Controllable Growth Of N-doped Graphene On Cu And Its Tunable Layer Number On Cu-Ni Alloy

Graphene,which is the two-dimensional monolayer form of sp~2-bond carbon,has gotten wide attention of people due to its outstanding physicochemical performance since it was prepared in the laboratory for the first time.However,graphene has no bandgap,and the low on/off current ratio restricts its application in electronic devices.Nitrogen atoms doped into graphene lattice can modulate the electrical properties of graphene,leading to n-type doping.Chemical vapor deposition（CVD）is the most promising method to prepare large-area and high-quality nitrogen doped graphene（NG）films.However,due to the N content of NG prepared by CVD method is generally low and NG in which mixed pyridinic N,pyrrolic N and graphitic N coexistence is still very common,the carrier mobility of NG cannot reach the expected value.In this paper,NG was synthesized by low pressure CVD.The evolution of N content and nitrogen configurations influenced by the growth parameters in NG is reported.In addition,this work introduced a reliable method of growing monolayer and bilayer NG films using CVD on Cu-Ni alloy catalyst films.The main contents of this paper are summarized as follows:In the first part,we have demonstrated the CVD method for NG growth,where acetonitrile,ethanol and ammonia,pyridine and ammonia were used as carbon and nitrogen sources,respectively.The defect density,nitrogen content and nitrogen bonding configurations of NG were controlled through growth temperature and partial pressure of precursors.The N content and defect density increased with the decrease of growth temperature,indicating that lower temperature is advantageous for obtaining high nitrogen doping by CVD.There are significant differences in thermal stability of the three kinds of nitrogen configurations.For instance,with the growth temperature rising,the percentage of graphitic N increased,while the content of pyrrolic N decreased.Therefore,we can control the configurations of the doped nitrogen in NG by changing the growth temperature.We found that N content decreased gradually with the increase of the ethanol partial pressure when ethanol and ammonia were used as precursors,while when acetonitrile,pyridine and ammonia were used as precursors,the N content increased with the rise of precursors partial pressure,indicating that the selection of C and N feedstocks also has a significant effect on nitrogen doping.In the second part,Ni was deposited on Cu foil by magnetron sputtering and then annealed at high temperature to obtain Cu-Ni alloy.The synthesis of uniform monolayer and bilayer NG films were realized on Cu-Ni alloy by optimizing the growth time as well as the partial pressure of acetonitrile.Layers of NG films can be verified by optical microscope and Raman characterization.The uniform monolayer and bilayer NG films were further confirmed by optical transmittance measurements,the former showed a transmittance of 97%for 550 nm wavelength,while for the latter,the transmittance decreased to 95%.Through the above research work,we realized the controllable preparation of NG on Cu foil by CVD method.The effect of precursors type,partial pressure and growth temperature on nitrogen doping was studied,which provides experience for controlled synthesis of NG by choosing proper growth parameters.In addition,the synthesis of large-area monolayer and bilayer NG films on Cu-Ni alloy will broaden the application of NG based electronic devices.