High-Temperature Electrochemical Studies of Metal Diffusion through Noble Metal Layers

We studied high-temperature cyclic voltammetry (HT-CV) and high-temperature chronoamperometry for diffusion (HT-CAD) as fast and reliable techniques for investigating the interdiffusion behavior of different material combinations. Diffusion of nickel through a gold layer is used as a model system. HT-CAD detects inhomogeneous diffusion in situ and in real time without requiring high vacuum conditions. The diffused species is assigned reliably by applying HT-CV. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to analyze the elemental composition and the spatial distribution of elements within the sample. The electrochemical cell consists of a disc made of yttria-stabilized zirconium dioxide (YSZ) as a solid electrolyte conductive for oxygen ions, with a working-, reference- and counter electrode. A platinum plate is pressed onto the YSZ as a reference electrode. A multilayer structure consisting of sputtered gold and nickel has been fabricated to serve as the working electrode. On the reverse side, a porous platinum layer serves as a counter electrode. Chronoamperometric and cyclic voltammetric measurements are carried out at elevated temperatures of around 300 °C. These methods enable targeted oxidation of the diffused nickel by controlling the potential. This research enhances understanding of diffusion in metallic multilayers, providing insights into diffusion behavior.