Abstract
We discuss the effect of the in-plane electric field on the Raman spectroscopy for few-layered MoS2. The characteristic Raman modes of MoS2 show gradual red shift, while the intensity increases by 45–50% as the electric field is increased, showing a large electro-optical effect. Structural analysis suggests that our few-layered MoS2 belongs to P6/m2 space group with broken inversion symmetry. We attribute this gradual red shift to this broken symmetry-driven piezoelectricity in MoS2, which generates tensile strain along the perpendicular direction when the electric field is applied. The enhancement of the effect upon reversing the electric field direction adds credence to our interpretation. Our first principal density-functional theory calculation further substantiates the claim. This optical probing of the electromechanical coupling may lead to applications as a nonextensive technique for electric field/strain sensors in the nanoelectronics devices.
Highlights
Tunability of two-dimensional quantum materials (2DQM) through an external perturbation has strongly excited condensed matter research in recent years due to its possibility of applications, if not by the rich physics they offer[1]
The bulk 3D transition metal dichalcogenides (TMDCs) are formed by the stacking of individual layers through a weak van der Waal’s force, making them easy to cleave and get a monolayer, whereas the atoms within each 2D plane are bound through a strong covalent bonding[12]
We describe the effect of moderate in-plane electric field on the phonon modes of few-layered MoS2, probed by Raman spectroscopy at room temperature
Summary
Tunability of two-dimensional quantum materials (2DQM) through an external perturbation has strongly excited condensed matter research in recent years due to its possibility of applications, if not by the rich physics they offer[1]. Among the vast library of 2DQM6, atomically thin semiconducting transition metal dichalcogenides (TMDCs) (having formula MX2, M = Mo and W and X = S, Se, and Te) have attracted particular interest in optoelectronic application due to their strong light–matter interaction owing to the presence of van-Hove singularity in their electronic structure[11,12]. The huge difference between in-plane and outof-plane interatomic interaction strengths often results in highly anisotropic electronic and mechanical properties in these layered systems. Coupling of these anisotropic properties may lead to interesting phenomena
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