Raman And PL Study Of 2D TMDC And Its Heterostructure

Atomic-scale transition metal dichalcogenides(TMDC)two-dimensional layered materials have unique electronic and optical properties,and in particular,van der Waals heterostructures constructed by TMDC monolayers can generate new photoelectric property and physical phenomena,which have important prospect in optoelectronic field.Therefore,it is necessary to study the optical properties of TMDC monolayers and the interactions between van der Waals heterostructures constructed by them.In this dissertation,firstly micro-area Raman and PL spectroscopy techniques were performed in order to study the Raman phonon mode and PL properties of monolayer MX2(M:Mo W;X:S,Se)in supported substrate and suspended state.Secondly,the interlayer interactions in WS2/WSe2 heterostructure were studied.The main results obtained are as follows:Mechanical exfoliation method were used to prepare MX2 monolayers and dry-transfer technique were applied to transfer monolayer MoS2,WS2,and WSe2 on SiO2/Si substrate and the etched holes on the SiO2/Si substrate respectively,which allows single layer to be supported and suspended.PL spectra showed that the monolayer samples have significant differences in PL intensity,peak shape and peak position of the supported and suspended status.Substrate interference effect changes peak intensity of PL spectra.Charge transfer between monolayer samples and substrate affected the ratio of excitons and trions in monolayer samples,thus changing the peak position,shape and intensity of PL spectra.The WS2/WSe2 heterostructure was prepared by mechanical exfoliation method.Interlayer interactions and interface charge transfer in the heterostructure were studied by temperature-varying Raman and PL spectra.The existence of interlayer phonons and interlayer excitons were observed from Raman and PL spectra,indicating that there are significant interlayer interactions in van der Waals heterostructure constructed by WS2 and WSe2 monolayers.As WS2 and WSe2 form a type-? band alignment,electrons transfereed from WSe2 to WS2,significantly affecting PL intensity of trions and excitons.