Strain tuning of optical emission energy and polarization in monolayer and bilayer MoS2

Abstract

We use micro-Raman and photoluminescence (PL) spectroscopy at 300K to investigate the influence of uniaxial tensile strain on the vibrational and optoelectronic properties of monolayer and bilayer MoS2 on a flexible substrate. The initially degenerate E 1 2g Raman mode is split into a doublet as a direct consequence of the strain applied to MoS2 through Van der Waals coupling at the sample-substrate interface. We observe a strong shift of the direct band gap of 48meV/(% of strain) for the monolayer and 46meV/% for the bilayer, whose indirect gap shifts by 86meV/%. We find a strong decrease of the PL polarization linked to optical valley initialization for both monolayer and bilayer samples, indicating that scattering to the spin-degenerate Γ valley plays a key role.

Single photon emission from deep-level defects in monolayerWSe2

“…The PC of X 0 peak reflects a blue-shift rate of band edge of the direct K-K interband transition. [18][19][20][21] Here, the PC of X 0 at low temperature is nearly a half of the value for 2D-X 0 at room temperature reported elsewhere. 22 The discrepancy in the PC values obtained at different temperatures is at moment not understood.…”

Spectroscopic Signatures for Interlayer Coupling in MoS2–WSe2 van der Waals Stacking

“…40 The result of Raman scattering modes is shown in Figure 3, where all the modes, not the resonant second order or combinations of first order modes, are shown in the It is known that the Raman E' peak of monolayer MoS2 is sensitive to strain and strain could induce a red-shift in the E' modes that have been observed for MoS2 monolayer or multilayers in other reports. 33,[41][42][43] The red-shift of the MoS2 E' peak after the two layers are coupled (thermally treated)…”

Dirac cones and Dirac saddle points of bright excitons in monolayer transition metal dichalcogenides

“…Due to rotational symmetry of the monolayer TMDCs, the valley pseudospin splitting must vanish at k ¼ 0. However, an in-plane uniaxial tensile strain [35][36][37] that breaks the rotational symmetry can introduce a finite splitting at k ¼ 0. Our ab initio calculation on monolayer WSe 2 shows that the strain realizes an in-plane Zeeman field on the valley pseudospin (see Supplementary Note 2), and the exciton Hamiltonian becomeŝ…”