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Isostructural metal-insulator transition in VO <sub/>2</sub>
摘要： The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.
关键词： electronic phase transition,vanadium dioxide,metal-insulator transition,correlated materials,heterostructures
更新于2025-09-23 15:21:01
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Layered Nonstoichiometric V <sub/>7</sub> O <sub/>16</sub> Thin Films with Controlled Oxygen-Deficient Multivalent States and Crystalline Phases
摘要： Layered nonstoichiometric vanadium oxides have aroused strong interest in energy conversion, storage, chemical catalysis, sensors and optoelectronic devices. It is still a critical challenge to control unique atomic-layer constructions and oxygen-dependent multivalent states in layered metal oxides. Here, we demonstrated the layered nonstoichiometric V7O16 thin films with controlled multivalent states and crystalline phases obtained by the combination of atomic layer deposition (ALD) and oxygen-dependent crystallization. The nonstoichiometric composition and crystalline microstructures are dominated by the oxidation states of vanadium and the thicknesses of the pristine films during the formation of layered V7O16 thin films. Variable-temperature optical and electrical behaviors suggest that no abrupt electronic and structural transitions are observed in the layered V7O16 thin films at a temperature ranging from 78 to 475 K. We expect that the oxygen-dependent multivalent states and crystalline phases in layered V7O16 will provide more opportunities to fabricate layered oxides and electrochemical devices based on nonstoichiometric vanadium oxides.
关键词： atomic layer deposition,vanadium oxide,layered oxide,V7O16,oxygen-dependent crystallization
更新于2025-09-23 15:19:57
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All-Room-Temperature Processed 17.25%-Crystalline Silicon Solar Cell
摘要： In creating the next-generation of crystalline silicon (c-Si) solar cells, the goals are to improve energy conversion efficiency and reduce costs. Here, we demonstrate all-room-temperature-processed high-efficiency thin-film/c-Si heterojunction solar cells. Functional thin film multilayers of ITO/Ni/vanadium oxide (VOx) and barium oxide (BaOx)/Al are stacked on the front and rear sides, respectively. The comprehensive analysis revealed Ni and BaOx interlayers facilitated the selective collection of charge carriers. With the MgF2 antireflection layer, the efficiency of 17.25% was achieved, suggesting a strategy for the room-temperature fabrication of high-efficiency c-Si solar cells.
关键词： Si solar cells,Room-temperature,Vanadium oxide,Contact resistivity,Barium oxide
更新于2025-09-23 15:19:57
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Chiral coding metasurfaces with integrated vanadium dioxide for thermo-optic modulation of terahertz waves
摘要： In the field of electromagnetics, there are many limitations to achieve simultaneous polarization conversion and wavefront control. The chiral coding metasurface based on the Pancharatnam-Berry (PeB) phase effectively helps to alleviate these restrictions and shows strong control over the terahertz radiation field. In this paper, the principle of chirality is theoretically analyzed and verified by simulation results. The circular dichroism DR (chiral effect) achieves 0.8. By combining the chirality and thermo-optic effect of vanadium dioxide (VO2), we propose three switchable metasurfaces for quantitative splitting and high-efficiency focusing (low-efficiency divergence) of terahertz beams. The amplitude switching efficiency of the circularly polarized (CP) and linearly polarized (LP) pencil beams is above 0.85. Under the excitation of LP waves, the first two chiral metasurfaces have one and two temperature-switchable reflective right-handed circularly polarized (RCP) pencil beams, respectively. The third chiral metasurface generates high-efficiency focusing for RCP waves and low-efficiency divergence for left-handed circularly polarized (LCP) waves. This work provides new methods for more flexible modulation of CP and LP waves and promotes the application of terahertz coding metasurfaces in communication.
关键词： Pancharatnam-Berry (PeB) phase,Vanadium dioxide,Thermo-optic effect,Chiral coding metasurface
更新于2025-09-23 15:19:57
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Growth dynamics and photoresponse of the Wadsley phase V <sub/>6</sub> O <sub/>13</sub> crystals
摘要： The preparation of a pure phase has long been the key obstacle for the fundamental research and device application of Wadsley vanadium oxides (VnO2n+1) due to the mixed-valence feature and closeness in thermodynamic phase diagrams. Herein, we demonstrate a melt-assisted pyrolysis process to prepare pure V6O13 (n = 6) using a V2O5 precursor film. V6O13 with an atomic flat (00l) terrace and length up to a millimeter was prepared on a c-cut sapphire surface. Both ex situ and in situ real-time investigations on the growth process reveal that the melting and decomposition of V2O5 started as synchronization processes for the nucleation of V6O13. The endothermic melting process provides the main driving force for the rapid growth of V6O13 crystals along the melt/solid interface. The as-prepared V6O13 crystal sheets show a broadband photoresponse capability (0.4–8.8 mm) with a rise/fall time of 42 ms/50 ms, and the maximum EQE of 5.4 (cid:2) 104%. Spatial photocurrent imaging reveals that both photoelectric and bolometer effects contribute to the photoresponse. This study offers a feasible and scalable method for the preparation of high quality mix-valence vanadium oxide for future opto-electrical and energy storage devices.
