- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Periodic Amplification of Radiative Heat Transfer
摘要： The thermal excitation of materials with a periodic heat flux or temperature modulated in time is a reliable and accurate tool usually applied to determine thermal properties, through techniques such as thermoreflectance, photothermal radiometry, 3ω, photoacoustics, thermal-wave resonant cavity, etc. Moreover, over the past years, the control of heat flux has been improved by means of phase-change materials (PCMs), whose internal structures are strongly driven by their temperature, which results in significant variations of their thermal, optical, and electrical properties. Thermochromic materials (VO2, nitinol) or superconductors are examples of such PCMs, where the material can be either in an insulator phase, with low thermal/electrical conductivity and high emissivity, or in a metallic one characterized by a high thermal/electrical conductivity and low emissivity. This metal-insulator transition (MIT) occurs at the critical temperature of each PCM and can therefore be used to tune the heat currents that the PCM exchanges with the environment, which paves the wave for novel applications.
关键词： radiative heat transfer,metal-insulator transition,thermochromic materials,thermal excitation,phase-change materials
更新于2025-09-11 14:15:04
-
Charge Dynamics and Metal–Insulator Transition in Perovskite SrIr <sub/>1?</sub><i> <sub/>x</sub></i> Sn <i> <sub/>x</sub></i> O <sub/>3</sub>
摘要： We investigate the variation of charge dynamics upon the metal–insulator transition for perovskite SrIr1?xSnxO3 by employing the optical spectroscopy. The Dirac semimetal of SrIrO3 turns into the antiferromagnetic insulator with a gap of 0.1 eV by the Sn-substitution, accompanying the reconstruction of electronic structure on an energy scale of 1 eV. The spectral intensity of optical excitation between Je? = 1=2-orbitals is signi?cantly reduced with increasing x, while that between the Je? = 3=2- and 1=2-orbital shows merely moderate x-dependence. We anticipate that the substituted Sn signi?cantly renormalizes the e?ective bandwidth of Je? = 1=2-orbital while modestly changing the Je? = 3=2-orbital.
关键词： charge dynamics,optical spectroscopy,electronic structure,Je? = 3=2-orbital,perovskite,metal–insulator transition,Dirac semimetal,Je? = 1=2-orbitals,SrIr1?xSnxO3,antiferromagnetic insulator,Sn-substitution
更新于2025-09-10 09:29:36
-
V2O5 Thin Films as Nitrogen Dioxide Sensors ?
摘要： Vanadium pentoxide thin films were deposited onto insulating support by means of rf reactive sputtering from a metallic vanadium target. Argon-oxygen gas mixtures of different compositions controlled by the flow rates were used for sputtering. X-ray diffraction at glancing incidence (GIXD) and Scanning Electronic Microscopy (SEM) were used for structural and phase characterization. Thickness of the films was determined by the profilometry. It has been confirmed by GIXD that the deposited films are composed of V2O5 phase. The gas sensing properties of V2O5 thin films were investigated at temperatures from range 410–617 K upon NO2 gas of 4–20 ppm. The investigated material exhibited good response and reversibility towards nitrogen dioxide. The effect of metal-insulator transition (MIT) on sensor performance has been observed and discussed for the first time. It was found that a considerable increase of the sensor sensitivity occured above 545 K, which is related to postulated metal-insulator transition.
关键词： reactive sputtering,vanadium pentoxide,metal-insulator transition (MIT),electrical properties,thin film,gas sensor,nitrogen dioxide
更新于2025-09-10 09:29:36
-
Enhanced Thermochromic Properties of Vanadium Dioxide (VO2)/Glass Heterostructure by Inserting a Zr-Based Thin Film Metallic Glasses (Cu50Zr50) Buffer Layer
摘要： Vanadium dioxide (VO2) with reversible metal–insulator transition (MIT) is one of the most promising energy-efficient materials. Especially for VO2-based smart windows, the visible transmittance and solar modulation ability are the most critical parameters. However, VO2 thin films that are directly deposited onto glass substrates are of poor crystallinity and MIT performance, limiting the practical applications of VO2/glass heterostructures. In this paper, a buffer layer of Cu50Zr50 was introduced to build a novel Zr-based thin film metallic glass (VO2/Cu50Zr50/glass) with multilayer structures for thermochromic applications. It is observed that the insertion of a Cu50Zr50 buffer layer with appropriate thickness results in a clear enhancement of crystalline quality and MIT performance in the VO2/Cu50Zr50/glass thin films, compared with the single-layer VO2/glass thin films. Moreover, the VO2/Cu50Zr50/glass bi-layer films exhibit better optical performance with enhanced solar modulation ability (?Tsol = 14.3%) and a high visible transmittance (Tvis = 52.3%), which represents a good balance between ?Tsol and Tvis for smart window applications.
