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Simulation of quantum transport in doped carbon nanotube diode controlled by transverse electric field
摘要： Using first-principle and semi-empirical methods, optical responses and transport characteristics of hybrid CNT-based diodes are studied. The junction is realized by a combination of doping of one half of a nanotube and applying a transverse electric field to the other. Calculations are carried out in the framework of the density functional theory and the nonequilibrium Green function method. The possibility of using these rectifiers in optical nanoantennas is discussed.
关键词： density functional theory,nonequilibrium Green function method,transverse electric field,doped carbon nanotube diode,quantum transport,optical nanoantennas
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - In vivo and online temperature monitoring based on fiber Bragg greatings during tumor treatment with nanosecond pulse electric field
摘要： the clinical practice, a compact, in-vivo and online monitoring scheme is an important requirement. A fiber Bragg grating (FBG) sensing system was used to online monitor the temperature at the surface of / inside the liver tissue of a rabbit under nanosecond pulse electric field (nsPEF). Single point measurement between the electrodes and multi-point measurement surrounding one electrode were both carried out. Experimental results show that, due to equally spaced (Δt=0.5 s) 300 ns-pulses with E=20 kV/cm at a repetition rate of 4 Hz, the temperature rise in the rabbit liver tumor usually does not exceed ΔΤ=6℃ for 300 pulses. Theoretical analysis of Joule heating model fits well with the experimental results. Both direct measurements and theoretical modelling demonstrated that nsPEF could not deliver enough energy to heat the treated tissue significantly, thus a hyperthermic effect on the tissue can be excluded during this kind of treatment with much high electric field strength and extremely short duration.
关键词： Fiber Bragg grating,Nanosecond pulse electric field,In-vivo temperature monitoring
更新于2025-09-16 10:30:52
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Electric Field Controlled Indirect-Direct-Indirect Band Gap Transition in Monolayer InSe
摘要： Electronic structures of monolayer InSe with a perpendicular electric field are investigated. Indirect-direct-indirect band gap transition is found in monolayer InSe as the electric field strength is increased continuously. Meanwhile, the global band gap is suppressed gradually to zero, indicating that semiconductor-metal transformation happens. The underlying mechanisms are revealed by analyzing both the orbital contributions to energy band and evolution of band edges. These findings may not only facilitate our further understanding of electronic characteristics of layered group III-VI semiconductors, but also provide useful guidance for designing optoelectronic devices.
关键词： Monolayer InSe,Electric field,Indirect-direct-indirect band gap transition
更新于2025-09-16 10:30:52
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Exciton states in InGaAsP/InP core–shell quantum dots under an external electric field
摘要： The effect of an external electric field on the exciton states of InGaAsP/InP core–shell quantum dots is investigated through the variational method. The effect of the shell thickness, core radius, electric field strength, and material components on the exciton states are analyzed in detail. The numerical results show that the electron and hole energies decrease as the shell thickness or core radius is increased. The Bohr radius is a nonmonotonic function of the shell thickness or core radius, and the change of the exciton binding energy is nonlinear as the shell thickness or core radius is increased. With increasing electric field strength, the Bohr radius increases while the exciton binding energy decreases. The exciton binding energy decreases (increases) as the Ga (As) component is increased.
关键词： Electric field,Core–shell quantum dot,Exciton binding energy
更新于2025-09-16 10:30:52
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Electrically controlled growths of 4-N,N-dimethylamino-4a?2-Na?2-methyl-stilbazolium tosylate (DAST) organic microcrystals
摘要： 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) is one of the most important organic nonlinear optical (NLO) materials, but its controlled growth remains a challenge. Herein, we describe a novel method to control the growth of DAST on the surfaces of indium tin oxides coated with the patterned photoresists by electric field. Results indicate that zero-dimensional (0D) spherical DAST microcrystals tend to grow along the photoresist lines if an electric field with a low frequency of 500 Hz is applied. Rather differently, one-dimensional (1D) DAST microwires preferentially grow along the gaps of the photoresist lines under the control of an electric field with a high frequency of 1000 Hz. Growth of DAST microcrystals controlled by electric field leads to the increase in the crystallinity, but the chemical structures remain unchanged. Moreover, second harmonic generation signal was measured from the as-grown DAST microcrystals. The results presented in this work are helpful for rationally controlling the growth of 0D or 1D DAST microcrystals, and particularly, the strategy can be further expanded to control the growth of DAST derivatives or other organic NLO materials with similar chemical structures.
关键词： Spectral analyses,Growth mechanism,Electric field induction,DAST microcrystals,Nonlinear optical material
更新于2025-09-16 10:30:52
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Synthesis of colloidal aluminum nanoparticles by nanosecond pulsed laser and the effect of external electric field and laser fluence on ablation rate
摘要： In this paper, the ablation of aluminum was induced by a Q-switched Nd:YAG laser (1064 nm, ~10 ns and 10 Hz) in ethanol at room temperature for producing colloidal nanoparticles. Two different experimental schemes (i.e. the electric field parallel, and perpendicular to the laser propagation path) were used to investigate the dependence of ablation rate on the external electric field characteristics and the laser fluence. The results show that at a constant laser fluence, regardless of the type of scheme, the ablation rate is increased in the presence of electric field. However, the characteristics of craters strongly depend on the direction of the electric field. The results also show that at both schemes with a constant electric field, the ablation rate rises when the laser fluence is increased. According to the results, it can be concluded that the ablation rate enhanced by applying electric field and increasing laser pulse energy.
