Fig. 6: Thermoelectric transport properties in surface re-engineered tellurium nanowires.
a Temperature-dependent conductivity (σ) measurements (from 90 to 225 K) on thin films of undoped p-type (Te-PVP, blue spheres) and sulfur-doped n-type (Te–S2−, red spheres) tellurium nanowires normalized to the respective conductivity values at 90 K (σ90K). While the undoped nanowire films show activated (semiconductor-like) transport with conductivities increasing with increasing temperature, the doped nanowire films demonstrate band-like transport with decreasing values of conductivities with increasing temperature. b Proposed doping scheme wherein sulfur dopes tellurium n-type and most of the electrons are located in the dopant band with the Fermi level inside the band (similar to a metal) at low temperatures (below 225 K), and hence the band-like transport behavior. Above 225 K, the electrons gain sufficient thermal energy to get promoted to the conduction band. c Temperature-dependent conductivity measurements for the n-type (Te–S2−) samples wherein above 225 K the conductivity increases sharply with increasing temperature. Temperature-dependent d electrical conductivity, e Seebeck coefficient, and f power factor of the n-type Te nanowire film demonstrating extremely high monotonously increasing power factors with increasing temperature.
