Photoelectric Sensing Properties Of The Graphene Nanocrystallites Embedded Carbon Film/Silicon-based Heterojunction

With the development of mechanical engineering technology,people have higher and higher requirements on the accuracy and speed of the automatic control process.The photoelectric sensor has the characteristics of non-contact,high reliability,high precision,fast response and no influence on the operation of the system under test,which is exactly what modern industrialization needs.Silicon is an excellent semiconductor material that is used in most heterojunction photosensors.Another material of a heterojunction is generally a two-dimensional material,such as molybdenum disulfide or antimony disulfide.Graphene is gradually applied to photoelectric sensors as a material with excellent optical and electrical properties.However,due to the zero band gap characteristics of graphene,the leakage current will be relatively large,and the light response rate is also low on the order of mA/W.Moreover,the production cost of graphene is high,the manufacturing process is complicated and it is difficult to commercialize on a large scale.In view of the above research background,this study used a convenient,fast and large-area preparation method for the preparation of graphene nanocrystallite embedded carbon(GNEC)films,Electron cyclotron resonance plasma processing system,and studied the photoelectric characteristics of the heterojunction photosensor composed of GNEC films and silicon.In this study,a closed-field electric field electron irradiation process in electron cyclotron resonance is used to deposit carbon atoms to form a carbon film,which can change the nanostructure of the deposited carbon film when adjusting the electron irradiation energy.The nanostructures were characterized by Raman spectroscopy and transmission electron microscopy.It was found that the graphene nanocrystals structure could not be formed when the electron irradiation energy was low.As the electron irradiation energy increased,the graphene nanocrystals gradually formed in the amorphous carbon atoms.The number of grain layers gradually increases,and the area gradually becomes larger.Through the photoelectric research on this heterojunction photosensor.It was found that the heterojunction sensor composed of P-type silicon exhibited obvious diode characteristics,and the photoelectric responsivity was up to 0.21 A/W under illumination of 785 nm wavelength.Compared to ultraviolet and visible light,these photoelectric sensors are most sensitive to near-infrared light.And have an ultra-fast response speed of 260 ns.The heterojunction photosensor formed by the GNEC films and the N-type silicon does not have the diode characteristic,and the photoelectric effect is low when no external bias is applied.but the photoelectric responsivity is greatly improved when the applied bias voltage is applied,and the highest Up to 0.32 A/W.And found a method of transferring the chemically stripped GNEC films to the surface of the N-type silicon.This Van Der Waals contact method can greatly reduce the area of the photosensor to less than 0.2 mm~2,and such photosensors have excellent response to weak light intensity.The photoelectric responsivity can reach up to 22.8 A/W.