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A comprehensive study on the interface states in the ECR-PECVD SiO2/p-Si MOS structures analyzed by different method
摘要： The electrical properties of SiO2/p-Si films deposited by ECR-PECVD were studied at different frequencies (100-1 MHz) and gate voltages (-6–3 V). Results showed a frequency dispersion of C-Vg and G/ω-Vg. With increasing frequency, the capacitance and conductance are strongly decreased. An apparent peak in the depletion regime of the G/ω-Vg plots can be attributed to the existence of density Nss at Si/SiO2. The (Nss)value vary from 1.5 × 10^12 to 0.5 × 10^11 eV^-1 cm^-2, it has been determined by High-Low frequency capacitance technic. The Nss- Vg curve presents a peak at about -3 V, suggesting the presence Nss between the (Si)/SiO2 interface. Hill and Coleman method shows that the Nss decreases with increasing frequency which explains the high value of capacitance at low frequency. The Nss and their relaxation time τ by the conductance method ranged from 1.8 × 10^13 to 1.37 × 10^11 eV^-1 cm^-2 and 5.17 × 10^-7 to 8 × 10^-6 s, in the range (0.189-Ev) and (0.57- Ev) eV, respectively. The Nss was responsible for the non-ideal behavior of C-Vg and G-Vg leading to the breakdown of such device. Comparing the three method results show that parallel conductance is very precise and accurate.
关键词： Capacitance method,Relaxation time,Frequency,Interface states,Metal/Oxide/Semiconductor (MOS),Conductance method
更新于2025-09-23 15:23:52
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Analyzing role of relaxation time on second harmonic generation and optical dielectric function of impurity doped quantum dots under the aegis of noise
摘要： Present study monitors the influence of relaxation time (τ) on second harmonic generation (SHG) and total optical dielectric function (TODF) of impurity containing quantum dot (QD) under the stewardship of Gaussian white noise. Two distinct roadways viz. ‘additive’ and ‘multiplicative’ have been exploited for the entrance of noise to the system. Both in absence and presence of noise the SHG and TODF peak positions do not exhibit any shift with increase in τ. The SHG peak values display monotonic behavior with the variation of τ. However, the TODF peak values delicately depend on variation of τ being guided by the presence of noise and also on its mode of introduction. Presence of additive (multiplicative) noise causes enhancement (suppression) of SHG and TODF peak values as τ varies over a range. The findings appear to be crucial in the fabrication of QD-based opto-electronic devices where role of noise deserves to be properly addressed.
关键词： Quantum dot,Gaussian white noise,Impurity,Total optical dielectric function,Relaxation time,Second harmonic generation
更新于2025-09-23 15:21:01
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-type PbTe from first principles
摘要： We present an ab initio study that identifies the main electron-phonon scattering channels in n-type PbTe. We develop an electronic transport model based on the Boltzmann transport equation within the transport relaxation time approximation, fully parametrized from first-principles calculations that accurately describe the dispersion of the electronic bands near the band gap. Our computed electronic mobility as a function of temperature and carrier concentration is in good agreement with experiments. We show that longitudinal optical phonon scattering dominates electronic transport in n-type PbTe, while acoustic phonon scattering is relatively weak. We find that scattering due to soft transverse optical phonons is by far the weakest scattering mechanism, due to the symmetry-forbidden scattering between the conduction band minima and the zone center soft modes. Soft phonons thus play the key role in the high thermoelectric figure of merit of n-type PbTe: they do not degrade its electronic transport properties although they strongly suppress the lattice thermal conductivity. Our results suggest that materials like PbTe with soft modes that are weakly coupled with the electronic states relevant for transport may be promising candidates for efficient thermoelectric materials.
