Heat-induced Chemical Modification, Patterning Of Graphenen And Its Raman Spectra

As the only one-atom thick material that human can fabricate, graphenehas shownmagnificent properties in electronics, optics, mechanics, calorifics, biology. The valenceband and conduction band of pristine graphene touch at Dirac points, making it "semi-metal", which remamarkably limits its application. It has been attracting many researchers’attention to open a band gap while maintaining its physical and chemical properties..In this Thesis, CVD-grown graphene was convalently functionalized by heat-inducedchemical reaction. Combining with micro-contact printing technique, graphenepatterning was realized.First high-quality, large-size, single-layer graphene was synthesized on copper foilusing low pressure CVD method. Through hundreds of experiments on growingconditions, it was found that the gas flow ratio of CH4(carbon source) to H2(carrier gas)played a crucial role in the growth.effects the products greatly.Large-size graphene cannot be obtained with low ratio (CH4:H2), while high ratio leads to low quality even bi-layer graphene. Growth temperature could affect the quality of the graphene. Highergrowth temperature brought better quality.Second, graphene was chemically modified after transferred to SiO2substratewith nano-transfer technique and was characterized by Raman spectra. Heat-inducedchemical reaction between benzoyl peroxide (BPO) and graphene was develop for safetyand economical efficiency. A series of temerature-dependency experiments showed that80℃was the optimal reaction temperature.75℃greatly decrease the reaction rate andmodification level. The reaction would be not uniform above85℃. The reaction vs timeexperiments showed that there were two stages. In stage1, D*and G peaks were foundbroadened, ID/IGand ID*/IGboth increased,2D peak intensity decreased, D*and2D peaksgradually blue-shifted, indicating the defects in graphene was not too many and growingwith time. In stage2, D*peak was found narrowed, ID/IGand ID*/IGdecreased, indicatingthe increase of defects in grapheneBut The narrowing G peak,gradually red-shifted D*and2D peaks, as well as increasing2D peak intensity were found.Third, For the purpose of graphene-device produce, covalently patterning ofgraphene was realized by combining heat-induced chemical reaction and micro-contact printing. BPO molecule pattern was prepared on graphene by micro-contact printing.Subsequently, the reaction between BPO and graphenen was activated by heat. Aconvalently patterned graphenen grating with700nm wide strips was fabricated.