Ma. Ansell et al., Coordinate covalent cobalt-diisocyanide multilayer thin films grown one molecular layer at a time, LANGMUIR, 16(3), 2000, pp. 1172-1179
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.