The influence of post-deposition annealing on thermoelectric properties of Bi–Sb–Te films prepared by sputtering

Bi–Sb–Te thin films were prepared for p-type thermoelectric material in micro Peltier cooling devices. Films with four different compositions were elaborated by co-sputtering of BiSb(1:3) alloy and Te targets. Rapid thermal annealing was carried out for the improvement of thermoelectric properties of the as-grown films under a reducing atmosphere. The effects of the thermal treatment on the characteristic properties of the films were investigated with measurements of the electrical transport properties and Seebeck coefficients. The variation of the charge carrier concentration of a film was found to be dependent on the film's composition and closely related to the thermoelectric properties. The decrease of carrier concentration and the increase of mobility due to the crystallization of the chalcogenide phase resulted in the enhancement of the thermoelectric properties. Maximum values of the Seebeck coefficient (∼178 µV K −1 ) and power factor (∼1.2 × 10 −3 W K −2 m −1 ) were obtained for a film close to the stoichiometric composition (Bi 0.5 Sb 1.5 Te 3 ).