Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 41: Poster Session I (Semiconductor Substrates: Epitaxy and growth; Semiconductor Substrates: Adsorbtion; Semiconductor Substrates: Solid-liquid interfaces; Semiconductor Substrates: Clean surfaces; Oxides and insulators: Epitaxy and growth; Oxides and insulators: Adsorption; Oxides and insulators: Clean surfaces; Organic, polymeric and biomolecular films - also with adsorbates; Organic electronics and photovoltaics, Surface chemical reactions; Heterogeneous catalysis; Phase transitions; Particles and clusters; Surface dynamics; Surface or interface magnetism; Electron and spin dynamics; Spin-Orbit Interaction at Surfaces; Electronic structure; Nanotribology; Solid/liquid interfaces; Graphene; Others)
O 41.78: Poster
Tuesday, March 23, 2010, 18:30–21:00, Poster B1
Influence of Neon Spacer Layers on Image-Potential States on Cu(100) — •Nico Armbrust1, Jens Güdde1, Peter Feulner2, and Ulrich Höfer1 — 1Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität, D-35032 Marburg — 2Physik-Department E20, TU München, D-85748 Garching, Germany
The binding energy and lifetime of image-potential states on metal surfaces can be drastically altered by the presence of insulating spacer layers. Previous investigations of Xe, Kr or Ar on Cu(100) showed that the effect of the decoupling depends systematically on the electron affinity of the rare-gas. Here we present an investigation of the influence of Ne spacer layers on the image-potential states on Cu(100) using time-resolved two-photon photoemission (2PPE). Neon represents a particularly interesting case because its large negative electron affinity of −1.3 eV should result in a large tunneling barrier even for very thin Ne adlayers. Experimental challenges are posed by the requirement of a low sample temperature (≤ 7 K) in combination with the optical experiment which requires an unshielded sample. Furthermore the optical excitation leads to unwanted desorption of the Ne adlayers. We find that the binding energies of the first two image-potential states are reduced by about 30% to E1=438 meV and E2=139 meV and that the lifetime of the n=1 state increases from 40 fs on the clean surface to 300 fs for only one monolayer of Ne coverage. This is an almost three times larger increase of the lifetime than that caused by one monolayer of Ar/Cu(100). With Kr or Xe layer thicknesses of more than 4 ML are required to achieve a similar degree of decoupling.