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 E12g (∼385.3 cm−1) and A1g (∼402.4 cm−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 Gr¨uneisen
parameters for the E1g, E1 2g, A1g, and A2u 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.