"One Dimensional pi-Conjugated Band Dispersion In Polymeric Chains"
Who: Guillaume Vasseur, Institut Jean Lamour, Université de Lorraine-CNRS, France
Place: Donostia International Physics Center (DIPC).Paseo Manuel de Lardizabal, 4, Donostia
Date: Monday, 19 May 2014, 12:00
One Dimensional Pi-Conjugated Band Dispersion In Polymeric Chains
G.Vasseur1, Y. Fagot-revurat1, J. Lipton-Duffin2, V. Meunier3, M. Di Giovannantonio4, D. Perepichka5, L. Cardenas2, G. Contini4, F.Rosei2, D.Malterre1
1. Institut Jean Lamour, Université de Lorraine - CNRS, Vandoeuvre-les-Nancy, France
2. Institut National de la Recherche Scienti?que, Varennes, Canada
3. Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, New York, United States
4. Istituto di Struttura della Materia, CNR, Roma, Italy
5. Department of Chemistry and Centre for Self-Assembled Chemical Structures,McGill University, Montreal, Canada.
During the last two decades, the development of novel architectures based on molecular or supramolecular devices becomes a key challenge in the field of nanotechnology. The functionalization of surfaces by self-assembling of covalently bounded networks from single molecular building blocks is an increasing popular field with potential applications in nano-electronic and optoelectronic . In this way, the synthesis and assembly of Pi-electron functional organic molecules has been recently studied extensively .
In the context of a collaboration between the INRS (Montréal), the ISM (Rome) and the IJL (Nancy), a surface-catalyzed dehalogenative polymerization has been evidenced for the (1,4)-dibromobenzene (DBB) on copper (110) interface by combining scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), near edge X-ray absorption fine structure spectroscopy (NEXAFS) and first-principles calculations . Above 200°C, the organometallic (OM) intermediate, obtained for room temperature deposition, polymerize into a very well organized 1D polymer formed by phenyl cycles assembled in arm-chair configuration. Similarly, the same dynamic can be evidenced for diiodobenzene (DIB) evaporated on copper (110). During this seminar I will present our last results on electronic properties of organometallic and polymeric phases for DBB and DIB investigated by STS and ARPES. First, we will discuss on the chemical sensitivity in STS to metallic bonds which allowed us to determine the structure of two new organometallic phases for DIB and 1ML-DBB / Cu(110). Then I will focus on the study of a "transverse" polymer formed at the saturation of the surface. ARPES intensity maps allowed us to identify a one dimensional graphene-like strongly dispersive Pi-band on 7.2 eV, below the Fermi energy, interpreted as a consequence of the polymerization process. By STS we also observed LUMO's confined states for small chains over the Fermi level. By increasing the length of chains, the loss of confinement induces the formation of a continuous dispersive band which crosses the Fermi energy, conferring a metallic character to the polymer.
 L. Grill, M. Dyer, L. Lafferentz, M. Persson, M.V. Peters and S. Hecht, Nature nanotech. 2, 687-691 (2012)
 J. Cai, P. Ruffieux, R. Jaafar, M. Bieri, T. Braun, S. Blankenburg, M. Muoth, A.P. Seitsonen, M. Saleh, X. Feng, K. Mullen and R. Fasel, Nature 466, 470-473 (2010)
 M. Di Giovannantonio, M. El Garah, J. Lipton-Duffin, V. Meunier, L. Cardenas, Y. Fagot Revurat, A. Cossaro, A. Verdini, D.F. Perepichka, F. Rosei and G. Contini, ACS Nano 7, 8190 (2013)