Controlling the shape of hexagonal structure by growth condition improves the thermoelectric properties of p-type Bi-Te films

Improving the thermoelectric (TE) properties of typical p-type Bi_0.5Sb_1.5Te₃ film is crucial for power generation in film-based thermoelectric devices. The shape of the hexagonal structure in the Bi_0.5Sb_1.5Te₃ film can be controlled by adjusting the magnetron sputtering parameters. The results indicate that a high nucleation rate under high sputtering power promotes island growth with a preferred orientation of (015). Thermal energy influences the growth in the in-plane direction along the (00 l) orientation and induces the c-axis orientation in the out-of-plane direction. Consequently, a dense layered hexagonal structure with a high grain boundary density is formed, leading to increased defect density, carrier concentration, and phonon scattering. In this case, the power factor reaches 3149.01 μW·m^-1·K^-2 at 480 K and the ZT value is 1.14 at 480 K. These results indicate that the film with a dense layered hexagonal structure enhances the TE properties.