Optical Composite Structures Enhance Light Absorption Of Two-Dimensional Transition Metal Dichalcogenides

In recent years,with the in-depth study of two-dimensional materials,two-dimensional transition metal dichalcogenides?TMDCs?have attracted great attention from researchers due to their excellent properties.Two-dimensional TMDCs with suitable band gaps are matched to planar semiconductors in process and can be modularized to replace some conventional semiconductor materials.Two-dimensional TMDCs have broad application prospects in new nanodevices such as field effect transistors,photodetectors,sensors,and photovoltaic devices.However,the absorption of light by two-dimensional TMDCs is low,and the performance of optoelectronic devices made by them is poor,which is not conducive to their practical application.Based on the finite difference time domain?FDTD?method,the localized surface plasmon resonance?LSPR?,cavity structure and guided mode resonance are used to enhance the light absorption of two-dimensional TMDCs.The specific work is:three optical composite structures enhance the light absorption of two-dimensional TMDCs.1.A silicon?Si?/distributed Bragg reflector?DBR?/monolayer tungsten disulfide?WS₂?/silver?Ag?grating structure is proposed to enhance the light absorption of the monolayer WS₂ in the visible light band.Both DBR and Ag gratings play an important role in the enhancement of monolayer WS₂ light absorption in composite structures.The average absorption of 420 nm-700 nm light by monolayer WS₂ in the structure can reach 52.9%.The results show that the Ag metal grating duty cycle and height can be used to adjust the monolayer WS₂ light absorption.Monolayer WS₂ still maintains high light absorption when the light is incident obliquely.2.Enhancing the light absorption of monolayer molybdenum diselenide?MoSe₂?through a multilayer structure.The multilayer structure consists of an Ag metal layer,a Bragg grating,a spacer dielectric silicon dioxide?SiO₂?and monolayer MoSe₂ embedded in the interior of the spacer medium.When light is incident on the multilayer structure,the Tamm plasma?TP?pattern formed inside the structure showes strong restrictions on the light field,and thus the light absorption of the monolayer MoSe₂ is enhanced.At 661 nm,the light absorption of monolayer of MoSe₂ can reach 81%.The multilayer structure can be adjusted by adjusting the Bragg grating structure parameters and the monolayer MoSe₂ position.With the increase of incident Angle,the wavelength of light absorption peak appears blue shift.3.Designing the guided mode resonance structure to achieve the perfect absorption of monolayer molybdenum disulfide?MoS₂?to the resonant wavelength light.The guided mode resonance perfect absorber is formed by stacking a gold?Au?back reflector,a Si photonic crystal plate etched with a periodic cross recess,and monolayer of MoS₂.The critical coupling effect caused by the guided mode resonance in the structure achieves the perfect absorption of the resonant wavelength?663 nm?light by the monolayer MoS₂.The adjustment of the light absorption peak can be achieved by changing the geometric parameters of the air cavity?cross recess?in the perfect absorber.The increase of the incident angle of light causes blue shift of absorption peak,but still maintains high absorption of light.