Graphene formed on SiC under various environments: comparison of Si-face and C-face

The morphology of graphene on SiC {0 0 0 1} surfaces formed in various environments including ultra-high vacuum, 1 atm of argon and 10(-6)-10(-4) Torr of disilane is studied by atomic force microscopy, low-energy electron microscopy and Raman spectroscopy. The graphene is formed by heating the surface to 1100-1600 degrees C, which causes preferential sublimation of the Si atoms. The argon atmosphere or the background of disilane decreases the sublimation rate so that a higher graphitization temperature is required, thus improving the morphology of the films. For the (0 0 0 1) surface, large areas of monolayer-thick graphene are formed in this way, with the size of these areas depending on the miscut of the sample. Results on the (0 0 0 (1) over bar) surface are more complex. This surface graphitizes at a lower temperature than for the (0 0 0 1) surface and consequently the growth is more three-dimensional. In an atmosphere of argon the morphology becomes even worse, with the surface displaying markedly inhomogeneous nucleation, an effect attributed to unintentional oxidation of the surface during graphitization. Use of a disilane environment for the (0 0 0 (1) over bar) surface is found to produce improved morphology, with relatively large areas of monolayer-thick graphene.