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[Interface Science and Technology] Graphene Surfaces - Particles and Catalysts Volume 27 || Characterization
摘要： Graphene characterization is an important part of graphene research and contains measurements based on various microscopic and spectroscopic methods. Characterization includes layer number determination and the sample purity in terms of absence or presence of defects. Optical images of graphene samples in different solutions are the most effective method for the identification of the graphene production. This method is based on the color arising from the dispersibility of graphene and graphene oxide (GO).
关键词： Microscopic techniques,Spectroscopic methods,Graphene oxide,Graphene,Characterization
更新于2025-09-23 15:21:21
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Ultrasonic spray pyrolyzed copper oxide and copper-aluminum oxide thin films: optical, structural and electronic properties
摘要： A study of the structural, electrical and optical properties of copper oxide and copper-aluminum oxide thin films deposited by ultrasonic spray pyrolysis is presented in this work. On one hand copper oxide films were deposited at working temperatures in the range from 300 °C to 500 °C. These films present a mixture of Cu2O and CuO phases, CuO phase being more abundant at higher temperatures; all samples present p-type conductivity. On the other hand, copper-aluminum oxide samples were deposited at 350 °C but with different copper-aluminum ratios in the start solution (0, 12.5, 25, 50, 100, and 200 at.%). The films present a mixture of Cu2O and Al2O3 phases, being the Cu2O the most abundant and becoming amorphous as aluminum concentration rises. Electrical characterization indicates that electronic conductivity depends on the amount of Cu2O, while ionic conductivity increases with aluminum concentration. Aluminum concentration also provokes a shift in the valence band towards lower binding energies, as well as an increase in the optical band gap (from 2.6 to 3.7 eV). Upon a thermal annealing at 800 °C the samples turned to CuAl2O4 spinel structure.
关键词： Optical characterization,Electrical characterization,Semiconducting copper-aluminum compounds,Spray pyrolysis
更新于2025-09-23 15:21:01
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Growth of high purity zone-refined Boron Carbide single crystals by Laser Diode Floating Zone method
摘要： We report the growth of 4 mm diameter x 50 mm long Boron Carbide (B4C) with large single crystal regions using a Laser Diode Floating Zone (LDFZ) method at varying growth rates of 5-20 mm/hr. These materials were grown using polycrystalline B4C as a seed. Microstructural characterization shows the presence of a significant number of twinning-boundaries along the growth direction ([001]h) oriented in the (1210)h plane. At faster growth rates >10 mm/hr, the crystal orientation was reproducible, suggesting a twin-plane mediated growth mechanism. On the contrary, at slower growth rates <10 mm/hr the crystal orientation was not reproducible, suggesting a critical rate for twin-plane mediated growth to dominate. Zone refinement of these crystals led to a significant reduction of trace impurities to better than 99.999 wt % purity, at the expense of increased twinning. Powder x-ray diffraction confirms that the bulk is rhombohedral B4C, consistent with the microstructural analysis. The X-ray reciprocal space maps reveal the growth direction to be close to the [001]h direction, and the corresponding ω-rocking curve width is ~530arcsec. The rocking curve consisted of 3 distinct peaks, indicating in-plane mosaicism, consistent with the twinning observed. Berkovich nano-indentation of the key (001)h plane showed 41 ± 1 GPa hardness, with a Young’s modulus of 520 ± 14 GPa, comparable to literature reports.
关键词： A2. Single crystal growth,A1. Defects,A1. X-ray diffraction,A1. Characterization,A2. Growth from melt
更新于2025-09-23 15:21:01
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Multicore Multimode Fiber-A New Type of Fiber Using Coupled-Core Structures
摘要： A new type of multimode fiber, multicore multimode fiber (MCMMF), which uses coupled multicore structure is proposed. The fiber has a large number of single mode cores with optimized coupling to achieve high bandwidth. A theoretical model for analyzing the MCMMF is developed. The effect of fiber parameters, such as index contrast, core radius, and core spacing on the bandwidth is systematically studied. Numerical simulations show that the bandwidth of a MCMMF can be optimized by choosing correct ratio of core spacing to core radius for a given profile design. In addition, mode coupling among the super-modes can further increase the bandwidth due to the small spacing in effective indices in coupled core structures. A MCMMF with 165 cores is fabricated. High bandwidth of 8.4 GHz·km in the 850 nm window is achieved. Using this fiber and a VCSEL-based 25 Gb/s SR transceiver, error free transmission though 150 m fiber is demonstrated.
