Vanadium dioxide is an intensively studied material that undergoes a temperature-induced metal-insulator phase transition accompanied by a large change in electrical resistivity. Electrical switches based on this material show promising properties in terms of speed and broadband operation. The exploration of the failure behavior and reliability of such devices is very important in view of their integration in practical electronic circuits. We performed systematic lifetime investigations of two-terminal switches based on the electrical activation of the metal-insulator transition in VO thin films. The devices were integrated in coplanar microwave waveguides (CPWs) in series configuration. We detected the evolution of a 10 GHz microwave signal transmitted through the CPW, modulated by the activation of the VO switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO-based switching (more than 260 million cycles without failure) compared with the voltage-activated mode (breakdown at around 16 million activation cycles). The evolution of the electrical self-oscillations of a VO-based switch induced in the current-operated mode is a subtle indicator of the material properties modification and can be used to monitor its behavior under various external stresses in sensor applications.
International audienceA new principle for the implementation of tunable split ring resonators (SRRs) is presented. The rings forming the SRRs are partly fixed to the substrate (anchor) and partly suspended (up-curved cantilever). Through electrostatic actuation, the suspended parts are deflected down, the distributed capacitance between the pair of coupled rings is modified, and hence the resonance frequency of the SRR can be electrically tuned. To obtain electrically movable rings, a cantilever-type micro-electro-mechanical-system (MEMS) design and fabrication process is applied. The resonance frequencies at the different switching states are measured by coupling the tunable SRR to a host microstrip line, and reveal that significant tuning ranges can be achieved. This novel tuning concept is applied to the implementation of tunable stopband filters at Ku band as proof-of-concept demonstrators
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