The growth of nanoscopic oligophenylene and oligothiophene aggregates on muscovite mica by vacuum deposition has been investigated. In the case of para-phenylenes a dipole assisted self assembly generation of needle-like aggregates is observed on mica. At optimum fiber growth temperature phenylene aggregates grow in most cases without a layer of upright oriented molecules. In contrast, vacuum deposition of oligothiophenes results simultaneously in fibers of laying molecules as well as islands of upright molecules. Since both phenylenes and thiophenes are strongly polarizable but differ in the lattice parameters of the resulting crystalline overlayers a direct comparison between the two classes of molecules allows us to study the role of epitaxy on the growth of nanoaggregates. Besides straight aggregates we also observe thiophene rings on water and methanol treated mica surfaces, which consist of radially oriented, laying molecules.
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