Transition Metal Sulfide Photodetector Based On Surface Plasmon Effect

Transition metal sulfide have received extensive attention by researchers.They have many advantages such as high carrier mobility,high photon energy absorption,and excellent chemical stability.The energy band structure of transition metal sulfide can be changed with the number of layers,which makes them have unique advantages in the field of optoelectronics and are wide use in optoelectronic devices such as solar cells,photodetectors,and transistors.Molybdenum disulfide（MoS₂）as a representative of transition metal sulfide has attracted extensive attention of researchers.However,owing to the limited light absorption of molybdenum disulfide,which leads to the low interaction of transition metal sulfides with light,the performance of the fabricated photodetectors is limited,especially in the mid-infrared range.The method of noble metal structure modification based on surface plasmon effect is a feasible method to improve the performance of photodetectors because of its relatively simple preparation process and the ability to effectively broaden the light absorption range of two-dimensional material semiconductors.Compared with traditional noble metals,transition metal nitrides such as TiN have similar energy band structures to metals and similar surface plasmon polaritons（SPP）properties to metals,and are widely used in the excitation of SPP.In summary,we combine the TiN nanoparticle structure with molybdenum disulfide to fabricate a photodetector with a wider detection range and better performance.In this thesis,MoS₂ was used as the research object,and a near-infrared photodetector of molybdenum disulfide based on the surface plasmon effect of TiN nanoparticles（TiN NPs）was fabricated by the self-assembly method of polystyrene nanospheres（PS NPs）and magnetron sputtering process.The main work is as follows:（1）First,MoS₂ were fabricated by mechanical exfoliation method and their morphology was characterized.Then,the photodetector based on MoS₂ was studied,and then its performance was characterized.The PS bead array was fabricated by the self-assembly method of PS NPs,and TiN NPs were fabricated by magnetron sputtering titanium nitride after cleaning the PS beads.We introduced TiN NPs into the photodetector based on MoS₂ and explored the effect of TiN NPs on the performance of the photodetector based on MoS₂,and the performance of this photodetector was parameterized.After optimization,it was finally obtained that the device enhanced the performance of the MoS₂ photodetector in the near-infrared band under the effect of SPP.The light absorption value of the device has been significantly improved,and the ratio of bright and dark current has reached about twice.Secondly,we use the finite difference time domain method to simulate and analyze MoS₂ material added with TiN NPs,and then simply analyze the enhancement mechanism of the device added with TiN NPs believe that after the addition of TiN NPs,the interface coupling between TiN NPs and MoS₂ produces a localized SPP.The electric field strength in this region is enhanced,which stimulates the effect of SPP.Due to the enhancement of the local field generated by the SPP,the response of the device in the near-infrared range is significantly improved.（2）In this work,we found that the introduction of TiN NPs into MoS₂ photodetector resulted in a certain boost in the device response in the infrared range.However,we found that after the introduction of TiN NPs,the dark current of the device increased a little.Therefore,we use atomic layer deposition technology（ALD）to fabricate Al₂O₃ film as a passivation layer to reduce the dark current of the device.We optimize the Al₂O₃ film with different thicknesses and select the optimal thickness of Al₂O₃ film to further improve the surface based on TiN NPs Plasmonic effect of MoS₂ near-infrared photodetectors.In conclusion,this paper proposes a method using the SPP to achieve improved detection performance for MoS₂ photodetectors by adjus TiNg the parameters of TiN NPs.In addition,we also use atomic layer deposition technology to fabricate Al₂O₃ thin film as a passivation layer to reduce the dark current of the device and further improve the performance of the device.The research results of this paper provide a certain research idea for effectively improving the photodetector performance of TMDCs in the future.