Nucleation stages of carbon nanotubes on SiC(0001) by surface decomposition

Nucleation stages of carbon nanotubes (CNTs) on a SiC(0001) Si-face (4 degrees off toward [11 (2) over bar0]) by surface decomposition are investigated by means of in-situ scanning tunneling microscopy (STM). After a relatively short heating time at 1600 degrees C, moire patterns and small nuclei appear on the surface due to the evaporation of Si atoms and, as a result of this, surface graphitization. Modelling of the moire pattern indicates the formation of a single graphene sheet on top of the SiC surface. Local swelling (similar to 1 nm in diameter) of such a graphene sheet, possibly resulting from the compressive stress at the graphene/ SiC interface, gives rise to a CNT nucleus. In the stages that follow, the nucleus is continuously and unidirectionally prolonged and rolled-up, which may result in a final form such as a CNT.