Electrodeposition of Copper-Zinc Alloy and Zinc Telluride in Zinc Chloride-1-ethyl-3-methylimidazolium Chloride Molten Salts

• Main Authors: Mei-Chen Lin, 林梅楨
• Other Authors: I-Wen Sun
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/63265931823280554176

碩士 === 國立成功大學 === 化學系 === 88 === ZnTe, one member belongs to the II-VI semiconductor family, is of interest due to its applications in optoelectronics and as a top layer over p-CdTe for achieving lower contact resistance in CdS/CdTe photovoltaic hetero-junctions. The synthesis of ZnTe by electrodeposition is a more economic and more convenient method than vacuum evaporation techniques and the systems that high operating temperature is necessary. In this study, the electrodeposition of ZnTe was investigated on GC and Ni electrodes in a [40-60mol% ZnCl2-EMIC: propylene carbonate = 1:1(w/w)] molten salt containing TeCl4. Stationary cyclic voltammograms show that the reduction wave of Te4+ to Te0 was divided to two separate waves when propylene carbonate was added into this melt. The co-deposition of Zn and Te onto the electrodes was accomplished by underpotential deposition of zinc on tellurium or the reaction of Te2-, which is produced by reduction of Te deposits on electrodes, and Zn2+, depending on the potentials of electrodeposition. Addition of oxine into the melt improves the quality of ZnTe electrodeposits produced in the melt. The electrodeposition of Te on GC and Ni electrodes both involves a three-dimensional progressive nucleation /growth process in 40-60mol% ZnCl2-EMIC at 80oC. When enough amounts of oxine was added into the [40-60mol% ZnCl2-EMIC : propylene carbonate = 1:1(w/w)]melt, the nucleation process of electrodeposition of Te on both electrodes became to the instantaneous nucleation. In S/S2- electrolyte solution, the deposited ZnTe film showed photoelectro- chemical property if the ZnTe film had been annealed. The flatband potential of the films was determined by two methods; photocurrent method and AC-impedance analysis. The band gap of the ZnTe film was determined by UV-VIS spectroscopy. The second part of this study is the electrodeposition of Cu-Zn alloy from the ZnCl2-EMIC melt.The electrodeposition of copper and Cu-Zn alloys was investigated on tungsten and nickel electrodes in 50-50mol% ZnCl2-EMIC molten salt containing CuCl. The composition of the electrodeposited Cu-Zn alloys can be varied by deposition potential, temperature and CuCl concentration in the plating bath. The electrodeposition of Cu on both W and Ni electrodes proceeds via three-dimensional instantaneous nucleation. However, as the deposition potential crosses from Cu metal into the alloy-forming range, the nucleation process changes to progressive nucleation. The XRD analysis indicates that the electrodeposited Cu-Zn alloys exhibit α and β phases. And the β phase increases as the Zn content in the electrodeposited Cu-Zn alloy increases.