Electrodeposition of zinc telluride from a zinc chloride-1-ethyl-3-methylimidazolium chloride molten salt

The electrodeposition of tellurium and zinc telluride was investigated on a nickel electrode in the 40-60 mol % zinc chloride-1-ethyl-3-methylimidazol ium chloride molten salt containing propylene carbonate as a cosolvent at 4 0 degreesC. Tellurium(IV) can be electrochemically reduced to tellurium in this solution. Addition of 8-quinolinol (oxine) to the solution shifts the reduction of Te(IV) to more negative potential. Deposits of Zn-Te can be ob tained through the underpotential deposition of zinc on tellurium which occ urs at a potential neat -0.1 V. At potentials more negative than ca. -0.5 V , tellurium can be further reduced to tellurium(-II) species which may reac t with zinc(II) to form Zn-Te. Energy-dispersive spectroscopy data indicate that the composition of the Zn-Te deposits is dependent upon the depositio n potential and the Te(IV) concentration in the plating solution. Character istic X-ray diffraction patterns of cubic ZnTe are observed for the electro deposited Zn-Te samples that have been annealed at temperatures ranging fro m 250 to 400 degreesC. The flatband potential of the Zn-Te electrodeposits was determined by photocurrent and impedance (Mott-Schottky plot) experimen ts. The optical band.-ap of the ZnTe deposits determined by optical absorpt ion spectrometry is 2.3 V, which agrees well with the literature values. (C ) 2001 The Electrochemical Society.