Conducting and Transparent Graphene-Containing Thin Silica Films (27057)
Transparent, conductive composite silica thin films produced by a sol gel process incorporating exfoliated graphene.
ADVANTAGE: Simple process to create conductive, highly transparent, robust thin films on variety of substrates versus current complex deposition techniques.
SUMMARY: Electrically conductive glass is used in a range of applications including solar reflecting glass, self-cleaning windows, electrostatic charge-dissipating coatings, solar cells and sensor devices. Conductive glasses are typically prepared by metal oxide film coating employing magnetron sputtering or chemical vapor deposition, both complex and expensive operations. Significant research has been devoted to identify a simple solution-based route to fabricate stable electrically conductive thin films.
Graphene sheets, generated from reduced exfoliated graphite oxide, have been demonstrated to impart electrical conductivity in a range of organic composites (see NU 25052). This invention now establishes that graphene can be incorporated in a silica matrix affording a conductive inorganic thin film on silicon substrates. Graphite oxide (GO), exfoliated in aqueous medium, is suspended in a silicon sol-gel, spin-coated on glass or hydrophilic SiOx/silicon substrates, chemically reduced and dried to a stable conductive and transparent thin film. Graphite oxide loadings of 11 wt% are readily produced. SEM images indicate overlapping graphene sheets with primarily in-plane orientation. The 11wt% initial GO films upon 400 ºC curing exhibited ~20 nm thickness and ~12 Å roughness (Fig. 1)
Film conductivity is proportional to graphene loading affording 0.45 S/cm at 11wt% initial GO film loading (Fig. 2), comparable to reported MWCNT/silica (0.57 S/cm at 9.3 wt% loading). Graphene incorporation produces a slight reduction in transparency as a function of loading (Fig 2). Nevertheless high transparency (~0.95) remains between 380-1000 nm wavelengths at the 11wt% initial GO loading (Fig. 3).
These transparent conductive ceramic graphene composites present a uniform, stable, tailorable material resistant to ion diffusion deterioration. The synthetic route promises a simple, efficient, and scalable manufacture process for a variety of substrates and devices.
Rodney Ruoff, SonBinh Nguyen, Sasha Stankovich, Dmitriy Dikin
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