We report the fabrication of VO2-based two terminal devices with ∼125-nm gaps between the two electrodes, using a simple, cost-effective method employing optical lithography and shadow evaporation. Current-voltage characteristics of the obtained devices show a main abrupt metal-insulator transition (MIT) in the VO2 film with voltage threshold values of several volts, followed by secondary MIT steps due to the nanostructured morphology of the layer. By applying to the two-terminal device a pulsed voltage over the MIT threshold, the measured switching time was as low as 4.5 ns and its value does not significantly change with device temperature, supporting the evidence of an electronically driven MIT.

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 audienceThermomagnetic patterning TMP of 4 m thick high performance NdFeB hard magnetic films deposited on Si substrates has been achieved using single pulsed laser irradiation. Uniaxially magnetised chessboard and stripe patterns with lateral feature sizes in the range 50-100 m were produced. The depth of reversal was estimated, using both global vibrating sample magnetometry and localized scanning Hall probe measurements, to be in the range of 1.1-1.2 m. A simple model provides semiquantitative agreement with the experimental results. A linear Halbach array was fabricated to demonstrate the potential of TMP for the realization of complex multidirectional microflux sources

Articles you may be interested inEffect of conductive TiN buffer layer on the growth of stoichiometric VO2 films and the out-of-plane insulator-metal transition properties J. Vac. Sci. Technol. A 32, 041502 (2014); 10.1116/1.4874844Sharp semiconductor-to-metal transition of VO2 thin films on glass substrates Structural, electrical, and terahertz transmission properties of VO2 thin films grown on c-, r-, and m-plane sapphire substrates Geometric confinement effects on the metal-insulator transition temperature and stress relaxation in VO2 thin films grown on silicon

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Highlights A zero-reflection-induced phase singularity is achieved through precisely controlling the resonance characteristics using two-dimensional nanomaterials. An atomically thin nano-layer having a high absorption coefficient is exploited to enhance the zero-reflection dip, which has led to the subsequent phase singularity and thus a giant lateral position shift. We have improved the detection limit of low molecular weight molecules by more than three orders of magnitude compared to current state-of-art nanomaterial-enhanced plasmonic sensors. Abstract Detection of small cancer biomarkers with low molecular weight and a low concentration range has always been challenging yet urgent in many clinical applications such as diagnosing early-stage cancer, monitoring treatment and detecting relapse. Here, a highly enhanced plasmonic biosensor that can overcome this challenge is developed using atomically thin two-dimensional phase change nanomaterial. By precisely engineering the configuration with atomically thin materials, the phase singularity has been successfully achieved with a significantly enhanced lateral position shift effect. Based on our knowledge, it is the first experimental demonstration of a lateral position signal change > 340 μm at a sensing interface from all optical techniques. With this enhanced plasmonic effect, the detection limit has been experimentally demonstrated to be 10–15 mol L−1 for TNF-α cancer marker, which has been found in various human diseases including inflammatory diseases and different kinds of cancer. The as-reported novel integration of atomically thin Ge2Sb2Te5 with plasmonic substrate, which results in a phase singularity and thus a giant lateral position shift, enables the detection of cancer markers with low molecular weight at femtomolar level. These results will definitely hold promising potential in biomedical application and clinical diagnostics.

International audienceNanostructured vanadium dioxide is one of the most interesting and studied member of the vanadates family performing a reversible transition from an insulating state to a metallic state associated with a structural transition when heated above a temperature of 68 C. On the other hand, noble metal nanoparticles (NPs) support localized surface plasmon resonance which causes selective absorption bands in the visible and near-IR regions. The purpose of this letter is to study structural, optical, and electrical properties of vanadium dioxide thin films containing gold nanoparticles synthetized using pulsed laser deposition process. Thus, we have performed x-ray diffraction, optical transmission, and four point probe electrical measurements to investigate the nanocomposite properties versus its temperature. Interestingly, we have observed switching behavior for VO2 film containing gold NPs with a resistivity contrast of four orders of magnitude and a decrease of its transition temperatur