Nano Lett. 12, 4503–4507 (2012)

Almost immediately after the discovery of the extraordinary transport properties of graphene it was realized that using this material in devices required the synthesis of large-area, high-quality single-layer sheets. Among the various procedures attempted so far, growing graphene on metal surfaces seems to be the most promising. Unfortunately, the electrical conductivity of the metal substrate masks that of graphene. The issue can be overcome by transferring the material to an insulating substrate, but this usually degrades the quality of the graphene. Rosanna Larciprete, Philip Hofmann and colleagues have now developed an elegant solution to the problem by inserting a layer of silica between the graphene and the metal substrate to isolate them electrically.

The researchers — who are based at various institutes in Italy and Denmark — first grew graphene on a ruthenium surface using a commonly used procedure. Then they exposed it to a silicon atmosphere at very high temperature (720 K). X-ray photoemission spectroscopy (XPS) confirmed the formation of a ruthenium silicide layer under the graphene sheet, and subsequent exposure to an oxygen atmosphere induced the formation of a silica layer, which was also confirmed by XPS.

Intercalation of various elements, including silicon, between graphene and metal substrates has been demonstrated before, but the intercalation of silica ensures electrical isolation of graphene. This was corroborated by resistance measurements, which recorded resistances much higher than that expected for ruthenium but typical of a two-dimensional conductor.