Comparison of thermoelectric properties of flexible bismuth telluride thin films deposited via DC and RF magnetron sputtering

Bi2Te3 thin films were deposited onto polyamide sheets with direct current (DC) or radio frequency (RF) magnetron sputtering techniques. The films were prepared using a Bi2Te3 target at a varying pre-heating temperature from 150 to 350 °C. It was observed that the type of plasma excitation and pre-heating temperature can significantly change the composition, preferred orientation, crystallinity, and thermoelectric properties of the films. The pre-heat treatment significantly affected the non-stoichiometric composition. In addition, it was shown that crystallinity and (0 0 l) planes were enhanced in the DC sputtered coatings at a high pre-heating temperature. The maximum power factor of 3.5 × 10−3 W/m K2 at 285 °C was obtained for the films deposited using DC magnetron sputtering and a pre-heating temperature of 350 °C. The carrier concentration and mobility of the film were 5.40 × 1020 cm−3 and 13.04 cm2/V s, respectively. Compared with an ordinary Bi2Te3 film, the power factor of such film has been greatly increased. The results indicated that DC magnetron sputtering can enhance the (0 0l ) plane orientation in the Bi2Te3 film.