Counter-Electrode-Free Thin Cu Film Deposition Based on Ballistic Electron Injection into CuSO4 Solution from Nanosilicon Emitter

概要

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It is shown that a nanocrystalline silicon (nc-Si) ballistic electron emitter acts as an active electrode in a metal--salt solution (such as CuSO4 solution). The nc-Si emitter is composed of a thin Au film (10 nm thick), anodized polycrystalline layer (1 μm thick), and single-crystalline n+-Si substrate. In accordance with the results of an analysis by cyclic-voltammogram measurements under the standard three-electrode configuration, the electron injection effect into the solution is clearly observed at a potential within the electrochemical window where no electrolytic reactions appear. When the nc-Si emitter is driven alone in a CuSO4 solution without using any counter electrodes, a polycrystalline thin Cu film is uniformly formed on the emitting surface. This is presumably due to the preferential reduction of Cu2+ ions at the interface by injected energetic electrons. The observed deposition mode is different from both the conventional electroplating and electroless plating. This technique is an alternative low-temperature wet process that will be applicable to the deposition of various thin metal films.
2011-01-25