Showing papers on "Mean free path published in 1982"
TL;DR: In this article, the product of the atomic number density (D) and the electron mean free path (EMFP) as a function of depth for gate oxides was derived using an analytical method based on oxide/substrate intensity ratios.
Abstract: Device quality gate oxides (~ 850 A) grown on Si (100) substrates are irradiated with 0 - 20 eV electrons during in situ XPS measurements. These structures have been thinned stepwise to 25 to 60 A using a relatively benign wet-chemical depth-profiling procedure. An analytical method based on oxide/substrate intensity ratios is used to deduce the product of the atomic number density (D) and the electron mean free path (?) as a function of depth for these structures. Samples showing a wide variety of hole trapping efficiencies were examined. Si+3 species are formed in the region of the Si/SiO2 interface and are observed during the course of their relaxation and annihilation. These formation results are correlated with the presence of strained Si-O-Si bonds at the interfaces. Radiation hard and soft structures show different strained bond distributions in the interfacial region. The direct observation of bond cleavage and bond strain gradients in these samples is used to extend silica devitrification models to explain the generation of fixed oxide charge and interface states. This bond strain gradient (BSG) model is shown to be consistent with a variety of experimental EPR and electrical observations of hole- and electron-trap generation by ionizing radiation.
184 citations
TL;DR: The effects of multiple scattering on the interpretation of the time dependence of elastic backscattering of laser pulses from the ocean (lidar) are investigated through solving the radiative transfer equation by Monte Carlo techniques.
Abstract: The effects of multiple scattering on the interpretation of the time dependence of elastic backscattering of laser pulses from the ocean (lidar) are investigated through solving the radiative transfer equation by Monte Carlo techniques. In particular, after removal of the geometric loss factors, it is found that the backscat-tered power is a decaying exponential function of time, over the time interval required for photons to travel four attenuation lengths through the water. The effective attenuation coefficient of this exponential decay is found to be strongly dependent on the parameters of the lidar system and on the optical properties of the water. The significant parameter is the ratio of the radius of the spot on the sea surface viewed by the lidar receiver optics to the mean free path of photons in the water. For values of this parameter near zero, the decay is determined by the beam attenuation coefficient, while for values greater than ~5-6, the decay is given by the attenuation coefficient for downwelling irradiance, often referred to as the diffuse attenuation coefficient. Between these two extremes the interpretation of the effective attenuation coefficient requires, essentially, complete knowledge of the inherent optical properties of the water: the beam attenuation coefficient and the volume scattering function.
169 citations
TL;DR: In this article, a simple one-mode approximation for the wavevector and frequency-dependent energy loss function is employed to derive an expression for the electron inverse mean free path, including the effect of exchange between the incident electron and the electrons in the medium.
88 citations
TL;DR: In this article, the main characteristics of localized states (electron density distribution p∞(x), frequency dependence of complex conductivity σ(ω) etc.) were calculated in one-dimensional disordered lattices.
79 citations
TL;DR: In this article, the role of mean free paths of product particles in high-energy nuclear collisions has been studied, suggesting that particles with longer mean free path probe most sensitively the early, highly excited, hot phase of the collision.
Abstract: The role of mean free paths of product particles in high-energy nuclear collisions has been studied. In inclusive energy spectra the observed slope difference among p, ..pi.., and K/sup +/ can be interpreted as due to the difference in mean free paths of these particles, suggesting that particles with longer mean free paths probe most sensitively the early, highly excited, hot phase of the collision. With use of the data of pp and ..pi pi.. interferometries further discussions on the space-time evolution of the system are developed.
62 citations
TL;DR: In this article, the angular dependences of photoelectron peak intensities have been calculated for substrates covered with films of various thicknesses D. The importance of the results obtained is discussed with reference to the determination of photo-electron mean free paths in solids and of thin-film thicknesses by means of ESCA.
61 citations
TL;DR: In this paper, the attenuation of the mean field is merely a statistical effect caused by phase interference among different realizations of the random wave ensemble, and does not represent the amplitude attenuation.
