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Science 20 July 2007:
Vol. 317. no. 5836, pp. 351 - 355
DOI: 10.1126/science.1143239
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Reports

Intra- and Intermolecular Band Dispersion in an Organic Crystal

G. Koller,1*{dagger} S. Berkebile,1* M. Oehzelt,1 P. Puschnig,2* C. Ambrosch-Draxl,2 F. P. Netzer,1 M. G. Ramsey1*{dagger}

The high crystallinity of many inorganic materials allows their band structures to be determined through angle-resolved photoemission spectroscopy (ARPES). Similar studies of conjugated organic molecules of interest in optoelectronics are often hampered by difficulties in growing well-ordered and well-oriented crystals or films. We have grown crystalline films of uniaxially oriented sexiphenyl molecules and obtained ARPES data. Supported by density-functional calculations, we show that, in the direction parallel to the principal molecular axis, a quasi–one-dimensional band structure of a system of well-defined finite size develops out of individual molecular orbitals. In contrast, perpendicular to the molecules, the band structure reflects the periodicity of the molecular crystal, and continuous bands with a large dispersion were observed.

1 Institute of Physics, Surface and Interface Physics, Karl-Franzens University Graz, 8010 Graz, Austria.
2 Chair of Atomistic Modeling and Design of Materials, University of Leoben, 8700 Leoben, Austria.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: georg.koller{at}uni-graz.at (G.K.); michael.ramsey{at}uni-graz.at (M.G.R.)

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Reconstruction of Molecular Orbital Densities from Photoemission Data.
P. Puschnig, S. Berkebile, A. J. Fleming, G. Koller, K. Emtsev, T. Seyller, J. D. Riley, C. Ambrosch-Draxl, F. P. Netzer, and M. G. Ramsey (2009)
Science 326, 702-706
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