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Improvements in the synaptic operations of ferroelectric field-effect transistors using Hf <sub/>0.5</sub> Zr <sub/>0.5</sub> O <sub/>2</sub> thin films controlled by oxygen partial pressures during the sputtering deposition process
摘要： To control the polarization switching characteristics of ferroelectric HfxZr1?xO2 (HZO) thin films, the effects of oxygen partial pressure (PO2) during the sputtering deposition of HZO and the area ratio (SI/SF) of metal–ferroelectric–metal–insulator–semiconductor (MFMIS) gate stacks were investigated for ferroelectric synapse transistors. An increase in PO2 resulted in a relative decrease in the ferroelectric orthorhombic phase owing to the compensation of oxygen vacancies into the HZO films. The introduction of an MFMIS gate stack with a smaller SI/SF ratio effectively reduced the electric field applied across the HZO gate insulator. The polarization switching times for the HZO thin films could be modulated in a wide range by means of these two strategies, which were clearly examined to facilitate the synaptic operations of ferroelectric field-effect transistors (FeFETs) using HZO gate insulators. Typical synaptic operations, including paired-pulse facilitation and spike timing-dependent plasticity, were clearly demonstrated to exhibit gradual modulations of the channel conductance of the FeFETs with the evolution of spike signals, and these behaviors were enhanced upon increasing PO2 and decreasing the SI/SF ratio by controlling the switching kinetics of the ferroelectric partial polarizations of the HZO gate insulators in the proposed synapse FeFETs.
关键词： oxygen partial pressure,ferroelectric,Hf0.5Zr0.5O2,sputtering deposition,MFMIS gate stacks,synaptic operations
更新于2025-09-23 15:21:01
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Plasmonic Sensing of Refractive Index and Density in Methanol-Ethanol Mixtures at High Pressure
摘要： The localized surface plasmon resonance (LSPR) of gold nanospheres dispersed in methanol-ethanol 4:1 was measured as a function of pressure up to 60 GPa. The LSPR exhibits an intense redshift with pressure in the range of 0-10 GPa, followed by a slower blueshift at higher pressures. This is because an increase in the solvent refractive index with pressure leads to a redshift of the LSPR peak wavelength while an increase in the electron density of the gold nanospheres with pressure leads to a blueshift. Solvent solidification at 10 GPa and associated non-hydrostatic effects have a negligible influence on the LSPR shifts in the case of nanospheres. Here we show that both the LSPR shifts and changes in the nanospheres absorption coefficient can be explained on the basis of Gans’ model, and this enables the solvent refractive index and the density of the solvent to be determined across the hydrostatic pressure range from 0-60 GPa. Interestingly, plasmonic sensing shows no evidence of crystallization or glass phase transitions in MeOH-EtOH (4:1) solvents within the explored pressure range.
关键词： High Pressure,Optical,Hybrid Materials,Methanol-Ethanol Mixtures,Density,Plasmonics,Magnetic,Refractive Index
更新于2025-09-23 15:21:01
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Black Phosphorus Quantum Dots in Aqueous Ethylene Glycol for Macroscale Superlubricity
摘要： In this study, black phosphorus quantum dots (BPQDs) have been successfully prepared at a low cost and high yield by liquid-based high energy ball milling method. The obtained BPQDs with an average lateral size of 6.5 ± 3 nm and a thickness of 3.4 ± 2.6 nm dispersed stably in ethylene glycol (EG). A robust macroscale superlubricity state (μ: 0.002) was achieved under a high contact pressure of 336 MPa via the lubrication of BPQDs-EG aqueous suspension (BPQDs-EGaq) at the Si3N4/sapphire frictional interface. The wear rate lubricated by BPQDs-EGaq suspension account for 5.96% of that lubricated by EG aqueous solution (EGaq), demonstrating the improvement in the anti-wear property with the addition of BPQDs. The rolling effect of BPQDs and the low shear stress between the BPQDs interlamination played important roles in the improvement in the anti-wear property. The oxidative products of BPQDs (PxOy) contributed to the effective realization of macroscale superlubricity. This work realized macroscale superlubricity at a high contact pressure by combining the BPQDs with special liquid molecules and provided the great potential in industrial applications.
关键词： Interface,Black phosphorus quantum dots,Mixed lubrication,high contact pressure,Liquid macroscale superlubricity
更新于2025-09-23 15:21:01
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Vital role of Ar ambient pressure in controlled properties of nanocrystalline CdS thin films
摘要： A report on the manipulation of structural, optical, and electrical properties of nanocrystalline CdS (ncCdS) thin films in the framework of varying Ar ambient pressure in pulsed laser deposition (PLD) is presented here. Increase in Ar ambient pressure results in reduction of crystallite size which in turns increases the structural imperfections and structural phase transformation of ncCdS thin films. The most significant observation here is the bleaching of multiphonon Raman modes (MRMs) particularly LO + 2E2, 2LO + 2E2, etc. in ncCdS thin films. An acute investigation on the reason of bleaching of LO + 2E2, 2LO + 2E2, etc. modes is carried out here and concluded that it is due to the fading of E2 mode with increasing Ar pressure as confirmed by low-frequency micro-Raman measurements. UV–visible absorption and photoluminescence spectroscopies are used to examine the optical properties like bandgap and possible electronic transitions in ncCdS thin films. Further, transport properties of ncCdS thin films are investigated using Hall measurement and I–V characteristics.
