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Ultrafast Fabrication of Thermoelectric Films by Pulsed Light Sintering of Colloidal Nanoparticles on Flexible and Rigid Substrates
摘要： Sintered thermoelectric (TE) nanoparticle films are known to have a high figure-of-merit ZT factor and are considered for waste heat recovery and heating and cooling applications. The conventional process of thermal sintering of TE nanoparticles requires an inert environment and long heating times, and cannot be used on polymer substrates due to the requirements of the process (e.g., heating up to 400 °C). In this communication, the authors demonstrate for the first time the use of an intense flash of UV light from a Xenon lamp to sinter TE nanoparticles within milliseconds under ambient conditions on flexible polymer as well as glass substrates to create functional TE films. Photonic sintering is used to fabricate Bismuth Telluride thermoelectric films with a conductivity of 3200 S m?1 (a 5–6 orders of magnitude increase over unsintered films) and a peak power factor of 30 mW m?1 K?2. Modeling is used to gain an insight into the physical processes occurring during photonic sintering process and identify the critical parameters controlling the process. This work opens-up an exciting possibility of extremely rapid fabrication of TE generators under ambient conditions on a variety of flexible and rigid substrates.
关键词： power factor,ZT factor,thermoelectrics,Bi-Te nanoparticles,energy harvesting,photonic sintering
更新于2025-09-09 09:28:46
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Energy response characterization of InGaP X-ray detectors
摘要： Two custom-made In0.5Ga0.5P p+-i-n+ circular mesa spectroscopic X-ray photodiodes with different diameters (200 μm and 400 μm) and a 5 μm i layer have been characterized for their response to X-ray photons within the energy range 4.95 keV to 21.17 keV. The photodiodes, operating uncooled at 30 °C, were coupled, in turn, to the same custom-made charge-sensitive preamplifier. X-ray fluorescence spectra of high-purity calibration foils excited by a Mo target X-ray tube were accumulated. The energy resolution (Full Width at Half Maximum) increased from 0.79 ± 0.02 keV at 4.95 keV to 0.83 ± 0.02 keV at 21.17 keV, and from 1.12 ± 0.02 keV at 4.95 keV to 1.15 ± 0.02 keV at 21.17 keV, when using the 200 μm and 400 μm diameter devices, respectively. Energy resolution broadening with increasing energy was attributed to increasing Fano noise (negligible incomplete charge collection noise was suggested); for the first time, the Fano factor for In0.5Ga0.5P was experimentally determined to be 0.13, suggesting a Fano limited energy resolution of 145 eV at 5.9 keV. The charge output of each system had a linear relationship with photon energy, across the investigated energy range. The count rate of both spectroscopic systems increased linearly with varying X-ray tube current up to ～105 photons s?1 cm?2 incident photon fluences. The development of In0.5Ga0.5P based spectrometers is particularly important for hard X/γ-ray astronomy, due to the material’s large linear X-ray and γ-ray absorption coefficients and the ability to operate uncooled at high temperatures.
关键词： Fano factor,InGaP,spectroscopy,energy response,X-ray detectors
更新于2025-09-09 09:28:46
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Single-beam resonant spin amplification of electrons interacting with nuclei in a GaAs/(Al,Ga)As quantum well
摘要： The dynamic polarization of nuclear spins interacting with resident electrons under resonant excitation of trions is studied in a nominally undoped GaAs/(Al,Ga)As quantum well. Unlike in common time-resolved pump-probe techniques, we used a single-beam approach in which the excitation light is modulated between the circular and linear polarization states. The time-integrated intensity of the excitation laser re?ected from the sample surface, proportional to the optical generation rate and changing due to the pumping of the resident electrons, is detected. Polarized electrons, on the other hand, transfer their spin to the lattice nuclei via the hyper?ne interaction. Exciting the sample with a train of pulses in an external magnetic ?eld leads to resonant spin ampli?cation observed when the Larmor precession frequency is synchronized with the laser pulse repetition rate. A buildup of the nuclear spin polarization causes a shifting of the resonant spin ampli?cation peaks since the resulting nuclear ?eld alters the strength of the external magnetic ?eld experienced by the electrons. It was established that the nuclear spin polarization time T1 is temperature dependent and, owing to the electron localization at lower temperatures, becomes shorter. “Locking” of the nuclear (Overhauser) ?eld in the oblique external magnetic ?eld, related to the anisotropy of the electron g factor, was observed. The g factor ratio between the in-plane (g(cid:2)) and out-of-plane (g⊥) components was estimated to be g⊥/g(cid:2) = 1.3.
