Controllable electrodeposition and mechanism research of nanostructured Bi2Te3 thin films with high thermoelectric properties

Nanostructured Bi₂Te₃ thin films were electrodeposited in the electrolyte of TeO₂ and Bi(NO₃)₃·5H₂O without any additive. Electrochemical tests proved that Bi³⁺ was reduced to Bi firstly, which induce the reduction of HTeO₂⁺ to fulfill the co-position. The stoichiometric ratio of Bi₂Te₃ was controlled by the adjustment of depositing duration under suitable deposition potential. The EIS results illustrated that the rate of stable growth of the films was determined by the applied potential. The nucleation of Bi₂Te₃ was a progressive process, during which all the nuclei formed uniformly. The subsequent stable growth of the Bi₂Te₃ thin films was controlled by Nernst diffusion process at a suitable depositing rate. The uniform nucleation and growth caused the ideal (110) texture. The hydrogen evolution reaction and the over growth was avoided, so that the compact rice-like nanostructure could be obtained. The Bi₂Te₃ thin films were controlled to a state of stoichiometry composition, single phase structure, compact rice-like nano-morphology and (110) texture. Their electrical conductivity reached as high as 1.240 × 10⁵ S·m⁻¹, which caused the maximum PF of 5.234 × 10⁻⁴ W·m⁻¹·K². This facile synthetic approach is promising for the preparation of nanostructured Bi₂Te₃ thin films as the thermoelectric materials.