Junghun Choi

Surface property change of graphene using nitrogen ion

We introduced nitrogen ions to modify the graphene surface and its property changes were investigated. A graphene layer grown on 6H-SiC(0001) was irradiated with 100 eV nitrogen ions. Surface property changes were studied using photoemission spectroscopy (PES), near edge x-ray adsorption spectroscopy (NEXAFS), and atomic force microscopy(AFM). N 1s core level spectra show that three kinds of nitrogen species, nitrogen gas, graphite-like and pyridine-like nitrogen were induced on the nitrogen ion implanted graphene surface.

Structure and electronic properties of self-assembled Pt silicide nanowires on Si(100)

We investigated the formation of Pt silicide nanowires on a Si(100) surface using scanning tunnelling microscopy and high-resolution photoemission spectroscopy. Pt silicide nanowires with a tetragonal Pt2Si structure are formed along the step edges of Si(100). Pt-induced c(4 × 2) reconstructions also appear adjacent to the tetragonal Pt2Si nanowires. Formation of the Pt2Si nanowires is attributed to the anisotropic lattice mismatches between the tetragonal Pt2Si structure and Si(100). Scanning tunnelling spectroscopy data show that the nanowires are metallic. The stoichiometry of Pt silicide is confirmed by high-resolution photoemission spectroscopy.

Unidirectional Pt silicide nanowires grown on vicinal Si(100).

We investigated the structure and electronic properties of unidirectional Pt(2)Si nanowires (NWs) grown on a Si(100)-2 degrees off surface. We found that Pt(2)Si NWs were formed along the step edges of the Si(100)-2 degrees off surface with c(4x6) reconstructions that occurred on the terraces of Si(100) using scanning tunneling microscopy and the structure of formed NWs was found to be Pt(2)Si by core-level photoemission spectroscopy. Moreover, we confirmed that the electronic band structures of the NWs along the NW direction are different from those perpendicular to the NWs and the surface state induced by the Pt(2)Si NWs was observed with a small density of state using the angle-resolved photoemission spectra.