H. Razafitrimo et al., INTERFACE FORMATION OF CA WITH POLY(P-PHENYLENE ALPHA,ALPHA'-DIPHENYLVINYLENE) AND POLY(P-PHENYLENE ALPHA-PHENYLVINYLENE), Polymer international, 36(2), 1995, pp. 147-153
We have investigated the interface formation of Ca with poly(p-phenyle
ne alpha,alpha'-diphenyl vinylene) (PPV-DP) and poly(p-phenylene alpha
-phenyl vinylene) (PPV-P) using X-ray photoemission spectroscopy (XPS)
. Similarly to our earlier findings in metal/PPV interface formation,
the O 1s peak shifted toward a lower binding energy as soon as Ca was
deposited on to the polymers. This was accompanied by the formation of
Ca-O, suggesting a chemical origin for the O 1s shift. By contrast, t
he C 1s peak shift toward a lower binding energy was observed relative
ly later, after about 4 Angstrom of Ca deposition. At the same time, a
new C 1s component became noticeable at about -1.5 eV relative to the
initial C 1s peak. This component signifies the possibility of polyme
r disruption by the Ca atoms to form Ca-C species. The C 1s peak shift
is attributed to Ca induced surface band bending and barrier formatio
n, as in the case of metal/PPV interface formation. The disruption of
the polymer may also induce changes in the interface electronic states
and contribute to the C 1s peak shift. From the intensity attenuation
analysis, we conclude that the initial 15 Angstrom of Ca overlayer is
contaminated by the Ca-O and Ca-C species and the overlayer is pure b
eyond 15 Angstrom of Ca coverage.