Controlled synthesis and Se doping of WTe 2 nanowires for enhanced thermoelectric performance

Abstract WTe 2 nanowires were synthesized using solvothermally grown W 18 O 49 nanowires as a precursor, followed by vacuum-sealed thermal treatment with NaBH 4 and Te and/or Se. X-ray diffraction analysis confirmed the Td structure of WTe 2 . In Se-doped WTe 1.6 Se 0.4 samples, a shoulder on the 002 peak and an additional peak near 2 θ = 34° were observed, indicating partial Te→Se substitution and suggesting the possible emergence of a 1T′-related structural component. Raman spectroscopy revealed broadening of the A 1 2 -related mode, consistent with partial structural modification induced by Se incorporation. TEM observations confirmed layered nanowires with diameters of ∼25 nm and an interlayer spacing of ∼0.7 nm along [002]. Thermoelectric and Hall-effect measurements were performed using pelletized nanowire samples. The WTe 2 nanowires exhibited relatively high carrier mobility (5.28 × 10 3 cm 2 V −1 s −1 , while Se doping reduced mobility to 2.78 × 10 3 cm 2 V −1 s −1 due to enhanced carrier scattering. The power factor and ZT values were improved compared with WTe 2 powders.