Electronic Devices In The Copper And The Corrosion Behavior Of The Ito Film Electrode

Copper thin film has gained tremendous application in electronic devices, thanks to its excellent electronic, thermal and mechanical properties. It can be found in many functional devices like sensors and photoelectric memorizers. As the size of electronic devices goes down and the thickness of thin films decreases, corrosion problems in manufacturing and processing are becoming severe, especially thin film oxidation. In real application environment, water vapor is also unavoidable. To clarify the law of transport in thin film will have great impact on both science and practice.Indium Tin Oxides (ITO) thin films are important optoelectronic materials, which are are both transparent to visible light and electrically conductive. ITO films have been widely used in the fields of flat panel display, solar cells, anti-frost glass, gas sensing devices, energy saving window, aeronautics and astronautics etc. In addtion, ITO films have a broad application as transparent electrodes for electrochemical deposition, with which transmission spectrums of reactants could be obtained after deposition. In these applications, the electrochemical stability turns to be a very significant scientific issue.In this paper, copper and ITO films are chosen to be studied. Firstly, the transport mechanism of copper thin film oxidation in water vapor is studied by using H216O/H218O isotopic labeling. Secondly, the electrochemical corrosion behaviors of ITO films during cathodic polarizations are investigated in sodium hydroxide solutions by means of Electrochemical Impedance Spectrums. The impacts of reaction parameters on corrosion rate and extent are also obtained. The results are as follows:1. Isotopic labeling was proved to be effective and direct in studying the transport mechanism of metal materials. Copper thin films were exposed to H216O and H218O vapor in succession. The distribution of 16O and 18O in the oxide film was then analysed by means of secondary ion mass spectroscopy (SIMS), according to which the transport mechanism of copper film oxidation was discussed.2. The SIMS results demonstrated that the transport mechanism of copper thin film oxidation is short circuit diffusion mechanism.3. Electrochemical impedance spectrums (EIS) had been built to characterize electrochemical corrosion of ITO thin films. In detail, cathodic polarization process of ITO thin films was studied by EIS. 4. According to EIS, the equivalent circuits of ITO film electrode were obtained. The parameters of equivalent circuit elements at different steps of the corrosion were calculated. With huge transfer resistance of solid-liquid interface between original ITO films and solutions, it decreased a lot during the corrosion process.That's because the surface area of ITO electrode increased and metallic In was generated and absorbed to the surface, which made original semiconductor-solution interface turned to be metal-solution one.5. With the increased pH value, temperature of the solutions and the concentration of Cl+, both the rate and the extent of the ITO films'electrochemical corrosion were enhanced.