With its industrial adaptability, epitaxial graphene (EG), formed by a UHV annealing of SiC substrates, is attracting recent attention. While hexagonal SiC bulk substrates have been solely used for this purpose, benefits in use of 3C-SiC virtual substrate founded on Si substrates could be enormous. We have succeeded in fabricating a graphene film on a 3C-SiC(111) virtual substrate, which was preformed on a Si(110) substrate by gas-source molecular beam epitaxy using monomethyl silane. The geometrical matching in this configuration greatly suppresses the strain in the SiC film, which is related to this successful formation of graphene.

By conducting a 1200 • C vacuum annealing of a 3C-SiC(111) ultrathin film preformed on a Si(110) surface, we have succeeded in forming a graphene layer on a Si substrate. Raman-scattering spectrum from this surface presents a distinct 2D band, whose deconvolution into four subcomponents indicates that the film mostly consists of a two-layer graphene. The peak position is blue-shifted from that of a free-standing graphene formed by a mechanical exfoliation method, suggesting a compressive stress in the film.

Few-layers graphene is epitaxially grown on silicon substrates via SiC thin films inserted in between. We have conducted a detailed structural characterization of this graphene-on-silicon (GOS) material by Raman spectroscopy and transmission-electron microscopy, to obtain insights into the impacts of process parameters on defect formation. Results suggest that defects in graphene preferentially dwell at steps. Future flattening of the SiC surface, prior to graphene growth, is thus expected to contribute to the improvement of GOS quality.

Room temperature terahertz (far infrared) radiation emission from double grating coupled GaInAs∕AlGaAs∕GaAs heterojunctions is reported. Theoretical calculations of plasmon absorption spectrum are performed using a first principles electromagnetic approach. They correctly reproduce the frequency range and overall shape of the main (broad-band) part of the experimental spectra. The results clearly indicate that important part of the observed room temperature terahertz emission spectra can be due to the radiative decay of hot two-dimensional plasmons in the grating structure.