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Big organic molecules deposited by vacuum sublimation on reactive surfaces form highly-ordered superstructures which are often commensurate to the substrate if covalent, nondissociative bonding occurs. The orientation of the molecules at the interface can be varied depending on reactive groups, substrate surface, and coadsorbates. Deposition of highly-ordered thin films, or even organic molecular beam epitaxy (OMBE), is difficult but appears possible under certain conditions. Organic nanostructures can be produced by self-organization of covalently-bound molecules and substrate steps on high-index surfaces. Experiments with different aromatic molecules like NDCA and PTCDA as well as with oligothiophenes (a4T and EC4T) on various substrates such as Ag(l1 I), Ag(7751, Ni(l1 l), and Si(l11) are reviewed using a variety of complementary surface sensitive techniques.

The adsorption and in‐situ polymerization of monothiophene on Ag(111) has been studied by X‐ray photoemission (XPS), programmed thermal desorption (TDP) and mass spectrometry. Thiophene is physisorbed on Ag(111) and desorbs entirely below 250 K. Three different desorption peaks representing multilayers and two different monolayer states can be distinguished by TPD. X‐ray irradiation leads to polymerization in multilayers which is accelerated by enhanced substrate temperatures, whereas the polymerization process is quenched at the Ag surface.