Julien Givernaud

Voltage and current-activated metal-insulator transition in VO2-based electrical switches : a lifetime operation analysis

Abstract 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 VO2 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 VO2 switches in both voltage- and current-controlled modes. We demonstrated enhanced lifetime operation of current-controlled VO2-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 VO2-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.

Microwave Power Limiting Devices Based on the Semiconductor–Metal Transition in Vanadium–Dioxide Thin Films

We present a novel concept of microwave (MW) power-limiting devices based on reversible semiconductor-to-metal transition (SMT) of vanadium-dioxide thin films integrated on coplanar waveguides. We designed, simulated, and fabricated devices, which can be reversibly driven from a low-loss (<; 0.7 dB) transmission state into an attenuating state (> 20 dB) as the VO2 material is changing from semiconductor to the metal state when the incident MW power exceeds a threshold value. These devices are broadband and present a tunable threshold power value. They could be easily integrated as protection circuits from excess power in a large variety of MW components.

Tunable band stop filters based on Metal-Insulator Transition in vanadium dioxide thin films

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.

Generation of electrical self-oscillations in two-terminal switching devices based on the insulator-to-metal phase transition of V02 thin films

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.).

CPW self-resetting power limiting devices based on microwave power induced semiconductor-metal transition in vanadium dioxide

We present a novel concept of microwave power limiting devices (reversible self-resetting fuses and power limiters) based on reversible semiconductor-to-metal transition (SMT) of vanadium dioxide thin films integrated on coplanar waveguide transmission lines (CPW). We designed, simulated and fabricated devices which can be reversibly driven from a low-loss (≪0.7 dB) transmission state into a high-loss state (attenuation higher than 32 dB from 100 MHz to 40 GHz) as the VO2 material is changing from semiconductor to metal when the incident microwave power exceed a threshold value. These simple devices can be easily integrated as broadband protection circuits from excess power or DC transients for a large variety of RF and microwave components.

Vis-IR optical switching/ modulation based on the electrically- activated phase transition of VO 2 thin films

We report on fabrication and preliminary characterization of novel optical switches based on phase transition VO2 thin films. The electrically-induced VO2 phase transition leads to radical changes in materials optical properties, which may be further implemented in fast modulators for short-pulsed lasers applications.