Research Of Photodetectors Based On Two-Dimensional MoS₂

Photoelectric transfer is a core part of current and future technology applications.Photodetectors have played an important role in many aspects of production and life such as biology,medicine,energy,and communications.The diversified application environment has continuously put forward new requirements for photodetectors,and Traditional photodetectors are facing huge pressure and challenges in the evolving application environment of diversification and intelligence.The discovery of two-dimensional materials represented by graphene have brought great inspiration to the development of future photodetectors.Among them,ultra-thin two-dimensional transition metal dichalcogenides represented by molybdenum disulfide,owning unique semiconductor properties and outstanding physical,electrical,and optoelectronic properties,have great potential in many aspects of optoelectronic detection,including flexibility,miniaturization and diversification.Although the research of molybdenum disulfide photodetection has begun to bear fruit,there are still challenges in terms of device responsiveness,response speed,and response spectral range.In this paper,ultra-thin molybdenum disulfide-based photodetectors are studied.Two-dimensional materials are prepared using micromechanical lift-off method and assembled into photodetectors through dry transfer technique.Materials are characterized using optical microscope,atomic force scanning microscope,Raman spectroscopy and so on.Molybdenum disulfide photodetectors modified with gold nano-particles and photodetectors based on molybdenum disulfide/molybdenum ditelluride van der Waals heterojunction are researched.Vacuum sputtering coating was used to modify the gold nano-particles of two-dimensional materials,and the influence of vacuum sputtering coating parameters on the gold nano-particles was discussed.Experiments have confirmed that the modification of gold nanoparticles by vacuum sputtering can improve the performance of molybdenum disulfide photodetectors.Among them,a 30-mA-current single-sputtered gold nanoparticle?5 nm height,7 nm pitch?modified MoS₂ detector has the maximum responsivity to 980 nm incident light,which is 64 mA W^-1,with a response spectral range up to 980 nm.The finite-difference time-domain simulation results show that the interface between the nano-gold particles and MoS₂ has a local plasmon resonance effect induced by the incident light,thereby enhancing the absorption rate of near-infrared light.In addition,the molybdenum disulfide/molybdenum ditelluride van der Waals heterojunction was stacked using dry transfer technique,and the substrate of patterned indium tin oxide electrode was used in photodetector assembly.The optoelectronic test results show that the detector is a self-driving device,and can detect visible light and near-infrared light without applying a bias voltage,and it displays a unique two-direction photocurrent response property.At the same time,the device shows excellent stability,and has a responsivity of 146 mA W^-1 for 520 nm incident light.The response time is only 167?s,better than most similar devices.The band theory analysis shows that the type II van der Waals heterojunction formed by molybdenum ditelluride and molybdenum disulfide promotes light absorption and carrier separation,thereby improving responsivity and response speed and achieving self-driving characteristics.Molybdenum ditelluride and the contact barrier between the electrode and the heterojunction barrier are coupled to achieve a bidirectional photocurrent response.The excellent performance of the two types of photodetectors indicates the great research value of ultra-thin molybdenum disulfide photodetectors.