54 citations
TL;DR: In this paper, the elastic and inelastic mean free paths in the (0-8.5)-eV energy region were extracted from Xe films (0, 3000 \AA{}) deposited at various temperatures on different metal substrates [Nb,Pt,W(100].
Abstract: Electron transmission experiments in the (0-20)-eV energy range have been performed on Xe films (0-3000 \AA{}) deposited at various temperatures on different metal substrates [Nb,Pt,W(100)]. A theoretical model is used to extract from these experiments the elastic and inelastic mean free paths in the (0-8.5)-eV energy region. Some structures in the transmitted current arise from inelastic processes and yield information on electronic excitations (excitons and electron-hole-pair creation) and the energy of the bottom of the conduction band. Other structures present in the elastic mean free path appear to be caused by structural effects and thermal disorder of the deposited film.
49 citations
46 citations
TL;DR: In this article, it was shown that these secondary nuclei show anomalously short mean free paths near their point of origin, which can be interpreted as being due to all fragments having cross sections about twice normal for some 10 to -10 seconds after creation, or to a small fraction having cross-sections an order of magnitude greater than normal.
Abstract: Cosmic-ray nuclei have been observed to produce 2072 secondary fragments in nuclear interactions detected in nuclear emulsions. These fragments produce 557 further interactions. Previous reports that these secondary nuclei show anomalously short mean free paths near their point of origin are confirmed. This effect can be interpreted as being due to all fragments having cross sections about twice normal for some 10 to the -10 sec after creation, or to a small fraction having cross sections an order of magnitude greater than normal.
41 citations
TL;DR: In this article, the thickness-dependent conductivity of aluminium, gold and copper films was measured during evaporation by a process-controlled experiment and four parameters were evaluated by applying an extended Fuchs' theory.
TL;DR: In this paper, a linear approximation scheme for spin-polarized low-energy electron diffraction from ferromagnetic surfaces is presented, which can reduce the computing time required for the analysis of magnetic structures involving a layer-dependent magnetization by at least 24.
TL;DR: In this article, a detailed investigation of the energy deposition in, and surface reflection from, an infinite half-space has been made, where two types of source are considered: the first is a line source embedded in the medium perpendicular to the surface and the second is an incident pencil of arbitrary direction, incident at a point.
Abstract: A detailed investigation of the energy deposition in, and surface reflection from, an infinite half-space has been made. Two types of source are considered: the first is a line source embedded in the medium perpendicular to the surface and the second is an incident pencil, of arbitrary direction, incident at a point. The resulting problem involves three dimensions in space and therefore requires description by a transport equation in the appropriate coordinates. The physical problem considered is that of a beam of incident ions or a line ion source in the medium. Only the fate of the foreign incident ions is considered and no attempt is made to follow the recoil atoms generated. Progress is made in the analytical solution of the problem by assuming an energy-independent mean free path and the transport approximation for the scattering kernel. The Wiener-Hopf method is used together with Fourier transforms for transverse directions. Considerable success has been achieved in obtaining exact solutions for some special limiting cases, and the numerical results which emerge are tabulated.
TL;DR: In this article, the spin-lattice relaxation rate in the rotating frame of 27 Al has been measured as a function of the plastic strain rate ϵϵ at 77 K.
TL;DR: In this article, the pitch angle diffusion coefficient at 1 AU (Dμμ) leads to a parallel mean free path which is roughly independent of particle energy, λ∥≃0.03 AU.
Abstract: Energetic particle (1–100 MeV) pitch angle scattering in the Interplanetary Magnetic Field (IMF) is studied using spacecraft magnetometer data at 1 AU (IMP 7 and HEOS 2) and at 5 AU (Pioneer 10). Particle trajectories are followed by a computer simulation of their movement in a realistic model of the IMF. Determination of the pitch angle diffusion coefficient at 1 AU (Dμμ) leads to a parallel mean free path which is roughly independent of particle energy, λ∥≃0.03 AU. At the lowest energy our result is at least a factor of 3 larger than the predictions of quasi linear theory. Results at 5 AU lead to a radial mean free path which is between 2 to 6 times smaller than at 1 AU, probably indicating a greater importance for perpendicular diffusion at large heliodistances. In fact a roughly constant radial mean free path (λ r ≃0.01 AU) is obtained when the contribution of perpendicular diffusion at 5 AU is taken into account (Moussaset al., 1981).
