Orientation and electronic properties of phthalocyanines on polycrystalline substrates

We review the molecular orientation of phthalocyanines as representatives of flat, pi-conjugated molecules on different polycrystalline substrates. Thin films with a thickness of similar to 10-50 nm are often highly ordered on several substrates. The molecular orientation, however, can be radically different for single crystalline model substrates and for relatively ill defined polycrystalline substrates. Moreover, it is important to distinguish between the growth of the first organic layer(s) at the substrate surface and the growth in films of a thickness of several nanometers: Differently oriented, buried interfacial layers of few monolayers were observed in particular for polycrystalline substrates. The growth mode is discussed in terms of different molecule-molecule and molecule-substrate interactions. Consequences for our understanding of the behavior of such films in devices are considered in context with electronic interface properties. [GRAPHICS] Possible growth models for organic molecules on rough, polycrystalline substrates. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim