Enhancement of fatigue resistance of Bi-Sb-Te films on flexible substrates by current-assisted thermal annealing

Brittle nature of chalcogenide compounds is a major concern for implementation of bismuth telluride based compound films in flexible thermoelectric devices. In this study we report that the fatigue resistance of Bi-Sb-Te films sputtered on a polyimide substrate is improved by applying a high-density electric current (1-2×103 A/cm2) through the film during post-deposition thermal treatment. The electrically stressed film was found to suffer less conductivity degradation caused by cyclic stretching than the film thermally annealed at the same temperature. The increase of electrical resistance is well correlated to the enlarging crack width observed in the stretched film. It is proposed that the electromigration-induced Sb-rich precipitates suppress the propagation of microcracks along grain boundaries during cyclic stretching and thus improves the fatigue resistance of the sputtered Bi-Sb-Te films.