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The charge transport in the amorphous Si3N4 is studied experimentally and theoretically. We have found, that widely accepted Frenkel model of the trap ionization gives the unphysical low value of the attempt to escape factor, and the enormously high value of the electron tunnel mass. Experimental data are well described by theory of the two-bands conduction and the phonon-assisted trap ionization in Si3N4.

Grazing incidence x-ray scattering and x-ray diffraction techniques have been employed to investigate the microstructures in various ZnSe-based semiconductor thin films grown on GaAs substrates by molecular beam epitaxy and metalorganic chemical vapor deposition methods. The results are also used for a comparison of the interfacial roughness and overall quality of the II–VI thin films prepared by these two different growth methods. Structural parameters such as the interfacial roughness and layer thickness obtained from the scattering measurements and lattice constants obtained from the x-ray diffraction pattern around the GaAs(004) peak can be correlated with the film deposition rate, compound composition, and lattice strain in the epilayers. We thus demonstrate that x-ray scattering techniques in conjunction with diffraction measurements are useful tools for nondestructive characterization of buried interfaces in semiconductor layer materials.

p-i-n photodiodes were fabricated on nitrogen ion implanted undoped ZnSe/n-type ZnSe epilayers grown on n+GaAs (100) substrates by molecular beam epitaxy. To obtain a quasi-uniform p layer doping profile, nitrogen ions at multiple energies and ion doses were implanted at room temperature. The activation of implanted species was carried out by an optimized post-annealing in a nitrogen ambient. Optical studies were performed on the implanted/annealed devices by photoluminescence spectroscopy at 10 K, which indicated donor–acceptor pairs at an energy of 2.7 eV and its phonon replicas with 30 meV intervals. The circular p-i-n diodes with a 1 mm diam contact area showed a device breakdown voltage to be linearly dependent on the thickness of the undoped ZnSe epilayer. For p-i-n diodes fabricated on an initial 0.5 μm thick undoped ZnSe layer, an ideality factor of 1.19 and a reverse bias breakdown voltage of 12 V was observed. A large photocurrent, good linearity with light intensity, and low dark current were o...

The grating light valve (GLV) is a micro-electromechanical reflection phase grating that operates on the electrostatic deflection of microbeams. In a conventional GLV, each beam is coated with a surface electrode that spans its length. In this paper, a GLV with partial electrode coverage is studied. An analysis is presented of the deflection profile and switching voltage for a series of electrode lengths. These results are compared with the performance of a conventional GLV.

The effects of B and C substitution for Sn on phase components, Curie temperature T-C, and magnetocaloric effect of melt-spun Mn3Sn2-xMx (M = B, C; x = 0-0.5) ribbons have been investigated. X-ray diffraction (XRD) results show that the main phase in the as-spun Mn3Sn2-xMx (M = B, C; x = 0-0.5) ribbons is Mn3Sn2 of Ni3Sn2-type (Pnma). Minor Mn2B (when x >= 0.1) or Mn5C2 (when x > 0.1) secondary phase is formed, and their amounts increase with increasing B and C concentration, respectively. The Curie temperature T-C of these ribbons varies in the temperature range of 240-250K. The peak values of the maximal magnetic entropy change, -Delta S-M(max), are about 13.6-18.3 mJ/cm(3) K for B-substituted ribbons and 13.6-17.5 mJ/cm(3) K for C-substituted ribbons, respectively, at a maximum applied field of 50 kOe. These values are about one fifth that of Gd (81.4 mJ/cm(3) K). However, the relatively broader temperature range of the half maximum of Delta S-M peak (similar to 100K), low-cost and nontoxic elements still make Mn3Sn2-based ribbons the promising candidates for magnetic refrigeration applications close to room temperature. (C) 2012 American Institute of Physics. [doi:10.1063/1.3671789]

The problems of stress analysis for linearly viscoelastic materials are considered. This is the simplest group of materials which exhibit the general stress‐strain characteristics found in polymers and plastics. Three basic aspects are considered: measurement of material properties, determination from these of the operator equations between stress and strain or equivalently of the viscoelastic model, and use of this in the theoretical analysis of stress distributions. Quasi‐static analysis, in which inertia forces are negligible, is treated quite generally. The wave problems which arise when inertia effects are included are restricted to one‐dimensional space variations. A series of typical solutions of these types is discussed.

Two methods of determining the variation of real and complex modulus with frequency from vibrating reed test results are detailed. One is based on measurements of the relative amplitude and phase lag of the motion of the free and driven ends of the reed, the other on amplitude resonance measurements only. The analysis is based on a general linear viscoelastic law, and takes into account the influence of the frequency dependent moduli of the material on the frequency and amplitude of the resonance peaks. This influence has not been correctly accounted for in previous analyses which have included the assumption that the material behaves according to a particular, simple viscoelastic law, which will in general not be borne out by the final results.The method is applied to a series of tests. For the material and frequency range used the imaginary part of the complex modulus was small compared with the real part, and the influence mentioned in the foregoing was small. A simpler method of analysis might thus be...

In the generation of plane waves in metal plates by detonation of contact explosives, the pressures reached can be sufficiently high to produce finite elastic and plastic strain components, and appreciable changes in temperature due to thermomechanical coupling effects. A theory of elastic—plastic deformation is developed to include these conditions. Finite elastic and plastic deformations are represented in terms of the initial and final configurations of the body, and an unstressed configuration subject only to plastic flow. In general, this configuration cannot be represented by a continuous displacement function. The analysis of the kinematics of these three states is carried out for general deformation history. The discussion of the application of finite deformation thermoelastic theory is limited to the conditions in a plane wave with fixed principal directions. Plasticity theory with the consideration of variable temperature is also restricted to the plane‐wave situation. The influence of the therm...

The paper is concerned in the main with a Maxwell material, which corresponds to a model having a spring and dashpot in series. The equation for longitudinal wave propagation in rods is shown to be equivalent to the telegraph equation, and solutions of transient wave problems are treated briefly in the Appendix using the Laplace transform technique. Impact on a semi‐infinite rod is considered in detail in the report. A method of superposition of images is discussed to use this solution to solve boundary value problems for finite rods. The resulting stress distributions are discussed and contrasted with those for an elastic rod. The natural grouping of problems is discussed according to the relative magnitude of the duration of interest, the relaxation time, and the wave traverse time. The influence of the idealization involved in the Maxwell model is briefly touched upon.