An in situ XPS study of the formation of nickel—polyethylene and nickel—polypropylene interfaces

Abstract

AbstractThe initial stages of formation of nickel–polyethylene and nickel–polypropylene interfaces have been investigated by X‐ray photoelectron spectroscopy (XPS). Nickel was sputter‐deposited on the polymer surfaces in the UHV chamber attached to the spectrometer, and the Ni 2p3/2 and C1s regions were analysed in situ as a function of deposition time, until the completion of a metallic overlayer of ∼30 Å. The examination of the measured XPS spectra shows that there is no additional signal in the C1s region which would be associated with the formation of a strong chemical bond with charge transfer, in contrast with previous findings for aluminium sputter‐deposited on the same polymers. Accordingly, the Ni 2p3/2 region does not show any additional signal, but it exhibits a marked shift in the binding energy for the small amounts of deposited nickel (0.7 eV for the shortest deposition time). This shift in binding energy decreases with increasing amount of deposited metal. This observation gives evidence of the presence of small clusters on the surface, which finally form a continuous metallic layer with a thickness of ∼8 Å.