| Summary: | 碩士 === 國立中央大學 === 光電科學與工程學系 === 101 === Graphene is a two-dimensional monolayer of sp2-bonded carbon atoms. In cases where synthesized by chemical vapor deposition (CVD), graphene is especially a promising candidate for the flexible transparent conductive films due to its flexibility, high optical transmittance and exceptional electrical conductivity. However, when graphene is deposited by CVD, it will be polycrystalline with grain (or domain) boundaries segregating grains, which means that graphene’s electrical properties would consequently be degraded. Both multilayer stacking and carrier doping have often been adopted to reduce the sheet resistance of the graphene films, but both have their own flaws. This study aims at increasing the grain size of the graphene films in order to reduce the quantity of grain boundaries, achieving a result of low sheet resistance of single-layer graphene.
We have developed a unique method to analyze the grain density, the grain shape and the growth model of the graphene films at different processes: in order to investigate the grains of the graphene films comprehensively and find out a best procedure to fabricate graphene films with lowest sheet resistance, ImageJ, an image processing program, was utilized to analyze the grains of the grapheme films. Besides, the crystallized quality and the sheet resistance were surveyed respectively by Raman spectroscopy and four-point probe. Finally, the best procedure we have been able to find is: to grow the graphene films on electrochemical polishing Cu foils at 1070℃ with 1000 sccm Argon, 30 sccm Hydrogen and 0.5 sccm methane by ambient pressure CVD; the resulting sheet resistance of the single-layer grapheme has reached 310 Ω/□ and the average transmittance is 97.7 % between 350-1000 nm wavelengths; the sheet resistance has further reduced to 180 Ω/□ after doping process. It meets the industrial requirements of the transparent conductive films.
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