Optical Properties Of The Two-dimensional Thin Film Materials Tungsten Disulfide And Study Of Interlayer Coupling Of Double Heterojunctions

Two-dimensional thin film materials of graphene analogues have been emerging research hot spot in semiconductor materials and optoelectronic devices field in recent years,for its rich,unique,novel physical and chemical properties and excellent?potential?performances.The monolayer or few layers of tungsten disulfide?WS₂?,which has been especially concerned as a typical representative of graphene analogues materials.The atoms in the layer are bonded by covalent bonds,the layers are bonded by weak van der Waals force,this unique structural characteristics endows its special physical and chemical properties,so it has broad application prospects in photovoltaic devices,sensors,solar cells,supercapacitors,and other fields.WS₂ has a striking feature is that the band gap from 1.3 to 2.1eV can be regulated by layers,this suggests that the WS₂ optical properties have great scope to regulated.The WS₂ photoelectric properties can be further regulated when it and other two-dimensional thin film materials formed heterojunction.This paper aim at WS₂ this feature and the current research hot spot,to study the surface modification and WS₂/GaTe,WS₂/GaSe,WS₂/GaS0.5Se0.5 heterojunction influences WS₂ thin film optical properties.Details are as follows:?1?The monolayer WS₂ is prepared by using chemical vapor deposition?CVD?method.The optical properties of the samples are studied,PL and Raman tests show that the preparation of samples are the high quality monolayerWS₂.?2?By using thiourea and silver nitrate as a source of reaction solution for modifying the surface of WS₂,to study the optical properties of WS₂ influenced by silver sulfide modification time.Raman test results show that with the increase of modification time in-plane vibration mode E12g peak position constantly move in the direction of low energy,the out-plane vibration mode A1g peak position unchanged,as the sulfur atoms are electronegative with silver ions via electrostatic interaction makes the strain of the in-plane vibration mode slack lead to the peak redshift,but the electrostatic interaction has no effect on the out-plane vibration mode.Moreover,with the increase of modification time,the intensity of two Raman peaks increases gradually,because the WS₂ surface enhanced Raman scattering modified by silver sulfide.?3?The GaTe/WS₂/GaSe double heterojunction is prepared by mechanical stripping and transfer method.Raman test results show that the interlayer coupling between multi-layer GaTe and monolayer WS₂ is strong;The interlayer coupling between multi-layer GaSe and monolayer WS₂ is weak,but the interlayer coupling is enhanced by annealed.Photoluminescence?PL?test results show that the heterojunction glowing from the superposition of light of components,which greatly expand the scope of WS₂ emission.?4?The WS₂/GaS0.5Se0.5/GaSe double heterojunction is prepared by mechanical stripping and transfer method.Raman test results show that the interlayer strain between multi-layer GaSo.sSeo.s and monolayer WS₂ is weak,but the interlayer strain is enhanced by annealed,the interlayer strain between multi-layer GaSe and multi-layer GaSo.sSeo.s is strong,the strain is enhanced by annealed.Strong interlayer coupling between the layers with the broadening,shift of PL peak,so can get more widely light spectrum.