Study Of Microwave Plasma Chemical Vapor Deposition Growth Of Graphene

Graphene is a two-dimensional crystal of carbon atoms in a honeycomb structureformed in accordance with sp2hybrid orbital, it demonstrates an excellent performance inelectricity, thermology, magnetism, optical and so on due to its unique stable structure. Ithas become a research hotspot around the world. Currently, preparation of graphene usingthe method of microwave plasma chemical vapor deposition (MPCVD) has the advantagesof lower reaction temperature, shorter time and less energy consumption. But theintroduction of the plasma can increase the defect content and reduce the continuity of thefilm. Aiming at above-mentioned practical problems, this paper investigates the effects ofprocess on the quality of films systematically, the preparation of graphene films on thenickel substrate is achieved in the MPCVD apparatus of2kW manufactured by theWoosinent company from Korea, using methane as the main carbon source and hydrogen,nitrogen and argon as the auxiliary gases. The samples are characterized by opticalmicroscopy, Raman spectroscopy and atomic force microscopy, the effects of differentprocess parameters and auxiliary gas on the deposition of graphene are analyzed, and theprocess parameters to achieve high-quality graphene films are obtained. The main researchwork includes:1. The influence of deposition pressure on growing graphene film was researched.The results indicate that the film was fewer layers and low coverage at lower air pressure.The air pressure increasing to2.7kPa, the film is reduced to about2layers, the coverageand quality have reached the optimal. Continue to increase pressure, the film layers willincrease, the surface will appear crack, coverage and continuity will decrease.2. To systematically research the effect between microwave power and the quantity ofgraphene film. The results show that film can’t be deposited at lower power, contain muchimpurity carbon. It’s difficult to identify the graphene phase clearly. With the increase ofthe microwave power, the impurity will be reduced, and the uniformity will be increased. At the condition of800W, the continuity of the film is the best. The number of films willreduce to a minimum and appear split phenomenon when the power at900W. Continue toincrease microwave power, the number of film will be increased and continuity will bereduced.3. The introduction of hydrogen on the deposition film has two sides, one handimproving the uniformity of the film, another hand increase the amount of wrinkles anddefects. The experimental results shows that the film is too many layers, uniformity is poorand cracks appear when at low hydrogen concentrate. Add hydrogen up to80sccm, the filmuniformity will increase, the whole film layers will reduce, the films at3~4layers.Continue to rise the flow of hydrogen, wrinkles and regional delaminated will appear, thenumbers of film is different, and coverage is also reduced.4. To research the influence of secondary gas to the deposition of graphenesystematically, the result shows that the introduction of the argon gas can significantlyreduce the defect of the film. The introducing of nitrogen gas can reduce the cleavage ofthe carbon source and hinder the deposition of film. It was found that the defect will reduceand the continuity will increase with the increase of the argon flow. Too much argon willbe made film layers increase. Under the condition of the introduction of nitrogen, it willmake crystal carbon increase at low methane concentration, and accelerate the type of sp3hybridization defect at very high concentrations of methane.