EPITAXIAL-GROWTH OF ULTRATHIN VANADYL-NAPHTHALOCYANINE FILMS ON RBI, KI AND KBR

Ultrathin films of vanadyl-naphthalocyanine (VONc) have been prepared on the (001) faces of RbI, KI, and KBr by molecular beam epitaxy. Molecular arrangements were determined by reflection high-energy electron diffraction. VONc molecules form square lattices (square-root 10 x square-root-R +/- 18.4-degrees-) on these substrates. The lattices are commensurate to the substrates and the intermolecular distance varies from 1.64 nm on RbI to 1.48 nm on KBr, in keeping with the lattice constant of the substrates. The position of the molecules is primarily determined by electrostatic interaction between molecules and the substrates. VONc molecules stay on the surface via electrostatic interaction and steric hindrance between projecting naphthalene rings is avoided by minimizing the van der Waals interaction between molecules.