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Facile synthesis of SiO2@TiO2 hybrid NPs with improved photocatalytic performance
摘要： SiO2@TiO2 hybrid nanoparticles (NPs) were successfully prepared via a simple solvothermal approach using tetrabutyl titanate (Ti(OBu)4) as a titanium source. The morphology and crystal structure of the sample were characterised by scanning electron microscope, transmission electron microscope, and X-ray diffraction. The photocatalytic properties of SiO2@TiO2 hybrid NPs were also investigated in detail. The results showed that the layers of TiO2 NPs have been successfully coated onto the uniform silica sphere and transformed into anatase after calcination at 500°C. In addition, the photocatalytic activity of the as-obtained product was higher than that of the commercial P25-TiO2. The method for producing hybrid NPs has potential applications in building various types of hybrid NPs.
关键词： SiO2@TiO2 hybrid nanoparticles,photocatalytic performance,solvothermal approach,anatase titanium dioxide
更新于2025-09-23 15:21:21
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Phase separation and transformation of binary immiscible systems in molten core-derived optical fibers
摘要： This work studies phase-separated ?bers in the CaO–SiO2 and NiO–SiO2 systems. The nature of the phase-separated microstructures and underlying phase equilibria are discussed, including dimensionality, composition, and phase formation as well as the realization of ferrimagnetic behavior in the NiO–SiO2 ?bers based on the formation of metallic Ni inclusions. In addition to understanding the composition/processing relationships in these systems, the work represents a step forward toward novel magneto-optic ?bers. It is important to understand the underlying materials science in order to advance the properties of novel optical ?bers possessing engineered heterogeneities in the core.
关键词： CaO–SiO2,ferrimagnetic behavior,phase-separated ?bers,NiO–SiO2,magneto-optic ?bers
更新于2025-09-23 15:21:01
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Synthesis of SiO <sub/>2</sub> @Ag core-shell photonic crystals for SERS application
摘要： Core-shell SiO2@Ag composite spheres with dense, complete and nanoscaled silver shell were prepared by using facile chemical reduction method. Self-assembly of the composite microspheres into 3D photonic crystals (PhCs) was carried out using the vertical deposition method. The core-shell PhCs composites were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy and energy dispersive X-ray spectroscopy (EDX). The results of amplification of Raman scattering by these composite substrates are presented.
关键词： SiO2@Ag,photonic crystals,SERS,core-shell,Raman scattering
更新于2025-09-23 15:21:01
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SiO<sub>2</sub> nanoparticle-regulated crystallization of lead halide perovskite and improved efficiency of carbon-electrode based, low temperature planar perovskite solar cells
摘要： SiO2 nanoparticles were used to regulate the crystallizing process of lead halide perovskite film that prepared by the sequential deposition method, which was used in the low temperature processed, carbon-electrode basing, hole-conductor-free planar perovskite solar cells. It was observed that, after adding small amount of SiO2 precursor (1% in volume ratio) into the lead iodide solution, performance parameters of open-circuit voltage, short-circuit current and fill factor were all upgraded, which helped to increase the power conversion efficiency (reverse scan) from 11.44(±1.83)% (optimized at 12.42%) to 14.01(±2.14)% (optimized at 15.28%, AM 1.5G, 100 mW/cm2). Transient photocurrent decay curve measurements showed that, after the incorporation of SiO2 nanoparticles, charge extraction was accelerated, while transient photovoltage decay and dark current curve tests both showed that recombination was retarded. The improvement is due to the improved crystallinity of the perovskite film. X-ray diffraction and scanning electron microscopy studies observed that, with incorporation of amorphous SiO2 nanoparticles, smaller crystallites were obtained in lead iodide films, while larger crystallites were achieved in the final perovskite film. This study implies that, amorphous SiO2 nanoparticles could regulate the coarsening process of the perovskite film, which provides an effective method in obtaining high quality perovskite film.
关键词： SiO2 (61.46.Hk),crystallization(81.10.-h),low temperature(84.60.Jt),perovskite solar cell(88.40.H-),lead iodide(61.82.Rx),carbon-electrode(88.40.HJ)
更新于2025-09-23 15:21:01
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Polarization selective metasurface formed by interference laser writing
摘要： Polarization dependent optical response of the periodically nanostructured SiO2-Ag nanocomposite material is investigated. As a result of the laser-based surface structuring, the reflection is found to be particularly enhanced and blueshifted for parallel polarisation. This result is attributed to the interaction between photonic and plasmonc resonances, namely to the coupling of the grating caused Rayleigh-Wood anomaly mode (described by using grating theory) with localized surface plasmon modes of the embedded Ag nanoparticles (described by using effective medium approach). The laser-induced formation of such metasurface allows precise control of the effect that is essential for practical application in photonics devices and optical filters.
关键词： photonic resonances,plasmonic resonances,polarization selective metasurface,interference laser writing,SiO2-Ag nanocomposite
更新于2025-09-23 15:21:01
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Wafer Scale Graphene Field Effect Transistors on Thin Thermal Oxide
摘要： In this study, we present the feasibility to fabricate back-gated graphene field-effect transistors (GFETs) on 10 nm thermal SiO2 substrate. Here, we compare the mobility of graphene devices at different locations of the transferred CVD graphene. We observed that there is a n-type doping of the graphene devices with Dirac points within ± 0.5 V from an ideal value of 0 V. The downscaling of the back-gate dielectric thickness reduces the operating voltage range, commonly required for low power electronics, and the devices are stable during operation in air under ambient conditions. The extracted contact resistance is comparable to the earlier reports found in literature and this provides a feasibility to fabricate low power futuristic graphene based nanoelectronics.
