We present a combined experimental and theoretical study of resonant Raman spectroscopy in single- and triple-layer MoTe$_2$. Raman intensities are computed entirely from first principles by calculating finite differences of the dielectric susceptibility. In our analysis, we investigate the role of quantum interference effects and the electron-phonon coupling. With this method, we explain the experimentally observed intensity inversion of the $A^\prime_1$ vibrational modes in triple-layer MoTe2 with increasing laser photon energy. Finally, we show that a quantitative comparison with experimental data requires the proper inclusion of excitonic effects.
We performed polarized Raman spectroscopy on mechanically exfoliated few-layer MoTe2 samples and observed both 1T' and Td phases at room temperature. Few-layer 1T' and Td MoTe2 exhibited a significant difference especially in interlayer vibration modes, from which the interlayer coupling strengths were extracted using the linear chain model: strong in-plane anisotropy was observed in both phases. Furthermore, temperature-dependent Raman measurements revealed a peculiar phase transition behavior in few-layer 1T' MoTe2. In contrast to bulk 1T' MoTe2 crystals where the phase transition to the Td …
Understanding of electron-phonon coupling (EPC) in two dimensional (2D) materials manifesting as phonon renormalization is essential to their possible applications in nanoelectronics. Here we report in-situ Raman measurements of electrochemically top-gated 2, 3 and 7 layered 2H-MoTe$ _{2} $ channel based field-effect transistors (FETs). While the E$ ^{1}_{2g} $ and B$ _{2g} $ phonon modes exhibit frequency softening and linewidth broadening with hole doping concentration (\textit{p}) up to $\sim$ 2.3 $\times$10$ ^{13} $/cm$ ^{2} $, A$ _{1g}$ shows relatively small frequency hardening and linew…
Bulk 1T$^\prime$-MoTe$_2$ shows a structural phase transition from 1T$^\prime$ to Weyl semimetallic (WSM) $ T_{d} $ phase at $\sim$ 240 K. This phase transition and transport properties in the two phases have not been investigated on ultra-thin crystals. Here we report electrical transport, $1/f$ noise and Raman studies in ultra-thin 1T$^\prime$-MoTe$_2$ ($\sim$ 5 to 16 nm thick) field-effect transistors (FETs) devices as a function of temperature. The electrical resistivities for thickness 16 nm and 11 nm show maxima at temperatures 208 K and 178 K, respectively, making a transition from semi…
Field-Effect Transistors Based on Few-Layered alpha-MoTe_2
本文报道了在SiO_2上用机械剥离法生长的几层化学气相传输法生长的α- MoTe_2晶体的场效应晶体管的特性。我们进行了场效应和霍尔迁移率测量，以及拉曼散射和透射电子显微镜。与MoS_2和MoSe_2相比，我们的MoTe_2场效应晶体管（FET）被观察到是空穴掺杂的，显示超过106的开/关比和典型的亚阈值摆幅为每十倍约140 mV。场效应迁移率和霍尔迁移率的最大值接近或超过10 cm ^2/Vs，这与以前报道的室温下单层或双层MoS_2和/或MoSe_2在SiO_2上剥离的数据相当。拉曼散射揭示了尖锐的模式与以前的报告，其频率被发现显示很少或没有依赖于层数。由于两种MoS_2都是电子掺杂的，MoTe_2在MoS_2上的堆叠可以产生双极场效应晶体管和间隙调制。尽管MoTe_2的总体电子性能与MoS_2和MoSe_2相当，但较重的元素Te应该会导致更强的自旋轨道耦合，并可能伴随着更长的激子谷和自旋指数的退相干时间。
Transition metal dichalcogenides (TMDs) are layered materials which show excellent potential for nanoelectronic and optoelectronic applications. However, as many of the exciting features of these materials are controlled by the anharmonic effects, a proper understanding of the phonon properties and anharmonicity associated with these materials is essential for the proposed applications to be realized. We present here a comprehensive study on the phonon properties of two different TMDs; viz., MoS2 and MoTe2, as a function of temperature, laser excitations, and polarization, as well as flake-thi…
In this article, we address the optomechanical effects in surface-enhanced resonant Raman scattering (SERRS) from a single molecule in a nano-particle on mirror (NPoM) nanocavity by developing a quantum master equation theory, which combines macroscopic quantum electrodynamics and electron-vibration interaction within the framework of open quantum system theory. We supplement the theory with electromagnetic simulations and time-dependent density functional theory calculations in order to study the SERRS of a methylene blue molecule in a realistic NPoM nanocavity. The simulations allow us not o…
