NEXAFS study of a Pt-containing rod-like organometallic polymer (Pt-DEBP): molecular orientation onto HOPG, Au/Si(111), Cr/Si(111) and Si(111) surfaces

The influence of different substrates on the molecular orientation of organometallic polymer Pt-DEBP, [-Pt-(PBu3)(2)--Cequivalent toC-C12H8-Cequivalent toC-](n), has been investigated by NEXAFS spectroscopy. Thin films were deposited on HOPG, Au/Si(111), Cr/Si(111), Si(111) and stainless steel. The assignment of the spectral features has been carried out on the basis of previous STEX calculations performed on phenylacetylene model molecule in gas phase and adsorbed on Pt(111) and Cu(100). Angular dependent analysis of the pi* resonance occurring at 285.50 eV photon energy deriving by the benzene carbon orbitals showed a polarisation effect for all substrates. A preferential molecular orientation at nearly 400 to the surface normal was observed. This result might be explained by the strong interaction between sp and sp(2) carbons of the organic diethynylbiphenyl DEBP moiety contained in close chains, leading to polymer self-assembling. (C) 2004 Elsevier B.V. All rights reserved