关键词： CVD graphene,n-type doping,thermal SiO2,mobility,Dirac points,low power electronics,field-effect transistors,graphene,contact resistance
更新于2025-09-23 15:21:01
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Ar-Plasma-Modulated Optical Reset in the SiO <sub/>2</sub> /Cu Conductive-Bridge Resistive Memory Stack
摘要： Our study using conductive atomic force microscope shows that the resistive switching voltage in the SiO2/Cu stack is reduced by 33% after Ar plasma treatment of the oxide. Besides, the negative photo-conductivity (NPC) effect, normally observed on many locations following electrical soft-breakdown, is suppressed. The NPC effect arises because the electrically-formed filamentary conductive path, comprising both Cu and oxygen vacancies, may be disrupted by the recombination of the vacancies with nearby light-excited interstitial oxygen ions. Increase of the O-H peak, as seen from FT-IR spectroscopy, indicates that surface defects generated by the Ar plasma may have adsorbed water molecules, which in turn act as counter anions (OH?) accelerating Cu-ion diffusion into the oxide, forming a more complete Cu filament that is non-responsive to light. The finding offers the possibility of both electrical and optical resistance control by a simple surface treatment step.
关键词： Ar plasma treatment,negative photo-conductivity,conductive atomic force microscope,resistive switching,SiO2/Cu stack
更新于2025-09-23 15:21:01
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Channel-Length Dependent Performance Degradation of Thermally Stressed IGZO TFTs
摘要： The focus of this work is on the performance degradation of thermally stressed IGZO TFTs with SiO2 for both the gate dielectric and back-channel passivation material. I-V characteristics of TFTs with bottom-gate (BG) and double-gate (DG) electrode configurations were observed to left-shift and degrade with thermal stress. Experimental results indicate the instability occurs either directly or indirectly due to the influence of H2O within the passivation oxide above the IGZO channel region. An atomic layer deposition (ALD) alumina capping layer applied immediately following the passivation oxide anneal was successful in improving thermal stability. Channel length dependence was observed where longer channel DG devices were more prone to degradation. A hypothesis has been developed with H2O as the expected origin of this phenomenon. Experiments have been specifically designed to establish the feasibility of the proposed mechanism. Furthermore, DG devices which exhibit enhanced thermal stability are presented.
关键词： thermal stability,SiO2 passivation,ALD alumina capping,IGZO TFTs,channel length dependence
更新于2025-09-23 15:21:01
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Investigation of laser damage of grating waveguide structures submitted to sub-picosecond pulses
摘要： Grating waveguide structures (GWS) are reflective diffractive optical elements that operate based on the combination of sub-wavelength gratings (periodic microstructures) integrated with planar waveguides. They can be used for high-power laser applications for pulse compression, spectral stabilization, wavelength multiplexing, as well as polarization shaping. In this work, we investigate the laser-damage resistance of GWS based on Ta2O5/SiO2 multilayers at pulse durations of 500 fs and wavelength of 1030 nm. We particularly study the influence of the material of the multilayer sequence, the designed grating structure, and the operational conditions (angle of incidence and polarization of the laser beam) on the laser-damage resistance of the GWS. Comparison of measurements to simulation of the electric-field distribution in the structure reveals a good correlation between laser-induced damage threshold (LIDT) values and electric-field enhancement in the structure. Based on this work, an optimized design has been defined to increase the LIDT of the GWS. An improvement of the LIDT of a factor 2 has been obtained.
关键词： Ta2O5/SiO2 multilayers,Grating waveguide structures,Electric-field distribution,Sub-picosecond pulses,Laser-damage resistance
更新于2025-09-23 15:21:01
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Ultrathin TiO2-coated SiO2 nanoparticles as light scattering centers for quantum dot-sensitized solar cells
摘要： SiO2/TiO2 core/shell nanoparticles (ST-NPs) with an ultrathin and conformal TiO2 shell were fabricated via atomic layer deposition (ALD) technique with a specially-designed rotary reactor. We successfully employed the ST-NPs as light scattering centers in a mesoporous TiO2 photoanode in quantum dot (QD)-sensitized solar cells (QDSSCs). ST-NPs enhanced the light scattering in the TiO2 photoanode without deterioration of QD loading behavior. Consequently, visible light absorbance was improved in the PbS QDs-sensitized TiO2 photoanode, and thus the photocurrent density increased from 14 to 17 mA/cm2. Detailed electron microscopy was utilized to reveal the uniqueness of the ultrathin TiO2 shell in ST-NPs, and in-depth electrochemical impedance spectroscopy divulged the increase in photogenerated carrier lifetime and improved recombination resistance for the QDSSC with ST-NPs.
关键词： Core-shell,SiO2,Atomic layer deposition,QDSSCs,Light scattering
更新于2025-09-23 15:21:01