Preparation,Characterization And Field Effect Performance Modulation Of Functional Two-Dimensional Materials

Since its discovery,graphene has generated great interest in this two-dimensional structure material due to its special structure and excellent physical properties,and has conducted extensive and in-depth research.Due to the prosperity of graphene research,graphene-related functional derivatives such as graphene oxide and nitrogen-doped graphene have also received extensive attention.Graphene oxide?GO?and nitrogen-doped graphene can regulate the structure and properties of graphene through a series of oxidation,doping,reduction and other means to achieve specific functional applications.At the same time,functional two-dimensional materials of other elements such as boron nitride,transition metal sulfides and black phosphorus have also appeared.Among them,black phosphorus,as a semiconductor,has become a new focus in the field of two-dimensional materials due to its excellent electronic and optical properties,such as high carrier mobility and modulable direct bandgap.This thesis mainly explores the modification and doping of graphene oxide and the preparation of black phosphorus single crystals.The main research contents are as follows:1.Field effect transistors?FETs?based on reduced graphene oxide?RGO?heterostructure in which RGO is sandwiched between octadecyltrichloro-silane?OTS?self-assembled monolayers?SAMs?exhibit intrinsic symmetric ambipolar field-effect behavior with the Dirac point at the 0 V gate voltage and negligible hysteresis.The compact OTS SAM on the surface of RGO eliminates the doping effect of ambient air,while the SAM on the SiO₂/Si substrate remove the trapped charge,both leading to the intrinsic symmetric ambipolar field-effect without hysteresis.Moreover,the devices exhibit good stability,and the ambipolar field effect maintains for about one week under ambient condition.2.Pyrazine and pyridine nitrogen doped graphene were synthesized by Schiff base condensation reaction between the amino groups of the o-aryl diamine compound and carbonyl groups of GO,and the effects of nitrogen configuration and electron-withdrawing groups on its electrical properties of nitrogen doped RGO were studied.When GO is doped by the o-aryl diamine compound with strong electron-withdrawing groups such as trifluoromethyl groups,the FETs exhibit p-type doping.The symmetry of the transfer curve is significantly reduced,and the Dirac point shifts towards the positive gate voltage.The electron transport characteristic apparently weakens,and the devices show hole-transport-dominated ambipolar behavior.When the trifluoromethyl groups were eliminated and the electron-withdrawing ability of o-aryl diamine compound decreases,the devices gradually shift to ambipolar field effect,or even turning to weak n-type doping effect.Furthermore,the introduction of pyridine nitrogen makes the devices shift to weak p-type doping,indicating the different doping effect of different configuration of nitrogen.3.Large-area high-quality single-crystalline BP crystals were synthesized for the first time via ambient pressure chemical vapor deposition?CVD?by employing PBr5 as source on melting AuSn alloy.The growth mechanism of black phosphorus is further studied.The cooling rate has a great influence on morphology,indicating the growth mechanism is segregation like the growth of graphene on nickel,which is also verified by the characterization of the electron beam sputtering in situ Auger Electron Spectroscopy?AES?.Surprisingly,on the melting alloy surface,gold atoms dissolve into black phosphorus with the segregation process.This is similar to the effect of metal-ion-modified black phosphorus,the lone pair electrons in BP are occupied by metal ion,which prevent the reaction between oxygen and phosphorus,ultimately mitigating oxidation of BP.The stability of black phosphorus increases significantly,which makes the following transfer and device application possible.