| Summary: | 碩士 === 國立中央大學 === 物理學系 === 105 === With all range of striking properties from high surface-to-volume ratio to extremely high electron mobility, graphene, the truly two-dimensional (2D) material, has gathered attention of researchers in various fields. However, the lack of band gap limits applicability in graphene device. Reduction form of graphene oxide (GO) is one the most popular method to engineer band gap through introduction of sp3 bonding. The electric properties can be tuned by controlling the degree of oxidation. Nevertheless, reduction of GO done by thermal process cannot recover the excellent electronic properties of graphene due to residue of oxygen-related functional groups. Hence, understanding the mechanism of reduction of graphene oxide is necessary for both the application of graphene and interaction of functional groups on a 2D material.
In this study, we show the reduction dynamics of micron-scaled defective graphene oxide patterns done on CVD-grown graphene by scanning probe lithography (SPL), which provides localized functionalization of graphene. These patterns were subsequently reduced by the irradiation of photoelectrons induced by a focused beam of soft x-ray. By in-situ monitoring the chemical configuration of the irradiated defects during the reduction process, the evolution of each oxygen functional group is resolved by scanning photoelectron microscopy (SPEM) and x-ray photoelectron spectra (XPS). Micro-Raman spectroscopy acquired before and after the reduction process revealed the structural evolution. Moreover, the characteristic time for each functional group dissociation/ formation process involved during reduction have been identified by the proposed reaction model using a set of coupled differential equations. These finding gives the details physic picture of the reduction dynamics.
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