Ag-doped ZnO films were prepared by direct current reactive magnetron sputtering using a zinc target with various Ag-chips attached. The influence of Ag doping on the microstructure, photoluminescence and Raman scattering of ZnO films were systematically investigated. The results indicate that ZnO films doped with Ag can still retain a wurtzite structure, although the c-axis as preferred orientation is decreased by Ag doping. The near band edge emission of ZnO film can be enhanced by Ag doping with a concentration of 1.6–2.8 at.% and quench with a further increase in the Ag concentration. A local vibrational mode at 411 cm−1 induced by Ag dopant can be observed in the Raman spectra of the Ag-doped ZnO films, which might be used as an indication of Ag incorporation into the ZnO lattice.
We demonstrate an electrolyte-based voltage tunable vanadium dioxide (VO2) memory metasurface. Large spatial scale, low voltage, non-volatile switching of terahertz (THz) metasurface resonances is achieved through voltage application using an ionic gel to drive the insulator-to-metal transition in an underlying VO2 layer. Positive and negative voltage application can selectively tune the metasurface resonance into the “off” or “on” state by pushing the VO2 into a more conductive or insulating regime respectively. Compared to graphene based control devices, the relatively long saturation time of resonance modification in VO2 based devices suggests that this voltage-induced switching originates primarily from electrochemical effects related to oxygen migration across the electrolyte–VO2 interface.
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