Field-Effect Transistors Based on Few-Layered α‑MoTe₂

Abstract

Here we report the properties of field-effect transistors based on a few layers of chemical vapor transport grown α-MoTe₂ crystals mechanically exfoliated onto SiO₂. We performed field-effect and Hall mobility measurements, as well as Raman scattering and transmission electron microscopy. In contrast to both MoS₂ and MoSe₂, our MoTe₂ field-effect transistors are observed to be hole-doped, displaying on/off ratios surpassing 10⁶ and typical subthreshold swings of ∼140 mV per decade. Both field-effect and Hall mobilities indicate maximum values approaching or surpassing 10 cm²/(V s), which are comparable to figures previously reported for single or bilayered MoS₂ and/or for MoSe₂ exfoliated onto SiO₂ at room temperature and without the use of dielectric engineering. Raman scattering reveals sharp modes in agreement with previous reports, whose frequencies are found to display little or no dependence on the number of layers. Given that MoS₂ is electron-doped, the stacking of MoTe₂ onto MoS₂ could produce ambipolar field-effect transistors and a gap modulation. Although the overall electronic performance of MoTe₂ is comparable to those of MoS₂ and MoSe₂, the heavier element Te leads to a stronger spin–orbit coupling and possibly to concomitantly longer decoherence times for exciton valley and spin indexes