Limited grain growth in multilayered Bi/Te thin films and the influence on the thermal and electrical conductivity

Bi₂Te₃ alloys were fabricated through thermal annealing of multilayered Bi/Te thin films as well as by co-sputtering of Bi and Te. In both cases, sharp X-ray diffraction peaks of Bi₂Te₃ were evidenced, indicating good crystallinity. It was found that the heterogeneous interface suppressed the grain growth in the multilayered samples considerably, and thus the thermal conductivity was reduced as a result of enhanced phonon scattering at the grain boundaries, but the electrical conductivity changed a little with temperature. However, the ZT figure (0.39) of the multilayered thin films was a little lower than that (0.43) of the single-layer ones at room temperature, suggesting the combined effect of power factor (PF) and thermal conductivity.