关键词： Cu50Zr50 buffer layers,metal–insulator transition,vanadium dioxide thin film,thermochromic property,smart window
更新于2025-09-10 09:29:36
-
Thermal hysteresis measurement of the VO <sub/>2</sub> dielectric function for its metal-insulator transition by visible-IR ellipsometry
摘要： The real and imaginary parts of the dielectric function of VO2 thin films, deposited on r-plane sapphire via pulsed laser deposition, are measured by means of visible-infrared ellipsometry for wavelengths ranging from 0.4 to 15 μm and temperatures within its phase transition. For both the insulator-to-metal (heating) and metal-to-insulator (cooling) transitions, it is shown that the two ellipsometric signals exhibit three temperature-driven behaviors, which are well described by appropriate combinations of the Tauc-Lorentz, Gaussian, and Drude oscillator models. By fitting Bruggeman’s effective medium model for the dielectric function to the corresponding measured experimental values, using the volumetric fraction of the VO2 metallic domains as a fitting parameter for different temperatures within the VO2 phase transition, we have found that this model is suitable for describing the dielectric function in visible and near-infrared wavelengths (～0.4 to ～3.0 μm), but it generally fails for longer infrared ones. Furthermore, the hysteresis loop of the VO2 emissivity averaged over a relevant interval of wavelengths is determined and shown to vary from ～0.49, in the insulator phase, to ～0.16, in the metallic one. These values, based on the VO2 dielectric function, are consistent with previous measurements reported in the literature, and therefore, our measured data are expected to be useful for describing the behavior of VO2 films involved in optical and radiative applications.
关键词： metal-insulator transition,ellipsometry,emissivity,VO2,dielectric function
更新于2025-09-10 09:29:36
-
Metal-insulator transition in V <sub/>2</sub> O <sub/>3</sub> thin film caused by tip-induced strain
摘要： We have demonstrated pressure-induced transition in a c-axis oriented vanadium sesquioxide (V2O3) thin film from a strongly correlated metal to a Mott insulator in a submicrometric region by inducing a local stress using contact atomic force microscopy. To have an access to a pressure range of sub-gigapascal, a tip with a large radius of 335 nm was prepared by chemical vapour deposition of platinum onto a commercial tip with a focused ion beam (FIB). The FIB-modified tip gives a good electrical contact at low working pressures (0.25–0.4 GPa) allowing unambiguously to evidence reversible metal-insulator transition in a pulsed laser-deposited V2O3 thin film by means of local investigations of current-voltage characteristics. A finite element method has confirmed that the diminution of the c/a ratio under this tip pressure explains the observed phase transition of the electron density of states in the film.
关键词： tip-induced strain,Mott insulator,metal-insulator transition,V2O3 thin film,atomic force microscopy
更新于2025-09-09 09:28:46
-
Toward reproducible metal-insulator transition characteristics in V <sub/>2</sub> O <sub/>3</sub> thin films sputter-deposited on glass
摘要： Vanadium sesquioxide (V2O3) exhibits remarkable property changes through its metal-insulator transition near 150 K and is a very promising candidate for device applications. Thin V2O3 films were deposited on SiO2 glass by reactive DC magnetron sputtering. While resistivity changes over four orders of magnitude were demonstrated, films deposited under nominally identical conditions exhibited significant differences in electrical characteristics, which would hinder reproducibility under deposition techniques appropriate for industrial scale production with standard control features. These differences were attributed to small deviations from exact stoichiometry. A post-deposition thermal treatment consistent with equilibrium temperature and oxygen pressure conditions for V2O3 applied to the samples succeeded in nearly equalizing their characteristics within a relatively short time and without negatively impacting the glass substrate or film continuity. Analysis of film structure, morphology, and resistivity measured from room temperature through the metal-insulator transitions, both before and after the thermal process, revealed information about the interplay between non-stoichiometry, residual stress, and electrical characteristics of the films. The approach employed can lead to reproducible results for V2O3 films and is applicable to similar materials which exhibit metal-insulator transitions.
