The Study Of Photoelectric Conversion Based On Plasmon-induced Hot Electron And Two-dimensional Materials

Two-dimensional materials have attracted much attention in recent years because of their excellent properties.Different from traditional three-dimensional optical materials,the existence of quantum confinement effect of two-dimensional materials in the direction perpendicular to the two-dimensional plane brings many unique photoelectric properties,such as large exciton binding energy and strong light-matter interaction,which have a broad application prospect in optoelectronic devices.As a member of optoelectronic devices,photodetector is widely used in optical communication,imaging and remote sensing.At present,there is a large demand for high-performance photodetectors with high sensitivity,high speed and broadband photoresponse.However,the two-dimensional photodetectors based on photoconductive and photovoltaic effect are encountering the challenges in achieving fast photoresponse and high sensitivity,respectively.In order to solve the field bottleneck and meet the application demand,it is particularly urgent to explore new photoelectric conversion mechanisms.It is an important strategy for achieving efficient and high-speed photoelectric conversion by employing plasmonic nanostructures and two-dimensional materials hybrid structure.Surface plasmon effect can break the diffraction limit and restrict the light to sub-wavelength scale,which highly localize the electromagnetic field and significantly enhances the light-matter interaction.A large number of non-equilibrium hot electrons can be generated in plasmonic nanostructures assisted by surface effect and hot spots.The energy loss caused by electron-phonon scattering can be avoided if the plasmon-induced hot electrons are harvested immediately,which will improve the efficiency of photoelectric conversion.Besides,ultrafast plasmon-induced hot-electron transfer can prevent the occurrences of carrier cooling and trapping,which has a great potential in improving the speed of photoelectric conversion.Plasmon-induced hot-electron transfer can also overcome the spectral limit of the bandgap of semiconductor in traditional photodetectors,which provides a new way for infrared detection.In this paper,hot electron transfer in the heterostructure between plasmonic semiconductor nanostructures and two-dimensional materials is studied.Moreover,high-performance photodetection has been achieved based on this.The main research contents are as follows:1.Optical and electrical properties of two-dimensional materials are the foundations in the application of photodetection.Optical contrast imaging method is employed to analyze the impact of layer number distribution of graphene on light absorption and carrier mobility.It was found that the presence of bilayer domains in the graphene prepared by chemical vapor deposition(CVD)method introduces more scattering sources and therefore results in a significant reduction in the carrier mobility.2.A WO_2.9-graphene near-infrared photodetector based on hot electron transfer is constructed.It is demonstrated that plasmon-induced hot electron transfer is a sufficiently fast process to prevent carrier cooling and trapping,which provides a new method for achieving fast photoelectric conversion.The response time of this device(?35?s)is 3 orders of magnitude faster than that based on common band-edge electron transfer.At the wavelength of 633 nm and 1550 nm,the responsivity of the device reaches?202.3 A/W and?8.24 A/W,respectively.In addition,hot electron transfer can overcome the spectral limit of the bandgap of tungsten oxide and extend the photoresponse to the communication band of 1550 nm.3.An ITO-graphene hybrid photodetector with two kinds of photoresponse mechanisms is demonstrated.The positive and negative photoconductance of the device are caused by the injection of holes detrapped from defect states and plasmon-induced hot electrons from ITO,respectively.The positive photoconductive mode has a characteristics of high sensitivity,with responsivity of?3.3×10⁵ A/W.The negative photoconductive mode has a characteristics of fast response with response time of?110?s,and the responsivity reaches?37.4 A/W.