Epitaxial graphene is formed on vicinal SiC͑0001͒ surfaces via high temperature annealing in vacuum. Steps act as a significant "kicker" of graphene nucleation to feed C atoms. At elevated temperatures, graphene growth is controlled by the decomposition of Si-C bonds at step edges, Si desorption, and C diffusion on the surface. The limited Si desorption is due to the dependence of the growth rate on the thickness of graphene layers. The fabricated graphene layer͑s͒ acts as a Si-diffusion barrier, which in turn induces local thermal equilibrium between the graphene layer and the SiC surface. C atoms preferentially diffuse along the steps, resulting in anisotropic layer-by-layer growth, which is characteristic in this system.

Without any assumptions regarding residual impurity species in an undoped semiconductor, it is experimentally demonstrated that the densities and energy levels of impurities can be precisely determined by the graphical peak analysis method based on Hall-effect measurements, referred to as free carrier concentration spectroscopy (FCCS). Using p-type undoped GaSb epilayers grown by molecular beam epitaxy (MBE), the densities and energy levels of several acceptor species are accurately determined. Five acceptor species are detected in the undoped GaSb epilayers grown by MBE, while two are also found in ptype undoped GaSb wafers. A 21-41 meV acceptor and a 75-99 meV acceptor exist both in the epilayers and in the wafer. On the other hand, a 164-181 meV acceptor is detected in epilayers grown at an Sb 4 /Ga flux beam equivalent pressure ratio of 8 or 10, while a 259 meV acceptor is found in the epilayer grown at Sb 4 /Ga = 6. In addition, a very shallow acceptor, which is completely ionized at 80 K, is found in the epilayers. The densities of the very shallow acceptor and the 21-41 meV acceptor are minimum at Sb 4 /Ga ¼ 8, which makes the hole concentration lowest in the temperature range of the measurement.

Thermal decomposition of vicinal SiC substrates with self-organized periodic nanofacets is a promising method to produce large graphene sheets toward the commercial exploitation of graphene's superior electronic properties. The epitaxial graphene films grown on vicinal SiC comprise two distinct regions of terrace and step; and typically exhibit anisotropic electron transport behavior, although limited areas in the graphene film showed ballistic transport. To evaluate the role of terraces and steps in electron transport properties, we compared graphene samples with terrace and step regions grown on 4H-SiC(0001). Arrays of field effect transistors were fabricated on comparable graphene samples with their channels parallel or perpendicular to the nanofacets to identify the source of measured reduced mobility. Minimum conductivity and electron mobility increased with the larger proportional terrace region area; therefore, the terrace region has superior transport properties to step regions. The measured electron mobility in the terrace region, ∼1000 cm2/Vs, is 10 times larger than that in the step region, ∼100 cm2/Vs. We conclusively determine that parasitic effects originate in regions of graphene that grow over step edges in 4H-SiC(0001)

The amount of pyridine (py) is essential for the outcome of the efficient addition of aryl copper compounds to [60]fullerene on a 20‐mg to 1‐g scale (see scheme). It controls—in addition to the installation of an ortho‐methyl group on the aryl reagent—the regioselectivity and the number of aryl groups introduced. The tenfold‐addition adduct may be further converted into the corresponding double‐decker metallocene.

Anisotropic transport in graphene field-effect transistors fabricated on a vicinal SiC substrate with a self-organized periodic nanofacet structure is investigated. Graphene thermally grown on a vicinal substrate contains two following regions: atomically flat terraces and nanofacets (atomically stepped slopes). The graphene film at a nanofacet is continuously connected between two neighboring terrace films. Anisotropic transport properties are clearly observed, indicating a difference in the graphene properties of the two regions. The observed anisotropic properties are discussed in terms of the effects of nanofacet structures on conductivity and electron mobility.