Response Of Terahertz Wave In Graphene-like Materials

With the discovery of graphene,many two-dimensional materials(2D materials)with graphene-like structure and excellent photoelectric properties have attract ed lots of research.Among them,the van der Waals(vd W)heterostructures which consists of two different two-dimensional materials,is particularly attractive.This novel structure can not only combine the fine photoelectric properties of two 2D materials but perform some interesting physical phenomena.However,the physical mechanism of excited state relaxation in these materials is still unclear and most of studies are in the visible light region,so it is necessary to explore their carrier dynamics and broaden the field of applications.As an effective means of spectral analysis,terahertz spectroscopy has unique advantages in the study of photocarrier dynamics in 2D materials and vd W heterostructures.In this paper,the response and carriers dynamics of gallium selenide(GaSe),stannic sulfide(SnS₂)and the vd W heterostructures consists of them(GaSe/SnS₂ heterostructure)in terahertz region are studied by terahertz spectroscopy,Our findings are relevant both for the fundamental studies of the interlayer phenomena and for potential applications of van der Waals heterostructures in optoelectronic devices and new THz devices.1.A THz-TDS system and OPTP system with high signal-to-noise ratio and single pulse waveform are built.2.The few-layers GaSe,SnS₂ and GaSe/SnS₂ heterostructure laminates are fabricated by liquid phase exfoliation,both atomic force microscopy(AFM)and scanning electron microscopy(SEM)are applied to characterize the samples.And the band gap of them was obtained through visible absorption spectra.In order to prove the generation of the vd W heterostructure,Raman spectrum was also employed.3.The response of the layered GaSe,SnS₂ and GaSe/SnS₂ heterostructure in THz region are analyzed by THz-TDS and the refractive index and conductivity of them are extracted.4.The photocarrier dynamics in isolated GaSe and GaSe/SnS₂ heterostructure are explored by OPTP,the variation of photo-induced conductivity for them are extracted and illustrated by Drude-Smith model.