| Graphene exhibits superior mechanical strength,high visible light transparency(97.7%),high thermal conductivity,and,in particular,unique electronic properties——high electron mobility up to 200000 cm2V-1s-1 and long electron migration distance up to micron level.All of these excellent physical properties has made it an extraordinary research hotspot in the past decade and.However,the absence of an intrinsic electronic bandgap in this material is a major hindrance in implementing a graphene-based high-performance transistor.With the development of the research in two-dimensional materials,especially the emergence of two-dimensional hexagonal boron nitride(h-BN),a new idea has gradually emerged in front of researchers.Hexagonal boron nitride(h-BN),is an isomorph of graphene with a smooth surface at atomic level,few hanging bonds or charge traps,most importantly,the lattice mismatch between h-BN and graphene is only 1.7%,and it shows a wide bandgap of 5.97 e V.Many computational and experimental results show that if the atomic structure contains complex bonds between B,N and C,a novel two-dimensional composite material with graphene and h-BN properties,i.e.two-dimensional(2D)hexagonal boron-carbonnitrogen(h-BCN)atomic layers,can be obtained,clean up the main obstacles to the wide application of graphene electronic devices.However,it is still a hard work to obtain high quality 2D h-BCN atomic layers.So,in this work we focus on the preparation and properties of graphene,h-BN and h-BCN atomic layers.The main results of our work are listed as follows:1)The direct growth of graphene materials on Cu foils was realized by using ion beam sputtering deposition(IBSD)equipment.By studying the nucleation and growth process of graphene under different deposition conditions,we find that the ion beam density has a greater influence on the growth of graphene than the substrate temperature.By adjusting the concentration of CH4 precursor and the growth time,large area graphene flakes with different shapes can be synthesized on Cu.Through this method,the pollution of the external environment can be effectively avoided,and providing a strong foundation for the one-step preparation of 2D hBCN layers.2)The 2D h-BCN atomic layers with full range of compositions were grown directly on copper substrates by ion beam reactive sputtering deposition under mixed Ar/CH4 atmosphere.The h-BCN layers have been thoroughly characterized by various techniques,aiming at the determination of their structure evolution and properties.We find that the C content in the h-BCN layers can be tuned from 0 to 100 at.% by adjusting the CH4 flow rate and the size of ion beam aperture.Homogeneous h-BCN layers consisting of graphene and h-BN nanodomains can be obtained at an appropriate C content,whereas too high or too low C contents result in the segregation of large-sized graphene or h-BN islands.Furthermore,the band gap of h-BCN layers slightly decreases with increasing C content,while their electric properties can be tuned from insulating to highly conducting.This work provides a novel approach for synthesizing 2D h-BCN atomic layers and paves way for the development of h-BCN-based devices. |
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