Fig. 5
From: Applications of remote epitaxy and van der Waals epitaxy
a. Structural schematic of the Fe2O3/ZnO/mica heteroepitaxy, b. Cross-sectional TEM image of the ZnO/mica and Fe2O3/ZnO interface, c. Linear-sweep voltammograms of pure Fe2O3, ZnO, and the Fe2O3/ZnO electrodes with visible-light illumination and the inset photograph of flexible Fe2O3/ZnO/mica [114], d. The atomic structure of monolayer AlN and four possible adsorption sites, e. Charge density difference plots for CO2/AlN, H2/AlN, CO/AlN, O2/AlN, NO/AlN [120], f. Photograph of an e-skin attached on the back of hand (top) and Schematic illustrations and wireless ion sensors based on GaN SAW device coated with Na+ ion–selective membranes, g. Resonant frequency shift in the wireless signals obtained from a GaN SAW ion sensor in response to changes in Na+ ion concentration, h. Continuous wireless recordings collected from a SAW ion sensor during a series of alternating injections of 0.86 mM NaCl solution and distilled water over the e-skin [74]