title: Intra- and intermolecular band dispersion in an organic crystal.
abstract: 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.
authors.affiliation: Institute of Physics, Surface and Interface Physics, Karl-Franzens University Graz, 8010 Graz, Austria. georg.koller@uni-graz.at
authors.forename: G
authors.initials: G
authors.lastname: Koller
authors.forename: S
authors.initials: S
authors.lastname: Berkebile
authors.forename: M
authors.initials: M
authors.lastname: Oehzelt
authors.forename: P
authors.initials: P
authors.lastname: Puschnig
authors.forename: C
authors.initials: C
authors.lastname: Ambrosch-Draxl
authors.forename: F P
authors.initials: FP
authors.lastname: Netzer
authors.forename: M G
authors.initials: MG
authors.lastname: Ramsey