Copper–polyvinyl alcohol interface: A study with XPS

Abstract

It has been known for some time that oxygen treatment of a polymer surface can lead to enhanced adhesion with metals. This has prompted us to investigate the metal–polymer interface of an oxygen-containing polymer, polyvinyl alcohol. We have vapor-deposited copper on the clean polymer surface and examined the interface with x-ray photoemission spectroscopy (XPS). At very low copper coverages, about 0.005 monolayer, the copper 2p3/2 core level binding energy is 1.2 eV larger than the bulk copper value. As the copper coverage increases, this core level shift decreases; at a coverage of one monolayer this shift is sometimes as large as 0.2 eV. At a copper coverage of two monolayers, the 2p3/2 core binding energy is the same as it is in bulk copper, 932.85 eV. In addition to these changes, the carbon 1s and oxygen 1s core levels are observed to change with the addition of copper. The intensity of the C 1s level at 286.6 eV, associated with a C–O group, is observed to decrease faster than that at 285.0 eV which is associated with a CH2 group. At the same time a new peak in the 0 1s spectrum is formed at 530.6 eV, 2.4 eV less than the original level. These changes indicate the formation of a copper–oxygen–carbon complex at the interface.