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The description of quantum dielectric function for insulators over Bethe surface
摘要： A new expression for the dielectric function is suggested here, which is the Mermin–Belkacem-Sigmund (MBS) model derived from the Belkacem–Sigmund (BS) model based on the conservation of a local particle number in the Mermin model. The energy loss function expressions are reviewed analytically for both models, and these dielectric functions were used to calculate the Bethe sum rule, the energy loss function (ELF), as well as the differential inelastic inverse mean free path (DIIMP) for H2O. The indication from the results is that, compared to the BS dielectric function, the MBS dielectric function is more compatible in its consistency with the exact Bethe sum rule. The ELF for the MBS type is compatible relatively in high and low momentum transfers, while the ELF for the BS type is suitable for high-k. The two models of ELF were also applied to evaluate DIIMP for electron kinetic energy 1 keV, and these were compared with the results predicted in several ways via the SESINIPAC program, using the Mermin dielectric function and the extended Drude and Monte–Carlo method. These predicted results are in reasonable agreement with those estimated from other methods at the range of energy transfer (0–50) eV.
关键词： Bethe surface,differential inelastic inverse mean free path,local particle number,Energy loss function,dielectric function
更新于2025-09-23 15:23:52
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Structural and electrical properties of copper doped In<sub>2</sub>O<sub>3</sub> nanostructures prepared by citrate gel processes
摘要： Copper doped indium oxide (In2?xCuxO3) nanostructures were prepared by a simple citrate gel process using indium nitrate and copper nitrate as precursors. The influence of the dopant concentration (x = 0, 0.03, 0.05 and 0.07) on the structural, morphological and the electrical properties of indium oxide was studied. The crystallite size and the surface roughness (root mean square roughness and the mean roughness) of the prepared samples increased as a function of the dopant concentration. However, the copper (Cu) concentration did not affect the basic host crystal structure. The prepared samples showed an n-type semiconducting behavior and a variation in the electrical parameters, which might be due to the confinement of the electronic states of the dopants to small volumes (less than 100 nm). Implication of the degenerate electron gas model to the experimental electrical data revealed the role of the different scattering centers in conduction electron scattering.
关键词： Indium oxide,Mean free path,Electron gas model,Citrate gel route
更新于2025-09-23 15:23:52
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Monte Carlo Simulation of Laser-Ablated Particle Splitting Dynamic in a Low Pressure Inert Gas
摘要： A Monte Carlo simulation method with an instantaneous density dependent mean-free-path of the ablated particles and the Ar gas is developed for investigating the transport dynamics of the laser-ablated particles in a low pressure inert gas. The ablated-particle density and velocity distributions are analyzed. The force distributions acting on the ablated particles are investigated. The in?uence of the substrate on the ablated-particle velocity distribution and the force distribution acting on the ablated particles are discussed. The Monte Carlo simulation results approximately agree with the experimental data at the pressure of 8 Pa to 17 Pa. This is helpful to investigate the gas phase nucleation and growth mechanism of nanoparticles.
关键词： Monte Carlo simulation,instantaneous mean-free-path,ablated particles,transport dynamic,low pressure
更新于2025-09-23 15:19:57
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Electronic transport through defective semiconducting carbon nanotubes
摘要： We investigate the electronic transport properties of semiconducting (m, n) carbon nanotubes (CNTs) on the mesoscopic length scale with arbitrarily distributed realistic defects. The study is done by performing quantum transport calculations based on recursive Green’s function techniques and an underlying density-functional-based tight-binding model for the description of the electronic structure. Zigzag CNTs as well as chiral CNTs of different diameter are considered. Different defects are exemplarily represented by monovacancies and divacancies. We show the energy-dependent transmission and the temperature-dependent conductance as a function of the number of defects. In the limit of many defetcs, the transport is described by strong localization. Corresponding localization lengths are calculated (energy dependent and temperature dependent) and systematically compared for a large number of CNTs. It is shown, that a distinction by (m ? n)mod 3 has to be drawn in order to classify CNTs with different bandgaps. Besides this, the localization length for a given defect probability per unit cell depends linearly on the CNT diameter, but not on the CNT chirality. Finally, elastic mean free paths in the diffusive regime are computed for the limit of few defects, yielding qualitatively same statements.
关键词： defect,electronic transport,density-functional-based tight binding (DFTB),Carbon nanotube (CNT),recursive Green?s function formalism (RGF),strong localization,elastic mean free path
更新于2025-09-19 17:15:36
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Low-frequency noise in irradiated graphene FETs
摘要： We present a quantitative analysis of the low-frequency noise in irradiated monolayer graphene. In this study, we repeatedly irradiate a back-gated graphene transistor with argon ions at 90 eV and measure its low-frequency noise and channel conductivity after each irradiation. Our results indicate that the noise amplitude decreases monotonically with the increasing density of vacancy defects. The combination of our low-frequency noise measurements and carrier transport studies reveals that the mobility fluctuation model can explain this observation and that the density of vacancy defects, the density of charged impurities, and the mean free path of charge carriers determine the noise amplitude.
关键词： mobility fluctuation model,low-frequency noise,charged impurities,irradiated graphene,vacancy defects,mean free path
更新于2025-09-10 09:29:36