The Influence Of Heat Treatment On The Structure And Resistance Performance Of Graphene Film

Graphene is a two-dimensional material which comprises layers of carbon atoms arranged in six-membered rings. Since its high surface area and excellent electrical conductivity, graphene is promising for Energy storage, electronics, photovoltaic materials and energy materials. With Simple process, low cost and industrialized production, the oxidation-reduction method is widely applied in preparation of graphene film, but the graphene oxide film cannot conduct since the high resistance. Therefore, the conductivity restoration of graphene oxide film is an aporia.In this study, graphene films was synthesized by two-step method. The first step consists of oxidation of graphite and self-assembly of graphene oxide film. The second step is the reduction process, in which graphene oxide film was respectively reducted by sodium borohydride(NaBH4), hydrazine hydrate(N2H4) and heat treatment under Ar. Scanning electron microscope (SEM), Transmission electron microscopy (TEM) and Raman spectra were used to characterize the morphology and microstructure of the samples. Besides, RTS-9 double electrical measurement four-point probe tester was employed to measure the resistance properties of films after heat treatment. Meanwhile, The effects of different reducting conditions like heat treatment temperature, time and film thickness on film sheet resistance were investigated.The results showed that:(1) Graphene oxide with order structure has great water-soluble because of many oxygen functional groups. Then, self-assembly Graphene oxide films have the continuous layered structure, a large surface area and excellent light transmittance. Meanwhile the film’s thickness and size are controlled by the experimental conditions.(2) Graphene films were successfully prepared by reduction of sodium borohydride, hydrazine hydrate and heat treatment. Results of FT-IR, Raman and water-solubility indicate that reduction performance of NaBH4is worse than N2H4,but heat treatment is better than N2H4.(3) The more oxygen-containing functional groups of graphene oxide films were removed with increasing heat treatment temperature, which π-bond of graphene were recovered. At the same time, the electrical conductivity of films was restored, and sheet resistance of films decreased exponentially, finally kept stable at800℃.(4) The characteristic peaks’ intensity of some oxygen-containing functional groups declined with increasing heat treatment time up to4h on heat treatment at400℃, which brought about that the sheet resistance of films dramatically reduced. However, the characteristic peaks’ intensity of those did not change significantly with increasing heat treatment time up to4h on heat treatment at800℃, which caused the sheet resistance of films remained stable about50Ω□-1.