INTERFACIAL CHEMISTRY IN AL AND CU METALLIZATION OF UNTREATED AND PLASMA-TREATED POLYETHYLENE AND POLYETHYLENETEREPHTHALATE

The growth of Cu and Al films thermally evaporated onto polyethylene ( PE) and polyethyleneterephthalate (PET) surfaces is followed in situ b y XPS (X-ray Photoelectron Spectroscopy) and XAES (X-ray Auger Electro n Spectroscopy) from the early submonolayer stages up to the completio n of a metallic film. PE and PET surfaces were metallized first withou t any preliminary treatment. A second series of metallization experime nts were run on the polymer surfaces but pretreated by a remote O-2 mi crowave plasma (2.45 GHz). These metal films have also been investigat ed by AFM (Atomic Force Microscopy) in air. Both metals are shown not to undergo chemical interaction with low surface energy polyolefin suc h as PE. While an abrupt interface is seen with Al, 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 Al are bot h shown to react with PET, but not in the same way. In the case of Al, 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 gr afted by Oz 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 incre ase with the plasma treatment. A metal-CO type complex is clearly obse rved with Al/treated PE and Cu/treated PET. No chemical interaction wa s observed at the Cu/treated PE interface.