关键词： stoichiometry,sputtering,thin films,V2O3,thermal treatment,metal-insulator transition
更新于2025-09-09 09:28:46
-
Effect of MIT in epitaxial VO <sub/>2</sub> films on THz transmittance
摘要： The development of THz technologies (communication, imaging, spectroscopy etc.) requires the design of materials for high-speed modulation of radiation in THz range. For such applications, the thin films based on oxides showed a metal-insulator transition (MIT) are interesting due to large different of optical transmittance before and after critical point. Among the oxide materials with MIT vanadium dioxide, which has a transition temperature the closest to the room temperature (68oC for bulk samples), is of particular interest, with the MIT characterized by a record speed (<1 ps) and a large amplitude (a change in the conductivity is 105 times for single crystals). It is known that the MIT transition in VO2 is accompanied by a first-order phase transition, while the crystalline structure from the monoclinic (crystal type MoO2) with the properties of the semiconductor transforms into a tetragonal (rutile type) with metallic conductivity. The electronic transition in the vanadium dioxide can be caused by the temperature, the electric field and laser radiation. A set of these unique properties makes vanadium dioxide a promising key component of optoelectronic devices (switches, modulators, lenses, etc.) for the THz range controlled by thermal action, electric voltage or laser pulse.
关键词： vanadium dioxide,epitaxial films,metal-insulator transition,THz transmittance,THz technologies
更新于2025-09-09 09:28:46
-
Strain Induced Metal–Insulator Transition of Magnetic SrRuO3 Single Layer in SrRuO3/SrTiO3 Superlattice
摘要： Ferromagnetic phase in a two-dimensional system plays an important role not only in applications but also in studies of phase transition theory. Among numerous ferromagnetic materials, SrRuO3 is famous for its half-metallicity, itinerant ferromagnetism and non-Fermi liquid metalicity. Single layer SrRuO3 in SrRuO3/SrTiO3 (SRO/STO) superlattice has been predicted as a two-dimensional half-metallic ferromagnetic system based on density functional theory (DFT). However, experiments show that metal–insulator transition associated with ferro–antiferromagnetism (FM–AFM) transition occurs when the thickness of SRO is less than 4 u.c. Combining DFT calculations with Monte Carlo simulations, we demonstrate in this work that the bulk ferromagnetic metallicity can be realized in single layer SRO in SRO/STO superlattice by manipulating the strain effect to trigger the metal–insulator transition, achieving two-dimensional (2D) half-metallic SRO thin film beyond the experimental observation of AFM insulator.Our results pave a new route to fulfill the ultrathin spin-polarized-2D electron gas (SP-2DEG).
关键词： superlattice,metal–insulator transition,half-metal,magnetism,2DEG
更新于2025-09-04 15:30:14
-
Effects of Surface Termination and Layer Thickness on Electronic Structures of LaNiO <sub/>3</sub> Thin Films
摘要： We investigate the e?ects of surface termination and layer thickness on the electronic structures of LaNiO3 thin ?lms on SrTiO3 substrate using ?rst-principles density-functional theory calculations. The NiO2-terminated ?lm with one unit cell thickness shows a pseudogap at the Fermi level owing to the negative charge transfer energy, whereas the 1.5-unit-cell-thick LaO-terminated ?lm exhibits an insulating gap of 1.0 eV as a result of the large exchange splitting. The metallic state is quickly restored for thicker ?lms with either NiO2 or LaO termination, resembling that in bulk nickelate. Our results indicate the strong dependence of the electronic properties on layer thickness and provide insightful information into the metal–insulator transition in LaNiO3 thin ?lms.
关键词： surface termination,electronic structures,layer thickness,LaNiO3 thin films,metal–insulator transition
更新于2025-09-04 15:30:14