On The Mechanisms Of Synthesis Of Graphene By MEVVA Source Ion Implanatation On The Nikel Foils

Graphene is a monolayer carbon material of two-dimensional honeycomb lattice structure,which has become the subject of intense study by many experts and scholars in the last decade for its excellent physical properties,including high electronic mobility,outstanding conductivity,extreme mechanical strength,and superior optical performance.A major goal in graphene research is the synthesis of large-scale high-quality graphene with controllable thickness and repeatable production.At present,the common synthesis methods of graphene can be classified into mechanical cleavage,epitaxy on SiC,graphite oxidation reduction method,chemical vapor deposition and ion implantation.Ion implantation is a technology of modifying and doping materials surface,has been commonly used in the electronic industrial production.Ion implantation can accurately control the carbon ion implantation dose,is one of the most promising synthetic method,which would not be affected by the substrate solubility and diffusion coefficient.Since 2010,graphene has been successfully synthesized by ion implantation on the metallic films,especially on the nickel films.High-quality graphene has been successfully synthesized,but and the size and uniformity of graphene remains to be improved.Therefore,the study of the mechanism of graphene synthesis by ion implantation is of great importance.The Metal Vapor Vacuum Arc(MEVVA)source ion implantation is an advanced ion implantation technology.It can use almost all the heavy metals as the sources as well as some nonmetallic elements.Its beam size and uniformity is superior compared to other implantation thchnologies.In this study,graphene was successfully synthesized by MEVVA ion implantation on polycrystal nikel foils.With polished nickel foils,the experimental parameters were optimized,such as carbon ion implantation dose,annealing temperature,N2/H2 gas flow rate,and so on.SEM observing of the sample showed some black spots on the surface of the specific grains.And micro-Raman measurement confirmed the black spots are grapheme grains.The results of EDX measurements excluded the non-uniform implantation effect caused by the channel effect in different grains.EBSD observation show that only the nickel foils(101)orientation appears graphene.With the knowledge of crystallography,the atomic density of the(101)plane is the minimum.So,the path of carbon atoms segregation is the minimum for(101)oriented grains.Our observation found that graphene can be formed on nickel surface directly by segregation of the carbon atom through certain crystal planes.This is contrast to previous report that suggesting the carbon atoms only can segregate through the grain boundaries.In this study,I successfully synthesised few layered graphene by MEVVA ion implantation.And I proposed a new interpretation for the mechanisms of precipitation of graphene: 1)It is not the only way that graphene nucleates through segregated from the grain boundary then spread to the surface of nikel foils;2)carbon atoms precipitated directly from the surface of the nickel grain;3)surface density of the different nikel grain orientation have influence on the formation of graphene.