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[IEEE 2018 11th Global Symposium on Millimeter Waves (GSMM) - Boulder, CO, USA (2018.5.22-2018.5.24)] 2018 11th Global Symposium on Millimeter Waves (GSMM) - High-Resolution Antenna Near-Field Imaging and Sub-THz Measurements with a Small Atomic Vapor-Cell Sensing Element
摘要： Atomic sensing and measurement of millimeter-wave (mmW) and THz electric fields using quantum-optical EIT spectroscopy of Rydberg states in atomic vapors has garnered significant interest in recent years towards the development of atomic electric-field standards and sensor technologies. Here we describe recent work employing small atomic vapor cell sensing elements for near-field imaging of the radiation pattern of a Ku-band horn antenna at 13.49 GHz. We image fields at a spatial resolution of λ/10 and measure over a 72 to 240 V/m field range using off-resonance AC-Stark shifts of a Rydberg resonance. The same atomic sensing element is used to measure sub-THz electric fields at 255 GHz, an increase in mmW-frequency by more than one order of magnitude. The sub-THz field is measured over a continuous ±100 MHz frequency band using a near-resonant mmW atomic transition.
关键词： atom,microwave,electric field,metrology,quantum sensing,millimeter-wave,THz,antenna,mmW,Rydberg,terahertz,Atomic sensors,antenna characterization
更新于2025-09-19 17:15:36
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Switching dynamics and modeling of multi-domain Zr-Doped HfO2 ferroelectric thin films
摘要： HfO2-based ferroelectrics have attracted attention as promising materials for advanced memory applications owing to their negative capacitance effect, high scalability, and full-CMOS compatibility. Accordingly, the switching dynamics of HfO2 thin films have been actively discussed and simulated using the Landau-Khalatnikov equation (LK model). Although the simulated results agree with experimental results in many studies, there is a slight dissimilarity near the coercive field in the polarization-electric field curve. For accurate and general modeling, a new model that combines the conventional LK model and Euler's equation was proposed in this work. The model was examined under single-domain and multi-domain conditions. The simulated curves using the Landau-Euler method better fit with measured curves than those using the LK model.
关键词： polarization-electric field curve,HfO2,Switching dynamics,Ferroelectric
更新于2025-09-19 17:15:36
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Binding energy of an exciton in a GaN/AlN nanodot: Role of size and external electric field
摘要： We report the impact of an external electric field on the energy spectrum of an exciton inside a spherical shaped GaN/AlN core/shell nanodot. The modulation of the confined exciton lowest state energy by the nanodot size is also treated. Our theoretical approach, based on a variational calculation, predicts a remarkable decrease in the exciton's energy when the electric field is switched on. Furthermore, our investigation shows that for a fixed nanodot size, the energy redshift is a unique function of the external electric field strength. On the other hand, it was observed that as the nanodot size increases the lowest exciton energy decreases and vice versa.
关键词： electric field,core/shell materials,nanostructures,quantum dots,exciton
更新于2025-09-19 17:15:36
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Efficient synthesis of graphene oxide by Hummers method assisted with an electric field
摘要： An electric field-assisted Hummers method for the synthesis of graphene oxide (GO) is reported which can enhance the efficiency of oxidation processes, while decreasing destructive effects on the resultant graphite lattice. The electric field varies from 0~167 V/cm was applied outside the reaction system and operated on three temperature stages of Hummers method which use a low dose of oxidizer. The as-prepared GO nanoplate has a layer spacing of 1 nm. This improved method may be important for preparing high-quality GO with low cost and light pollution.
关键词： Graphene,Electric field,Graphene oxide,Hummers method
更新于2025-09-19 17:15:36
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Thermopower Modulation Clarification of the Operating Mechanism in Wide Bandgap BaSnO <sub/>3</sub> -SrSnO <sub/>3</sub> Solid-Solution Based Thin Film Transistors
摘要： The transparent oxide semiconductor (TOS) with large bandgap (Eg ≈ 4 eV) based thin-film transistors (TFTs) showing both high carrier mobility and UV–visible transparency has attracted increasing attention as a promising component for next generation optoelectronics. Among TOSs, BaSnO3–SrSnO3 solid-solutions (Eg = 3.5–4.2 eV) are good candidates because the single crystal shows very high mobility. However, the TFT performance has not been optimized due to the lack of fundamental knowledge especially the effective thickness (teff ) and the carrier effective mass (m*). Here, it is demonstrated that the electric field thermopower (S) modulation method addresses this problem by combining with the standard volume carrier concentration (n3D) dependence of S measurements. By comparing the electric field accumulated sheet carrier concentration (n2D) and n3D at same S, it is clarified that the teff (≈n2D/n3D) of the conducting channel becomes thicker with increasing Sr concentration, whereas the m* becomes lighter. The former would be due to the increase of Eg and latter would be due to the enhancement of overlap population of neighboring Sn 5s orbitals. The present analyses technique is useful to experimentally clarify the teff and m*, and essentially important to realize advanced TOS-based TFTs showing both high optical transparency and high mobility.
