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Defining the composition and electronic structure of large-scale and single-crystalline like Cs2AgBiBr6 films fabricated by capillary-assisted dip-coating method
摘要： Owning the merits of both lead-free and air-stable, the double-perovskite Cs2AgBiBr6 has attracted increasing attention, but suffers low visible-light absorption coefficient due to its large indirect bandgap. Moreover, the electronic structure of its synthesized films has not been explored clearly yet. In this work, we developed a general and promising method to fabricate continuous, uniform and highly orientated Cs2AgBiBr6 films in large scale on various substrates through capillary-assisted dip-coating method. Strikingly, those optimized films are single crystalline verified by 4-scan XRD. Its electronic structure was carefully studied independently by multi-photo-physical characterizations. Its bandgap can be tuned from 2.65 to 2.25 eV by changing the substrate temperature in growth from 40 to 160 °C. Essentially, their work-function (WF) was determined at ~5.01 eV and WF-VBM is around 2 eV. This novel band structure with typical n-type characteristic, was further confirmed by DFT calculations, which reveals that the Cs interstitials and Br vacancies derived deep defect levels were fixed around its Fermi level, closer to the conduction band. This conclusion is different from its widely accepted p-type feature, but definitely deepens our understanding of this material and inspires us to find more valuable strategies of modulating its band structure and optoelectronic properties.
关键词： Single-crystalline perovskite films
更新于2025-11-20 15:33:11
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Electrical Detection of Singlet Fission in Single Crystal Tetracene Transistors
摘要： We present the electrical detection of singlet fission in tetracene by using a field-effect transistor (FET). Singlet fission is a photo-induced spin-dependent process, yielding two triplet excitons from the absorption of a single photon. In this study, we engineered a more deterministic platform composed of an organic single crystal FET rather than amorphous or polycrystalline FETs to elucidate spin-dependent processes under magnetic fields. Despite the unipolar operation and relatively high mobility of single crystal tetracene FETs, we were able to manipulate spin dependent processes to detect magnetoconductance (MC) at room temperature by illuminating the FETs and tuning the bias voltage to adjust majority charge carrier density and trap occupancy. In considering the crystalline direction and magnetic field interactions in tetracene, we show the MC response observed in tetracene FETs to be the result of the singlet fission process.
关键词： organic field effect transistors,singlet fission,magnetoconductance,single crystalline organic semiconductors
更新于2025-09-23 15:22:29
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Ag nanocrystals with nearly ideal optical quality: synthesis, growth mechanism, and characterizations
摘要： Though Ag nanocrystals are predicted as the best material for localized surface plasmon resonances (LSPR) in the visible light region, realization of their ideal LSPR properties is hindered by the stringent requirement, i.e., simultaneous control of their size, shape, crystallinity, and surface structure. To achieve this goal, a synthetic scheme in non-polar solvent coupled with mild oxidative-etching by H+ ions is established. With a trace amount of Cl- ions as catalysts, H+ ions (in the form of carboxylic acids) become active for selectively etching the nuclei (and small nanocrystals) with imperfect crystal structure, which results in a new growth mechanism for formation of monodisperse nanocrystals, namely “self-focusing of size/crystallinity distribution”. H+ ions, ligands, and other reagents in the scheme are confirmed to possess negligible effects on the surface dielectric properties of Ag nanocrystals. To eliminate radiative damping of LSPR, single-crystalline and monodisperse spherical Ag nanocrystals in the size range between 7 and 20 nm are synthesized using this one-pot scheme. With excellent control of all the structural parameters, the full-width-at-half-maximum of LSPR spectra of single-crystalline Ag nanocrystals match theoretical predictions in the entire size range, and the maximum quality factor (~20) of LSPR predicted by theory is realized. Raman enhancement factor of the single-crystalline Ag nanocrystals for crystal violet (excitation at 514 nm) is 5 times higher than that of the typical multi-twinned ones with the same size.
