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Epitaxial Liftoff of Wafer‐Scale VO <sub/>2</sub> Nanomembranes for Flexible, Ultrasensitive Tactile Sensors
摘要： Highly sensitive tactile sensors with long-term stability and low power consumption are one of the key components for flexible electronics. Here, for the first time, the fabrication of VO2 nanomembrane tactile sensors by epitaxial liftoff from ZnO sacrificial layer is reported. The wafer-scale nanomembranes inherit the structural and electrical properties of the as-grown films, and the wet transfer generates negligible influence on the quality of VO2. Most importantly, giant electrical responses to external strains are found due to the release of substrate clamping, and a high gauge factor up to ≈1100 is derived. Furthermore, the electrical properties show no deterioration after repeatedly bending the nanomembranes for 10 000 times at a radius of 1 cm. The VO2 nanomembrane sensors are utilized to monitor the radial artery pulse, and totally reproducible waveforms with ultrahigh sensitivity to the tactile stimuli are observed. Moreover, the power dissipation of the VO2 tactile sensors can be lowered down to the picowatt level, allowing for the future construction of self-powered sensing systems together with nanogenerators. This study provides a substantial step toward large-scale preparation of oxide nanomembranes and therefore paves a promising way for flexible oxide electronics.
关键词： flexible electronics,piezoresistivity,vanadium dioxide,tactile sensors,epitaxial liftoff
更新于2025-11-14 17:03:37
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Numerical investigation of energy performance and cost analysis of Moroccan’s building smart walls integrating vanadium dioxide
摘要： Thermochromic materials such as vanadium dioxide (VO2) have the capability to regulate their infrared reflectivity depending on ambient temperature. Such smart materials are attractive for applications like smart windows and smart roofs. In this paper, we investigate numerically the impact of tungsten (W) doped VO2 application as a smart outdoor wall layer on the building energy consumption in the Mediterranean climate. Temperature distributions through wall configurations with and without W doped VO2 were calculated using finite differences method implemented in Matlab environment. Calculations take into consideration dynamic variations of W doped VO2 absorptivity depending on outdoor temperature variations. Decrement factor, time lag, transmission and peak loads of cooling and heating were calculated. Results have shown that the indoor surface temperature is attenuated during summer by 2–3 °C depending on orientation. Cooling energy saving due to the use of W doped VO2 in summer is around 70% monthly which is equivalent to save $21.6/month of electricity invoiced amount. During winter, W doped VO2 maintains the same value of absorptivity as the uninsulated wall. Thus, results show small differences for indoor surface temperature and heating energy consumption. The application of W doped VO2 in intelligent thermal wall insulation offers a real-time dynamic variation of building’s envelope solar absorptivity and makes smart walls concept more feasible.
关键词： Energy efficiency,Smart wall,Radiative thermal rectification,Thermochromic,Real-time dynamic absorptivity,Vanadium dioxide
更新于2025-09-23 15:23:52
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Oxidation/reduction control of the VO2 nanoparticle in the nano-confined space of the hollow silica nanoparticle
摘要： Vanadium dioxide (VO2) exhibits a good thermochromic property which can be used in a smart window. To improve its poor visible transparency, immobilization of the VO2 nanoparticles on the silica shell of hollow nanoparticles was proposed. In addition to improving the particle dispersibility of the VO2 and to reducing stress from repeated phase transitions of the VO2 between monoclinic and tetragonal, the hollow interior can reduce any undesirable oxidation of the VO2 to V3O7, V2O5, etc., along with the thermal decomposition behavior of organic compounds around the vanadium atom. The hollow silica nanoparticles with micropores (less than 2 nm) were prepared by a previously-reported template method. Through the pores, the vanadium precursor with a chelate ligand solution penetrates into the hollow interior. The vanadium intermediate formed by adding water was then captured by the silica shell. During the crystallization process under a nitrogen atmosphere, 10-30 nm of VO2 particles were immobilized on the silica shell with a high dispersibility by optimization of the vanadium precursor concentration, and ratios of vanadium/water and vanadium/hollow silica nanoparticles. The VO2/hollow silica nanoparticles in water exhibited a higher visible transparency than that of the commercial VO2. In addition, their thermochromic property in the infrared region was close to that of the commercial one.
