Low-Temperature Direct Growth of Nanocrystalline Multilayer Graphene on Silver with Long-Term Surface Passivation.

A wide variety of transition metals, including copper and gold, have been successfully used as substrates for graphene growth. On the other hand, it has been challenging to grow graphene on silver, so realistic applications by combining graphene and silver for improved electrode stability and enhanced surface plasmon resonance in organic light-emitting diodes and biosensing have not been realized to date. Here, we demonstrate the surface passivation of silver through the single-step rapid growth of nanocrystalline multilayer graphene on silver via low-temperature plasma-enhanced chemical vapor deposition (PECVD). The effect of the growth time on the graphene quality and the underlying silver characteristics is investigated by Raman spectroscopy, X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and cross-sectional annular dark-field scanning transmission electron microscopy (ADF-STEM). These results reveal nanocrystalline graphene structures with turbostratic layer stacking. Based on the XPS and ADF-STEM results, a PECVD growth mechanism of graphene on silver is proposed. The multilayer graphene also provides excellent long-term protection of the underlying silver surface from oxidation after 5 months of air exposure. This development thus paves the way toward realizing technological applications based on graphene-protected silver surfaces and electrodes as well as hybrid graphene-silver plasmonics.