Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)

O 17.10: Poster

Montag, 26. März 2007, 17:30–20:30, Poster C

Si-nanowires and 1D-electron confinement on SiC(1102) — •Chariya Virojanadara, Martin Hetzel, and Ulrich Starke — Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart

SiC surfaces oriented perpendicular or diagonal to the basal plane should expose the complicated polytype stacking sequence along the c-axis and thus provide large unit cell surface periodicities. In combination with the typical electronic correlation effects between dangling bonds found on the basal plane surfaces this opens a route for intrinsic nanostructures with low-dimensional electronic states. On the 4H-SiC (1102) surface, i.e. an orientation cut diagonally within the bulk unit cell, surface phases of according periodicities can indeed be observed. After Si deposition and annealing to 800-900^∘C a Si-rich surface develops which shows a well-ordered (2×1) superstructure in low-energy electron diffraction (LEED). Scanning tunneling microscopy (STM) reveals the presence of adatoms that form atomic nanowires with a separation of the (2×1) unit cell size. These adatoms are positioned on top of a Si adlayer. From core level photoemission data the Si thickness can be calculated to be about 3 Å. A prominent surface state can be observed in the valence band spectra of this phase. Applying angle resolved ultra-violet photoelectron spectroscopy (UPS) to this state we can identify a one-dimensional electron confinement. Dispersion is only observed along the direction of the nanowires, not between the wires. The band width of about 0.2 eV corresponds well to the dangling bond bands observed for several basal plane surface phases.