Effects of annealing electrodeposited bismuth telluride films

Thermoelectric thin films exhibit different qualities when compared with bulk materials. The goal however is to achieve thermoelectric properties of bulk materials from electrodeposited thin films. Thin films are produced by electrochemical deposition at room temperature. In order to optimize thermoelectric figure of merit proper carrier concentration must be obtained. The carrier concentration can be observed through resistivity measurements of thin film Bi₂Te₃ n-type depositions on thin chromium-gold substrates. Seebeck coefficient measurements are performed on Bi₂Te₃ n-type thin films deposited on molybdenum foil. Annealing samples in the presence of hydrogen argon forming gas increases thermopower and resistivity consistent with a decrease in carrier concentration. Annealing between 200 and 500 Celsius for 1 to 20 hours was tested. This produces films with resistivity of 1 mΩcm but a Seebeck coefficient of only -60 μV/K. Samples are suspected of remaining too heavily doped even after annealing. These results suggest there are defects in thin films that cannot be removed by annealing alone.