关键词： Ablation rate,Laser materials processing,Laser ablation efficiency,Electric field,Ethanol interaction ambient
更新于2025-09-16 10:30:52
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Stark Shift of Hydrogenic and Non-Hydrogenic Donor Impurity Excited States in Parabolic Quantum Dot: Under the Effect of Electric Field and Temperature
摘要： In the present study, we discuss theoretically the influence of lateral and normal electric field on the hydrogenic donor impurity (HDI) and non-hydrogenic donor impurity (NHDI) excited state energies in a cylindrical quantum dot (CQD) with parabolic potential. The variational approach is employed to obtain the donor impurities ground and excited state energies in the framework of the effective mass approximation; consequently, the binding energy is calculated. The comparisons between the influence of the lateral and the normal electric fields on the Stark shift of the electron (ΔE1) and Stark shift of the HDI (ΔEimp) are given. It has been found that the direction of the electric field has a considerable effect on ΔEimp. Our results showed that ΔEimp has shown a blue shift for some HDI excited states and the other states showed a red shift. The results of the combined effect of the lateral electric field and the temperature on the HDI and NHDI binding energy have been presented. It has been indicated that the HDI states in small CQDs are very sensitive to the weak lateral electric field strength than both the normal electric field strength and the temperature values. More, the Stark shift in HDI ground state energy is more affected by the temperature in large CQDs than in small CQDs.
关键词： Hydrogenic Donor Impurity,Normal Electric Field,Semiconductor Quantum Dot,Lateral Electric Field,Excited State,Non-hydrogenic Donor Impurity
更新于2025-09-12 10:27:22
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Quantitative Mapping of the Charge Density in a Monolayer of MoS <sub/>2</sub> at Atomic Resolution by Off-Axis Electron Holography
摘要： The electric potential, electric field and charge density of a monolayer of MoS2 has been quantitatively measured at atomic scale resolution. This has been performed by off-axis electron holography using a double aberration-corrected transmission electron microscope operated at 80 kV and a low electron beam current density. Using this low dose rate and acceleration voltage, the specimen damage is limited during imaging. In order to improve the sensitivity of the measurement, series of holograms have been acquired. Instabilities of the microscope such as the drifts of the specimen, biprism and optical aberrations during the acquisition have been corrected by data processing. Phase images of the MoS2 monolayer have been acquired with a sensitivity of 2π/698 rad associated to a spatial resolution of 2.4 ?. The improvement in the signal-to-noise ratio allows the charge density to be directly calculated from the phase images using Poisson’s equation. Density functional theory simulations of the potential and charge density of this MoS2 monolayer were performed for comparison to the experiment. The experimental measurements and simulations are consistent with each other and notably, the charge density in a sulphur mono-vacancy (VS) site is shown.
关键词： MoS2,high-resolution,charge density,electric potential,electric field,electron holography,sulphur vacancy
更新于2025-09-12 10:27:22
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Estimation of THz field strength by an electro-optic sampling technique using arbitrary long gating pulses
摘要： We demonstrate a simple approach to retrieve the original peak electric field (E-field) strength of high-intensity THz pulses using an electro-optic sampling (EOS) technique and the Poynting flux approach. The latter supposes assessment of THz pulse intensity by measurement of pulse energy, duration and spot size, but its applicability to a few-cycle THz pulse needs detailed consideration. We applied a deconvolution procedure to the raw EOS data to retrieve the THz field waveform. We describe a two-step procedure that allows us to assess the field strength of an extreme THz field. First, the EOS measurements of the THz field should be performed at low pulse energies to retrieve the THz waveform and estimate pulse duration and amplitudes of each particular oscillation. Next, the field strength of an extreme THz pulse can be assessed from the Poynting flux approach with correction to the abovementioned data obtained from the EOS measurements. We show good experimental coincidence between peak strength estimation from the EOS directly and from the combined approach at ‘low’ field strength. Hence, an extreme THz E-field strength can also be assessed from preliminary EOS measurements and full energy measurements based on the Poynting flux approach. We also show that the Poynting flux approach for extreme few-cycle THz pulses gives prominent, at least two-fold, underestimation without preliminary EOS measurements.
关键词： electro-optic sampling (EOS),intense terahertz pulse,electric field (E-field) strength
更新于2025-09-12 10:27:22
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All-Optical Detection of Neuronal Membrane Depolarization in Live Cells Using Colloidal Quantum Dots
摘要： Luminescent semiconductor quantum dots (QDs) have recently been suggested as novel probes for imaging and sensing cell membrane voltages. However, a key bottleneck for their development is a lack of techniques to assess QD responses to voltages generated in the aqueous electrolytic environments typical of biological systems. Even more generally, there have been relatively few efforts to assess the response of QDs to voltage changes in live cells. Here, we develop a platform for monitoring the photoluminescence (PL) response of QDs under AC and DC voltage changes within aqueous ionic environments. We evaluate both traditional CdSe/CdS and more biologically compatible InP/ZnS QDs at a range of ion concentrations to establish their PL/voltage characteristics on chip. Wide-field, few-particle PL measurements with neuronal cells show the QDs can be used to track local voltage changes with greater sensitivity (ΔPL up to twice as large) than state-of-the-art calcium imaging dyes, making them particularly appealing for tracking subthreshold events. Additional physiological observation studies showed that while CdSe/CdS dots have greater PL responses on membrane depolarization, their lower cytotoxicity makes InP/ZnS far more suitable for voltage sensing in living systems. Our results provide a methodology for the rational development of QD voltage sensors and highlight their potential for imaging changes in cell membrane voltage.
关键词： voltage sensing,photoluminescence,live cell,Quantum dots,electric field
更新于2025-09-12 10:27:22