Interfacial chemistry in Al and Cu metallization of untreated and plasma treated polyethylene and polyethyleneterephthalate

Abstract The growth of Cu and Al films thermally evaporated onto polyethylene (PE) and polyethyleneterephthalate (PET) surfaces is followed in situ by XPS (X-ray Photoelectron Spectroscopy) and XAES (X-ray Auger Electron Spectroscopy) from the early submonolayer stages up to the completion of a metallic film. PE and PET surfaces were metallized first without any preliminary treatment. A second series of metallization experiments were run on the polymer surfaces but pretreated by a remote O2 microwave plasma (2.45 GHz). These metal films have also been investigated by AFM (Atomic Force Microscopy) in air. Both metals are shown not to undergo chemical interaction with low surface energy polyolefin such as PE. While an abrupt interface is seen with A1, a diffusion of Cu into the bulk of the polymer is demonstrated. Large size clusters are evidenced by AFM in the initial steps of deposition. Cu and A1 are both shown to react with PET, but not in the same way. In the case of A1, the chemical interaction across the metal/polymer interface proceeds through an electron transfer from the metal toward the ester group O=C-O. With Cu, the chemical interaction is not so clearly evidenced and the Cu is found to diffuse into the PET. Oxygenated functionalities grafted by O2 plasma on PE and PET are C-O, C=O, O-C-O, O-C=O, and O2C=O. The roughness of the PE and PET surfaces is observed by AFM to increase with the plasma treatment. A metal-CO type complex is clearly observed with Al/treated PE and Cu/treated PET. No chemical interaction was observed at the Cu/treated PE interface. Keywords: Polymer metallizationpolyethylenepolyethyleneterephthalatecopperaluminiumchromiumX-ray photoelectron spectroscopyoxygen-plasma treatmentAugeratomic force microscopy