSe thin films

Electrodeposition mechanisms of Se, Cu and Cu2-xSe thin films were studied by means of the electrochemical quartz crystal microbalance (EQCM). The electrodeposition of Se was found to be faster at higher overpotentials, though with lower apparent efficiency. The formation of Cu2-xSe from a thiocyanate bath was confirmed to proceed via the induced co-deposition mechanism at more positive potentials than where Cu+ alone is reduced. The M/z value corresponding to Cu2-xSe formation first decreased gradually during the cyclic voltammogram, indicating that the previously formed Se film was converted into Cu2-xSe. After the Se film was consumed, the M/z value settled to a constant value, which corresponded to the formation of Cu2-xSe from Cu+ and Se4+ ions. The M/z value was constant over a wide potential range. In contrast, when the Cu2-xSe films were deposited at constant potentials, the M/z value was found to be dependent on the deposition potential. (C) 2000 Elsevier Science Ltd. All rights reserved.