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Your search keyword '"Auwarter W."' showing total 4 results
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4 results on '"Auwarter W."'

1. Electron coherence in a melting lead monolayer

Author

Baumberger, F., Auwarter, W., Greber, T., and Osterwalder, J.

Subjects
Monomolecular films -- Research -- Electric properties, Science and technology, Research, Electric properties
Abstract

We used angle-resolved photoemission spectroscopy to measure the electronic dispersion and single-particle spectral function in a liquid metal. A lead monolayer supported on a copper (111) surface was investigated as the temperature was raised through the melting transition of the film. Electron spectra and momentum distribution maps of the liquid film revealed three key features of the electronic structure of liquids: the persistence of a Fermi surface, the filling of band gaps, and the localization of the wave functions upon melting. Distinct coherence lengths for different sheets of the Fermi surface were found, indicating a strong dependence of the localization lengths on the character of the constituent atomic wave functions., The transition from the solid to the liquid state can have substantial effects on a material's electronic properties (1, 2). In the case of semiconducting germanium, for example, the forbidden [...]

Published
2004

2. Chiral kagome lattice from simple ditopic molecular bricks

Author

Schlickum, U., Decker, R., Klappenberger, F., Zoppellaro, G., Klyatskaya, S., Auwarter, W., Neppl, S., Kern, K., Brune, H., Ruben, M., and Barth, J.V.

Subjects
Aromatic compounds -- Structure, Aromatic compounds -- Chemical properties, Chirality -- Analysis, Gold -- Atomic properties, Gold -- Chemical properties, Nanotechnology -- Research, Chemistry
Abstract

Molecular-level scanning tunneling microscopy is used for showing the supramolecular engineering of complex, regular and long-range ordered periodic networks on a surface atomic lattice using simple linear molecular bricks. The two dimensional organic networks have ranged from a close-packed chevron pattern via a rhombic network to an unobserved supramolecular chiral kagome lattice.

Published
2008

3. Self-assembly of l-methionine on cu(111): Steering chiral organization by substrate reactivity and thermal activation

Author

Y. Pennec, Wilhelm Auwarter, Johannes V. Barth, Alexander Weber-Bargioni, Martina Dell'Angela, Agustin Schiffrin, Gregor Bavdek, A. Cossaro, Matthias Marschall, Dean Cvetko, Alberto Morgante, Joachim Reichert, Schiffrin, A., Reichert, J., Pennec, Y., Auwarter, W., WEBER BARGIONI, A., Marschall, M., Dell'Angela, M., Cvetko, D., Bavdek, G., Cossaro, A., Morgante, Alberto, and Barth, J. V.

Subjects
X-ray photoelectron spectroscopy, ADSORPTION, Dimer, Helium atom scattering, Substrate (electronics), self-assembly, amino acid, law.invention, chemistry.chemical_compound, law, Phase (matter), Cu(1 1 1), Reactivity (chemistry), Physical and Theoretical Chemistry, L-methionine, Chemistry, Carboxylic group, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Crystallography, General Energy, Self-assembly, Scanning tunneling microscope, Amino group
Abstract

The self-assembly of the amino acid L-methionine on Cu(111) was investigated under ultrahigh vacuum (UHV) conditions by scanning tunneling microscopy (STM), helium atom scattering (HAS) and X-ray photoelectron spectroscopy (XPS). The system is strongly influenced by the Substrate reactivity and the deposition temperature. The STM and HAS structural analysis yields that, for temperatures below 273 K, the biomolecules assemble in strings oriented with an angle of - 10 degrees with respect to the < 110 > axes of the substrate. For temperatures above 283 K, a regular and ordered one-dimensional (1D) phase arises following an angle of + 10 degrees with respect to the same directions. High resolution STM data of this ordered 1D arrangement evidence molecular dimerization and dimer alignment into ordered chains which are commensurate with the Cu(111) atomic lattice. XPS measurements reveal that the high temperature ordered phase consists of an exclusively anionic ensemble with a deprotonated carboxylic group and a neutral amino group, while the low temperature phase is heterogeneously composed of both zwitterionic and anionic species, depending on whether the molecules are immobilized in clusters of dimers on the free terraces or at the low-coordinated adsorption sites of the Substrate step-edges. These combined results evidence a structural transformation of the supramolecular assembly which is triggered by a thermally activated process involving the underlying Cu(111) substrate and which carries the intrinsic chiral signature of the adsorbed molecular units.

Published
2009
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4. Zwitterionic self-assembly of L-methionine nanogratings on the Ag(111) surface

Author

Dean Cvetko, Willi Auwärter, Agustin Schiffrin, Johannes V. Barth, Andreas Riemann, Y. Pennec, Alberto Morgante, Albano Cossaro, Alexander Weber-Bargioni, Schiffrin, A., Riemann, A., Auwarter, W., Pennec, Y., WEBER BARGIONI, A., Cvetko, D., Cossaro, A., Morgante, Alberto, and Barth, J. V.

Subjects
Photoemission spectroscopy, Surface Properties, SUBSTRATE-MEDIATED INTERACTIONS, METAL-SURFACES, AMINO-ACIDS, L-CYSTEINE, MOLECULAR-ORGANIZATION, NANOSTRUCTURES, Amino Acid Motifs, Molecular mechanics, Helium, law.invention, Molecular recognition, Methionine, law, Microscopy, Scanning Tunneling, Nanotechnology, Electrophoresis, Gel, Two-Dimensional, Amino Acids, Nanoscopic scale, chemistry.chemical_classification, Ions, Multidisciplinary, Molecular Structure, Temperature, Substrate (chemistry), Hydrogen Bonding, Amino acid, Crystallography, chemistry, Physical Sciences, Nanoparticles, Self-assembly, Gold, Scanning tunneling microscope
Abstract

The engineering of complex architectures from functional molecules on surfaces provides new pathways to control matter at the nanoscale. In this article, we present a combined study addressing the self-assembly of the amino acid l -methionine on Ag(111). Scanning tunneling microscopy data reveal spontaneous ordering in extended molecular chains oriented along high-symmetry substrate directions. At intermediate coverages, regular biomolecular gratings evolve whose periodicity can be tuned at the nanometer scale by varying the methionine surface concentration. Their characteristics and stability were confirmed by helium atomic scattering. X-ray photoemission spectroscopy and high-resolution scanning tunneling microscopy data reveal that the l -methionine chaining is mediated by zwitterionic coupling, accounting for both lateral links and molecular dimerization. This methionine molecular recognition scheme is reminiscent of sheet structures in amino acid crystals and was corroborated by molecular mechanics calculations. Our findings suggest that zwitterionic assembly of amino acids represents a general construction motif to achieve biomolecular nanoarchitectures on surfaces.

Published
2007

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