Fundamental Interactions at the Polyimide-Metal Interface

The physical and chemical mechanism(s) of polyimide -metal adhesion are of considerable scientific and technological interest. Interfaces between metals and the polyimide synthesized from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) and 4,4^'-oxydianiline (ODA) are widely used to model polyimide-metal interfaces in general. This thesis is an experimental study of both polyimide on metal and metal on polyimide interfaces. The bonding and orientation of polyimide precursor molecules and polyimide precursor model compounds adsorbed on Ni(110) were studied using X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS). PMDA, PMDA model compounds (benzoic acid, succinic anhydride and phthalic anhydride) and 1,3-phenylenediamine were vapor deposited, separately, in vacuo onto Ni(110). Multilayer films condensed at about 150 K and thin films chemisorbed at 300 K were studied. For benzoic acid and the smaller anhydride species, dissociative chemisorption occurs at 300 K with bonding through the oxygens of a carboxylate -like species. For PMDA, only one of the anhydride units is involved in adhesion. PMDA and the model compounds are oriented at a large angle with respect to the surface. M -phenylenediamine chemisorbs at 300 K via its nitrogen atoms; the aromatic ring is inclined at a large angle with respect to the surface normal. Vapor deposited PMDA-ODA films with both Cu and Ti evaporated overlayers were investigated using XPS and scanning tunneling microscopy (STM). Metal thicknesses up to about seven monolayers were investigated. Cu initially interacts with the planar imide ring--the nitrogen XPS signal is preferentially attenuated and the carbonyl XPS intensities are altered. No evidence is found for chemical interaction with the ODA moiety. Heating the surface at temperatures between 375 and 575 K leads to Cu redistribution. Ti chemically attacks PMDA-ODA. The first submonolayer reacts with oxygen atoms in the carbonyl and ether functionalities. At Ti coverages higher than about 1-2 monolayers, Ti reacts to form carbides and about 50% of the nitrogen sites are strongly attacked by the Ti. Heating at 575 K causes additional reaction. Ex situ STM measurements indicate that the Cu and Ti covered surfaces are much rougher than the underlying support substrates.