| Graphene and monolayer molybdenum disulfide,as typical two-dimensional materials,have many excellent physical and chemical properties that are widely used in optoelectronic devices.The zero band gap structure of graphene makes it have the advantages of ultra-wide spectral response range,ultra-high carrier mobility and tunable carrier concentration,while the direct band gap structure of monolayer molybdenum disulfide makes it have the characteristics of high mobility,low power,and high switching ratio,both of which show promising applications in the field of optoelectronic devices.However,because of single atomic layer thickness,the light absorption efficiency of these two materials is very low,which greatly limits their development in the field of optoelectronic devices.This paper focuses on the absorption characteristics of graphene/molybdenum disulfide-metal slot composite structure in visible-near infrared region.The main elements include:1.Asymmetric cavity structures with varying widths of left and right cavities are designed to widen the bandwidth of absorption efficiency greater than 70% in the absorption spectrum to1?m,which enables efficient broadband absorption of graphene in the near infrared band.In order to clarify the basic principle of broadband absorption in asymmetric cavity structure,the absorption spectrum and electromagnetic field distribution of single cavity,symmetrical cavity and asymmetric cavity structure are compared and analyzed respectively.Based on the finite element method,the resonance principle and the influence of structural parameters on optical absorption efficiency are analyzed.Based on the excellent photoelectric properties of graphene,the high-efficiency broadband absorption characteristics of the designed structure have high application value in the fields of light absorption,photoelectric detection and solar cells in the near-infrared region,and the simple shallow metal groove structure and low-cost materials are more conducive to the process realization.2.A light absorber based on molybdenum disulfide-metal groove structure is designed,and the corresponding absorption characteristics of the structure are calculated and analyzed.The simulation results show that the proposed ring-slot structure optical absorber can effectively enhance the overall optical absorption efficiency compared to the 10% absorption efficiency ofmonolayer molybdenum disulfide.Further,we propose an optical absorber with copper-shaped-slot structure,which has a certain broadening in the absorption bandwidth compared with the ring-slot structure.We further analyze the physical principle of generating broadband absorption by decomposing the structure.Finally,the influence of the parameters such as period,outer diameter of circle,thickness of dielectric layer on the optical absorption efficiency of the structure is explored.By adjusting the structural parameters,more than 80% of the optical absorption in the range of 469nm~784nm can be realized,and more than 90% in the range of 486nm~732nm.Our proposed absorber model can be used not only to enhance the light absorption of molybdenum disulfide,but also to enhance the absorption of other transition metal halides,such as tungsten disulfide,molybdenum disulfide,etc.Therefore,our designed molybdenum disulfide-based optical absorbers have certain reference value for wideband efficient absorbers and photodetectors operating in the visible light region. |
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