Strain imaging of electrochemical reactions of a solid electrolyte Cu2S

The electrochemical behavior of a solid electrolyte Cu2S was investigated using strain imaging. The precipitation or dissolution of Cu in Cu2S induces changes in volume. Scanning probe microscopy detects the changes in volume through surface displacements with high resolution, and so, we can observe the extension of redox-induced regions. The Cu filaments grew as the voltages were increased, and finally, a Cu bridge between the upper and lower electrodes was formed. When the Cu bridge was formed, electrochemical reactions were considerably suppressed because a large part of the current flowed through the Cu bridge. This was proven by the substantial decreases in the detected surface displacements. Further, growth of filaments was suppressed and the one-bridge connection was kept, which led to high-speed switching because the time required for disconnection was shortened. Copyright (c) 2014 John Wiley & Sons, Ltd.