Effect of annealing temperature on microstructure and thermoelectric properties of bismuth-telluride multilayer thin films prepared by magnetron sputtering

N-type bismuth-telluride (Bi-Te) multilayer thin films with total thickness of about 900 nm were deposited on amorphous structure glass substrate by magnetron sputtering at room temperature. The films were annealed at different temperatures under Ar ambient for 1 hour. The effect of annealing temperature was investigated for Bi-Te multilayer thin films by surface topography, chemical composition, crystal structure and thermoelectric properties. The results show that the Bi-Te multilayer thin films are all transformed into Bi-Te-based compounds. With the annealing temperature increasing, the films undergo an island growth mode with column structure, and grain size increases from 16.4 to 23.1 nm; in addition, the electrical conductivity and carrier mobility increase monotonously. The maximum Seebeck coefficient (-98.5 μV K^-1) and power factor (14.47 μWK^-2 cm^-1) can be obtained for stoichiometric Bi₂Te₃ films annealed at 150°C.