| Graphene,a two-dimensional carbon material with single atom thickness,has excellent properties such as high electron mobility,high transmittance and high thermal conductivity.It has great application value in the fields of electronic devices,energy storage materials,composite materials,and so on.At present,the graphene prepared by chemical vapor deposition(CVD)has small domain size,many lattice defects and low photoelectric properties.In addition,the relationship between the number of graphene layers and the optional and electric properties is not clear.In this paper,high quality single-layer graphene films were prepared by optimizing the graphene chemical vapor deposition process,and 1-5 layers graphene films were prepared by "transfer/superposition" method.The effects of graphene layers on the optional and electric properties were studied.The main work is as follows:Firstly,with methane as the precursor,the effects of process parameters such as growth chamber structure,methane flow rate,growth temperature,oxided substrate and heating atmosphere on the nucleation and growth of graphene during CVD growth were studied systematically.On this basis,the graphene single crystal domains with a size of 800 microns and regular hexagonal morphology were prepared by optimizing the process parameters.The preparation process of high quality graphene single crystal domains was optimized.In order to further prepare high-quality single-layer graphene films,the process of preparing single-layer graphene was optimized continuously.The surface structure of copper foil was optimized by heating and annealing in nitrogen atmosphere after oxidated for 20 minutes.The random nucleation density of graphene was inhibited at 1050℃,with 0.8sccm methane flow rate and 100sccm hydrogen flow rate at last.In these conditions,high quality single-layer graphene films were prepared.Finally,1-5 layers of graphene films were fabricated by "transfer/superposition" method.Raman characteristic peaks of graphene with different layers were measured by Raman spectrometer.The transmittance and square resistance of graphene films with different layer were respectively measured by ultraviolet-visible spectrophotometer and portable resistivity tester.The results show that the transmittance of single layer graphene film is 94.3%at wavelength of 550nm,and the square resistance is 678Ω/□.With the increase of layers,the transmittance and square resistance of graphene reduce constantly.With each layer increasing,the transmittance decreases by 3%,and the square resistance decreases by 100Ω/□. |
