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 17.18: Poster

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

Atomic Structure and Electronic Properties of Pt/Si(111)-√3 × √3 — •Florian Sandrock, Marc Wisniewski, Jörg Schäfer, and Ralph Claessen — Universität, Würzburg, Germany

Atomic Structure and Electronic Properties of Pt/Si(111)-√3 × √3

An increase of the electronic interaction is expected by decreasing the dimensionality of a system. In conjuction with suitably localized electrons, a metal-insulator transition can occur. While this is known from bulk structures, it is intriguing to look for such indications in surface systems. Metal adsorbates on semiconductor surfaces show a variety of two-dimensional superstructures which provide a playground to study such correlation phenomena. Among the quasi-two-dimensional reconstructions formed on the (111) surface of silicon and germanium, there are the √3 × √3 phases formed by e.g. Sn or Pb and other metals. In principle, such √3 × √3 systems can be instable against a two-dimensional charge density wave at low temperature. Moreover, the triangular lattice of this system is reminiscent of a crystal with a frustrated spin lattice, and it may be a candidate for a Mott transition at low temperature. A fascinating and yet sparsely examined system is the Pt/Si(111) √3 × √3 reconstruction, bringing a d-electron transition metal into play. Images obtained by scanning tunneling microscopy show a large area reconstruction. Dislocation defects lead to domains with threefold symmetry. Furthermore, ARPES measurements are underway which can serve to identify the metallicity of the system. Studies as a function of temperature will then explore possible phase transitions in this two-dimensional noble metal surface phase.