Studies of the structure and growth mode of dotriacontane films by synchrotron x-rayscattering and molecular dynamics simulations

Abstract

We report on synchrotron x-ray scattering experiments and moleculardynamics simulations of the structure and growth mode of dotriacontane(n-C32H66 or C32) films adsorbedon Ag(111) and SiO2-coatedSi(100) substrates. On the SiO2 surface, the x-ray measurements confirm a structural model of the solid film inferred fromhigh-resolution ellipsometry measurements in which one or two layers of C32 adsorb withthe long axis of the molecule oriented parallel to the interface followed by a monolayer inwhich the molecules have a perpendicular orientation. At higher C32 coverages,preferentially oriented bulk particles nucleate, consistent with a Stranski–Krastanov growthmode. On the Ag(111) surface, we again observe one or two layers of the ‘parallel’ film butno evidence of the perpendicular monolayer before nucleation of the preferentiallyoriented bulk particles. We compare the experimentally observed structures withmolecular dynamics simulations of a multilayer film of the homologous C24 molecule.