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Phase diagram of Bi2Sr2CaCu2O8+δ revisited
摘要： In cuprate superconductors, the doping of carriers into the parent Mott insulator induces superconductivity and various other phases whose characteristic temperatures are typically plotted versus the doping level p. In most materials, p cannot be determined from the chemical composition, but it is derived from the superconducting transition temperature, Tc, using the assumption that the Tc dependence on doping is universal. Here, we present angle-resolved photoemission studies of Bi2Sr2CaCu2O8+δ, cleaved and annealed in vacuum or in ozone to reduce or increase the doping from the initial value corresponding to Tc = 91 K. We show that p can be determined from the underlying Fermi surfaces and that in-situ annealing allows mapping of a wide doping regime, covering the superconducting dome and the non-superconducting phase on the overdoped side. Our results show a surprisingly smooth dependence of the inferred Fermi surface with doping. In the highly overdoped regime, the superconducting gap approaches the value of 2Δ0 = (4 ± 1)kBTc.
关键词： cuprate superconductors,Fermi surfaces,superconducting gap,doping,angle-resolved photoemission spectroscopy
更新于2025-09-04 15:30:14
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Large area stress free Si layer transfer onto Corning glass substrate using ion-cut
摘要： We report about the large area stress free single crystal silicon (Si) layer transfer onto the glass substrate using hydrogen ion (H+) implantation and heterogeneous direct wafer bonding (DWB) performed at different temperatures. The root mean square surface roughness of the H-implanted Si wafer and glass substrate was measured about 0.3 nm and 0.5 nm, respectively. At an annealing temperature of 330 oC, a thin layer of the Si wafer was transferred onto the glass substrate. The average thickness of the transferred layer was found to be ~605 nm with surface roughness 4 nm. Raman spectroscopy confirmed that the transferred Si layer was stress free and retained its crystallinity. Large area transfer of high quality stress free Si-on-glass substrate is demonstrated using heterogeneous DWB and ion-cut process.
关键词： Raman spectroscopy,Heterogeneous DWB,Ion-cut,Si
更新于2025-09-04 15:30:14
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Synthesis of amorphous carbon nanofibers on a surface of commercial polymers under the action of a high power ion beam of nanosecond duration
摘要： The irradiation of various commercial polymers (chlorinated polyvinyl chloride, polyvinyl chloride, polyvinyl alcohol, polymethyl methacrylate) by a high-power ion beam of nanosecond duration has been investigated. The amorphous carbon nanofibers formation was detected on the surface of low-cost commercial polymers (chlorinated polyvinyl chloride, polyvinyl chloride) containing a catalyst under the high power ion beam irradiation at room temperature. Various iron compounds (organic and inorganic) were used as catalytic additions. The electron microscopy (scanning and transmission) with an energy dispersive analyzer and Raman spectroscopy were used to investigate the morphologies and structure of irradiated polymers. Carbon nanofibers (CNFs) had a most probable diameter in the range 50-90 nm and a maximum length of up to 10 μm. The maximum CNFs growth rate was estimated as 160 μm/μs. A possible growth mechanism for CNFs is discussed.
