AVS 52nd International Symposium
    Surface Science Wednesday Sessions
       Session SS+EM-WeA

Paper SS+EM-WeA10
Para-Sexiphenyl Thin Films Grown by Hot Wall Epitaxy on KCl(001) Substrates

Wednesday, November 2, 2005, 5:00 pm, Room 202

Session: Organic Film Growth and Characterization
Presenter: A.Yu. Andreev, University Linz, Austria
Authors: A.Yu. Andreev, University Linz, Austria
A. Montaigne, University Linz, Austria
G. Hlawacek, University of Leoben, Austria
T. Haber, Graz University of Technology, Austria
R. Resel, Graz University of Technology, Austria
H. Sitter, University Linz, Austria
C. Teichert, University of Leoben, Austria
Correspondent: Click to Email
Para-sexiphenyl (p-6P) is a blue emitting organic semiconductor widely investigated for optoelectronic applications. Especially, p-6P thin films grown on mica(001) and KCl(001) substrates show large morphological, electrical and optical anisotropy, which makes them attractive for nano-scale optoelectronic and photonic devices. In this work, we use Atomic Force Microscopy (AFM) and X-Ray diffraction (XRD) to study the growth of p-6P on crystalline KCl substrates, in order to find the process controlling parameters. It is shown that the growth process of p-6P on KCl(001) is quite complex and can be divided preliminary in two steps. The initial growth stage is characterized by the formation of the long needle-like crystallites build of "laying" molecules (as shown by XRD), generating a rectangular network in accordance with substrate surface symmetry. If the surface coverage increases, terraced crystalline mounds composed of upright standing molecules start to develop between the needles. These mounds are clearly formed due to repeated 2D nucleation of p-6P molecules. Consequently, all terraces found are in average about 2.6 nm high, which corresponds to one monolayer of standing p-6P molecules. Further, growth is characterized by a coexistence of the constantly growing needles and mounds, whereby the last ones cover finally almost the whole surface between the needles. By means of phase imaging in AFM tapping mode, it could be clearly demonstrated that both needle-like crystallites and flat terraced mounds grow directly on the substrate surface, i.e., there is no wetting layer formed during the deposition of p-6P on KCl(001).