Quasi-1D pentacene structures assembled on the vicinal Cu(1 1 9) surface Luca Gavioli a, * , Mattia Fanetti a , David Pasca b , Miriam Padovani a , Massimo Sancrotti a,c , Maria Grazia Betti b a INFM, Dipartimento di Matematica e Fisica, Universit a Cattolica, via dei Musei 41, I-25121 Brescia, Italy b INFM, Universit a di Roma ‘‘La Sapienza’’, Piazzale Aldo Moro 2, I-00185 Roma, Italy c TASC- INFM, Strada Statale 14, Km 163.5, I-34012 Trieste, Italy Available online 11 June 2004 Abstract We present a morphological study of pentacene (C 22 H 14 ) long range ordered molecular wires assembled on the Cu(1 1 9) vicinal surface. At low pentacene coverage, scanning tunneling microscopy (STM) shows single molecules adsorbed flat on the surface, presenting the long side parallel to the terrace direction. At the completion of the first layer, the molecules line up in regular rows extending along the step edges. By increasing the coverage, the rows of pentacene molecules form a densely packed structure, presenting a pyramid-like shape perpendicular to the steps. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Scanning tunneling microscopy; Aromatics; Vicinal single crystal surfaces 1. Introduction The ability to produce high-quality films of organic molecules is an important requirement to produce new single-crystal organic-based devices [1]. The basic mechanism that controls the trans- port properties generally resides at the interface, and a complete understanding of the driving forces leading to the formation of long range ordered supramolecular structures with specific electronic properties is still an open research field. A good candidate for investigating organic material growth in the field of plastic electronics [2] is pentacene (C 22 H 14 ) [1]. The pentacene mole- cule, constituted by five linear benzene rings, generally does not show long range ordered structures when deposited on flat metal substrates at room temperature. A local order of a pentacene molecules layer laying flat on the Au(1 1 1) surface, arranged in rows showing different separation distances and molecular orientations, has been detected by STM [3]. A long range ordering with a (3 · 6) symmetry and a periodicity commensurate with the substrate lattice parameters has been also observed on the Au(1 1 0) surface [4]. A 2D or- dered layer on Cu(1 1 0) with the molecules adopting a close-packed side-by-side orientation has been obtained after a thermal treatment [5]. Previous studies of benzene or acenes (C 4nþ2 H 2nþ4 ) like naphthalene (n ¼ 2) or anthracene (n ¼ 3) deposited on surfaces of noble metals with unfilled * Corresponding author. Tel.: +39-030-2406-730; fax: +39- 030-2406-742. E-mail address: l.gavioli@dmf.unicatt.it (L. Gavioli). 0039-6028/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.susc.2004.05.123 Surface Science 566–568 (2004) 624–627 www.elsevier.com/locate/susc