The Effect of Annealing in Controlled Vapor Pressure on the Thermoelectric Properties of RF-Sputtered Bi2Te3 Film

To investigate the effect of annealing in controlled atmosphere on the thermoelectric properties of Bi-Te film, Te-deficient Bi-Te film was deposited by sputtering, and then annealed with various Bi-Te alloy powders with different Te concentrations in a closed system at 250°C for 24 h. Bi-Te phases other than Bi2Te3 in the as-deposited film could be removed when the film was annealed with Bi-Te source powder containing 62 at.% or higher content of Te. At the same time, the values of Seebeck coefficient and carrier concentration of the films approach −105 μV/K and 3 × 1019 cm−3 to 6 × 1019 cm−3, respectively. This result indicates that mass transport of Te to the film takes place, resulting in the formation of Bi2Te3 phase and reduction of the amount of p-type carriers due to compositional change of the film from Te-deficient to stoichiometric. Annealing in controlled Te-vapor atmosphere is an effective method to improve the thermoelectric properties of Bi-Te film by changing the composition and phase of Te-deficient film to stoichiometric Bi2Te3 film.