关键词： electron microscopy,amorphous carbon nanofibers,catalytic additions,Raman spectroscopy,high-power ion beam,commercial polymers
更新于2025-09-04 15:30:14
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[IEEE 2018 Global Smart Industry Conference (GloSIC) - Chelyabinsk, Russia (2018.11.13-2018.11.15)] 2018 Global Smart Industry Conference (GloSIC) - Mesophase Materials as Smart Media for Emerging Pressure Sensors: Capacitive Method of Measurement of DC Conductivity
摘要： Liquid crystals are a perspective type of materials for application in the field of tactile pressure sensors owning to their unique physical properties. One of such properties is the anisotropic electric conductivity, the value of which can be controlled by the external electric field. In this report we will consider a capacitive method of the measurement of the direct current conductivity in the liquid crystal layer, confined in the cell with blocking electrodes. It will be demonstrated that this technique allows estimating the direct current conductivity of a liquid crystal in a broad temperature range. The retrieved results can be used
关键词： blocking electrodes,impedance spectroscopy,liquid crystals,electric conductivity
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Low-pass Frequency Selective Surface for a Dual-band Gyro-multiplier Characterized by THz-TDS
摘要： This work investigates the performance of a low-pass frequency selective surface (FSS) fabricated from perforated hole array on a copper plate for the use in a dual-band high power gyro-multiplier. The output beam from the high power gyro-multiplier contains signals at two separating bands carrying peak power up to 2 kW. The frequency separating components therefore are required to stand high power and produce low insertion loss. Metallic perforated array is an ideal option to meet these requirements. Considering the fabrication accuracy, low-pass FSS is selected. The fabrication of the low-pass FSS is based on precision milling technology. The performance of the FSS is evaluated using a terahertz time domain spectroscopy.
关键词： gyro-multiplier,terahertz time domain spectroscopy,quasi-optics,frequency selective surface
更新于2025-09-04 15:30:14
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Detection of abnormality occurring over the whole cable length by frequency domain reflectometry
摘要： In previous papers, the authors reported that a combination of frequency domain reflectometry and inverse fast Fourier transform can locate the position of occurrence of degradation or abnormality in a polymer-insulated electric cable. This paper demonstrates that this method is also applicable even if the degradation or abnormality occurs uniformly over the entire cable length.
关键词： frequency domain reflectometry,broadband impedance spectroscopy,fault location,characteristic impedance,aging
更新于2025-09-04 15:30:14
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Occupied and unoccupied electronic structures of an L-cysteine film studied by core-absorption and resonant photoelectron spectroscopies
摘要： Unoccupied and occupied electronic structures of an L-cysteine film have been studied by absorption and resonant photoelectron spectroscopies. Core absorptions at S-L, C-K, N-K, and O-K levels indicate that the lower unoccupied states are predominantly composed of oxygen-2p, carbon-2p, and sulfur-4s+3d orbitals, while higher unoccupied states may be attributed dominantly to nitrogen-np (n ≥ 3), oxygen-np (n ≥ 3), and sulfur-ns+md (n ≥ 4, m ≥ 3) orbitals. Resonant photoelectron spectra at S-L23 and O-K levels indicate that the highest occupied state is originated from sulfur-3sp orbitals, while oxygen-2sp orbitals contribute to the deeper valence states. The delocalization lifetimes of the oxygen-1s and sulfur-2p excited states are estimated from a core-hole clock method to be about 9 ± 1 and 125 ± 25 fs, respectively.
关键词： resonant photoelectron spectroscopy,core-absorption,electronic structures,delocalization lifetime,L-cysteine
更新于2025-09-04 15:30:14
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Modeling core-level excitations with variationally optimized reduced-density matrices and the extended random phase approximation
摘要： The information contained within ground-state one- and two-electron reduced-density matrices (RDMs) can be used to compute wave functions and energies for electronically excited states through the extended random phase approximation (ERPA). The ERPA is an appealing framework for describing excitations out of states obtained via the variational optimization of the two-electron RDM (2-RDM), as the variational 2-RDM (v2RDM) approach itself can only be used to describe the lowest-energy state of a given spin symmetry. The utility of the ERPA for predicting near-edge features relevant to x-ray absorption spectroscopy is assessed for the case that the 2-RDM is obtained from a ground-state v2RDM-driven complete active space self-consistent field (CASSCF) computation. A class of killer conditions for the CASSCF-speci?c ERPA excitation operator is derived, and it is demonstrated that a reliable description of core-level excitations requires an excitation operator that ful?lls these conditions; the core-valence separation (CVS) scheme yields such an operator. Absolute excitation energies evaluated within the CASSCF/CVS-ERPA framework are slightly more accurate than those obtained from the usual random phase approximation (RPA), but the CVS-ERPA is not more accurate than RPA for predicting the relative positions of near-edge features. Nonetheless, CVS-ERPA is established as a reasonable starting point for the treatment of core-level excitations using variationally optimized 2-RDMs.
