title: Temperature-resolved optical spectroscopy of pentacene polymorphs: variation of herringbone angles in single-crystals and interface-controlled thin films.
abstract: The polarization-resolved absorption spectra are determined for different pentacene polymorphs, both, for thin films grown on ZnO as well as for free-standing single crystals. A clear interrelation between the Davydov splitting of the lowest-energy singlet-exciton type transitions and the herringbone angle of the molecules in the unit cell is found. The variation in oscillator strength of the individual excitonic Davydov components with temperature is explained by a variation of this herringbone angle. The extraordinarily strong variation of the herringbone angle for Campbell phase pentacene films grown on ZnO substrates is attributed to interface-mediated strain due to the different thermal expansion coefficients of the organic and inorganic constituents.
authors.affiliation: Philipps-University Marburg, Department of Physics and Material Sciences Center, Renthof 5, D-35032 Marburg, Germany. Wolfram.Heimbrodt@physik.uni-marburg.de.
authors.forename: Ingo
authors.initials: I
authors.lastname: Meyenburg
authors.forename: Tobias
authors.initials: T
authors.lastname: Breuer
authors.forename: Andrea
authors.initials: A
authors.lastname: Karthäuser
authors.forename: Sangam
authors.initials: S
authors.lastname: Chatterjee
authors.forename: Gregor
authors.initials: G
authors.lastname: Witte
authors.forename: Wolfram
authors.initials: W
authors.lastname: Heimbrodt