Enhanced electron–phonon scattering in Janus MoSSe

Abstract

Electron-phonon (e-ph) interaction in monolayer Janus MoSSe has been investigated using ab initio approach. We find that the asymmetric structure induced net dipole moment in MoSSe introduce an enhanced e-ph interaction compared to the symmetric MoS 2 . Through the mode resolved scattering analysis, we demonstrate that the out-of-plane optical mode in MoSSe contributing to the total eph scattering rates are much more than MoS 2 . Around the band edges, the maximum mean free paths (MFPs) of both electrons and holes along zigzag (ZZ) direction are found to be 4 nm in MoSSe, while the MFPs along armchair directions are significantly shorter than along ZZ direction, meaning the highly anisotropic transport properties in MoSSe.

Strained MoSi2N4 Monolayers with Excellent Solar Energy Absorption and Carrier Transport Properties

“…Obviously, the trends for the electron–phonon scattering rates with respect to energy are similar to the corresponding DOS of MoSi 2 N 4 (Figure d), which is consistent with the fact that DOS reflects the available phase space for electron–phonon scattering. The electron–phonon scattering rates in pristine MoSi 2 N 4 are distributed within 1.5 fs –1 , which is close to that in MoSSe . Meanwhile, the results show that the scattering rate near the band edges is not sensitive to tensile strain, but increases significantly in compressed MoSi 2 N 4 .…”

“…On the other hand, the MFP of carriers in pristine MoSi 2 N 4 is within 1.5 nm, and compressive strain slightly decreases the MFP. Surprisingly, tensile strain significantly increases the MFP, and some of them become as large as 3 nm, which is comparable to conventional semiconductor Si (less than 5 nm) and the newly discovered Janus MoSSe monolayer (about 4 nm). , Overall, tensile strain can significantly improve the transport properties of carriers in MoSi 2 N 4 , which is of great significance for improving its performance in optoelectronic applications.…”

Excitonic Dynamics in Janus MoSSe and WSSe Monolayers

“…Since the exciton formation in TMD monolayers is mainly achieved by optical phonon scattering, 35 the faster exciton formation process suggests that the optical phonon scattering is enhanced in Janus TMDs due to the built-in dipole moment, which is consistent with theoretical predictions. 27,28 After this initial fast decay, the differential reflectance signal drops exponentially, as shown in Figure 4c. This slow decay is caused by the recombination of excitons.…”

“…The broader width in MoSSe could be due to its lattice strain or the enhanced exciton−phonon interaction due to its Janus structure. 27,28 To compare their PL quantum yields (the ratio of emitted and absorbed photon numbers), we note that the spectrally integrated PL intensity (from 1.6 to 2.1 eV) of MoS 2 is about 2.65 times higher than that of MoSSe. Taking into account the different photon energies, the emitted photon number from MoS 2 is about 2.55 times larger than that of MoSSe.…”

Chemical Vapor Deposition of High‐Optical‐Quality Large‐Area Monolayer Janus Transition Metal Dichalcogenides

“…[25] This value could be evidence of stronger exciton-phonon coupling for Janus layers as compared to TMD monolayers due to the intrinsic electric dipole. [26] Janus TMD MLs are expected to possess momentum dependent spin splitting and to obey chiral optical selection rules. In Figure 3B, we detect the PL emission both coand counter-polarized with respect to the excitation laser polarization.…”