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Electrical field-induced alignment of nonpolar hexabenzocoronene molecules into columnar structures on highly oriented pyrolitic graphite investigated by STM and SFM

Cristadoro, Anna and Ai, Min and Raeder, Hans Joachim and Rabe, Juergen P. and Muellen, Klaus (2008) Electrical field-induced alignment of nonpolar hexabenzocoronene molecules into columnar structures on highly oriented pyrolitic graphite investigated by STM and SFM. JOURNAL OF PHYSICAL CHEMISTRY C, 112 (14). pp. 5563-5566.

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp711707w

Abstract

Scanning tunneling microscopy (STM) and scanning force microscopy (SFM) have been used to study ultrathin films of a kind of nanographene, hexa(p-n-dodecylpenyl)hexabenzocoronene (HBC-PhC12), on a highly oriented pyrolitic graphite (HOPG) surface. An electrical field, applied parallel to the substrate surface during adsorption from solution and subsequent drying, has been found to align columns of HBC-PhC12 molecules with their long axes perpendicular to the field direction, independently from the HOPG lattice orientation underneath. The molecules, under field influence, adopt a tilted edge-on arrangement on the HOPG surface. On the contrary, the corresponding drop-cast films, dried in the absence of an electrical field, shows a face-on arrangement of the extended aromatic pi-system of the HBC-PhC12 discs, and no columnar structures ordered parallel to the graphite surface are recognized. Formation of unidirectionally aligned columns of HBC-PhC12 molecules is, therefore, related to the influence of the electrical field during self-assembly of HBC-PhC12 molecules on top of the conducting substrate. The electrical field competes favorably with the strong intermolecular interactions between HOPG and HBC, avoiding the epitaxial growth of thin films with the molecules in face-to-face arrangements parallel to the substrate. Our results constitute an important step toward control of the order and arrangement of functional conjugated molecules in ultrathin layers using electrical fields.

Item Type:Article
Uncontrolled Keywords:scanning tunneling miccroscopy-scanning force microscopy-graphene-ultra thin films
Subjects:Analytical Science > Microscopy and probe methods
Material Science > Functional and hybrid materials
ID Code:6106
Deposited By:IoN
Deposited On:27 Aug 2009 12:56
Last Modified:27 Aug 2009 12:56

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