Research On The Growth Mechanism Of Graphene Single Crystals Based On Metal Chemical Vapor Depositio

Graphene is an allotropy of carbon element with two-dimensional honeycomb structure.The special sp2 orbital hybrid structure of graphene endows it with excellent physical properties such as conductivity,thermal conductivity,transparency,and mechanical flexibility.Therefore,it has broad application potential in fields such as highly sensitive detection,high-efficiency luminescence,and high energy storage and conversion.Efficient and simple preparation of graphene is a prerequisite for the application of graphene.Among numerous methods for preparing graphene,chemical vapor deposition(CVD)is considered the most likely method to achieve large-scale production.Although the scientific community has made significant progress in the CVD method for preparing graphene,further research is still needed in the growth of graphene large single crystals and rapid preparation of graphene.Taking the preparation of graphene large single crystals as an example,there are currently two strategies: one is to start from a single core and prepare graphene single crystals with macroscopic dimensions.This single crystal grows from the same nucleus,so graphene in different regions has the same crystal orientation.Therefore,the entire crystal exhibits uniform physical properties.However,the slow growth of single crystals and poor controllability of nucleation density are the drawbacks of single nucleus growth schemes.Another approach is to start from multiple cores and precisely control the orientation of graphene crystal domains by strictly controlling the surface properties of the copper substrate,so as to form parallel crystal domains and form graphene single crystals with uniform structures after crystal splicing.This method can greatly shorten the growth time of graphene,but it has strict requirements for the crystal plane and surface smoothness of the copper base surface.This article takes the single core growth strategy as the route to study the growth problem of graphene single crystals.We propose a method for rapidly preparing graphene large single crystals by addressing the issues of poor controllability of nucleation density and slow growth in CVD graphene large single crystals.This method uses defect rich upright graphene(VG)as an auxiliary growth source and a composite composed of ceramics as an auxiliary growth source.The function of upright graphene is to accelerate the decomposition of methane,thereby greatly increasing the growth rate of graphene.Its growth rate can reach500 μ m/min,which is more than 102 times faster than the traditional CVD process of graphene.Meanwhile,the trace oxygen released by ceramics at high temperatures significantly inhibits the nucleation density of graphene.Compared to graphene under conventional CVD conditions,the domain density of graphene prepared by modified CVD method can be reduced to only a few domains per square centimeter.Compared to the traditional CVD method,the nucleation density of graphene has decreased by 105 times.The synergistic effect of upright graphene as an auxiliary catalyst and the slow release of oxygen from ceramics on the inhibition of graphene crystal nuclei provides favorable conditions for the extremely rapid preparation of graphene large single crystals with millimeter size.By using this method,graphene single crystals with a size greater than 2mm were immediately prepared after 5 minutes of growth.