Rapid thermal annealing effects on the microstructure and the thermoelectric properties of electrodeposited Bi2Te3 film

Bismuth telluride thermoelectric films were prepared by galvanostatic process from 1 M nitric acid solution containing 8 mM Bi3+ and 8 mM HTeO2+. Both the n and p-type films were deposited. The thermoelectric properties of the films were measured before and after the rapid thermal annealing treatment to observe the annealing effects on the as-deposited film. Post annealing treatment was carried out under Ar environment at 200-300 °C for 2-10 min duration. Annealing effects on microstructure were examined from X-Ray diffraction (XRD) patterns and Scanning Electron Microscopy images. Electrical transport properties were analyzed by Hall Effect measurement system. The analysis revealed that the carrier density decreased and the carrier mobility increased with the enhancing of annealing temperature and duration. The Seebeck coefficient and power factor were improved significantly after rapid annealing treatment for both n and p-type Bi2Te3 films. For n-type Bi2Te3 film, the Seebeck coefficient improved about three-fold (from −57 to −169.49 μV/K) and the power factor improved around six-fold (from 2.74 to 17.37 μW/K2 cm) after annealing. On the other hand, for p-type Bi2Te3 film the Seebeck coefficient enhanced around three-fold (from 28 to 112.3 μV/K) and the power factor enhanced around two-fold (from 2.57 to 4.43 μW/K2 cm) after annealing.