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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 paper, an improved boundary condition may be written simply in terms of the linear extrapolation length λ, whose inverse is the logarithmic gradient of the particle density at the boundary.
Abstract: Diffusion theory is often employed to calculate the effects of wall destruction on the local concentration of an active species immersed in a scattering gas. In many situations the spatial dependence of the concentration is given to a good approximation by the fundamental diffusion mode, and the local loss frequency can be calculated using the container’s fundamental mode diffusion length Λ. The additional assumption that the density of the active species may be taken to be zero at the container boundaries gives a value of Λ=Λ0 which depends only on the container dimensions, but use of Λ0 can be seriously in error if the diffusion mean free path λm is comparable to the dimensions, or if the particle reflection coefficient R becomes of significance. An improved boundary condition may be written simply in terms of the linear extrapolation length λ, whose inverse is the logarithmic gradient of the particle density at the boundary. The equation λ=2(1+R)λm/3(1−R) allows the representation of the full range of ...
333 citations
TL;DR: In this article, the first experimental study of thermal transport at the nanoscale is reported in the case of a point-like heat source, providing a quantitative description of the transition between the ballistic and diffusive regimes.
Abstract: According to Fourier theory, thermal transport is a diffusive process. However, this cannot be the case at length scales smaller than the mean free path of the energy carriers. The first experimental study of thermal transport at the nanoscale is now reported in the case of a point-like heat source, providing a quantitative description of the transition between the ballistic and diffusive regimes.
330 citations
TL;DR: In this article, the mean free path of electrons is more or comparable with its wave length, i.e. some higher the localization edge, and it is shown that the electron-electron interaction in this situation leads to an anomaly in the density of states near the Fermi level.
330 citations
TL;DR: In this paper, an effective mobility was obtained from a solution of the Boltzmann equation for two types of potential functions: (a) a linear potential corresponding to a constant space-charge field, and (b) a Poisson's equation including an external bias applied normal to the surface.
Abstract: Carriers held to a region near the surface by the potential well of a space charge layer may have their mobility reduced by surface scattering, if the width of the well is of the order of a mean free path. An effective mobility, which may differ from the bulk mobility by as much as a factor of ten, has been obtained from a solution of the Boltzmann equation. Solutions have been carried out for two types of potential functions: (a) a linear potential corresponding to a constant space-charge field, and (b) a solution of Poisson's equation including an external bias applied normal to the surface. The results have been used to calculate changes in surface conductance of germanium with changes in surface potential and predict the "field effect" and "channel effect" mobilities.
323 citations
TL;DR: In this paper, it was shown that all germanium junctions break down as the result of the same avalanche process found in silicon, and an empirical expression for the multiplication inherent in this breakdown process was given for step junctions.
Abstract: It is shown that all germanium junctions studied break down as the result of the same avalanche process found in silicon. An empirical expression for the multiplication inherent in this breakdown process is given for step junctions. Ionization rates for holes and electrons in Ge are derived with the use of this expression. The ionization rate for holes is larger than that for electrons by about a factor of two. The agreement between these ionization rates as a function of field and the theory of Wolff is excellent. It is determined that the threshold for electron-hole pair production is about 1.50 ev and the mean free path for electron (or hole)-phonon collisions is about 130 A.
320 citations