Metal-Free Growth of Nanographene on Silicon Oxides for Transparent Conducting Applications

Conventional methods to prepare large-area graphene for transparent conducting electrodes involve the wet etching of the metal catalyst and the transfer of the graphene film, which can degrade the film through the creation of wrinkles, cracks, or tears. The resulting films may also be obscured by residual metal impurities and polymer contaminants. Here, it is shown that direct growth of large-area flat nanographene films on silica can be achieved at low temperature (400 degrees C) by chemical vapor deposition without the use of metal catalysts. Raman spectroscopy and TEM confirm the formation of a hexagonal atomic network of sp2-bonded carbon with a domain size of about 35 nm. Further spectroscopic analysis reveals the formation of SiC between the nanographene and SiO2, indicating that SiC acts as a catalyst. The optical transmittance of the graphene films is comparable with transferred CVD graphene grown on Cu foils. Despite the fact that the electrical conductivity is an order of magnitude lower than CVD graphene grown on metals, the sheet resistance remains 12 orders of magnitude better than well-reduced graphene oxides.