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

• Two types of Bi2Te3 thin films were fabricated through sputtering method followed thermal treatment.
• The grain growth in the multilayer thin films was suppressed owing to interface.
• The smaller grains reduced thermal conductivity and maintained electronic 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.