Cs/O Activation Process And Characteristic Evaluation Of Nickel-based Graphene Cathod

Graphene,as a two-dimensional material with excellent performance,is expected to bring new breakthroughs in the field of photoelectric detection.The properties of graphene itself,such as wide spectral response,high carrier mobility and very short carrier delay time,have attracted the attention of many researchers and been introduced into the research of photoelectric detection devices.The current applications of graphene in the field of photodetectors are mainly based on the internal photoelectric effect,and the application of the external photoelectric effect of graphene has not been reported.In this context,a new nickel cornerstone graphene composite photocathode responsive to visible light is prepared in this paper.Its long wave spectral response threshold is about 755 nm,and the quantum efficiency at 350 nm is 0.17%,while the quantum efficiency of traditional metal cathode is often less than0.1%,and usually responds to ultraviolet light.In this paper,a theoretical study is carried out on the adsorption of different cesium-oxygen ratio models on nickel-based graphene,based on the preparation and characterization of the photocathode,the ultra-high vacuum interconnection system and scanning focus X-ray photoelectron spectroscopy technology,for different temperatures,different graphene layers and different activations.Method of nickel-based graphene for activation performance evaluation and surface composition detection research.First of all,based on the first-principles method of density functional theory,different ratios of Cs and Cs/O adsorption models on the graphene/Ni(111)surface were constructed,and the effects of different adsorption models on the electronic structure and optical properties of graphene/Ni(111)systems were analyzed,and the comparison of work function and adsorption energy of different adsorption models,The model under the coverage of O adsorption 1 MLCs is a relatively ideal adsorption result,which provides a theoretical basis for the activation experiment.Secondly,the preparation process of nickel based monolayer and multilayer graphene was introduced.The surface morphology,surface defects,element composition and electronic structure of nickel based monolayer graphene and nickel based multilayer graphene were characterized by Raman spectroscopy,atomic force microscopy,optical microscopy,X-ray photoelectron spectroscopy and ultraviolet electron spectroscopy.Then,the ultra-high vacuum interconnection system for photocathode preparation and characterization of the research group is introduced,with emphasis on the ultra-high vacuum activation part of the system.In order to reduce the influence of impurities on the surface of nickel cornerstone graphene cathode,improve the photoelectric emission performance of nickel cornerstone graphene,and explore the high temperature purification temperature suitable for nickel based graphene cathode.Through the analysis of the surfacee lement content of four groups of samples before and after high-temperature purification experiment,it is appropriate to choose 450 ℃ as the high-temperature purification temperature.Finally,three groups of control experiments were designed for nickel based monolayer and multilayer graphene,namely room temperature cesium activation,heated cesium activation and heated cesium oxygen activation.The experimental results show that the activation photocurrent value and spectral response curve are better than the other two activation methods through heated cesium oxygen activation.The XPS analysis results show that,The content of cesium oxide deposited on the surface by heating cesium oxygen activation is the highest.UPS analysis results show that the minimum work function of the sample in the way of heating cesium oxygen activation is 1.341 e V.Combined with the analysis of activation photocurrent value and spectral response curve,heated cesium oxygen activation is a suitable activation mode for nickel graphene.