Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 88: Electronic structure II
O 88.3: Vortrag
Freitag, 30. März 2012, 11:00–11:15, MA 043
Electronic structure of spatially aligned graphene nanoribbons — •Steffen Linden1, Dingyong Zhong1, Alexander Timmer1, Haiming Zhang1, Nabi Aghdassi1, Xinliang Feng2, Klaus Müllen2, Harald Fuchs1, Helmut Zacharias1, and Lifeng Chi1 — 1Physikalisches Institut, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany — 2Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
On-surface covalent coupling under UHV conditions is a new concept to create robust, ordered molecular surface structures that may also exhibit novel properties [1]. Starting from specifically designed primer molecules, well-orientated armchair graphene nanoribbons (aGNRs) with well-defined widths have been obtained on a stepped gold surface. To study the structural and electronic properties of these GNRs, scanning tunneling spectroscopy (STM), angle-resolved ultraviolet photoemission spectroscopy (ARUPS) and inverse photoemission (IPE) have been conducted. STM shows the exclusive presence of 7-aGNRs and a few percent of 13-aGNRs on the substrate. The combination of ARUPS and IPE reveals bandgaps of 2.8 eV and 1.6 eV for 7-aGNRs and 13-aGNRs, respectively. These values are in between those obtained from LDA and GW calculations for freestanding aGNRs[2,3]. Thus a weak doping from the underlying gold substrate may occur. These results clearly show the development of a sizable bandgap in narrow aGNRs.
[1] J. Cai et al., Nature 466, 470 (2010), [2] J. W. Son et al., PRL 97, 216803 (2006), [3] Li Yang et al., PRL 99, 186801 (2007)