关键词： localized surface plasmon resonances,oxidative-etching,monodisperse,single-crystalline,Ag nanocrystals,Raman enhancement
更新于2025-09-23 15:21:21
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Time Dependent Facile Hydrothermal Synthesis of TiO2 Nanorods and their Photoelectrochemical Applications
摘要： In the present investigation, we report facile hydrothermal synthesis of TiO2 nanorods with high density rutile phase on Transparent Conducting Oxide (TCO) for enhanced solar cell application. The structural, optical, morphological, compositional and electrochemical properties are investigated by detailed XRD, UV-Vis-NIR spectrophotometer, FESEM, TEM, EDAX, XPS and photoelectrochemical studies. It is demonstrated that, the deposited TiO2 thin film shows pure rutile phase with tetragonal crystal structure. Optical spectra showed strong light absorption in UV region and FESEM images confirm the time dependent growth of TiO2 nanorods. EDAX and XPS Spectra confirm the formation of pure TiO2 nanorods. Photoelectrochemical performance with respect to time dependent growth of TiO2 nanorods showed highest photoconversion efficiency = 5.1%.
关键词： Hydrothermal synthesis,Photoelectrochemical cell property,Single crystalline,Photoconversion efficiency,TiO2 nanorods,Transparent conducting oxide (TCO)
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Interface Control for Enhancing Field Emission Properties from Single-Crystalline Molybdenum Nanopyramid Emitters
摘要： Interface control is an effective way to improve the field emission performance for an existing cold cathode. In this study, a series of pre- and post-treatments have been carried out to reduce the thickness of mid-layer, from over 30 nm to 3 nm, for the single-crystalline molybdenum nanopyramid emitters. Consequently, enhanced field emission properties have been achieved.
关键词： Molybdenum nanopyramid,Single crystalline,Field emission,Interface control
更新于2025-09-23 15:21:21
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Large-area grain-boundary-free copper films for plasmonics
摘要： Ultrasmooth single-crystalline metallic thin films provide several key advantages for the fabrication of well-defined and high-resolution plasmonic nanostructures, particularly complex integrated nanocircuits. For this purpose, copper is generally regarded as a poor plasmonic material compared to gold and silver because of its notorious oxidation issues when subjected to air exposure. Here, we report on the use of large-area grain-boundary-free copper films grown epitaxially on sapphire substrates in combination with focused ion beam milling to pattern plasmonic nanostructures with superior quality. The copper surfaces prepared using a single-crystalline copper sputtering target exhibit a very low roughness without any grain boundaries for varying film thicknesses and a strong resistance to oxidation, overcoming the bottleneck in conventional copper film fabrication. Surface plasmon resonance measurements show that improved dielectric constants with higher conductivity and long-term stability can be achieved using the single-crystalline copper films. Plasmonic nanohole arrays patterned from these high-quality films are found to display a stronger field enhancement compared to those made from polycrystalline copper films, thus resulting in an enhanced extraordinary optical transmission performance. This study suggests that our fabrication method is ideally suited for applications in copper-based plasmonic and nanophotonic devices as well as integrated nanocircuits on a large scale.
关键词： Single-crystalline films,Polycrystalline films,Surface plasmon resonances,Copper,Extraordinary optical transmission
更新于2025-09-23 15:19:57
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Single Molecule Nonlinearity in a Plasmonic Waveguide
摘要： Plasmonic waveguides offer the unique possibility to confine light far below the diffraction limit. Past room temperature experiments focused on efficient generation of single waveguide plasmons by a quantum emitter. However, only the simultaneous interaction of the emitter with multiple plasmonic fields would lead to functionality in a plasmonic circuit. Here, we demonstrate the nonlinear optical interaction of a single molecule and propagating plasmons. An individual terrylene diimide (TDI) molecule is placed in the nanogap between two single-crystalline silver nanowires. A visible wavelength pump pulse and a red-shifted depletion pulse travel along the waveguide, leading to stimulated emission depletion (STED) in the observed fluorescence. The efficiency increases by up to a factor of 50 compared to far-field excitation. Our study thus demonstrates remote nonlinear four-wave mixing at a single molecule with propagating plasmons. It paves the way toward functional quantum plasmonic circuits and improved nonlinear single-molecule spectroscopy.
