Highly oriented POPOP films grown on the KCl(001) surface

Some simple aromatic molecules have interesting electro-optical properties and potential for use in organic optoelectronic devices. The structure of t hin films of the electroluminescent molecule POPOP (1,4-bis(5-phenyloxazol- 2-yl)benzene) grown in vacuum on KCI(OO I) substrates was studied with graz ing-incidence X-ray diffraction. POPOP films consist of monoclinic bulk-lik e crystallites with (1 0 2)(POPOP)parallel to (0 0 1)(KCl) which show a str ong preferential orientation with [0 1 0](POPOP)parallel to [1 1 0](KCl). T he microstructure of the films is characterized by needle-shaped crystallit es forming 90 degrees, 180 degrees, and some 45 degrees domain walls. The m orphology of the films is determined by an internal (1 0 2) molecular packi ng plane in the bulk POPOP structure and the corrugation of the substrate. (C) 2000 Elsevier Science B.V. All rights reserved.