关键词： electrical properties,optical properties,Ar ambient pressure,structural properties,pulsed laser deposition,nanocrystalline CdS thin films
更新于2025-09-23 15:21:01
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External pressure induced liquid crystal defects for optical vortex generation
摘要： Simple and arbitrary creation of liquid crystal (LC) defects can be highly useful, in particular, for the creation of optical vortex. We report a novel method to create an isolated and stable +1 type concentric LC defect by combing an external pressure on a vertically aligned liquid crystal cell (VALC) and the application of electric fields. The method does not require special material in alignment layer, nor patterned electrodes such as in spatial light modulator, but it can produce stable and rewritable defects in a LC cell. We show that the created +1 defect can be used to generate optical vortices with ±2(cid:125) orbital angular momentum. The simple and cost-effective process and its tunability for the position of defect make the method useful in various applications such as advanced optical communication and quantum computation using tunable optical vortices.
关键词： electric fields,orbital angular momentum,liquid crystal defects,optical vortex generation,external pressure
更新于2025-09-23 15:21:01
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Raman high-pressure study of butane isomers up to 40 GPa
摘要： Raman spectroscopy studies on n and i-butane were performed at pressures of up to 40 GPa at ambient temperatures using the DAC technique. Normal butane undergoes two phase transitions at 1.9(5) GPa and 2.9(5) GPa and isobutane at 2.7(5) GPa and 3.5(5) GPa. These phase transitions were identi?ed based on observations of the splitting Raman modes and the appearance or disappearance of particular Raman peaks. Our results demonstrate the complex, high-pressure behavior of butane isomers.
关键词： Raman spectroscopy,high-pressure,DAC technique,phase transitions,butane isomers
更新于2025-09-23 15:21:01
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Temperature and hydrostatic pressure effects on the electronic structure, optical properties of spherical segment quantum dot/wetting layer and group velocity of light
摘要： To investigate hydrostatic pressure and temperature effects on electron energy levels of an InAs spherical segment quantum dot with wetting layer embedded in GaAs barrier, we use the finite element method to solve the Schr?dinger equation in the effective mass approximation. Results show that the ground, the first and the second excited state energies decrease (increase) as the hydrostatic pressure (temperature) increases for the constant temperature (pressure). Moreover, given the optical properties of the system interacting with two laser fields, red (blue) shifts are observed in the linear and nonlinear absorptions and dispersions for the probe pulse as the hydrostatic pressure (temperature) increases. Furthermore, as the hydrostatic pressure increases, the maximum of the group velocity of light inside the slow light frequency range increases and the slow light frequency range shifts to the lower probe frequencies.
关键词： temperature,group velocity of light,hydrostatic pressure,optical property,quantum dot/wetting layer
更新于2025-09-23 15:21:01
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THz cutoff frequency and multifunction Ti 2Ba2Ca2Cu3O10/GaAs photonic bandgap materials
摘要： By using the transfer matrix method (TMM), we theoretically explore the transmittance properties and cuto? frequency of one-dimensional photonic crystal (1DPCs) within the terahertz frequency region. The present structure consists of high-temperature superconductor and semiconductor layers. The results of the calculations represent the e?ects of various parameters on the cuto? frequency. We have used the two-?uid model as well as the Drude model to describe the permittivity of superconductor and semiconductor. Further, we consider that the permittivity of both the materials is depending on the hydrostatic pressure. The present results show that with the increasing of di?erent parameters as the operating temperature, the thickness of semiconductor, and the ?lling factor of semiconductor, then the cuto? frequency shift to lower frequencies regions. By the increasing of superconductor thickness, hydrostatic pressure, doping concentration and ?lling factor of the superconductor, we found the cuto? frequency shifts to higher frequency regions. These results indicate that cuto? frequency can be modi?ed through these di?erent parameters. Finally, the present design could be useful for many optical systems as the optical ?lter, re?ector and photoelectronic applications in the Terahertz regime.
关键词： Cuto? frequency,transfer matrix method,photonic crystal,doping concentration,hydrostatic pressure,two-?uid model,Drude model
更新于2025-09-23 15:21:01
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High-Pressure Electronic Structure and Optical Properties of N-Doped ZnO
摘要： The electronic structures and optical properties of N-doped ZnO under high pressure have been investigated using first-principles methods. The pressure effects on the lattice parameters, electronic band structures, and partial density of states (PDOS) of crystalline N-doped ZnO are calculated up to 8 GPa. The lattice parameters a, and c are decreases by 0.062 and 0.091 ?, respectively. Moreover, the evolution of the dielectric function, absorption coefficient (α(ω)), reflectivity (R(ω)), and the real part of the refractive index (n(ω)) at high pressure are also presented.
关键词： N-doped ZnO,density functional theory,optical properties,high pressure
更新于2025-09-23 15:21:01
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Two-step treatment of bulky keloids on the cheeks after deep chemical peeling: intralesional cryosurgery followed by pulsed dye and ablative fractional CO2 laser
摘要： Scarring of the face following chemical peeling is an uncommon and devastating complication. This case report describes the successful treatment of bulky mature keloids on both cheeks following deep chemical peeling by using a combined approach of intralesional cryosurgery followed by pulsed dye and ablative fractional CO2 laser therapy.
关键词： Keloid,Silicone occlusive sheets,Deep chemical peeling,Pressure garment,PDL ablative fractional CO2 laser,Intralesional cryosurgery
更新于2025-09-23 15:21:01