The Role Of Oxygen In The Growth Of Single Crystal Graphene And Its Nitrogen Doping

Graphene has emerged as an exciting,atomically thin two-dimensional material for fundamental studies and potential applications in future electronics.The growth of large-domain single crystalline graphene with the controllable number of layers is of central importance for large-scale integration of graphene devices.Introduction of oxygen on the Cu substrate can greatly increase the growth rate of graphene and decrease the nucleation density as well,which is beneficial to the growth of high-quality and large-area graphene.In this paper,we found that the growth of graphene on Cu oxide foil is significantly affected by the concentration of oxygen.The grain size of graphene grown on Cu substrate with relative high oxygen concentration is much smaller than that on the substrate with lower oxygen concentration.By controlling the oxidation of the Cu substrate at a proper degree,we can obtain millimeter scale graphene single crystal at a growth temperature of 1050.Based on our experimental observations,the dual role of oxygen in the CVD growth of graphene was revealed.i)oxygen on Cu surface can contribute to the decomposition of hydrocarbon feedstock and decrease the graphene growth barrier,resulting in increased growth rate and larger grain size of graphene;ii)excess oxygen in the Cu substrate leads to the etching of graphene edge.Our research provides insights to obtain large-area and single-crystalline graphene by choosing proper Cu-oxide substrate.However,since graphene is considered a semi-metal with no bandgap,there are substantial limitations for its practical utilization in many electronic and optical applications.The ability to dope graphene is highly important for modulating electrical properties of graphene.Heteroatom doping in graphene leads to bandgap opening and tunable electronic,magnetic and optical properties,which are important for graphene-based electronics applications.In our work,we used acetonitrile as a liquid carbon source to grow nitrogen doped single-crystal graphene by chemical vapor deposition.Ultra-fast growth with liquid carbon source has been realized successfully.The growth rate of nitrogen doped single-crystal graphene was up to 20.25?m min^-1.The atomic percentage of Nitrogen in the sample was about¹ at%.We provide a reliable synthetic route for the production of high-quality nitrogen doped single-crystal graphene,which is conducive to its wide application in commercial production.