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On-chip sensor solution for hydrogen gas detection with the anodic niobium-oxide nanorod arrays
摘要： Two types of anodic niobium-oxide nanofilms were synthesized via anodization of an Al/Nb bilayer sputter-deposited onto a SiO2-coated Si wafer. Type I nanofilm was composed of a 200 nm thick NbO2 layer holding the upright-standing 650 nm long, 50 nm wide, and 70 nm spaced Nb2O5 nanorods, of 7·109 cm?2 density, whereas the Type II nanofilm had similarly long but bigger Nb2O5 nanorods, 100 nm wide, 220 nm spaced, and of 8·108 cm?2 density, aligned directly on a niobium metal without any buffering oxide layer, which was achieved for the first time. Each film was then incorporated in an advanced 3-D architecture and multilayer layout on a silicon chip comprising 33 microsensors, with variable sizes and tuned electrical characteristics, by combining the high-temperature vacuum or air annealing, sputter-deposition, and lift-off photolithography to form Pt/NiCr top electrodes and a multifunctional SiO2 interlayer, chemical etching, laser dicing, and ultrasonic wire-bonding. The proposed on-chip sensor solution allowed for a sensitive, fast, and highly selective (toward NH3 and CH4) detection of hydrogen gas. Comprehensive gas sensing tests performed for Type II nanofilm ultimately confirmed the presence of a Schottky-type sensing mechanism, the contribution, however, being substantially weaker than that due to reactions over the surface of the oxide nanorods, especially when the rods show a transition from fully to partially depleted states when interacting with H2 gas. The film formation and chip fabrication technologies may be transferable to other PAA-assisted 1-dimensional metal-oxide nanomaterials suitable for on-chip gas sensing.
关键词： niobium oxide nanorods,anodic alumina,hydrogen,Schottky barrier,anodizing,on-chip sensor
更新于2025-09-23 15:23:52
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Transparent Electrodes Consisting of a Surface-Treated Buffer Layer Based on Tungsten Oxide for Semitransparent Perovskite Solar Cells and Four-Terminal Tandem Applications
摘要： For semitransparent devices with n-i-p structures, a metal oxide buffer material is commonly used to protect the organic hole transporting layer from damage due to sputtering of the transparent conducting oxide. Here, a surface treatment approach is addressed for tungsten oxide-based transparent electrodes through slight modification of the tungsten oxide surface with niobium oxide. Incorporation of this transparent electrode technique to the protective buffer layer significantly recovers the fill factor from 70.4% to 80.3%, approaching fill factor values of conventional opaque devices, which results in power conversion efficiencies over 18% for the semitransparent perovskite solar cells. Application of this approach to a four-terminal tandem configuration with a silicon bottom cell is demonstrated.
关键词： semitransparent solar cells,perovskite-silicon tandem,niobium oxide,tungsten oxide,perovskite solar cells
更新于2025-09-23 15:21:01
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One-Step Plasma Synthesis of Nb <sub/>2</sub> O <sub/>5</sub> Nanofibers and their Enhanced Photocatalytic activity
摘要： Fiberform nanostructured niobium (Nb) was fabricated by one step helium (He) plasma irradiation. He ion implantation formed He nano-bubbles on a Nb plate and led to formation of protrusions while migrating in Nb matrix; fiberform nanostructures (FN) were grown when the fluence became high (> 1026 m?2). The necessary conditions for the formation of Nb FN were revealed to be the surface temperature range of 900–1100 K and the incident ion energy higher than 70 eV. The sample was oxidized at 573–773 K in an air atmosphere, and Pt nanoparticles were photo-deposited on the Nb2O5 samples. The surface was analyzed by scanning electron microscope, transmission electron microscope, x-ray photoelectron spectroscopy, and ultraviolet-visible spectrophotometry. Photocatalytic activity of the fabricated materials was studied using methylene blue (MB) decolorization process. An enhanced photocatalytic performance was identified on FN Nb2O5 substrate with Pt deposition.
关键词： helium bubble,photocatalysis,niobium oxide,plasmas
更新于2025-09-23 15:21:01
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Strongly Coupled Amorphous Porous NbO <sub/>x</sub> (OH) <sub/>y</sub> /g‐C <sub/>3</sub> N <sub/>4</sub> Heterostructure Composite for Efficient Photocatalytic Hydrogen Evolution
摘要： Heterostructure composites are promising materials in photocatalytic hydrogen evolution due to their advantage on promoting photogenerated carrier separation efficiently. However, the weak interfacial interaction can block electron transfer and complicate synthesis methods restrict the practical application of catalysts. Here, we report an interfacial enhanced amorphous porous NbOx(OH)y/g-C3N4 heterostructure composite through a spontaneous coupling process. It was characterized by XRD, TEM, FT-IR, XPS, NH3-TPD and CO2-TPD, etc., which demonstrated that NbOx(OH)y possess amorphous porous structures with high specific surface area (205 m2/g) and plenty of acidic sites (418 μmol/g) as well as basic sites (184 μmol/g) contributed from uncoordinated Nb and -OH. These acidic and basic sites electrostatically attract -NHx and C-OH on the surface of g-C3N4 to form hydrogen bonds (Nb-O-H???NH2, Nb-O???H-O-C), showing a strong electron interaction between NbOx(OH)y and g-C3N4. When tested as a photocatalyst for water splitting under visible light, the optimal NbOx(OH)y/CN-0.05 heterostructure composite exhibits a hydrogen evolution rate of 53 μmol/g/h, which is about 14 times higher than that of g-C3N4 (3.8 μmol/g/h) and is even superior than P25 (16 μmol/g/h). These present findings lay a foundation for the synthesis of strongly interacting heterogeneous composites.