关键词： reduced-density matrices,extended random phase approximation,v2RDM,CASSCF,core-level excitations,x-ray absorption spectroscopy
更新于2025-09-04 15:30:14
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Short infrared wavelength quantum cascade detectors based on m-plane ZnO/ZnMgO quantum wells
摘要： This paper reports on the demonstration of quantum cascade detectors (QCDs) based on ZnO/ZnMgO quantum wells (QWs) grown by molecular beam epitaxy on an m-plane ZnO substrate. The TM-polarized intersubband absorption is peaked at a 3 lm wavelength. The sample has been processed in the form of square mesas with sizes ranging from 10 (cid:2) 10 lm2 up to 100 (cid:2) 100 lm2. The I-V characteristics reveal that 86% of the 260 devices are operational and that the surface leakage current is negligible at room temperature, which is not the case at 77 K. The photocurrent spectroscopy of 100 (cid:2) 100 lm2 QCDs reveals a photocurrent resonance at a 2.8 lm wavelength, i.e., slightly blue-shifted with respect to the intersubband absorption peak. The photocurrent persists up to room temperature. The calibrated peak responsivity amounts to 0.15 mA/W under irradiation at Brewster’s angle of incidence. This value allows us to estimate the transfer ef?ciency (1.15%) of the photoexcited electrons into the active QW of the next period.
关键词： quantum cascade detectors,m-plane ZnO substrate,intersubband absorption,ZnO/ZnMgO quantum wells,photocurrent spectroscopy
更新于2025-09-04 15:30:14
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Frequency-Modulated Wave Dielectrophoresis of Vesicles And Cells: Periodic U-Turns at the Crossover Frequency
摘要： We have formulated the dielectrophoretic force exerted on micro/nanoparticles upon the application of frequency-modulated (FM) electric fields. By adjusting the frequency range of an FM wave to cover the crossover frequency fX in the real part of the Clausius-Mossotti factor, our theory predicts the reversal of the dielectrophoretic force each time the instantaneous frequency periodically traverses fX. In fact, we observed periodic U-turns of vesicles, leukemia cells, and red blood cells that undergo FM wave dielectrophoresis (FM-DEP). It is also suggested by our theory that the video tracking of the U-turns due to FM-DEP is available for the agile and accurate measurement of fX. The FM-DEP method requires a short duration, less than 30 s, while applying the FM wave to observe several U-turns, and the agility in measuring fX is of much use for not only salty cell suspensions but also nanoparticles because the electric-field-induced solvent flow is suppressed as much as possible. The accuracy of fX has been verified using two types of experiment. First, we measured the attractive force exerted on a single vesicle experiencing alternating-current dielectrophoresis (AC-DEP) at various frequencies of sinusoidal electric fields. The frequency dependence of the dielectrophoretic force yields fX as a characteristic frequency at which the force vanishes. Comparing the AC-DEP result of fX with that obtained from the FM-DEP method, both results of fX were found to coincide with each other. Second, we investigated the conductivity dependencies of fX for three kinds of cell by changing the surrounding electrolytes. From the experimental results, we evaluated simultaneously both of the cytoplasmic conductivities and the membrane capacitances using an elaborate theory on the single-shell model of biological cells. While the cytoplasmic conductivities, similar for these cells, were slightly lower than the range of previous reports, the membrane capacitances obtained were in good agreement with those previously reported in the literature.
关键词： Cell,Frequency-modulated wave,Crossover frequency,The Clausius-Mossotti factor,Spectroscopy,Dielectrophoresis,Vesicle
更新于2025-09-04 15:30:14