title: Interface properties of organic para-hexaphenyl/α-sexithiophene heterostructures deposited on highly oriented pyrolytic graphite.
abstract: It was recently reported, that heterostructures of para-hexaphenyl (p-6P) and α-sexithiophene (6T) deposited on muscovite mica exhibit the intriguing possibility to prepare lasing nanofibers of tunable emission wavelength. For p-6P/6T heterostructures, two different types of 6T emission have been observed, namely, the well-known red emission of bulk 6T crystals and additionally a green emission connected to the interface between p-6P and 6T. In this study, the origin of the green fluorescence is investigated by photoelectron spectroscopy (PES). As a prerequisite, it is necessary to prepare structurally similar organic crystals on a conductive surface, which leads to the choice of highly oriented pyrolytic graphite (HOPG) as a substrate. The similarity between p-6P/6T heterostructures on muscovite mica and on HOPG is evidenced by X-ray diffraction (XRD), scanning force microscopy (SFM), and optical spectroscopy. PES measurements show that the interface between p-6P and 6T crystals is sharp on a molecular level without any sign of interface dipole formation or chemical interaction between the molecules. We therefore conclude that the different emission colors of the two 6T phases are caused by different types of molecular aggregation.
authors.affiliation: Institute of Semiconductor and Solid State Physics, Johannes Kepler University , Altenbergerstrasse 69, A-4040 Linz, Austria.
authors.forename: Günther
authors.initials: G
authors.lastname: Schwabegger
authors.forename: Martin
authors.initials: M
authors.lastname: Oehzelt
authors.forename: Ingo
authors.initials: I
authors.lastname: Salzmann
authors.forename: Francesco
authors.initials: F
authors.lastname: Quochi
authors.forename: Michele
authors.initials: M
authors.lastname: Saba
authors.forename: Andrea
authors.initials: A
authors.lastname: Mura
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bongiovanni
authors.forename: Antje
authors.initials: A
authors.lastname: Vollmer
authors.forename: Norbert
authors.initials: N
authors.lastname: Koch
authors.forename: Helmut
authors.initials: H
authors.lastname: Sitter
authors.forename: Clemens
authors.initials: C
authors.lastname: Simbrunner