Flash Evaporated Thin Films of Bismuth Telluride

Abstract

In this study, thermoelectric thin films are deposited on glass plates by using a flash evaporation method. We evaporated fine powders of 20% Bi2Te3-80% Sb2Te3 as a p-type and those of 90% Bi2Te3-10% Bi2Se3 as an n-type. We measured thermoelectric properties, such as Seebeck coefficient, alpha, the electrical resistivity, rho, and thermal conductivity, lambda, at room temperature. Flash evaporated p-type thin films show high values of thermoelectric properties: alpha = 199 muV/K, and rho = 14 mOmegamiddotcm at 300 K, and the n-type thin films show alpha = -30 muV/K, and rho = 3 mOmegamiddotcm. The fabricated thin films are annealed at 200 to 400 degC for 1 hour in argon for the improvement of the thermoelectric properties. The electrical resistivity of the p-type thin films reduces as annealing temperature increases, and it reaches 1.8 mOmegamiddotcm at annealing temperature of 400 degC. Seebeck coefficient of the thin films reaches 218 muV/K at annealing temperature of 300 degC. On the other hand, the electrical resistivity of the n-type thin films reduces to 2 mOmegamiddotcm at annealing temperature of 350 degC, and Seebeck coefficient of the thin films increases to -163 muV/K at annealing temperature of 300 degC. The measured thermal conductivity of an n-type thin film annealed at 200 degC is 1.2 W/(mmiddotK). EPMA measurements and SEM observations are carried out to consider the mechanisms of improvements of thermoelectric properties