Nb${}_2$SiTe${}_4$: A Stable Narrow-Gap Two-Dimensional Material with Ambipolar Transport and Mid-Infrared Response

Abstract

Two-dimensional (2D) materials with narrow band gaps (~0.3 eV) are of great importance for realizing ambipolar transistors and mid-infrared (MIR) detection. However, most of the 2D materials studied so far have band gaps that are too large. A few of them with suitable band gaps are not stable under ambient conditions. In this study, the layered Nb${}_2$SiTe${}_4$ is shown to be a stable 2D material with a band gap of 0.39 eV. Field-effect transistors based on few-layer Nb${}_2$SiTe${}_4$ show ambipolar transport with similar magnitude of electron and hole current and high charge-carrier mobility of ~ 100 cm${}^2$V${}^{-1}$s${}^{-1}$ at room temperature. Optoelectronic measurements of the devices show clear response to MIR wavelength of 3.1 $\hat{\mathrm{I}}¼$m with a high responsivity of ~ 0.66 AW${}^{-1}$. These results establish Nb${}_2$SiTe${}_4$ as a good candidate for ambipolar devices and MIR detection.

17 pages, 5 figures