关键词： hyper?ne interaction,resonant spin ampli?cation,resonant excitation,electron g factor,quantum well,dynamic polarization,single-beam approach,nuclear spins
更新于2025-09-09 09:28:46
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Bound states in the continuum in a bilayer photonic crystal with TE-TM cross coupling
摘要： Bound states in the continuum (BICs) in photonic crystals represent the unique solutions of wave equations possessing an infinite quality factor. We design a type of bilayer photonic crystal and study the influence of symmetry and coupling between TE and TM polarizations on BICs. The BIC modes possess C3v symmetry in the x-y plane while the mirror-flip symmetry in the z direction is broken, and they provide selective coupling into different layers by varying frequency. The enhanced TE-TM coupling due to broken mirror-flip symmetry in the z direction gives rise to high-Q-factor BIC states with unique spatial characteristics. We show the emergence of such BIC states even in the presence of coupling between the TE- and TM-like modes, which is different from the existing single polarization BIC models. We propose to study BICs in multilayer systems, and the results may be helpful in designing photonic settings to observe and manipulate BICs with various symmetries and polarizations for practical applications.
关键词： High-Q-factor,Bound states in the continuum,Bilayer systems,Photonic crystals,TE-TM coupling
更新于2025-09-09 09:28:46
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Current transport and capacitance-voltage characteristics of Sb2Se3/n-Si heterojunction diode prepared by electron beam evaporation
摘要： The Sb2Se3 thin film was successfully deposited on the n-Si substrate using an electron beam evaporated technique. The structural investigation was done by means of X-ray diffraction analysis. The surface morphology and elemental analysis of the synthesized films were studied by FESEM and EDAX, respectively. The electrical properties of the Sb2Se3/n-Si heterojunction were considered by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The I-V results of Sb2Se3/n-Si heterojunction diode show a rectifying behavior. The junction ideality factor, barrier height, and series resistance values were extracted from the rectifying curves at different temperatures. The capacitance-voltage results show the abrupt nature of the junction under consideration.
关键词： diode,ideality factor,Antimony selenide,Electron beam,FESEM,XRD
更新于2025-09-09 09:28:46
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Screening for retinopathy of prematurity by telemedicine in a tertiary level neonatal intensive care unit in France: Review of a six-year period
摘要： To analyze the prevalence and risk factors for retinopathy of prematurity (ROP) and severe (treatment-requiring) ROP. A retrospective study was conducted in a level III neonatal unit in Bordeaux, France, from 2009 to 2015. Four hundred and nineteen preterm infants who were screened for ROP exclusively by RetCam were included. ROP of any degree was diagnosed in 27.68% of infants. Stages 1, 2, 3 and 4 ROP was found in 44%, 46%, 9% and 1% of subjects, respectively. No stage 5 ROP was observed. 28/419 infants (6.6%) were treated exclusively with laser photocoagulation. No intravitreal anti-VEGF injections or surgical treatments were performed. No infants born at > 31 weeks or with BW > 1110 g required ROP treatment. On multivariate analysis, risk factors for ROP development were low birth weight, low gestational age at birth, high duration of invasive mechanical ventilation, shock or use of vasopressors. On multivariate analysis, risk factors for severe, treatment-requiring ROP were male gender, gestational age ≤ 27 weeks and Apgar score at 5 minutes ≤ 7. In our 6-year series, ROP was successfully identified on screening exclusively by telemedicine, and no surgical treatment was required. This study identifies known ROP risk factors, but the Apgar score at 5 minutes as a risk factor for severe ROP requires further studies in order to be confirmed.