关键词： Thermochromic,Hollow silica nanoparticle,Vanadium dioxide,Micropore
更新于2025-09-23 15:23:52
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Thickness-modulated thermochromism of vanadium dioxide thin films grown by magnetron sputtering
摘要： Vanadium dioxide (VO2) films were prepared on soda-lime glass by direct current magnetron sputtering at 320 °C. Effects of film thickness on the microstructure, surface morphology and thermochromic performance of VO2 films were investigated. X-ray diffraction showed that the deposited films have strong preferred orientation of VO2 (011) lattice when the film thickness higher than 102 nm. The calculated grain sizes of VO2 films increased from 16.05 nm to 34.56 nm continuously with the increasing of film thickness. UV/VIS/NIR spectrophotometer showed that the visible transmittance deceased while the infrared transmittance switching efficiency increased as the film thickness increased from 79 nm to 264 nm. Additionally, the optical band gaps of VO2 films were in a range of 1.15 eV–1.40 eV, and the thicker film exhibited the smaller value. Moreover, the results of measured temperature-dependent electrical resistivity of these VO2 films showed that the phase-transition temperature is in a range of 53–60 °C, which is much lower than that of single-crystal VO2 (68 °C). With the film thickness increasing, the metal–semiconductor phase transition becomes more obvious. Overall, films with thickness in the range of 80–100 nm showed comparatively relatively balanced combination of visible transmittance and solar switching efficiency.
关键词： Thermochromic performance,Film thickness,Vanadium dioxide,Magnetron sputtering
更新于2025-09-23 15:23:52
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Growth of vanadium dioxide nanostructures on graphene nanosheets
摘要： The metal oxide/graphene hybrid nanomaterials have been known as promising functional materials for advanced applications such as high capacitive electrode material of secondary batteries, and high sensitive material of high performance gas sensors. Here, morphology controlled vanadium dioxide (VO2) nanostructures were grown on Si wafer and exfoliated graphene by the vapor transport method using a horizontal furnace system. One-dimensional VO2 nanowires were grown on SiO2(300 nm)/Si substrate under 0.4 kPa condition. On the other hand, thick polycrystalline of VO2 platelets were grown on exfoliated graphene nanosheets under 0.4 kPa condition. In addition, polycrystalline VO2 platelets were only grown on exfoliated graphene nanosheets under 101 kPa (atmospheric pressure) condition. The growth of polycrystalline VO2 platelets on graphene nanosheets in atmospheric pressure condition is attributed to preferential growth on functional group of graphene surface such as carbonyl. The functional group is served as nucleation site of VO2 nanostructures.
关键词： Nanostructures,Hybrid Nanomaterials,Vapor Transport Method,Graphene,Vanadium Dioxide
更新于2025-09-23 15:23:52
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Gate-Tunable Thermal Metal–Insulator Transition in VO <sub/>2</sub> Monolithically Integrated into a WSe <sub/>2</sub> Field-Effect Transistor
摘要： Vanadium dioxide (VO2) shows promise as a building block of switching and sensing devices because it undergoes an abrupt metal-insulator transition (MIT) near room temperature, where the electrical resistivity changes by orders of magnitude. A challenge for versatile applications of VO2 is to control the MIT by gating in the field-effect device geometry. Here, we demonstrate a gate-tunable abrupt switching device based on a VO2 microwire that is monolithically integrated with a two-dimensional (2D) tungsten diselenide (WSe2) semiconductor by van der Waals stacking. We fabricated the WSe2 transistor using the VO2 wire as the drain contact, titanium as the source contact, and hexagonal boron nitride as the gate dielectric. The WSe2 transistor was observed to show ambipolar transport, with higher conductivity in the electron branch. The electron current increases continuously with gate voltage below the critical temperature of the MIT of VO2. Near the critical temperature, the current shows an abrupt and discontinuous jump at a given gate voltage, indicating that the MIT in the contacting VO2 is thermally induced by gate-mediated self-heating. Our results have paved the way for the development of VO2-based gate-tunable devices by the van der Waals stacking of 2D semiconductors, with great potential for electronic and photonic applications.
关键词： 2D materials,field-effect transistor,tungsten diselenide,phase-change materials,vanadium dioxide,metal-insulator transition,van der Waals heterostructures
更新于2025-09-23 15:22:29
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Acceleration of tungsten doping on vanadium dioxide (VO2) by alkali species
摘要： The monoclinic vanadium dioxide, VO2(M), undergoes reversible phase transition from monoclinic (semiconductor) to tetragonal (metal), which exhibits a good thermochromic property. VOSO4, as a vanadium source, is easy to handle produces VO2(M) under mild condition in the presence of alkali species. In this study, the effects of the additions of NH4HCO3, NH3·H2O, and NaOH on the VO2 crystal formation with/without tungsten doping for thermochromicity were investigated. NaOH, the strongest base of the three, provided the strongest and narrowest x-ray diffraction peak, while NH4HCO3, the weakest base, provided the opposite. Interestingly, for the tungsten doping to adjust the transition temperature, the use of NH4HCO3 was more suitable due to the possibility of a slow crystal frame formation as compared to the use of NaOH.
