Thermoelectric properties of layered ternary telluride Nb3SiTe6

Abstract

We report the study of the thermoelectric properties of layered ternary telluride ${\mathrm{Nb}}_{3}{\mathrm{SiTe}}_{6}$. The temperature dependence of the thermoelectric power (TEP) evolves from nonlinear to linear when the thickness of the devices is reduced, consistent with the suppression of electron-phonon interaction caused by quantum confinement. The magnitude of TEP strongly depends on the hole density. It increases with decreasing hole density when the hole density is low, as observed in ionic-liquid-gated thin flakes. However, the device with the largest hole density possesses the highest TEP. Theoretical analysis suggests that the high TEP in the device with the largest hole density can be ascribed to the phonon-mediated intervalley scatterings. The highest TEP reaches $\ensuremath{\sim}230\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{V}/\mathrm{K}$ at 370 K while the electrical resistivity of the device is maintained below $1.5\phantom{\rule{0.28em}{0ex}}\mathrm{m}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$. Therefore, a large power factor PF $\ensuremath{\sim}36\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{W}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$ comparable to the record values reported in $p$-type materials is obtained.