Study On Preparation Of Vertically-Oriented Graphene

Graphene has a honeycomb crystal structure closely arranged sp~2 hybrid carbon atoms.This single atomic layer two-dimensional crystal structure shows excellent physical and chemical properties and has attracted the attention of the whole research community in the past decade.Great progress has been made in basic research and applied research.compared with conventional graphene sheets randomly placed on substrates,vertically oriented graphene(VG)sheets have unique properties,including exposed sharp edges,non-packing morphologies,and large surface areas.their electrical,mechanical,thermal and other properties show great potential in environmental and energy fields.Plasma enhanced chemical vapor deposition(PECVD)method is widely used in the effective way of VG synthesis due to the advantages of relatively low substrate temperature,high growth selectivity and good control of nanostructure ordering.but because the morphology and structure of the VG sheets produced by PECVD strongly depend on the type of plasma source and a series of operating parameters,such as the type and composition of feedstock gas,substrate temperature and operating pressure,it is difficult to achieve large-scale controllable preparation.it is also necessary to continue to optimize the preparation process of vertically oriented graphene.This paper uses a self-designed RF plasma-enhanced chemical vapor deposition(RF-PECVD)device with methane as carbon source and hydrogen and argon as auxiliary gas.under the condition of no catalyst and post-transfer,the process of directly preparing vertically oriented graphene(VG)on different substrates(silicon wafer,copper foil,nickel foam)was investigated.Raman spectroscopy(Raman),scanning electron microscopy(SEM)and transmission electron microscopy(TEM)were used to characterize the experimental samples.The effects of different process parameters on the growth of vertically oriented graphene and the corresponding principles were analyzed to obtain the preparation process of high quality vertically oriented graphene,to lay the experimental technology foundation for the next step in the application of vertical orientation graphene.Specific content can be divided into the following parts:1、The RF plasma-enhanced chemical vapor deposition(RF-PECVD)device and the process of preparing vertically oriented graphene(VG)on silicon wafer using RF-PECVD method are systematically introduced.Through SEM、TEM、EDS、Raman comprehensive analysis of the test results,it is found that the vertically oriented graphene with good uniformity and high quality was successfully prepared on silicon wafer at 750℃growth temperature,20 min growth time and 200 W RF power.The possible growth mechanism of vertically oriented graphene is proposed by combining specific experiments and theoretical basis.2、The effects of different growth temperatures(650℃,750℃,850℃),growth time(10 min、20 min、30 min)and rf power(100 W、200 W、300 W)on the surface morphology and quality of vertically oriented graphene(VG)prepared on silicon wafers were systematically investigated.Through comprehensive analysis of SEM、TEM、EDS、Raman test results,750℃、20 min and 200W were obtained as optimal growth temperature、growth time and RF power,respectively.3、According to the best experimental parameters of the silicon wafer preparation VG,the process of preparing vertically oriented graphene on different substrates(copper foil,nickel foam,nickel plated silicon wafer,self-made graphene material)was systematically studied.Through the comprehensive analysis of SEM、TEM、EDS、Raman test results:at different growth temperatures(750℃,850℃,950℃,1050℃),1050℃is the best growth temperature for the VG prepared on copper foil;the preparation on nickel foam is consistent with the best experimental parameters for the preparation on silicon wafer;due to the presence of catalyst nickel particles,the nickel wafer can not be successfully prepared VG,but a new structure is derived;the graphene nanowall was successfully fabricated on self-made graphene materials at a growth temperature of 750℃,a growth time of 3 h and a RF power of 300 W.According to the above-mentioned different substrates(copper foil,nickel foam and silicon wafer),VG was successfully prepared,and the influence of different growth substrates on VG was further studied.