关键词： Sodium hydroxide,Vanadium dioxide,Ammonium hydrogen carbonate,Ammonium hydroxide,Tungsten doping
更新于2025-09-23 15:22:29
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Effect of photo-irradiation on metal insulator transition in vanadium dioxide
摘要： We report a large transition temperature (TC) decrease in a VO2 thin film device under photo-irradiation. With the increasing photo-irradiation intensity (PIntensity) with a wavelength of 405 nm, the TC of the VO2 device decreased at a rate of (cid:2)3:2 (cid:3) 10(cid:4)2 W=cm2 and reached as low as 40.0 (cid:5)C at a PIntensity of 8:4 (cid:3) 102 W=cm2. While the change in TC is primarily due to the photothermal effect when the PIntensity is below 3:6 (cid:3) 102 W=cm2, both the photothermal and photo-induced carrier density effects contribute to the change in TC when the PIntensity is above 6:4 (cid:3) 102 W=cm2.
关键词： metal-insulator transition,vanadium dioxide,photothermal effect,photo-induced carrier density,photo-irradiation
更新于2025-09-23 15:21:21
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Thermochromic Oxide-Based Thin Films and Nanoparticle Composites for Energy-Efficient Glazings
摘要： Today’s advances in materials science and technology can lead to better buildings with improved energy efficiency and indoor conditions. Particular attention should be directed towards windows and glass facades—jointly known as “glazings”—since current practices often lead to huge energy expenditures related to excessive inflow or outflow of energy which need to be balanced by energy-intensive cooling or heating. This review article outlines recent progress in thermochromics, i.e., it deals with materials whose optical properties are strongly dependent on temperature. In particular, we discuss oxide-based thin surface coatings (thin films) and nanoparticle composites which can be deposited onto glass and are able to regulate the throughput of solar energy while the luminous (visible) properties remain more or less unaltered. Another implementation embodies lamination materials incorporating thermochromic (TC) nanoparticles. The thin films and nanocomposites are based on vanadium dioxide (VO2), which is able to change its properties within a narrow temperature range in the vicinity of room temperature and either reflects or absorbs infrared light at elevated temperatures, whereas the reflectance or absorptance is much smaller at lower temperatures. The review outlines the state of the art for these thin films and nanocomposites with particular attention to recent developments that have taken place in laboratories worldwide. Specifically, we first set the scene by discussing environmental challenges and their relationship with TC glazings. Then enters VO2 and we present its key properties in thin-film form and as nanoparticles. The next part of the article gives perspectives on the manufacturing of these films and particles. We point out that the properties of pure VO2 may not be fully adequate for buildings and we elaborate how additives, antireflection layers, nanostructuring and protective over-coatings can be employed to yield improved performance and durability that make TC glazings of considerable interest for building-related applications. Finally, we briefly describe recent developments towards TC light scattering and draw some final conclusions.
关键词： thermochromism,vanadium dioxide,thin film,energy-efficient glazing,coating,sputter deposition,nanoparticle
更新于2025-09-23 15:21:01
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Dynamically tunable perfect absorption based on the phase transition of vanadium dioxide with aluminum hole arrays
摘要： Integrating plasmonic nanostructures with functional materials can further control over the optical resonant responses. A perfect absorber (PA) consisting of aluminum (Al) ring array intercalated with vanadium dioxide (VO2) disk is presented. The resonance wavelength of absorption peak can be tuned over a wide range in the visible (Vis) and near-infrared (NIR) regimes. The absorption peak shifts from 770 nm to 1336 nm while VO2 undergoes a structural transition from metallic phase (m-VO2) to insulator phase (i-VO2), resulting in a relative 73.5% wavelength shift. In addition, the absorption peak is strongly dependent on the height and radius of the ring disk as well as the period of lattice. Our work also suggests that the designed VO2-based absorber has the potential to overcome the di?culty in performing dynamically tunable resonances and near-unity absorbance with wide angle of incidence as well as weak polarization dependence.
关键词： Vanadium dioxide (VO2),Visible and near-infrared spectral,Phase change material,Perfect absorption
更新于2025-09-23 15:21:01