Coordinate covalent cobalt-diisocyanide multilayer thin films grown one molecular layer at a time

Multilayer thin films consisting of alternating layers of cobalt and 1,4-di isocyano-benzene (DiCNB) synthesized layer by layer on an amine functionali zed silicon substrate were first reported in 1996. This paper describes fur ther work in characterizing these films using X-ray photoelectron spectrosc opy (XPS), ellipsometry, attenuated total reflectance-infrared spectroscopy (ATR--IR), and reflection-absorption infrared spectroscopy (RAIRS). Ellips ometry shows the films grow uniformly, suggesting sequential binding of met al and diisocyanide components. Control experiments confirm that both compo nents are necessary for film growth and that 1-isocyano-2-phenylethane, a m ono-functional isocyanide, caps the film and terminates further growth. Alt hough the ellipsometry data suggests uniform film growth consistent with Di CNB molecules oriented perpendicular to the plane of the substrate, in acco rd with a simple model of these films, a more complex picture of the result ing film constituents is seen with further analysis. FTIR and XPS results i ndicate the presence of significant amounts of oligomeric isocyanide specie s in the films. We also report the growth of uniform multilayers of cobalt and 1,6-diisocyanohexane.