关键词： heterojunction,water splitting,amorphous niobium oxide,photocatalysis,g-C3N4
更新于2025-09-12 10:27:22
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Current Localization and Redistribution as the Basis of Discontinuous Current Controlled Negative Differential Resistance in NbO <i> <sub/>x</sub></i>
摘要： Devices exploiting negative differential resistance (NDR) are of particular interest for analog computing applications, including oscillator-based neural networks. These devices typically exploit the continuous S-shaped current–voltage characteristic produced by materials with a strong temperature-dependent electrical conductivity, but recent studies have also highlighted the existence of a second, discontinuous (snap-back) characteristic that has the potential to provide additional functionality. The development of devices based on this characteristic is currently limited by uncertainty over the underlying physical mechanism, which remains the subject of active debate. In situ thermoreflectance imaging and a simple model are used to finally resolve this issue. Specifically, it is shown that the snap-back response is a direct consequence of current localization and redistribution within the oxide film, and that material and device dependencies are consistent with model predictions. These results conclusively demonstrate that the snap-back characteristic is a generic response of materials with a strong temperature-dependent conductivity and therefore has the same physical origin as the S-type characteristic. This is a significant outcome that resolves a long-standing controversy and provides a solid foundation for engineering functional devices with specific NDR characteristics.
关键词： brain-inspired computing,negative differential resistance,niobium oxide,thermoreflectance imaging,transition metal oxides
更新于2025-09-11 14:15:04
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Low-temperature solution-combustion-processed Zn-Doped Nb2O5 as an electron transport layer for efficient and stable perovskite solar cells
摘要： Niobium oxide (Nb2O5) has been demonstrated as an ideal electron transport layer (ETL) material for perovskite solar cells (PSCs) due to its excellent optical transmittance and high carrier mobility. Herein, a low-temperature (200°C) solution-combustion method is adopted to prepare the Nb2O5 film used as an ETL in PSCs. Under optimized conditions, PSC with the Nb2O5 ETL obtains a power conversion efficiency (PCE) of 16.40%. Moreover, we find that Zn-doping of Nb2O5 can further improve the efficiency of the device. As a matter of fact, the results show that a champion PCE of 17.70% can be achieved for the PSC with a 5 mol% Zn-doped Nb2O5 ETL. Significantly, both Nb2O5- and Zn-doped Nb2O5-based devices exhibit obviously better stability than the traditional high-temperature-sintered (~500°C) mesoporous TiO2-based devices, maintaining 80% of their initial PCE after storage in air for 20 days. In contrast, the PCE of the device with a TiO2 ETL quickly drops to 30% of its initial value after 13 days under the same storage condition. Consequently, this work suggests that using Zn-doped Nb2O5 ETL prepared by the low-temperature solution-combustion method is promising towards efficient and stable perovskite solar cells.
关键词： Perovskite solar cells,Electron transport layer,Zinc doping,Niobium oxide,Low-temperature synthesis,Stability
更新于2025-09-11 14:15:04
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Novel and inexpensive Nb2O5/tannin-formaldehyde xerogel composites as substitutes for titanium dioxide in photocatalytic processes
摘要： This project studied the preparation of new Nb2O5/tannin-formaldehyde xerogel composites (XTF-wNb) for photocatalytical applications. The choice of tannin biomass and niobium recycled scraps as precursors is aimed at reducing costs and environmental impacts. The composites were characterized by diffuse re?ectance spectroscopy (DR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), infrared spectroscopy (IR), and X-ray diffraction (XRD). The photocatalytic properties of the composites were evaluated by methylene blue decomposition. The in?uence of the catalyst dosage and the initial concentration of dye in the adsorption and photocatalysis processes were studied. The X-ray pro?les of the XTF-wNb show the presence of niobic acid in the structure of the materials, proving the presence of the inorganic oxide in the matrix of these composites. The tannin/Nb ratio had a signi?cant in?uence on the morphology of the formed composites, causing changes in the shape and size of the particles composing each material. All materials have pHPZC < 5. The XTF-24Nb was the most effective photocatalyst, its photocatalytic ef?ciency superior to the one of titanium dioxide, evidencing the bene?cial effect of the xerogel coupling on the photocatalytic properties of the material.
关键词： Photocatalysis,Niobium oxide,Xerogel,Tannin
更新于2025-09-04 15:30:14