Physik: DPG Tagungen - Sitzung O 28 - Nano-science.de

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Physik: DPG Tagungen - Sitzung O 28 http://www.dpg-tagungen.de/archive/2004/o_28.html O 28.49 Poster Mi 16:00 Bereich C Generation of metal nanodroplets and experiments on their velocity and landing •Anja Habenicht, Michael Olapinski, Johannes Boneberg und Paul Leiderer Universität Konstanz, FB Physik SFB 513, 78457 Konstanz An interesting observation can be made when gold nanostructures placed on a substrate are illuminated with an intensive short laser pulse: Just above the melting threshold all particles leave the surface. The reason for this effect is the wetting behaviour: Gold does not wet the glass substrate, thus the liquid nanostructures can reduce their surface energy by reforming to spheres. If this transformation is sufficiently fast the liquid spheres take off from the surface. The velocity of the flying nanodroplets can be determined by analyzing the time dependent scattering signal which arises when the droplets cross a sheet of light. This signal can be converted into a velocity dependent particle density. The particles cool down during the flight due to thermal radiation. By catching the nanodroplets on a further substrate at different distances, the droplets can be landed either in liquid or in solid state. First results of velocity measurements and the impact experiments are shown. O 28.50 Poster Mi 16:00 Bereich C Nanostructuring using colloid crystals and dry and wet etching techniques •Manuel Gonçalves 1 , Moritz Trautvetter 2 , Oliver Dubbers 2 , Sebastian Fricker 2 , Alfred Plettl 2 , Paul Ziemann 2 und Othmar Marti 1 1 Department of Experimental Physics, University of Ulm, D-89069 Ulm, Germany 2 Department of Solid State Physics, University of Ulm, D-89069 Ulm, Germany Sub-wavelength structures produced using latex colloidal crystals have been intensively investigated in the last years, namely to produce photonic crystals. One of most known techniques to produce nanoparticles using monolayers of latex spheres as lithographic masks, has been developed by U. Ch. Fischer et al. in 1981 (Fischer projection patterns or FPP). This method, however, is restricted to few possible particle shapes. We have developed two techniques to extend the number the possible shapes and geometrical configurations, using colloidal crystals and FPPs combined with dry and wet etching techniques. Inverse projection pattens have been produced using the common FPPs combined with wet chemical etching. We have also developed a technique to produce sub-wavelength structures using monolayers of latex spheres etched by a plasma. The size and the separation of the particles can be controlled by the etching level and by selecting the size of the latex spheres. Several nanostructures using these techniques have been produced and characterized by scanning probe microscopy and scanning electron microscopy. The optical properties of some samples produced using metallic thin films are also presented. O 28.51 Poster Mi 16:00 Bereich C Application of imaging XPS for chemical analysis and mapping of magnetic domains •S. Schmidt 1 , M. Escher 2 , F. Forster 1 , D. Funnemann 3 , B. Krömker 3 , M. Merkel 2 , F. Reinert 1 und N. Weber 2 2 Focus GmbH 3 Omicron Nanotechnology GmbH 1 Universität des Saarlandes, FR 7.2 Experimentalphysik, Postfach 151150, 66041 Saarbrücken We present first scientific applications of a new NanoESCA [1] spectrometer: we have used the good spatial resolution to investigate the chemical structure of plain and decorated grain boundaries in two reference materials Al 0.98 Sn 0.02 and Cu 0.98 Bi 0.02 [2]. The data measured at the high-intensity small-spot beamlines of 18 of 32 07.06.2009 22:14
Physik: DPG Tagungen - Sitzung O 28 http://www.dpg-tagungen.de/archive/2004/o_28.html BESSY II also exhibit detailed information about the oxidation processes in such materials. In Al 0.98 Sn 0.02 we have detected small differences in the binding energy of the Al 2p XPS peak of 30-50 meV that could be related to different grain orientations. We also present data taken on the nanowire prototype system Cu/ZnSe 2 [3] where the Cu-nanowires are effectively protected against oxidation even during air-exposure. Using cicular polarization at the undulator we were able to map magnetic domains [4] in a Fe single crystal at the Fe 2p XPS core-level with high contrast. [1] D. Funnemann et al., Bessy Annual Report, 2002 [2] S. Schmidt et al., Bessy Annual Report, 2002 [3] R. Adelung et. al, Adv. Mater. 14, 15, p. [1056-1061, 2002 4] C. Schneider et al., Rep. Prog. Phys, 65, R1785-R1839, 2002 O 28.52 Poster Mi 16:00 Bereich C Lead on hydrogen terminated Si(111): A comparison of two different deposition techniques •C. Rettig 1,2 , H. Hövel 1 , V. Chamard 1 , S. Warren 2 , T. H. Metzger 2 und J. Zegenhagen 2 1 Universität Dortmund, Experimentelle Physik I, D-44221 Dortmund (Germany) 2 European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble (France) We studied the epitaxy of electrochemically deposited Pb clusters on Si(111):H dependent on the applied overpotential. The former measurements [1] and the present investigations are carried out in-situ using Cyclic Voltammograms and Surface X-ray Diffraction (SXRD). The specular measurements show a predominant alignment of the Pb(111) plane parallel to the Si(111) plane. In the sample plane the Pb Clusters are aligned along the high symmetry direction of Si confirmed by Grazing Incidence Diffraction (GID). New results indicate a dependency of the Pb clusters alignment in the sample plane on the applied overpotential. Presently we extend our measurements to Ultra High Vacuum (UHV) environment with in-situ deposition of Pb on Si(111):H. This system is studied by Scanning Tunneling Microscopy/Spectroscopy (STM/STS), Low Energy Electron Diffraction (LEED) and Ultraviolet Photoelectron Spectroscopy (UPS). [1] J. C. Ziegler et al., Surf. Sci. 452, 150 (2000). O 28.53 Poster Mi 16:00 Bereich C Lifetime of particle plasmon excitation in Ag-Nanoparticles •Daniela Bayer, Alexander Mönnich, Jörg Lange, Michael Bauer und Martin Aeschlimann Dep. of Physics, University of Kaiserslautern The dynamics of photoexcited hot electrons are of special interest for a large variety of modern fields such as fs-photochemistry and (magneto)electronics. These specific applications depend critically on the inelastic lifetime T 1 of these hot electrons. Hence, the question arises if it would be possible to manipulate T 1 in a specific way. In this poster, we will demonstrate that the specific structuring of the material on a nanometer scale can govern the effective electron dynamics. Our interest is focused on localized collective oszillations of the electron gas in metal particles of nanometer size, the so-called particle plasmons. A. Liebsch predicts that under certain conditions the plasmon dephasing time at off-resonance excitation can be longer than on resonance due to the wavelength dependence of radiation damping. Making use of the Time-Resolved Two-Photon-Photoemission (TR-2PPE), our investigation concentrates on elliptically shaped silver nano-particles under resonant and off-resonant conditions. Experimental results confirming Liebschs theory will be shown. O 28.54 Poster Mi 16:00 Bereich C 19 of 32 07.06.2009 22:14
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