关键词： Risk analysis,Retinopathy of prematurity,Pediatric ophthalmology,Retina,Risk factor
更新于2025-09-09 09:28:46
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Statistical Analysis of the Current–Voltage ( <i>I</i> – <i>V</i> ) and Capacitance–Voltage ( <i>C</i> – <i>V</i> ) Characteristics of the Au/Ir/ <i>n</i> -InGaN Schottky Barrier Diodes
摘要： In the present work, 20 Au/Ir/n-InGaN Schottky barrier diodes (SBDs) are fabricated using a electron beam evaporation technique. The Schottky barrier parameters such as ideality factor (n), Schottky barrier height (SBH) ((cid:2)b(cid:3) and donar concentration (Nd (cid:3) values are determined by current–voltage (I–V ) and capacitance–voltage (C–V ) measurements at room temperature. From I–V measurements, the statistical distribution of data gives the mean SBH value of 0.70 eV with a normal deviation of 10 meV and mean ideality factor value of 1.50 with a normal deviation of 0.0478. Two important parameters such as series resistance (RS(cid:3) and shunt resistance (cid:3) are also evaluated from the I–V characteristics. Furthermore, Norde and Cheung’s methods are used to evaluate the SBH, ideality factor and series resistance. The statistical distribution of C–V data gives the mean SBH value of 0.91 eV with a normal deviation of 12 meV and mean donar concentration of 0.71 × 1017 cm?3 with a normal deviation of 0.018 × 1017 cm?3, respectively.
关键词： Series Resistance,Schottky Barrier Height,Ideality Factor
更新于2025-09-09 09:28:46
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AIP Conference Proceedings [AIP Publishing LLC NANOFORUM 2014 - Rome, Italy (22–25 September 2014)] - Impact of energy injection on size of Al nanoparticles generated by electric explosion of metal foils
摘要： The process of electric explosion of Aluminium metal foil has been used to produce nano aluminium powder under ambient atmospheric conditions. The impact of average rate of energy injection and overheat factor on size distribution of particles was analyzed by TEM technique. It was observed that higher the rate of energy deposition, the smaller the particles formed.
关键词： overheat factor,Nano particles,Pulse discharge
更新于2025-09-09 09:28:46
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A Substrate Model for On-Chip Tapered Spiral Inductors With Forward and Reverse Excitations
摘要： In this brief, closed-form analytical expressions are obtained to accurately calculate the oxide and substrate (both lateral/vertical) capacitances of the π-equivalent circuit model for on-chip tapered spiral inductors. A lateral RC substrate network using the above-mentioned expressions is shown to significantly improve the model accuracy, especially with lower substrate resistivities. Furthermore, improvement in Qmax with reverse excitation in tapered spirals is also accurately predicted by the proposed model. The accuracy of the proposed model is validated till 15 GHz using several inductor geometries across process parameters suitable for the design of RF circuits. Excellent agreement is observed between the model, electromagnetic simulations, and measurements.
关键词： CMOS,forward excitation,spiral inductor,substrate model,taper,reverse excitation,Capacitive coupling,radio frequency integrated circuits,quality factor
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (WoW) - Montréal, QC, Canada (2018.6.3-2018.6.7)] 2018 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (Wow) - Power Handling Capability of Self-Resonant Structures for Wireless Power Transfer
摘要： The range and ef?ciency of resonant inductive wireless power transfer depends on the quality factor of the resonant coils. A multilayer self-resonant structure (MSRS), made of many alternating layers of thin foil conductors and dielectric, has been shown to have a quality factor many times higher than conventional resonant coils of similar size. To date, the MSRS has only been modeled and tested for small-signal excitations and the impact of large-signal excitations on the MSRS performance has not been considered. This paper explores large-signal effects such as Steinmetz core loss, temperature dependence of winding and core losses, and the thermal effect of loss in order to determine the power handling capability of the MSRS. The analysis shows that a 6.6 cm-diameter prototype MSRS is capable of transferring as much as 10.7 kW over a 0.5 cm gap and 760 W over 2.2 cm, for maximum 40 ?C temperature rise in a 25 ?C environment.
关键词： power handling capability,thermal modeling,multilayer self-resonant structure,wireless power transfer,quality factor
更新于2025-09-09 09:28:46