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