Functionalization Of Graphene Photodetector

This paper studies the performance of graphene photodetectors.In recent years,the good optical properties,electrical properties,mechanical properties and special energy band structure of graphene have attracted people's attention,especially the zero bandgap structure and the broad spectral absorption capability makes it a very good application prospect in the field of photodetection.The zero bandgap structure and high carrier mobility of graphene make the graphene-based photodetectors have an ultra-fast response.However,two disadvantages of graphene inhibit its development in the applications of photodetectors.First,only 2.3%absorption of light;second is the short lifetime of the energetic exciton of graphene,that is the ultra-fast carrier-carrier and carrier-phonon scattering rates.According to the above problems,a series of studies on graphene-based photodetectors were carried out.In this paper,the low responsivity performance of graphene photodetectors is introduced.The effects of functionalization of graphene photodetectors using N719,PbI₂,and TiO₂ are studied.The main research has the following three aspects:1.The preparation technology of graphene photodetectors was studied.First,transfer the graphene grown by the CVD method from Cu foil to SiO₂/Si substrate by a wet transfer method.Then,the ultraviolet lithography exposure machine,electron beam electrode evaporation and lift-off process were used to prepare graphene-based photoelectric detector.2.The graphene photodetectors were functionalized using N719 and PbI₂.Through Raman and optoelectronic performance tests,the functionalization effect of graphene photodetectors by different organics was determined.The results show that N719 and PbI₂have little effect on improving the photodetector's responsivity.With the increase of light intensity,there was only little change of photocurrent and responsivity.3.The graphene photodetector was functionalized by a thin film of TiO2 with a thickness of about 2 nm prepared by electron beam evaporation and oxygen plasma etching.The defect and integrity of graphene on the surface of the device were determined by Raman measurement.The thickness of the oxide film deposited on the surface of the hybrid photodetector was tested by AFM.Then the oxide film deposited on the graphene surface was proved to be titanium dioxide through XPS.Photoelectric performance tests were performed on Ti O₂/graphene hybrid photodetectors using the photoelectric test system.The influence of titanium dioxide films on the electrical and chemical properties of graphene photodetectors was analyzed.The results show that the titanium dioxide prepared by electron beam evaporation and oxygen plasma etching functionalizes the graphene photodetector,greatly improving the responsivity of the graphene photodetector,with a responsivity of 110.5 A/W and a 3 orders of magnitude improvement in responsiveness over pure graphene photodetectors,with a response time of 20 ms.The results of this work will contribute to the advancement of functionalization of graphene photodetectors,laying the foundation for further optimizing the performance of graphene photodetectors.The functional method used in this work is simple and suitable for industrial large-scale production.