Research On Key Technologies Of Terahertz Detector Based On Graphene Nanomesh

THz technology has great scientific research value and broad application prospects in national defense,anti-terrorism,environmental monitoring,broadband communication,medical diagnosis and radio astronomy.The development of terahertz technology puts forward higher requirements for terahertz detector.The rapid response and simple system of terahertz direct detection technology are the development trend of modern detection instruments.However,the existing terahertz direct detectors have some problems,such as complex structure,low temperature operation and low sensitivity,which have become the bottleneck restricting the development and application of terahertz technology.The room temperature terahertz direct detector with high sensitivity,fast response,simple structure and high integration is one of the main research directions in the field of terahertz detection technology.Aiming at the problems of terahertz direct detection technology,a new method of high sensitivity detection of terahertz wave is proposed,which uses graphene nanomesh as grating to improve the coupling efficiency of incident terahertz wave,and uses the energy gap of graphene nanomesh to enhance the excitation of plasmon.Based on the extended Huckel molecular orbital theory,the electronic band gap regulation mechanism of graphene nanomesh and its excitation and enhancement of plasmon are studied,the terahertz detection mechanism of graphene nanomesh plasmon is studied,the terahertz detector model based on graphene nanomesh is established,and the processing gateway of terahertz detector based on graphene nanomesh is studied.The principle sample of the detector was made by key technology,and the photoelectric performance of the detector was tested.A terahertz imaging system is built to demonstrate the imaging application of the detector.The main work of this paper is as follows:(1)The research status and development trend of terahertz direct detectors at home and abroad,especially graphene-based terahertz direct detectors,are investigated and analyzed.The existing technical problems are summarized,and the research objectives and contents are determined.(2)Based on the extended Huckel molecular orbital model,the electronic structure of graphene nanostructures was simulated and analyzed by ATK/VNL simulation platform.The effects of the size and edge morphology of graphene nanoribbons and nano-mesh structures on the electronic gap of graphene materials were analyzed.A design scheme of high sensitivity room temperature terahertz detector using graphene nanomesh to excite graphene terahertz plasmon is proposed.(3)Starting from Maxwell’s basic electromagnetic theory,the dispersion relationship of terahertz plasmon of graphene is studied;the mechanism of grating coupling and enhanced excitation of plasmon based on graphene nanomesh is studied;the terahertz detection theory of graphene plasmon is studied,and the terahertz detector model based on graphene nanomesh is established.The finite difference time domain(FDTD)method was used to analyze the influence of the device’s structural parameters on terahertz plasmon and detection performance,and the structural parameters of graphene terahertz detector were optimized.(4)High quality graphene materials were prepared by chemical vapor deposition(CVD).The preparation technology of graphene nanomesh was studied.Large area and uniform graphene nanogrid structure was fabricated by electron beam lithography(EBL).The fabrication process of terahertz detector based on graphene nanomesh was designed and the principle sample of terahertz detector was developed.(5)The testing method of terahertz detector based on graphene nanomesh was studied;and the electrical characteristics of graphene nanomesh were tested,which verifies the regulating effect of graphene nanomesh on energy gap.A test system was built to test the detector,suggesting that the THz detection sensitivity of the detector can reach 12mA/W at room temperature.The imaging demonstration of metal samples by graphene nanomesh terahertz detectors was realized by using a bifocal imaging system.