Electrodeposition of ZnTe Film with High Current Efficiency at Low Overpotential from a Citric Acid Bath

Abstract

The cathodic electrodeposition of ZnTe film was studied using an aqueous citric acid bath ͑pH 4; temperature 368 K͒ in which Zn͑II͒ and Te͑IV͒ species were dissolved to form Zn(Cit) 2 4Ϫ and HTeO 2 ϩ ions, respectively. The deposition mechanism was studied based on cyclic voltammetry. The influence of the deposition potential on the morphology, composition, and structure of the deposited film was also investigated. A smooth, dense polycrystalline ZnTe film with nearly stoichiometric composition was deposited at a constant cathode potential, ranging from Ϫ0.80 to Ϫ0.60 V vs. Ag/AgCl, from a solution containing 20 mmol dm Ϫ3 Zn͑II͒, 0.16 mmol dm Ϫ3 Te͑IV͒, 0.25 mol dm Ϫ3 H 3 Cit, and 0.25 mol dm Ϫ3 Na 3 Cit (Cit ϭ C 6 H 5 O 7 ). Potentials in this range provided the deposited ZnTe film with high current efficiency ͑above 98%͒. During electrodeposition of the nearly stoichiometric crystalline ZnTe, the current density was approximately stationary.

Polymorphic One-Dimensional (N2H4)2ZnTe: Soluble Precursors for the Formation of Hexagonal or Cubic Zinc Telluride

“…Zinc telluride (ZnTe) is a relatively high mobility p-type semiconductor (∼100 cm 2 V -1 s -1 for single-crystal material) with a direct band gap of ∼2.25 eV, , which has been considered for use in light-emitting diode, detector, photovoltaic, − and transistor applications. Copper-doped zinc telluride has been pursued, for example, as a potentially environmentally stable, low-resistance back-contact for CdS/CdTe solar cells. , Thin films of ZnTe are generally deposited using processes such as molecular beam epitaxy (MBE), , thermal evaporation, ,,, electrodeposition, ,, and metal−organic vapor-phase epitaxy (MOVPE). , However, these approaches are not amenable to low-cost, large-area, high-throughput deposition. Some examples of techniques that fit these processing criteria include spin-coating, stamping, and printing, which, however, all require a soluble semiconductor or a soluble precursor that can be cleanly decomposed to the desired semiconductor at low temperature.…”

Electrodeposition of mesoporous CdTe films with the aid of citric acid from lyotropic liquid crystalline phases

“…This apparent discrepancy in the film thicknesses of CdTe may be attributed to competing reactions such as hydrogen reduction at the chosen pH which can be expected to reduce the current efficiency of the electrochemical process significantly. 13,33 It should be noted that the presence of the liquid crystalline template phase requires a compromise to be made in terms of the pH range and deposition potential range that can be applied and may significantly differ from that which can be used in aqueous solutions.…”

“…It has recently been reported that the solubility of TeO 2 in acid solutions can be increased by using citric acid as a complexing agent. 32 For example, the solubility of TeO 2 as HTeO 2 + ions at pH 3 is 10 25 M, but with the addition of citric acid it improves to about 10 22 M. In a more recent work, Ishizaki et al 33 reported that high efficient electrodeposition of ZnTe thin films can be achieved from a citric acid bath. In this study the effect of citrate on the properties of ZnTe deposits was investigated and it was shown that including citrate in the bath suppressed the deposition of Te and promoted high ZnTe crystallinity.…”

Effect of pH on the Electrodeposition of ZnTe Film from a Citric Acid Solution

“…11) Although it is considered that Te soluble species could form a complex with citrate ligands, 12) there is no available complex formation data for them. Thus, the reduction reactions for Te were treated as the reaction used in Pourbaix-type diagram.…”