Noncatalytic synthesis of carbon nanotubes, graphene and graphite on SiC

Graphene and carbon nanotubes (CNT) can be produced by vacuum decomposition of SiC, but discrepancies and conflicting data in the literature limit the use of this method for CNT synthesis. A systematic study of the effects of SiC surface morphology and carbon transport through the gas phase leads to reproducible and controlled growth of arrays of small-diameter (1–4 walls) nanotubes, which show pronounced radial breathing modes in Raman spectra, on either carbon (0001¯) or silicon (0 0 0 1) face of 6H SiC wafers at 1400–1900 °C. These nanotube arrays have a very high density and are catalyst-free with no internal closures. They show a higher oxidation resistance compared to CNTs produced by catalytic chemical vapor deposition (CVD). Their integration with graphite/graphene or silica layers on SiC wafers is possible in a simple 2-step process and opens new horizons in nanoscale device fabrication.