Controllable Growth Of Graphene Nanostructure With High Quality Using CVD Method

Graphene,an atomic thin two-dimensional crystal arranged with sp2-bonded carbon atoms in a honeycomb lattice,has drawn increasing attention due to its unique properties since discovered in 2004.Nowadays,the chemical vapor deposition(CVD)has become the most popular method for the scalable production of high-quality graphene.At present,lots of strategies have been explored for researchers to obtain high-quality graphene nanostructure by CVD method,and a series of achievements have been achieved.However,how to realize the controllable growth of high-quality graphene nanostructure is still a challenge due to a lot of conditions and complicated factors involved in the CVD process.The growth process of CVD not only relies on controlling the growth parameters accurately,but also depends on deep understanding of the growth mechanism of graphene.The issues to be solved will be important for scientific research,as well as have an important meaning for application.In this paper,a two-step growth technique,namely nucleation and growth steps performed separately,was used to investigate the influence of the hydrogen on the growth of the graphene by CVD method.And then,a growth-etching technique was developed and the double hexagonal graphene ring was successfully synthesized for the first time.Additionally,the forming regularity of grain boundaries in graphene was further investigated and these may provide some guidances for developing method to synthesize high-quality graphene nanostructure.The main contents of the paper are illustrated as follows.Firstly,a two-step method which was able to divide the nucleation and growth process was developed,and the role of hydrogen on the growth of graphene nanostructure was studied systematically.At first,the graphene domains grown in the same conditions were obtained using the CVD method to eleminate the impact of the nucleation.Then,the influence of hydrogen on the growth of graphene nanostructure was carefully investigated by controlling the hydrogen concentration with graphene domains grown in the first step as the precusor.The evolution behavior of the graphene nanostructure with the hydrogen concentration was systematically investigated.Two roles of the hydrogen,namely growth and etching modes,were clearly disclosed and a possible mechanism was proposed.Secondly,a growth-etching method was developed using the CuO nanoparticle as nucleation and etching site,and the double hexagonal graphene ring was successfully synthesized on Cu foil for the first time.First,the CuO nanoparticle was used as nucleation and etching site,the influence of etching time on the hexagonal graphene ring was studied,which validated preliminarily the feasibility of the growth-etching method.The double hexagonal graphene ring was perfectly synthesized by repeating growth-etching technique with the suitable size of graphene as the precursor,which fully confirmed validity and controllability of the growth-etching method developed here.Moreover,the double hexagonal graphene ring is not only of high quality with a single-crystalline and monolayer structure,but also has excellent electrical performance by futher characterization and analysis.Finally,the forming regularity of grain boundaries in graphene have been studied preliminarily using the multinuclear growth method and mononuclear growth method respectively.Usually,the grain boundaries are uncertain and hard to be controlled using the multinuclear growth method.While the evolution behaviour and forming regularity of grain boundaries in graphene is well observed using mononuclear growth method.The results shown here provides valuable thought for studying dynamic formation of grain boundaries in graphene,and also may offer some meaningful instructions to develop method for synthesizing high-quality graphene nanostructure.