TL;DR: In this paper, non-local calculations have been made of the eddy currents set up in spherical metal particles, and the results are used to discuss the infrared absorption of such particles.
Abstract: Non-local calculations have been made of the eddy currents set up in spherical metal particles, and the results are used to discuss the infrared absorption of such particles. For diffuse surface scattering the absorption is reasonably approximated by the use of a mean free path equal to the particle radius, but for specular or mixed scattering the absorption is strongly enhanced. Comparison with experiment indicates that specular scattering may partially explain the almost universal observation that absorption by ultrafine metallic particles is larger than expected.
TL;DR: In this paper, the authors measured the thermal conductivity of pressed pellets of 99.999% AgI from 120 K to 500 K using a transient hot wire method and found that the temperature dependence changes from T −1.3±0.1 at the lowest temperatures to T − 1.8± 0.1 below the phase transition at 420 K, where AgI is a superionic conductor.
TL;DR: In this article, the energy loss per unit path length and inelastic mean free path of an electron with energy less than or equal to 10 keV are modified by including an exchange correction, a sum-rule constraint, and a small relativistic correction.
Abstract: Previous results for the energy loss per unit path length and inelastic mean free path of an electron with energy less than or equal to 10 keV are modified by including an exchange correction, a sum-rule constraint, and a small relativistic correction. These new results are compared with the previous results, tabulated values, and predictions from ''universal'' formulae for organic solids.
TL;DR: In this paper, the authors measured the electrical resistivity of annealed calcium films with a four-probe method with a constant current and showed that the resistivity was a function of the film thickness.
Abstract: Deposition and study of calcium films were achieved under ultrahigh vacuum. The latter was obtained with the use of an ion pump and a helium cryopump. The temperature of the substrate ranged between 90 and 400 K. The electrical resistance was measured with the use of a four-probe method with a constant current. Film thicknesses were in the range between 20 and 300 nm. To obtain a stable film structure, samples were annealed to a temperature near 400 K. The electrical resistivity of the annealed films exhibited a linear and reversible variation with temperature. It was shown to be thickness dependent. For the thickest deposits, electrical resistivity reached a constant value which no longer depended on the thickness, but was a function of the film-deposition temperature. With the help of electron photomicrographs and with use of the conduction model proposed by Mayadas and Schatzkes, we calculated the fraction $p$ of electrons which are specularly reflected at the surface of the film and the parameter $\ensuremath{\alpha}$ depending on the reflection on grain boundaries. The influence of grain boundaries was calculated and the mean free path was deduced from these results.
TL;DR: The relaxation of nonequilibrium quasiparticles at phase-slip centers in superconducting current carrying indium whiskers has been investigated in this paper, showing that the diffusion length depends on temperature.
IBM1
TL;DR: In this paper, the results of simultaneous currentvoltage and voltage noise measurements on granular tin films in the region of the superconducting transition are presented, and the results in terms of a phase-slip shot noise demonstrates that vortex motion is uniform only over some characteristic length.
Abstract: We present the results of simultaneous current-voltage and voltage noise measurements on granular tin films in the region of the superconducting transition. Interpretation of the results in terms of a phase-slip shot noise demonstrates that vortex motion is uniform only over some characteristic length. This effective mean free path increases as the temperature is lowered and is probably dominated by vortex-antivortex recombination.
TL;DR: In this paper, thin tin films of thickness in the range 340-3200 A were prepared by thermal evaporation under a vacuum of 10 −5 Torr and the films were deposited onto amorphous substrates with a deposition rate of 10 A s −1.
