X-ray photoelectron spectroscopy studies of the stability of Al/Mg/PET interfaces

The interfacial chemistry of an Al/Mg/PET sample, prepared by thermally evaporating first Mg and then Al on to a polyethyleneterephthalate (PET) film, was studied by X-ray photoelectron spectroscopy (XPS). The Mg/PET system showed two types of Mg species, namely an O-Mg-C complex, from reaction with the carbonyl group on PET, and metal-like clusters. The deposition of Al results in intermetallic mixing, which is manifested by alloy formation and Mg enrichment at the surface. It appears that some Al atoms penetrate the Mg region to react with carbonyl groups in the PET and form an interfacial complex with O-Al-C bonding. The stability of this sample was studied on exposing it to air and then rinsing it with water. The metal overlayers are strongly modified by these treatments, although the bonding at the PET interface appears relatively unchanged.