关键词： quantum emitter,nonlinear optics,stimulated emission depletion STED,two-wire transmission line,single-crystalline silver flake,plasmonic nanocircuit
更新于2025-09-23 15:19:57
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Surface plasma Ag-decorated single-crystalline TiO2?x(B) nanorod/defect-rich g-C3N4 nanosheet ternary superstructure 3D heterojunctions as enhanced visible-light-driven photocatalyst
摘要： Ag-TiO2-x(B)/g-C3N4 ternary heterojunctions photocatalysts are fabricated by hydrothermal-calcination, photo-deposition procedure, and followed by in-situ solid-state chemical reduction procedure. As-obtained photocatalysts are consisted with heterojunctions between 2D g-C3N4 sheets and 1D TiO2(B) single-crystalline nanorods. The band gap of Ag-TiO2-x(B)/g-C3N4 ternary heterojunctions photocatalysts is reduced to ~2.23 eV due to plasma Ag and surface engineering. Under visible light irradiation, it has an optimal photocatalytic property for the reduction of Cr6+ (95%) and degradation of NH4+ (93%). The apparent reaction rate constants (k) of ternary heterojunctions photocatalysts for NH4+ and Cr6+ are 25 and 12 folds higher than that of original TiO2(B). Furthermore, Ag-TiO2-x(B)/g-C3N4 also has excellent hydrogen production efficiency, which is up to 410 mmol h-1 g-1. This enhancement can be attributed to the unique heterojunction formed by 1D single-crystalline TiO2(B) nanorods and 2D g-C3N4 sheets, surface plasma resonance effect of plasma Ag nanoparticle, and surface engineering. A possible photocatalytic mechanism is also proposed by analysizing the XPS valence-band spectra and the Mott-Schottky.
关键词： Surface engineering,g-C3N4 sheet,Visible-light-driven photocatalysis,Single-crystalline TiO2(B) nanorod,Heterojunction
更新于2025-09-19 17:15:36
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Nascent SEI-Surface Films on Single Crystalline Silicon Investigated by Scanning Electrochemical Microscopy
摘要： Silicon is a promising high capacity host material for negative electrodes in lithium-ion batteries with low potential for the lithiation/delithiation reaction that is outside the stability window of organic carbonate electrolytes. Thus, the use of such electrodes critically depends on the formation of a protective solid electrolyte interphase (SEI) from the decomposition products of electrolyte components. Due to the large volume change upon charging, exposure of the electrode material to the electrolyte must be expected, and facile re-formation of SEI is a scope for improving the stabilities of such electrodes. Here, we report the formation of incipient SEI layers on monocrystalline silicon by in-situ imaging of their passivating properties using scanning electrochemical microscopy after potentiodynamic charging to different final potentials. The images show a local initiation of the SEI growth at potentials of around 1.0 V vs. Li/Li+ in 1 M LiClO4 in propylene carbonate.
关键词： silicon electrode,single crystalline electrode,solid electrolyte interphase,scanning electrochemical microscopy,incremental charging
更新于2025-09-19 17:15:36
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Carrier lifetime exceeding 81 ns in single crystalline perovskite nanowires enable large on-off ratio photodetectors
摘要： Single crystalline perovskite nanowires are ideal candidates for photodetection and other optoelectronic applications due to their unique advantage of allowing the manipulation of light and carriers in nanoscale via the naturally formed boundaries. Although significant efforts have been made to grow high quality single crystalline perovskite nanowires, their carrier life times are much shorter than their bulk single crystal counterparts. Here, based on the surface initiated solution growth method with fine kinetic control, we fabricate high quality single crystalline MAPbI3 nanowires with the carrier life time as long as 81 ns, which outperforms the performances of all other solution processed single crystalline MAPbI3 nanowires. The as-prepared metal-semiconductor-metal photodetector has an extremely low dark current of 180 fA under 1 V bias, and a current of 340 pA under illumination of 10.2 mW/cm2, corresponding to an on-off current ratio of 1880, which is the largest on-off ratio in photodetectors based on MAPbI3 nanowires without any passivation treatment. Such superior performance is attributed to the long carrier life time of the as-grown MAPbI3 nanowires with reduced grain boundaries. The realized high performance MAPbI3 nanowire photodetector would find potential applications in imaging sensors.
关键词： Nanowire,Perovskite,Single-crystalline,Photodetection,Carrier life time
更新于2025-09-19 17:13:59