TL;DR: In this article, the role of dislocation motion in deforming NaCl single crystals, using the technique of pulsed N.M.R. magnetic field, was investigated.
Abstract: Results are presented of investigations into the role of dislocation motion in deforming NaCl single crystals, using the technique of pulsed N.M.R. In particular, the spin-locking pulse sequence is used to measure T 1p, which is the spin-lattice relaxation time in the presence of a resonant r.f. magnetic field. T 1p, depends strongly on the mean free path L which is covered by the dislocations during successive jumps between obstacles in their glide plane. The mean free path is determined in crystals compressed in different directions, in which cases either the {110} or the {100} planes are primarily activated. It is shown that both the mean free path, measured as a function of strain rate and of the applied stress, and the work hardening differ remarkably for the two different primary slip planes. The magnitude of the mean free path is compared with the mean distance between dislocations in the crystal and the activation length of dislocations at obstacles, as obtained from mechanical stress relaxation experiments.
TL;DR: In this article, two methods for visualizing the target erosion pattern in the planar magnetron sputtering system are described, and the experimental results reveal that there exists a threshold vertical magnetic field corresponding to the erosion pattern boundaries.
Abstract: Two methods for visualizing the target erosion pattern in the planar magnetron sputtering system are described here. The experimental results obtained by one of the new methods reveal that there exists a threshold vertical magnetic field corresponding to the erosion pattern boundaries. The effect of the working pressure and of the cathode potential on the erosion pattern is explained in terms of the mean free path and the initial velocity of the secondary electrons, respectively.
TL;DR: Monte Carlo calculations of neutral particle flows in hollow collection probes and large area limiters used in recent experiments are presented in this paper, where the collected neutral hydrogen flux scales linearly with plasma density for n i 11 cm −3 where the plasma is essentially transparent to the neutrals.
TL;DR: In this article, a comparison between photoelectron-spectroscopic intensities and theoretical orbital ionization cross-sections was made, and it was shown that the deviation is attributable to the loss of U(4) photoelectrons through the degradation of their kinetic energies into the tail on the high binding energy side of the spectrum.
TL;DR: In this article, the damping of a vibrating wire at pressures between 0 and 16 bar showed no evidence for superfluidity down to 0.4 mK, and at low temperatures a collisionless flow regime was reached in which mean free path effects became dominant.
Patent•
IBM1
TL;DR: In this paper, an undoped region bounded by a tunneling junction of the order of the mean free path of an electron is assembled in series with larger thickness away from the light incident surface.
Abstract: Optical-to-electrical conversion is accomplished using an undoped region bounded by a tunneling junction of the order of the mean free path of an electron. A number of regions are assembled in series with larger thickness away from the light incident surface. The thickness and doping of the regions for maximum effectiveness in monochromatic light are tailored to produce similar quantities of carriers from the light. A nine section GaAs structure with 50 Å n + and p + tunneling bounding regions has a 90% quantum efficiency and delivers a 5 volt output with a 0.35 picosecond transit time.
TL;DR: In this paper, the effect of a magnetic field, B, on heat flow in a gas in an intermediate pressure range has been studied and it has been shown that the special features of the Senftleben-Beenakker effect observed with the decreasing pressure arise not only due to spherically symmetric molecule-surface interaction, but also to nonspherical scattering on walls.
Abstract: The effect of a magnetic field, B, on heat flow in a gas in an intermediate pressure range has been studied. The ratio of the heat flow changes in the fields B ⊥ ▿T and B ‖ ▿T was found to change nonmonotonically with pressure in N2 and CO. With the decreasing pressure, a difference is observed between the dependence of heat flow on field orientation and the corresponding angular dependence in the limiting case Kn→0 ( Kn = l /L , l is the mean free path, L is the geometric size). An expression has been obtained for the heat flow in a magnetic field for Kn ≲ 0.1 from the solution of an integral kinetic equation. In particular, it has been shown that the special features of the Senftleben-Beenakker effect observed with the decreasing pressure arise not only due to spherically symmetric molecule-surface interaction, but also to nonspherical scattering on walls.