Enhanced Photodetector Performance Of MoS₂ Via Surface Plasmon Resonance Coupling Of Au And Ag Nanoparticles With Sandwich Structure

Molybdenum disulfide（MoS₂）,as a representative of layered transition metal sulfides（TMDs）,has the characteristics of high carrier mobility,adjustable band gap,and strong visible light absorption capacity.In recent years,its research in the field of electronics and Photodetector devices has received strong attention from researchers.However,due to the low light absorption efficiency of single-layer or small-layer MoS₂ and the high composite rate of photogenerated carriers,MoS₂-based photodetectors generally have the problems of low light response and slow response speed.Although the surface plasmon resonance effect of precious metals is an effective means to improve the light response performance of the device,only one layer of precious metal nanoparticles（NPs）is modified,on the one hand,the particles modified on the surface of the material have a certain masking effect on the photosensitive material,affecting the absorption of light by the material,on the other hand,for the light path scattering and the increase in the length of the optical path of the incident photosensitive material is limited,which greatly limits the further improvement of the performance of the device.Therefore,this thesis aims to construct a double-layer precious metal modified MoS₂ photodetector with a sandwich structure,using the resonant coupling of plasma on the surface of the MoS₂ metal nanoparticles to improve the light response performance of the MoS₂ photodetector.The main findings of the study are as follows:（1）Using mechanical stripping and electron beam evaporation,a double-layer Au NPs modified less layer MoS₂（Au-MoS₂-Au）photodetector with sandwich structure was prepared for sensitive detection of visible light.Thanks to the enhanced local surface plasma resonance（LSPR）coupling between the two layers of Au NPs and the reabsorption of visible light by the lower Au NPs,the local electric field strength of Au NPs and the overall visible light absorption capacity of the material are effectively improved.Therefore,the photoelectric performance of the Au-MoS₂-Au photodetector is significantly better than that of the single-layer Au NPs modified MoS₂（Au-MoS₂）photodetector.The Au-MoS₂-Au photodetector has a light response（Rλ）and a specific detection rate（D*）of up to 1757 A/W and 3.44×10¹⁰ Jones,respectively,which are about 3 times the value of Au-MoS₂.At the same time,the device’s light response speed is also very fast,exceeding the detection limit of the device（24 ms）.（2）Single-layer Ag NPs modified MoS₂（Ag-MoS₂）and double-layer Ag NPs modified MoS₂（Ag-MoS₂-Ag）photodetectors were constructed.Studies have shown that under visible light excitation,the Ag NPs modified on the upper and lower surfaces of MoS₂ produce a greater electric field intensity than the Ag NPs that modify only one layer,resulting in more thermal electrons injected into the MoS₂,which greatly improves the light response performance of the device.At450 nm illumination,the Rλ,External Quantum Efficiency（EQE）,and D^*of Ag-MoS₂-Ag devices are up to 5.54×10⁴ A/W,1.53×10⁵%,and 1.07×10¹² Jones,respectively.（3）Based on the enhancement of the device performance by bilayer metal nanoparticle modification,Au and Ag NPs co-modified MoS₂（Au-MoS₂-Ag）photodetectors were prepared by using the resonance absorption properties of Au and Ag NPs in different visible wavelengths.Compared with Au-MoS₂,Au-MoS₂-Ag exhibits better photoresponse properties at 450 nm and532 nm,with Rλ,EQE and D^*reaching 7.66×10⁴ A/W,2.11×10⁵%and 7.63×10¹¹ Jones（450nm,77.56μW/cm²,5 V）,respectively.The thesis has 73 figures,3 tables and 143 references.