Enhanced thermoelectric properties in Bi/Te core/shell heterostructure nanowires through strain and interface engineering

Strain-engineered Bi/Te core/shell (C/S) nanowires (NWs) with various diameters were prepared by combining the on-film formation of NWs method with post-sputtering. Multiple devices were fabricated based on individual C/S NWs. The diameter-dependent electrical conductivity (sigma), Seebeck coefficient (S), and thermal conductivity (kappa) of the Bi/Te C/S NWs were systematically investigated. S and s were found to increase with increasing NW diameter until they maximized at diameters exceeding 400 nm. Together with the reduction in kappa, this generated a maximum thermoelectric figure of merit of 0.5 for a relatively large-diameter Bi/Te C/S NW (d= 456 nm) at room temperature. These results suggest that the C/S NW structure could be used to modify the thermoelectric performance of materials, as the figure of merit was significantly greater than previously reported values for pure Bi NWs (0.07) and bulk Bi (0.05). Furthermore, the enhanced performance of very large Bi/Te C/S NWs demonstrated the possibility of designing heterostructures that can be used in thermoelectric device and module applications.