Raman-scattering measurements and first-principles calculations of strain-induced phonon shifts in monolayer MoS₂

The effect of strain on the phonon modes of monolayer and few-layer MoS₂ has been investigated by observing the strain-induced shifts of the Raman-active modes. Uniaxial strain was applied to a sample of thin-layer MoS₂ sandwiched between two layers of optically transparent polymer. The resulting band shifts of the E2g1 (∼385.3cm^-1) and A _1g (∼402.4cm^-1) Raman modes were found to be small but observable. First-principles plane-wave calculations based on density functional perturbation theory were used to determine the Grüneisen parameters for the E_1g, E2g1, A_1g, and A_2u modes and predict the experimentally observed band shifts for the monolayer material. The polymer-MoS₂ interface is found to remain intact through several strain cycles. As an emerging 2D material with potential in future nanoelectronics, these results have important consequences for the incorporation of thin-layer MoS₂ into devices.