Epitaxial Growth And Photoelectric Properties Of Graphdiyne / Graphene Two-dimensional Heterostructure

Graphdiyne(GDY),as a new artificial two-dimensional(2D)carbon material,is formed by the combination of sp and sp² hybridized carbon atoms according to a certain periodic rule with high degrees of?-conjugation similar to graphene.According to the theoretical predictions,graphdiyne has shown its outstanding application potential in many fields such as photo/electrocatalysis,energy storage and conversion,water purification,and humidity sensing based on its excellent mechanical,electrical,thermal and optical properties,excellent mechanical,electrical,thermal and optical properties.Compared with other two-dimensional materials,the theoretical prediction of graphdiyne has a natural moderate band gap(0.44?1.47 e V),while maintaining an extremely high carrier mobility(10⁴?10⁵ cm²V^-1 s^-1),which makes graphdiyne have a very broad application prospects in the fields of electronics and optoelectronics.However,it is difficult to obtain a large-area,highly crystalline graphdiyne thin film due to the limitation of graphdiyne preparation technology,which greatly restricts related research on the device of graphdiyne.Recently,Prof.Jin Zhang and Prof.Zhongfan Liu proposed a"solution phase van der Waals epitaxial method"for growing high-quality graphdiyne films,which created conditions for the application research of graphdiyne in the field of optoelectronic devices.In this thesis,graphdiyne/graphene vertical heterostructure was prepared with graphene as epitaxial substrate with a filed effect transistor(FET)structure,and the photoresponse characteristics of graphdiyne/graphene heterostructure were studied.The results show that the graphdiyne/graphene heterostructure has a photoresponse that is controlled by the light dosage(light intensity×illumination time).Specifically,the device exhibits volatile photocurrent under the condition of low light dosage,while the photocurrent of the device does not disappear on termination of light stimulation with high dosage,showing persistent photoconductivity(PPC).Taking advantage of the light-dose-dependent photoresponse of the graphdiyne/graphene heterostructure,we further apply it to mimic the synaptic behaviors of retinal nerve.By switching the volatile and nonvolatile memory behaviors of graphdiyne/graphene films,we mimic the short-term plasticity,long-time plasticity,and paired-pulse facilitation.By constructing the graphdiyne/graphene phototransistor array,we verified that this new type of optoelectronic synaptic device integrated the functions of color image recognition,image sensing and memory,and real-time image preprocessing,making it an competitive candidate for future neuromorphic vision sensors.