Pressure Tuning Resonance Raman Scattering in Monolayer, Trilayer, and Many-Layer Molybdenum Disulfide

Abstract

We report a pressure-dependent resonance Raman study of mechanically exfoliated one-layer (1L), three-layer (3L), and many-layer MoS2 near the A excitonic transitions by using an excitation energy of 1.96 eV. Our results show a linear blue shift for the majority of phonon modes, except for the second-order phonons LA­(K) + TA­(K) and 2LA, whose pressure-dependent frequency is non-linear. The pressure dependence of these bands is explained by considering the dispersive scattering process that gives rise to these two modes, where both phonon and exciton energies blue-shift as the pressure increases. In addition, the resonance of the A1g mode in 1L-MoS2 is achieved at ∼7.0 GPa, while for 3L-MoS2 and many-layer MoS2, it occurs at ∼3.4 GPa. This difference is attributed to the smaller pressure coefficient of the A excitonic transition for 1L-MoS2, as compared with that of 3L-MoS2 and the MoS2 bulk. Our findings constitute an important step toward understanding and controlling the optoelectronic properties of few-layer MoS2 by means of strain/pressure, which are relevant in designing new flexible electronic and light-emitting devices.

Intrinsic Mechanical Strain in Chemical Vapor Deposition-Grown MoS2/MoSe2 Monolayer Heterostructures: Implications for Nanoelectronic Devices

“…18,22,45,46 More recent works, however, exhibit a phonon hardening of all Raman modes for MoS 2 and WSe 2 when subjected to high pressures. 47,48 In 2016, M. S. Kim et al, 49 when studying dry transferred TMDs, observed some small Raman shifts of the first order bands and related them to electron doping in MoS 2 and hole doping in MoSe 2 resulting from charge transfer. Nevertheless, when MoS 2 is submitted to electron gate doping, one observes that there is a downshift of the out-of-plane A′ 1 mode, together with an increase of its fwhm, while the E′ mode does not change, which is explained because of the weaker electron−phonon coupling of the in-plane mode.…”

Molybdenum disulfide-Zirconium dioxide composite with enhance supercapacitance performance

“…Figure 2 compares the Raman spectrum of the synthesized MoS2 layers with the bulk state. The bulk sample includes two peaks, E 1 2g and A1g, which are in the range of 381 cm -1 and 408 cm -1 [10]. But these peaks have shifted to positions of 385 cm -1 and 405 cm -1 for MoS2 layers, respectively, which confirms that they are multi-layered [11].…”