Effects Of Iron Impurity For Copper Substrate On The Growth Of Graphene By Chemical Vapor Deposition

Graphene is a two-dimensional material made of sp~2 hybrid carbon atoms packed together in a honeycomb.Graphene has excellent electrical,optoelectronic,mechanical and other properties,can be widely used in microelectronics,optoelectronic devices,aviation and other fields.The common preparation method of graphene films is chemical vapor deposition(CVD).Copper substrate is the most commonly used substrate for CVD preparation of graphene.It not only has good surface catalytic ability,but also has very low carbon solubility.Iron is an impurity that is difficult to avoid in existing commercial copper substrates.Therefore,it is very necessary to find out the influence law and mechanism of iron impurity on the growth of graphene on the copper substrate,and then put forward a solution.In order to solve this problem,this paper takes iron impurity elements on copper substrate as the research object,focuses on the effect of iron introduction method and introduced iron content on the nucleation and growth of graphene and the mechanism,and studies the effect of annealing on the content of introduced iron and the quality of graphene.The main research contents and conclusions are as follows:(1)The iron impurity was introduced into the copper substrate by solution titration and electrochemical deposition respectively,and the effect of two different introduction methods on the growth of graphene was studied.The results show that the introduction of iron inhibits the growth of graphene crystals,increases the nucleation density of graphene,decreases the domain size and mass of graphene crystals,and the growth of graphene is incomplete and the crystals are damaged in the area where iron is introduced.Compared with electroplating,the concentration of iron introduced by titration is lower but the distribution is not uniform.The defect density distribution of graphene is dependent on iron.Electroplating introduced uniform distribution of iron elements,but the surface of copper substrate was covered by iron particles,resulting in poor growth quality and integrity of graphene.(2)The effects of annealing and diffusion on the content of Fe on the surface of copper substrate and the growth quality of graphene were investigated.The results show that long time annealing and diffusion treatment can effectively reduce the content of iron impurity on the copper substrate surface and improve the surface morphology and roughness of the copper substrate,so as to effectively improve the growth quality of graphene films.(3)The effect of iron content on the nucleation and growth of graphene on electroplated copper substrate was studied.The results show that with the increase of Fe content,the nucleation density and defect density of the prepared graphene increase,and the greater the degree of film damage,the overall quality of the graphene decreases.Due to the inhibiting effect of iron on the growth of graphene,the introduction of iron content increases,leading to the increase of defects in the graphene crystals.In areas with high iron content,the growth of graphene even stops,leading to the damage of the graphene crystals.(4)The effect of iron impurity on the nucleation and growth mechanism of graphene was studied.The results show that in the nucleation stage,the nucleation density of graphene increases due to the increase of heteronucleation points by iron impurity.In the growth stage of graphene,the region with high iron concentration will inhibit the growth of graphene,or produce certain etching effect on graphene.