关键词： electron-phonon scattering,transport relaxation time approximation,thermoelectric materials,Boltzmann transport equation,n-type PbTe
更新于2025-09-23 15:21:01
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The effect of fractional derivative on photo-thermoelastic interaction in an infinite semiconducting medium with a cylindrical hole
摘要： In the present paper, the theory of generalized photo-thermoelasticity under fractional order derivative was used to study the coupled of thermal, plasma, and elastic waves on unbounded semiconductor medium with a cylindrical hole during the photo-thermoelastic process. The bounding surface of the cavity was traction free and loaded thermally by exponentially decaying pulse boundary heat flux. The medium was considered to be a semiconductor medium homogeneous, and isotropic. In addition, the elastic and thermal properties were considered without neglecting the coupling between the waves due to thermal, plasma and elastic conditions. Laplace transform techniques were used to obtain the exact solution of the problem in the transformed domain by the eigenvalue approach and the inversion of Laplace transforms were carried out numerically. The results were displayed graphically to estimate the effect of the thermal relaxation time and the fractional order parameters on the plasma, thermal and elastic waves.
关键词： Fractional calculus,Cylindrical cavity,A semiconducting material,Relaxation time,Laplace transform
更新于2025-09-23 15:21:01
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Progress in Endovenous Pulsed Laser Ablation
摘要： Continuous-wave (CW) lasers have been commonly used for endovenous laser ablation (EVLA). However, as some undesired side effects such as postoperative pain and bruising occasionally happens, longer laser wavelength and specially-fabricated laser fibers have been developed. On the other hand, the pulsed-wave (PW) laser, which has a heat production control by thermal relaxation, is independently developed for EVLA. This article discusses the implication of PW laser in EVLA from a theoretical point of view and a newly-developed micropulsation (MP) is introduced as a new concept. Since the MP yields adequate blood and vein wall heat degeneration by microseconds laser emission, efficacy and safety are improved compared with CW laser or conventional PW laser. Initial clinical outcome is favorable and promising for painless EVLA using inexpensive bare fiber.
关键词： varicose vein,thermal relaxation time,micropulsation,endovenous laser ablation,clear tip mode
更新于2025-09-23 15:19:57
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Transport in armchair graphene nanoribbons and in ordinary waveguides
摘要： We study dc and ac transport along armchair graphene nanoribbons using the k (cid:1) p spectrum and eigenfunctions and general linear-response expressions for the conductivities. Then, we contrast the results with those for transport along ordinary waveguides. In all cases, we assess the influence of elastic scattering by impurities, describe it quantitatively with a Drude-type contribution to the current previously not reported, and evaluate the corresponding relaxation time for long- and short-range impurity potentials. We show that this contribution dominates the response at very low frequencies. In both cases, the conductivities increase with the electron density and show cusps when new subbands start being occupied. As functions of the frequency, the conductivities in armchair graphene nanoribbons exhibit a much richer peak structure than in ordinary waveguides: in the former, intraband and interband transitions are allowed, whereas in the latter, only the intraband ones occur. This difference can be traced to that between the corresponding spectra and eigenfunctions.
关键词： transport,elastic scattering,armchair graphene nanoribbons,intraband and interband transitions,conductivities,relaxation time,Drude-type contribution
更新于2025-09-11 14:15:04
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Electron exchange energy of neutral donors inside a quantum well
摘要： We calculated the exchange energy of a pair of donor-bound electrons placed in the middle of an in?nite quantum well (QW). In order to obtain this energy for any interdonor distance and for any QW thickness, we have ?rst adapted to a QW the method developed by Gor’kov and Pitaevskii [L. P. Gor’kov and L. P. Pitaevskii, Dokl. Akad. Nauk SSSR 151, 822 (1963)] for a three-dimensional (3D) distribution of donors, and calculated the asymptotic form of the exchange energy. Second we have calculated the exchange energy of a “helium atom” in a QW; and third, inspired by the interpolation procedure proposed by Ponomarev et al. [I.V. Ponomarev et al., Phys. Rev. B 60, 5485 (1999)], we have obtained an interpolated expression for any interdonor distance. The obtained exchange energy is written in units of effective hartree, and the distance between the donors, as well as the width of the QW, are expressed in units of effective Bohr radius. We calculated the exchange energy for some commonly studied semiconductor materials, and discussed also the relationship between the exchange energy and the spin relaxation time for a donor concentration close to the insulator-metal transition.