关键词： fiber characterization,fiber bandwidth,data center,multimode fiber,Coupled multicore fiber,fiber design,fiber fabrication
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Conference on Power Electronics and Renewable Energy (CPERE) - Aswan City, Egypt (2019.10.23-2019.10.25)] 2019 IEEE Conference on Power Electronics and Renewable Energy (CPERE) - Common-Mode Voltage Analysis of Three-phase Quasi-Z Source Inverters for Transformerless Photovoltaic Systems
摘要： Reducing the capacitance of programmable capacitor arrays (PCAs), commonly used in analog integrated circuits, is necessary for low-energy applications. However, limited mismatch data are available for small capacitors. We report mismatch measurement for a 2-fF poly–insulator–poly (PIP) capacitor, which is the smallest reported PIP capacitor to the best of the authors’ knowledge. Instead of using complicated custom on-chip circuitry, direct mismatch measurement is demonstrated and veri?ed using Monte Carlo simulations and experimental measurements. Capacitive test structures composed of 9-bit PCAs are implemented in a low-cost 0.35-μm CMOS process. Measured data are compared to the mismatch of large PIP capacitors, theoretical models, and recently published data. Measurement results indicate an estimated average relative standard deviation of 0.43% for the 2-fF unit capacitor, which is better than the reported mismatch of metal–oxide–metal (MOM) fringing capacitors implemented in an advanced 32-nm CMOS process.
关键词： programmable capacitor array (PCA),Analog-to-digital converter (ADC),energy-ef?cient circuits,mismatch characterization,capacitance-to-digital converter (CDC),capacitor mismatch
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Simulation of Optical and Electrical Losses of PV Modules in Moderate and Desert Conditions
摘要： Measurements of the PV modules are based on standard test conditions. However, PV modules have significant difference in performance based on the locations, environmental conditions and mounting situation. One of the environmental factors which influence the performance of the PV module is the spectrum of incident light on the PV module. In this paper, we compare the optical reflection losses, thermal losses as well as electricity production of modules under moderate (AM1.5) and desert-like spectrums (AM1.0). The results show quantitatively that thermalization has the highest loss portion with an average of 29.5% of the total incoming power density for both spectrums. The highest relative change is for absorption of light in polymer encapsulant especially between 280-400 nm with 24.3% and total resistive losses (in cell and interconnection) with 21.3% extra losses from desert to moderate conditions. Finally, we show that similar modules in desert climate produce 5% extra power gain while it suffers from 7.2% extra heat and 5% extra reflections.
关键词： Photovoltaic cells,Si PV Modelling,Metrology and Characterization,PV,Crystalline Silicon PV
更新于2025-09-23 15:21:01
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Influence of Cu content on physical characterization and optical properties of new amorphous Ge-Se-Sb-Cu thin films
摘要： The present work aims to theoretically study the effect of Cu concentration through many physical parameters, including coordination number (CN), constraints number (CON), overall mean bond energy (<E>), and cohesive energy (CE), for Ge25Se65Sb10-xCux (where x = 0, 2.5, 5, 7.5 and 10 at. %) glasses. As well, the optical constants of the thin films were evaluated via the use of the Swanepoel technique. As the Cu concentration rises, it is found that CN, CON, <E>, and CE also rise. This relationship demonstrates the obvious evidence for incremental rigidity of the Ge25Se65Sb10-xCux glasses with the addition of Cu. The refractive index (n) of the films were fitted to the two-term Cauchy dispersion equation to get the single oscillator (Eo) and dispersion (Ed) energies. In addition, the estimations of the absorption coefficient (α) were acquired using the conditions suggested by Connell and Lewis. An energy gap (Eg) decrement from 1.79 to 1.47 eV was prompted by a Cu concentration rise from 0 to 10% at. %.
