Fig. 1
Microfabrication and geometry of the structured electrodes. a Scheme of the microfabrication of the structured electrodes (In2O3/Cu shown) with an image of the wafer at each main step: creation of a Cu surface on a Si wafer by sputtering (the underlying SiOx and Ta layers act as electrical and diffusion barriers, respectively), patterning of the sacrificial photoresist layer, deposition of In2O3 by electron beam evaporation, and lift-off of the photoresist. b Image of an individual structured electrode (In2O3/Cu, size 2 cm × 2 cm including edges, geometric active area Atotal = 2.25 cm2) and a SEM micrograph showing the distribution of the islands on the surface with a hexagonal unit cell with area Auc. The geometry of the arrangement is defined by the diameter of the islands (d) and the pitch (c). One of the islands and its interfacial perimeter are highlighted in blue and red, respectively. Optical micrographs show the size differences of the islands of two In2O3/Cu electrodes. Scale bars: 5 μm. c Actual interfacial density (ρint) and fraction of the electrode surface (SC) covered by In2O3 (or In), measured by optical microscopy after the microfabrication of the model electrodes, as a function of the nominal island diameter (d). Trendlines are added as a visual aid
