Electrodeposition of Bi₂Te₃ Films from Ammoniacal Basic Solutions Containing Nitrilotriacetic Acid

Abstract

Bi₂Te₃ thin films were electrochemically deposited from ammonia-alkaline solution containing Bi(NO₃)₃, TeO₂, nitrilotriacetic acid (NTA), in which Bi(III)- and Te(IV)-species were dissolving to form Bi(NTA)₂^3- complex and TeO₃^2-, respectively. This study revealed the relationship between [Bi]/[Te] ratio in the solution and the respective metal ratio in the deposited film. The [Bi]/[Te] ratio of the deposited film was successfully controlled by conducting electrodeposition under diffusion-limited conditions, i.e. the [Bi]/[Te] ratio in the solution was linearly related to that of the deposited film, where the partial current density originating from bismuth and tellurium ion was directly proportional to the concentration of respective ions. Dense and crystalline Bi₂Te₃ thin films with stoichiometric composition were electrodeposited at the potential ranging from −0.6 to −0.8 V from 5.0×10^-3 kmol m^-3 Bi(NO₃)₃ · 5H₂O, 3.0×10^-3 kmol m^-3 TeO₂ and 0.1 kmol m^-3 NTA solution, with cathodic current efficiencies being above 85%.