Phase-dependent thermal conductivity of electrodeposited antimony telluride films

Abstract

Electrodeposition is a unique technique that can readily control the phase and the degree of crystallinity of the deposit, and this capability provides special opportunities to investigate phase-dependent thermoelectric properties from amorphous to crystalline by annealing. While the electrical conductivity and the Seebeck coefficient of electrodeposited antimony telluride films have demonstrated unique annealing temperature dependencies, their thermal conductivity remains unknown. Here, we report the thermal conductivity of electrodeposited Sb₃₇Te₆₃ films and present its dependence on pre-annealing temperature, annealing time, and measurement temperature. By controlling the pre-annealing temperature from 50 °C to 200 °C, the thermal conductivity of Sb₃₇Te₆₃ films increases from 0.36 ± 0.07 W m⁻¹ K⁻¹ to 1.73 ± 0.18 W m⁻¹ K⁻¹ at room temperature, indicating the amorphous to crystalline phase transition, as supported by our X-ray diffraction patterns. By controlling the annealing time up to 5 hours at constant temperatures of 100 °C and 200 °C, the transient thermal conductivity measurements reveal the crystallization activation energies of 1.12 eV and 1.36 eV, respectively. By controlling the thermal conductivity measurement temperature from −73 °C to 187 °C, we identify dominant thermal transport mechanisms in each phase, in accordance with classical phonon models. The relationship between thermal conductivity and temperature shifts from a positive to a negative correlation in crystalline Sb₃₇Te₆₃ films, and we infer that Umklapp scattering dominates over other scattering mechanisms and effects of phase impurities, surface boundaries, and grain structures in thermal transport. These findings can guide optimal design and processing of chalcogenide thermoelectric materials.