Cr Metallization of Polyphenylacetylene Thin-film Investigated By Xps

The early stages of Cr/polyphenylacetylene (PPA) interface formation have been investigated by means of X-ray photoemission spectroscopy (XPS). The core level C 1s and Cr 2p3/2 spectra of the substrate and of the metal respectively, recorded at a constant metal evaporation rate, suggest the formation of a charge-transfer complex involving the pi-conjugated chain carbons mainly, while a weak interaction with the aromatic carbons of the phenyl group occurs at initial Cr coverages (0.5-3 angstrom). The growth-mode of Cr on PPA seems to proceed at first by metal monolayer deposition followed by cluster formation