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-methylimidazolium chloride molten salt containing propylene carbonate as a cosolvent at 40°C. 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 obtained through the underpotential deposition of zinc on tellurium which occurs at a potential near -0.1 V. At potentials more negative than ca. -0.5 V, tellurium can be further reduced to tellurium(-II) species which may react with zinc(II) to form Zn-Te. Energy-dispersive spcctroscopy data indicate that the composition of the Zn-Te deposits is dependent upon the deposition potential and the Te(IV) concentration in the plating solution. Characteristic X-ray diffraction patterns of cubic ZnTe are observed for the electrodeposited Zn-Te samples that have been annealed at temperatures ranging from 250 to 400°C. The flatband potential of the Zn-Te electrodeposits was determined by photocurrent and impedance (Mott-Schottky plot) experiments. The optical handgap of the ZnTe deposits determined by optical absorption spectrometry is 2.3 V, which agrees well with the literature values.