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Mean free path
About: Mean free path is a research topic. Over the lifetime, 4412 publications have been published within this topic receiving 114418 citations.
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TL;DR: In this article, a unified model that unifies the ballistic and diffusive transport mechanisms is applied to the carrier transport across potential barriers at grain boundaries in microcrystalline semiconducting materials.
Abstract: A recently developed model that unifies the ballistic and diffusive transport mechanisms is applied to the carrier transport across potential barriers at grain boundaries in microcrystalline semiconducting materials. In the unified model, the conductance depends on the detailed structure of the band edge profile and in a nonlinear way on the carrier mean free path. Equilibrium band edge profiles are calculated within the trapping model for samples made up of a linear chain of identical grains. Quantum corrections allowing for tunneling are included in the calculation of electron mobilities. The dependence of the mobilities on carrier mean free path, grain length, number of grains, and temperature is examined, and appreciable departures from the results of the thermionic-field-emission model are found. Specifically, the unified model is applied in an analysis of Hall mobility data for n-type μc-Si thin films in the range of thermally activated transport. Owing mainly to the effect of tunneling, potential b...
87 citations
TL;DR: In this article, the potential of WS2 as a thermoelectric material was assessed using a constant relaxation time approximation from the electronic band structure, whereas the lattice contribution was evaluated using self-consistently calculated phonon lifetimes.
Abstract: The potential of WS2 as a thermoelectric material is assessed. The electronic contribution to the thermoelectric properties is calculated within the constant relaxation time approximation from the electronic band structure, whereas the lattice contribution is evaluated using self-consistently calculated phonon lifetimes. In addition, the dependence of the lattice thermal conductivity on the mean free path of the phonons is determined.
87 citations
TL;DR: In this paper, a mean free path for the shell geometry under the assumptions of diffusive, isotropic, and billiard, or Lambertian, scattering was calculated for different models of electron scattering.
Abstract: Mean free path is calculated for the shell geometry under the assumptions of (i) diffusive, (ii) isotropic, and (iii) billiard, or Lambertian, scattering. Whereas in a homogeneous sphere case the difference between different models of surface scattering is reflected merely by a different slope of the linear dependence of a mean free path Leff on the sphere radius R, qualitatively different nonlinear dependencies on the inner and outer shell radii result for different model cases in the shell geometry. A linear behavior of Leff on the shell thickness (D) can only be established for the billiard model in the thin shell limit, in which case Leff ≈ 2D, whereas, in the same limit, Leff ≈ (D/2)ln(2R/D) in the diffusive case and Leff ≈ 14(2RD)1/2/[3ln(2R/D)] in the isotropic case. The shell geometry turns out a very sensitive setup to distinguish between the different models of electron scattering, which could be performed in future experiments on single and well-controlled dielectric core-metal shell nanopartic...
86 citations
TL;DR: In this paper, the acceleration of protons by a parallel collisionless shock to energies higher than have been obtained previously with self-consistent plasma simulations of this type was studied.
Abstract: Using one-dimensional hybrid simulations with very large spatial domains, we study the acceleration of protons by a parallel collisionless shock to energies higher than have been obtained previously with self-consistent plasma simulations of this type. Energy spectra and energetic particle fluxes are determined for four simulations with different-sized spatial domains. We find that the density of energetic particles upstream decays with distance from the shock and approaches a constant. The energetic particles also excite magnetic fluctuations. We find that the variance of these transverse fluctuations decreases with distance from the shock into the upstream region. This implies that the mean free path, λ, of the energetic particles increases with distance from the shock. Since our simulations are spatially limited, the downstream energy spectra are expected to deviate from a power law and become exponential at a characteristic energy Ec. However, we find that because λ increases with distance upstream, Ec is smaller than expected from a simple application of the diffusive theory (which assumes a constant mean free path and a free-escape boundary). Our results are qualitatively consistent with diffusive theories of the coupling of the particles and self-generated waves. However, in contrast to these theories, the hybrid-simulated energetic particle flux approaches a constant at some point far upstream, rather than vanishing, as assumed in the diffusion theory.
86 citations
TL;DR: Polarization-dependent surface extended x-ray absorption fine-structure (SEXAFS) measurements on the O(2/ifmmode/times\else\texttimes\fi{}1)/Cu(110) system show that every second [001] Cu row on the surface is missing, thus excluding the buckled-row model for the reconstruction as discussed by the authors.
Abstract: Polarization-dependent surface extended x-ray absorption fine-structure (SEXAFS) measurements on the O(2\ifmmode\times\else\texttimes\fi{}1)/Cu(110) system show that every second [001] Cu row on the surface is missing, thus excluding the buckled-row model for the reconstruction. A SEXAFS amplitude comparison clearly favors the missing-row over the sawtooth model. It also provides evidence for a strong anisotropy of both the surface mean free path and the surface Debye-Waller factor.
86 citations