关键词： Thin films,Optical properties,Physical characterization,Swanepoel method
更新于2025-09-23 15:21:01
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Handbook of Exoplanets || Spectroscopic Direct Detection of Exoplanets
摘要： The spectrum of an exoplanet reveals the physical, chemical, and biological processes that have shaped its history and govern its future. However, observations of exoplanet spectra are complicated by the overwhelming glare of their host stars. This chapter focuses on high-resolution spectroscopy (HRS) (R D 25;000–100;000), which helps to disentangle and isolate the exoplanet’s spectrum. At high spectral resolution, molecular features are resolved into a dense forest of individual lines in a pattern that is unique for a given molecule. For close-in planets, the spectral lines undergo large Doppler shifts during the planet’s orbit, while the host star and Earth’s spectral features remain essentially stationary, enabling a velocity separation of the planet. For slower-moving, wide-orbit planets, HRS, aided by high contrast imaging, instead isolates their spectra using their spatial separation. The lines in the exoplanet spectrum are detected by comparing them with high resolution spectra from atmospheric modelling codes; essentially a form of ?ngerprinting for exoplanet atmospheres. This measures the planet’s orbital velocity and helps de?ne its true mass and orbital inclination. Consequently, HRS can detect both transiting and non-transiting planets. It also simultaneously characterizes the planet’s atmosphere, due to its sensitivity to the depth, shape, and position of the planet’s spectral lines. These are altered by the planet’s atmospheric composition, structure, clouds, and dynamics, including day-to-night winds and its rotation period. This chapter describes the HRS technique in detail, highlighting its successes in exoplanet detection and characterization, and concludes with the future prospects of using HRS to identify biomarkers on nearby rocky worlds and map features in the atmospheres of giant exoplanets.
关键词： atmospheric characterization,molecular features,exoplanets,Doppler shifts,high-resolution spectroscopy
更新于2025-09-23 15:21:01
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Application of a suitable particle engineering technique by pulsed laser ablation in liquid (PLAL) to modify the physicochemical properties of poorly soluble drugs
摘要： Several disintegration procedures are well known in the field of pharmaceutical technology to improve the solubility, dissolution rate and bioavailability. Only a few, organic materials were applied for micro/nanoparticle generation by pulsed laser ablation in liquid (PLAL), however in the last decade, several studies presented successful production from different active agents. PLAL could be a non-conventional approach by the preformulation of the drug, as a simple, clean (no additional chemicals are needed) and a rapid wet grinding method. It can be stated about the novelty of the work that a poorly water-soluble meloxicam was milled first time by pulsed laser ablation in liquid, where the effect of three different wavelengths, fluence values (energy density) and polymer type (PVP, PVA, Poloxamer) on the habit, structure, solubility and in vitro properties of the drug were investigated. Nearly spherical amorphous micro- and nanoparticles could be reached in a size range between 60-700 nm. Fourier-transform infrared spectroscopy (FT-IR) was applied to check the purity, secondary interaction and High performance liquid chromatography (HPLC) method was used for the determination of the presence of the meloxicam content and the final yield. The results suggest that laser ablation a useful approach to modify the physicochemical properties of the active agents, introduced a novel preparation method in drug preformulation with improved solubility (from 0.0203 mg/mL to 0.0797 mg/mL), dissolution rate (~85%) and also to produce a suitable intermediate product for traditional and alternative drug administration (e.g. pulmonary, nasal, transdermal).
关键词： physicochemical characterization,novel wet-milling,meloxicam,in vitro dissolution,nanosuspension,laser fragmentation
更新于2025-09-23 15:21:01
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Light intensity modulated photoluminescence for rapid series resistance mapping of perovskite solar cells
摘要： The champion efficiency of small area perovskite solar cells is marginally behind their silicon counterpart. However, when up-scaled to large area modules, the performance of perovskite solar cells drops significantly due primarily to the inclusion of defects during fabrication. The future of perovskite solar cells depends greatly on the ability to fabricate high efficiency large area devices which requires methods for rapidly and reliably identifying the presence of damage or imperfections that limit their performance. In this work we employ, for the first time, intensity modulated photoluminescence to spatially map the series resistance of perovskite solar cells with high spatial resolution. The technique permits the rapid identification of a range of different macroscopic defects and quantifies the impact on the local series resistance. It is performed under steady-state conditions to avoid complications of transient behaviour occurring in the perovskite film. The robustness of the approach is demonstrated by characterising an entire batch of perovskite solar cells with the mean series resistance values validated using established electrical analysis methods. Our method can be readily applied by other research groups for device optimisation or scaled to large areas for automated process control and validation.
关键词： Photoluminescence,Device characterization,Perovskite solar cells,Series resistance
更新于2025-09-23 15:21:01