Organic thin films made of 3-trans-2-(pyrid-4-yl-vinyl) benzoic acid are pr
oduced by molecular beam deposition under ultra-high vacuum conditions. We
demonstrate by optical transmission measurements and second harmonic genera
tion that oblique incidence of the molecular beam results in thin films wit
h a preferential orientation of the organic molecules on amorphous substrat
es. Using Pd(110) as crystalline substrate, our STM images reveal improved
ordering due to preferential adsorption at specific lattice sites. (C) 1999
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