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.

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We present the non-linear electrical properties of simple two-terminal switching devices based on vanadium dioxide (VO2) thin films. The current–voltage characteristics of such devices present negative differential resistance (NDR) regions allowing generating electrical self-oscillations across the investigated devices, with frequencies ranging from several kHz up to 1 MHz. We investigate and compare the factors determining the onset of oscillatory phenomenon in both voltage- and current-activated oscillations and explain its origin. For both activation modes, we will correlate the properties of electrical oscillations (amplitude and frequency) with the amplitude of the continuous excitation signal, the physical geometry of the devices or ambient temperature. We conclude by mentioning several possible applications for the oscillation generation in the radiofrequency (RF)/microwave domains (inverters, integrated a.c. signal generators, pressure and temperature sensors, etc.).

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We present the design, simulation and fabrication of innovative tunable band stop filters realized using switching devices based on the fast, reversible Metal-Insulator Transition of vanadium dioxide thin films. The filters are designed to operate in the 11-13 GHz frequency range and consists in a transmission line coupled with four U-shaped resonators. We developed two types of tunable filters based on VO2 switches integration namely a "switchable stop band filter" for which the rejection band can be switched on and off and a "discrete tunable stop-band filter" for which the width and position of the stopband can be discretely tuned.

Microwave switches in both shunt and series configurations have been developed using the semiconductor to metal (SC-M) transition of vanadium dioxide (VO 2 ) thin films deposited by in situ pulsed laser deposition on C-plane sapphire and SiO 2 /Si substrates. The influence of geometrical parameters such as the length of the switch is shown. The VO 2 -based switches exhibit up to 30-40 dB average isolation of the radio-frequency (RF) signal over a very wide frequency band (500 MHz-35 GHz) with weak insertion losses, when thermally activated. Furthermore, they can be electrically activated. Finally, these VO 2 -based switches are integrated in the fabrication of innovative tunable band-stop filters which consist of a transmission line coupled with four U-shaped resonators and operate in the 9-11 GHz frequency range. Its tunability is demonstrated using electrical activation of each VO 2 -based switch.

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