Electrodeposition of Ni on Bi₂Te₃ and Interfacial Reaction Between Sn and Ni-Coated Bi₂Te₃

Bismuth-telluride (Bi₂Te₃)-based compounds are common thermoelectric materials used for low-temperature applications, and nickel (Ni) is usually deposited on the Bi₂Te₃ substrates as a diffusion barrier. Deposition of Ni on the p-type (Sb-doped) and n-type (Se-doped) Bi₂Te₃ substrates using electroplating and interfacial reactions between Sn and Ni-coated Bi₂Te₃ substrates are investigated. Electrodeposition of Ni on different Bi₂Te₃ substrates is characterized based on cyclic voltammetry and Tafel measurements. Microstructural characterizations of the Ni deposition and the Sn/Ni/Bi₂Te₃ interfacial reactions are performed using scanning electron microscopy. A faster growth rate is observed for the Ni deposition on the n-type Bi₂Te₃ substrate which is attributed to a lower activation energy of reduction due to a higher density of free electrons in the n-type Bi₂Te₃ material. The common Ni₃Sn₄ phase is formed at the Sn/Ni interfaces on both the p-type and n-type Bi₂Te₃ substrates, while the NiTe phase is formed at a faster rate at the interface between Ni and n-type Bi₂Te₃ substrates.