High-Electrical-Conductivity Multilayer Graphene Formed by Layer Exchange with Controlled Thickness and Interlayer.

The layer exchange technique enables high-quality multilayer graphene (MLG) on arbitrary substrates, which is a key to combining advanced electronic devices with carbon materials. We synthesize uniform MLG layers of various thicknesses, t, ranging from 5 nm to 200 nm using Ni-induced layer exchange at 800 °C. Raman and transmission electron microscopy studies show the crystal quality of MLG is relatively low for t ≤ 20 nm and dramatically improves for t ≥ 50 nm when we prepare a diffusion controlling AlO interlayer between the C and Ni layers. Hall effect measurements reveal the carrier mobility for t = 50 nm is 550 cm/Vs, which is the highest Hall mobility in MLG directly formed on an insulator. The electrical conductivity (2700 S/cm) also exceeds a highly oriented pyrolytic graphite synthesized at 3000 °C or higher. Synthesis technology of MLG with a wide range of thicknesses will enable exploration of extensive device applications of carbon materials.