Theoretical Study Of Electron-phonon Interaction And Their Influence In Transition Metal Dichalcogenides Heterobilayer

The coupling interaction between out-of-plane phonon vibration and electronic state shows essential influence on interlayer transfer and recombination of excited charges in two-dimensional semiconductor heterostructures with type-II band alignment.Howe Ver,the electron-phonon coupling conditions and their influence mechanism on the electronic structure and the interlayer transfer and recombination of excited charges are still unclear,which seriously hinders the high efficient separation of excited charges.In this dissertation,the electronic structure,vibrational structure,electron-phonon coupling and their influences on the interlayer transfer and recombination of excited charges in Mo SSe/WTe Se?Mo SSe/WS₂heterobilayers with two different interface stacking configurations are investigated by first-principles method and non-adiabatic molecular dynamics calculation based on density functional theory(DFT).The main contents include the following two aspects:1.The influence of out-of-plane phonon vibration on the electronic structure of Mo SSe/WTe Se heterobilayers.Our results show that,firstly,the heterobilayers with the four different stacking configurations have the different interlayer band gaps but all possess type-II band alignment.Secondly,the vibrational structures of Te-Se configuration with the most stable energy were calculated,and the in-plane and out-of-plane phonon vibrations are found to show certain spatial localization.Lastly,the influences of the four phonon modes of 425,339,225 and 204 cm^-1on electronic structures of Te-Se configuration are investigated in details.The results show that the out-of-plane phonon vibrations can induce the essential changes of interfacial distances,intralayer band gaps and transition dipole moments,and these changes are closely related to the spatial localization of electronic and phonon states.2.The regulation of interlayer transfer and recombination of excited charges by using out-of-plane phonon vibration in Mo SSe/WS₂heterobilayers.By changing the interface stacking configuration,the spatial distribution of out-of-plane phonon vibration can be regulated,and the interaction between out-of-plane phonon vibration and electronic state can be effectively enhanced and suppressed,respectively.For the S-S stacking configuration,the out-of-plane phonon vibrations are delocalized at the Mo SSe and WS₂layers.Due to the substantial spatial overlap,the out-of-plane phonon vibration can simultaneously couple with the donor and acceptor electronic states,which leads to the fast interlayer transfer and recombination of excited charges.For the S-Se configuration,the out-of-plane phonon vibration is localized at the Mo SSe layer,but this phonon vibration distribution at the WS₂layer can be negligible.Therefore,the out-of-plane phonon vibration localized at Mo SSe cannot couple with the donor and acceptor electronic states at the same time,and thus the phonon vibration has little effect on the transfer and recombination of excited charge due to the spatial separation.Moreover,in the S-S configuration the delocalized out-of-plane phonon vibration also increases the interface atom vibration velocity,decreases the interface distance and reduces the energy difference between the donor and acceptor electronic states,further accelerating the interface transfer and recombination of excited charges.Distinctively,in the S-Se configuration,the corresponding influence from the localized out-of-plane phonon vibration is slight.Thus the effect of the out-of-plane phonon vibration on the interlayer transfer and recombination of excited charge can be ignored.This work provides a theoretical basis for understanding the electronic structure,vibrational structure and electron phonon coupling of transition metal chalcogenide heterobilayers,and paves a way to improve the separation efficiency of excited charges by regulating phonon vibration distribution.