关键词： Wadsley phase,V6O13,photoresponse,melt-assisted pyrolysis,vanadium oxides
更新于2025-09-23 15:19:57
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Laser-induced breakdown spectroscopy of uranium in the VUV range
摘要： Quantitative analysis of impurities in nuclear materials is necessary in a number of areas, including process control during manufacturing, quality control of products, or for nuclear forensics purposes. Due to the important handling constraints induced by the samples radioactivity and their containment inside airtight enclosures, optical analytical techniques have great advantages over standard ones that require sample preparation, like ICP-based techniques. Therefore, laser-induced breakdown spectroscopy (LIBS) is developed for fast quantitative analysis of impurities in uranium. Actinides are well-known to have a very large number of emission lines in the UV-visible spectral range, hence making the detection of trace or minor elements a real challenge. Therefore, in this study we explored the vacuum ultraviolet range (VUV), i.e. below 200 nm, in order to investigate if this spectral region is more favorable for elemental analysis of uranium by LIBS. As practically no data on VUV spectroscopy of uranium are available, we first analyzed the spectra obtained to assess the spectral density of uranium lines, both in the UV and VUV. Then, the detection limits of two elements, carbon and vanadium, were estimated. It was found that, in spite of a less dense and less intense uranium background in the VUV, this spectral region is not relevant for metal impurities whose spectra are marginally analytically useful in the VUV. Conversely, for non-metals having intense lines in the VUV, the detection limit can be significantly better than in the UV. This was already known for non-nuclear samples. This study extends that conclusion to nuclear materials and has important practical consequences on the implementation of a LIBS analyzer in a nuclear facility.
关键词： vanadium,uranium,Laser-induced breakdown spectroscopy,impurities detection,carbon,VUV range
更新于2025-09-23 15:19:57
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A Mixed-Dimensional van der Waals Heterostructure Photodetector
摘要： Van der Waals (vdW) heterostructures, integrated two-dimensional (2D) materials with variously functional materials, provide a distinctive platform for next-generation optoelectronics with unique flexibility and high performance. However, exploring the vdW heterostructures combined with strongly correlated electronic materials is hitherto rare. Herein, a novel temperature-sensitive photodetector based on the GaSe/VO2 mixed-dimensional vdW heterostructure is discovered. Compared with previous devices, our photodetector exhibits excellently enhanced performance, with external quantum efficiency up to 109.6 % and the highest responsivity (358.1 mA?W?1) under a 405 nm laser. Interestingly, we show that the heterostructure overcomes the limitation of a single material under the interaction between VO2 with GaSe, where photoresponse is highly sensitive to temperature and can be further shut at the critical value. The metal-insulator transition of VO2, which controls the peculiar band-structure evolution across the heterointerface, is demonstrated to manipulate the photoresponse variation. This study enables us to elucidate the method of manipulating 2D materials by strongly correlated electronic materials, paving the way for developing the high-performance and special optoelectronic application.
关键词： gallinum selenide,Vanadium dioxide,MIT-controlled photoresponse,mixed-dimensional van der Waals heterostructure,band engineering
更新于2025-09-23 15:19:57
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Effect of neutron irradiation on the structural, electrical and optical properties evolution of RPLD VO2 films
摘要： This study reports on the effect of neutron irradiation at different fluences on the properties of VO2 thin films. The irradiations were performed at NUR research reactor, Algiers at a temperature of about 40 °C, with fast neutron fluence (En > 1 MeV) up to 1.9 × 1018 n.cm?2. The induced defects have been investigated using structural, optical and electrical measurements. Both bulk sensitive characterization techniques, Raman and grazing incident angle X-ray diffraction (GIXRD) analysis, show that no structural transformation is induced by neutron irradiation, although strain induced defect production are generated throughout the films while surface sensitive techniques, X-ray photoelectron spectroscopy (XPS) and work function measurements, show that the charge carrier (electron) concentration at room temperature decreases after irradiation. Potentially due to fast neutron irradiation induced defects, mainly in the form of Frenkel pairs, swelling and color center formation occurs in VO2 thin films without amorphization. This is further corroborated by an increase of the room temperature resistivity through the irradiated films. Temperature-dependent electrical and optical transmission measurements confirm that the characteristic semiconductor-to-metal transition of the VO2 films is preserved upon irradiation. We therefore conclude that VO2 is an excellent candidate for thermal shielding and thermal management of small satellites.
关键词： Smart radiator device,Vanadium dioxide,Neutron irradiation,Phase transition,Pulsed laser deposition
更新于2025-09-19 17:15:36
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Tunable Optical Antennas Using Vanadium Dioxide Metal-Insulator Phase Transitions
摘要： Here, we investigate the possibility of exploiting the insulator-to-metal transition in vanadium dioxide (VO2) to tune and optically control the resonances of dipole nanoantennas in the visible near-infrared region. We compare the results obtained in the case of antennas completely made by VO2 with those of previous works and highlight the key role of the substrate to perform dynamical tuning. We also present a highly efficient configuration composed of dipole gold antenna loaded with VO2 and give some general guidelines to optimally exploit phase transitions to tune nanodevices.
关键词： Phase-changing materials,Nanoantennas,Plasmonics,Vanadium dioxide
更新于2025-09-19 17:15:36
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Optimization of the doping of polyaniline via response surface method to prepare polymer electrolytes for dye sensitized solar cells
摘要： parameters in the preparation of polymer composite which is used as an electrolyte in dye doping of vanadium pentoxide and conductance of the polymer composite has been presented for preparation of polymer composite. These parameters do effect the efficiency of the DSSC sensitized solar cell (DSSC). Optimisation of two different parameters such as percentage In this work, the response surface methodology (RSM) has been applied to optimize the process and it has been evaluated using ANOVA results of polynomial regression. The results showed that the value of R2 and adjusted R2 are 0.9894 and 0.9818 respectively, which is quite high. open circuit voltage (VOC) of 799 mV, short circuit current (ISC) of 29.3 mA with 3.62% Furthermore, there was good agreement between predicted and experimental values of efficiency. The iodine and indium free environmentally benign DSSC fabricated using vanadium pentoxide doped polyaniline as electrolyte resulted in high fill factor (ff) of 58.3%, efficiency.
关键词： optimization,dye,vanadium pentoxide,solar cell,polyaniline
更新于2025-09-19 17:13:59