Copper Substrate Based CVD Synthesis Of High-quality Graphene

Graphene is considered as the most promising candidate material to replace the current silicon material. It has focused the research interents for the scientists since it was discovered in 2014,due to its unique physical and chemical properties.Among the various methods for graphene preparation,chemical vapor deposition(CVD) is most widely used because of its simple operation process,controllability of area and number of layers and high quality.However, there still esxists many difficulties for the synthesis of high quality graphene film and large-scale single crystal graphene by CVD process.In this paper,the copper foil is selected as the basal material to synthesize graphene film and single crystals.Related,electrical properties of graphene field effect transistor is tested.Firstly,through our research,we found that the pretreatment of the copper substrate and the growth temperature are important to influence the quality of graphene film.Compared with the original copper,the electropolished copper was more smooth and uniform under the scanning electron microscopy.Moreover,the stripe,concave and convex like morphology was almost invisible.This was further confirmed by Raman characterization.Then we studied the quality of graphene grown under different growth temperatures and their Raman characterization was carried out.The results showed that the higher growth temperature led to better quality of the graphene film and when the growth temperature reached to 1050 ?,the defect(D) peak intensity was nearly invisible.Finally we integrated the factors influencing the quality of graphene film and the large-area and high-quality graphene film was prepared under the optimal conditions.Subsequently,we applied it to the field effect transistor and its electrical properties were tested.Secondly, the centimeter scale single crystal graphene was achieved in the atmospheric pressure CVD used the oxygen assisted method,which was currently the advanced level of in the research field.Compared with the previous graphene film,the performance of the single crystal graphene was much better,because of the absence of grain boundaries,and this was also the reason why we synthesized single crystal graphene.The influence of the flow rate of methane,hydrogen,oxygen and the water vapor dopped in the hydrogen for the nucleation density of graphene was investigated indetails.The results showed that the flow rate of methane and hydrogen have a significant impact for the nucleation of single crystal graphene. Preparation of single crystal graphene is a reversible reaction and the size of hydrogen flow is the reverse reaction agents.An excessive amount of hydrogen will lead to the etching of graphene.In addition,the effect of oxygen and water vapor on the nucleation of single crystal graphene were similar,which could be called etching effect.Considering whether it was controllable, we choosed to remove the effect of the water vapor during our experimental process.Finally,the centimetre scale single crystal graphene was successfully prepared under the optimal conditions.Then we also applied it to the field effect transistor and its electrical properties were tested.