关键词： electric field thermopower modulation,effective thickness,thin film transistors,BaSnO3–SrSnO3 solid solution,effective mass
更新于2025-09-19 17:15:36
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Underlayer dependence of electric field effect on magnetic anisotropy and its volatility in CoFeB/MgO structures
摘要： We report the dependence of voltage-controlled magnetic anisotropy (VCMA) effect and its volatility on an underlayer (UL) in CoFeB/MgO structures. For a sample with Ta or Pt UL, the VCMA effect occurs when the applied gate voltage (Vg) exceeds a critical value, and it persists even after removing Vg. This is in contrast to the volatile VCMA effect and its linear dependence on Vg in a sample with W UL. Furthermore, we demonstrate that the volatility of the VCMA effect can be modified by introducing a Ta/W bilayer, enabling arbitrary control of the magnetic properties via VCMA effect.
关键词： Voltage controlled magnetic anisotropy,Underlayer dependence,Perpendicular magnetic anisotropy,Electric-field effect
更新于2025-09-19 17:15:36
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Interfacial coupling effects in g-C3N4/SrTiO3 nanocomposites with enhanced H2 evolution under visible light irradiation
摘要： The g-C3N4/SrTiO3 nanocomposite is an important material in photocatalysis, but little attention has been paid to their interfacial interaction in photocatalytic reaction. Herein, we prepare the g-C3N4/SrTiO3 nanocomposites via a two-step mechanically milling and calcination process. The composite exhibited the highest H2 evolution activity superior to that of the pure g-C3N4 and SrTiO3 in the visible light. The results of UV-vis DRS, PL and photoelectrochemical measurements demonstrated that g-C3N4/SrTiO3 exhibited more visible light adsorption and faster photo-generated charge transfer. Furthermore, with the help of a strong built-in electric field presenting in the g-C3N4/SrTiO3 interface, the photo-generated electrons flow to the SrTiO3 from g-C3N4, leading to the highly-efficient electron separation and more H2O molecules photo-reduction to H2. This work explicates the significant role of built-in electric field in H2 evolution on g-C3N4/SrTiO3 photocatalyst.
关键词： built-in electric field,g-C3N4,visible light,H2 evolution,SrTiO3
更新于2025-09-19 17:15:36
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Enhanced photocatalytic hydrogen evolution of?CdWO4 through polar organic molecule modification
摘要： In this work, a polar molecule 4-mercaptobenzoic acid (4-MBA) is anchored on the surface of CdWO4 by forming CdeS and WeS bond. Photocatalytic hydrogen evolution is significantly enhanced (about 3.41 times) after the modification. The reason is due to the modification of 4-MBA, which results in a polar surface and built-in electric field. The polar surface is confirmed by the steady state and time-resolved PL spectra, Voc and SHG results.
关键词： CdWO4,Photocatalytic hydrogen evolution,4-mercaptobenzoic acid,Surface modification,Built-in electric field
更新于2025-09-19 17:15:36
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[IEEE 2018 International Computers, Signals and Systems Conference (ICOMSSC) - Dalian, China (2018.9.28-2018.9.30)] 2018 International Computers, Signals and Systems Conference (ICOMSSC) - Three-Dimensional Pulse Electric Field Test System with Optical Fiber
摘要： A three-dimensional pulse electric field system with optical fiber is developed. It is made up of electric field testing probe, optical transmission system, optical receiver and display, which can realize three-dimensional pulse electric field measurement in the whole space. This paper introduced the three-Dreceiving antenna, the three-D electric field signal synthesis and photoelectric receiver and then analyzed the design of the three-D receiving antenna and the method of three dimensional electric field synthesis. At last, the performance of the testing system is measured. Results show that the system has good test performance whose bandwidth can reach 1KHz-1GHz, dynamic range can be up to 60dB.
关键词： dynamic range,3-D electric field sensor,bandwidth test,Pulse electric field
更新于2025-09-19 17:13:59
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Nonlinear optical properties of lens-shaped core/shell quantum dots coupled with a wetting layer: effects of transverse electric field, pressure, and temperature
摘要： In this study, we numerically determined the intra-band transition lifetime of carriers as well as, the linear, nonlinear, and total absorption coefficients fro lens-shaped core/shell quantum dot structures. Our computations considered the combined effects of the wetting layer, pressure, applied transverse electric field, temperature, and core/shell sizes. By using suitable choices for these parameters, we found that a red or blue shift in the energy of the absorption spectrum could be achieved. In addition, the largest absorption coefficient was obtained when an intense transverse electric field was applied along the diagonal of the cross section of the structure considered. Hence, the magnitude of the absorption coefficient increased by 50%. Moreover, our results showed that the transition lifetime of the carriers decreasedas the temperatureincreased, whereas it increased as the pressure increased. Comparative analysis of a semi-spherical core/shell quantum dot system showed that the transition lifetime was shorter than that of the lens-shaped core/shell quantum dot structure, which was 255 ns.
关键词： Nonlinear optical properties,Electric field,Pressure,Temperature,Lens-shaped core/shell quantum dot
更新于2025-09-19 17:13:59