Structural templating effects in molecular heterostructures grown by organic molecular-beam deposition

Powder x-ray diffraction has been used to study the structural properties of multilayered heterostructures grown by organic molecular-beam deposition and based on the molecular materials H2Pc, perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA) and Alq(3). Structural templating has been observed for multilayers of PTCDA and H2Pc, with the first layer completely disrupting the structure of subsequent layers. H2Pc adopts a new structure when deposited on PTCDA, in which the molecular plane is oriented parallel to the substrate and this configuration is retained for film thicknesses > 380 nm. The templating effect extends through molecular thin-film structures involving several different layers, but is attenuated by insertion of an amorphous layer such as Alq(3). (C) 2000 American Institute of Physics. [S0003-6951(00)02251-8].