A 2.5 monolayer (ML) thick graphene film grown by chemical vapor deposition of thermally dissociated C(2)H(4) on MgO(111), displays a significant band gap. The apparent six-fold low energy electron diffraction (LEED) pattern actually consists of two three-fold patterns with different 'A' and 'B' site diffraction intensities. Similar effects are observed for the LEED patterns of a 1 ML carbon film derived from annealing adventitious carbon on MgO(111), and for a 1.5 ML thick graphene film grown by sputter deposition on the 1 ML film. The LEED data indicate different electron densities at the A and B sites of the graphene lattice, suggesting that the observed band gap results from lifting the graphene HOMO/LUMO degeneracy at the Dirac point. The data also indicate that disparities in A site/B site LEED intensities decrease with increasing carbon overlayer thickness, suggesting that the graphene band gap size decreases with increasing number of graphene layers on MgO(111).

Electrons may experience inelastic coupling with the organic spacer layer during tunneling between two ferromagnetic electrodes. To probe the transport behavior of spin-polarized electrons in organic materials, organic spin valves were fabricated utilizing a relatively thin organic barrier of 3,4,9,10-perylene-teracarboxylic dianhydride (PTCDA) dusted with alumina at the organic/ferromagnetic interfaces. These structures, with an organic barrier layer, exhibited magnetoresistance up to 12% at room temperature. In studies of the inelastic tunneling spectrum, the observed characteristic peak of the organic layer provides direct evidence of the interplay between the spin-polarized electrons and the organic molecules. Combining the inelastic tunneling results with a simple molecular vibration calculation yields further information on the configuration of the molecular thin film and the possible tunneling states of the spin-polarized electrons. Such interplay indicates a true transport of spin-polarized electrons through organic material rather than through defects or interdiffusion compounds formed at the interfaces within the organic spin valve.

The surface termination of In4Se3(001) and the interface of this layered trichalcogenide, with Au, was examined using x-ray photoemission spectroscopy. Low energy electron diffraction indicates that the surface is highly crystalline, but suggests an absence of C2v mirror plane symmetry. The surface termination of the In4Se3(001) is found, by angle-resolved x-ray photoemission spectroscopy, to be In, which is consistent with the observed Schottky barrier formation found with this n-type semiconductor. Transistor measurements confirm earlier results from photoemission, suggesting that In4Se3(001) is an n-type semiconductor, so that Schottky barrier formation with a large work function metal, such as Au, is expected. The measured low carrier mobilities could be the result of the contacts and would be consistent with Schottky barrier formation.

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