Deposition and Characterization of Metal/Polyaniline Bi-Layers
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Deposition And Characterization Of Metal/Polyaniline Bi-Layers Y. Liu, M. J. O’Keefe, and A. Beyaz1, C. Singleton1, T. P. Schuman1 University of Missouri-Rolla, Dept. of Metallurgical Engineering and Materials Research Center, Rolla, MO 65409, U.S.A. 1 University of Missouri-Rolla, Dept. of Chemistry and Materials Research Center, Rolla, MO 65409, U.S.A. ABSTRACT In this study bi-layers of metal/polyaniline (PAni) films were deposited and characterized in order to investigate the interaction of thin film metals with doped and de-doped PAni. The bilayers were fabricated by depositing PAni films on flat substrates via solution chemistry and then depositing metallic films by physical vapor deposition. The oxidation state of the PAni was varied from the doped emeraldine salt to a de-doped emeraldine base to a de-doped and fully reduced leucoemeraldine base. Aluminum and iron thin films were then magnetron sputter deposited onto the PAni films to form bi-layer structures. Characterization of the fabricated bilayers by scanning electron microscopy, current-voltage measurements, and Auger electron spectroscopy was done to investigate the morphology, electrical properties and chemical composition of the samples. Results from the study indicate that the type of metal and the doping level of the PAni influence the interactions and properties of metal/PAni interfaces and films. INTRODUCTION Interest in electrically conducting polymers, such as polyaniline (PAni), has increased dramatically in recent years. Applications including solid-state devices [1,2], electro-catalysts [3,4], chemical sensors [5] and corrosion inhibiting coatings [6,7] have utilized the properties of PAni to provide improved or unique performance over alternative materials. PAni can be reversibly doped and de-doped and oxidized and reduced over a large range of chemical states [8]. Polyaniline oxidation states range from the pernigraniline base (black/purple) to the electrically conducting emeraldine salt (green) and non-conducting emeraldine base (blue), to the fully reducded leucoemeraldine salt and base (clear). In many applications, PAni is in direct contact with metallic films and surfaces and the influence of PAni’s oxidation state on interactions with the metal determines the usefulness of the metal/polymer system. In previous studies on metal/PAni interactions the formation of metal particles or clusters dispersed in doped PAni films by electrochemical deposition [3,4,5,9,10] or electroless precipitation [11] was demonstrated. Thin metal films deposited onto doped, electrically conducting PAni layers has been investigated by other researchers [12-17] to look at the interaction of the metal with PAni for microelectronic applications such as polymer-based transistors and organic light-emitting diodes. Investigations into the interaction of doped and dedoped PAni with thin metal films prepared under similar conditions have not been reported in the literature. The physical and chemical properties of the interface can also play a critical role in determ
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