PACS: 68.55.B; 71.20.H; 82.65.M
Springer Online Journal Archives 1860-2000
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Abstract. Large and symmetric organic molecules (〉200 amu) can form highly-ordered adsorbate layers and thin films when they are deposited by vacuum sublimation on clean reactive surfaces. In such cases covalent bonding often occurs via the molecular π-system leading to a parallel orientation of the adsorbate as shown for oligothiophenes and PTCDA on Ag(1 1 1). A proper choice of the substrate and/or a preadsorbate may also cause an upright orientation with bonding via a reactive group of the molecule (example: NDCA/Ni(1 1 1)). Most of the used molecules yield long-range ordered monolayers with large, almost defect-free domains. The stronger the bonding and the smaller the molecule the more likely is the formation of commensurate superstructures which indicate site-specific adsorption even for such large molecules as PTCDA or EC4T. Organic epitaxy is discussed and shown for a particular system, PTCDA on Ag(1 1 1), for which the structure of the monolayer is nearly identical to that of the β-modification of PTCDA crystals, whereas on other substrates (e.g. Si(1 1 1), Ge(1 0 0)) a disordered interface and hence no true epitaxy is found.
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