关键词： insulator-metal transition,exchange energy,donor-bound electrons,spin relaxation time,quantum well
更新于2025-09-10 09:29:36
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Sensing coated iron-oxide nanoparticles with spectral induced polarization (SIP): Experiments in natural sand packed flow-through columns
摘要： The development of nanoparticle-based soil remediation techniques is hindered by the lack of accurate in situ nanoparticle (NP) monitoring and characterization methods. Spectral induced polarization (SIP), a non-invasive geophysical technique, offers a promising approach to detect and quantify NPs in porous media. However, its successful implementation as a monitoring tool requires an understanding of the polarization mechanisms, the governing NP-associated SIP responses and their dependence on the stabilizing coatings that are typically used for NPs deployed in environmental applications. Herein, we present SIP responses (0.1-10,000 Hz) measured during injection of a poloxamer-coated super-paramagnetic iron-oxide nanoparticle (SPION) suspension in flow-through columns packed with natural sand from the Borden Aquifer. An advective-dispersive transport model is fitted to outflow SPION concentration measurements to compute average concentrations over the SIP spatial response domain (within the columns). The average SPION concentrations are compared with the real and imaginary components of the complex conductivity. Excellent correspondence is found between the average SPION concentrations the columns and the imaginary conductivity values, suggesting that NP-mediated polarization (that is, charge storage) increases proportionally with increasing SPION concentration. Our results support the possibility of SIP monitoring of spatial and temporal NP distributions, which can be immediately deployed in bench-scale studies with the prospect of future real-world field applications.
关键词： Maxwell-Wagner polarization,relaxation time,super paramagnetic iron-oxide nanoparticles (SPIONs),Spectral induced polarization (SIP),chargeability
更新于2025-09-09 09:28:46
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Physical Properties of Pure and Nano Ag Doped Liquid Crystalline Compounds Containing 1,3,4-Oxadizole Unit
摘要： Dielectric properties and other physical properties such as electrical conductivity (AC) and relaxation time or activation energy have been studied for two systems pure LC [V]6,6, [V]7,6, [V]8,6, [V]6,7, [V]7,7 and [V]8,7 and their doped with silver nanoparticles. The results show the increasing in real dielectric permittivity ? with increasing length terminal chain. So the real dielectric permittivity increasing with raising temperature. To compare between the values of (400) Hz and (4000) Hz we observe these values at the low frequency are larger than that in high frequency. Generally, one can see that the doping of Ag nano particles effectively reduced the permittivity of the LC materials with its large electric dipole moment. The electrical conductivity σ value for pure LC samples in general increases with increasing temperature. So we observed increasing of electrical conductivity values at high frequency. The time scale is discussed in terms of the Arrhenius plot. Generally, with increasing the temperature the time period that spends by molecules at the transition state will increase. The activation energy Ea values show the increase in the activation energy to the doped systems.
关键词： Dielectric permittivity,Doped liquid crystals,Liquid crystals,Relaxation time,Electrical conductivity,Activation energy,Silver nanoparticles
更新于2025-09-04 15:30:14
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Calculation of the frequency shifts and damping constant for the Raman modes (A$_{1g}$, B$_{1})$ near the tetragonal-cubic transition in SrTiO$_{3}$
摘要： Raman shifts of the soft mode A 1g and the B 1 mode are calculated at various pressures at room temperature for the cubic-tetragonal transition (P C = 9.5 GPa) in SrTiO 3 . This calculation is performed using the observed volume data through the mode Gr(cid:127)uneisen parameters of A 1g and B 1 , which vary with pressure, by (cid:12)tting to the experimental wavenumbers in this crystalline system. Calculated Raman shifts are then used as order parameters to predict the pressure dependence of the damping constant and the inverse relaxation time for the cubic-tetragonal transition in SrTiO 3 . Our predictions from the pseudospin-phonon coupling and the energy (cid:13)uctuation models can be compared with the experimental measurements when available in the literature.
关键词： SrTiO 3,inverse relaxation time,Raman wavenumber,mode Gr(cid:127)uneisen parameter,damping constant
更新于2025-09-04 15:30:14