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Journal of Applied Physics

Issue 4 • Date Aug 1985

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Displaying Results 1 - 25 of 53
  • Highly conductive and wide band gap amorphous‐microcrystalline mixed‐phase silicon films prepared by photochemical vapor deposition

    Page(s): 1427 - 1431
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    Doped hydrogenated amorphous‐microcrystalline mixed‐phase silicon (μc‐Si:H) films were prepared by the mercury photosensitized decomposition of a disilane‐hydrogen gas mixture, by adding phosphine and diborane for n and p type, respectively. The maximum dark conductivity and optical band gap of the films were, respectively, 20 S cm-1 and ∼2.0 eV for n type, and 1 S cm-1 and 2.3 eV for p type. It is most significant that the gaseous ratio of hydrogen to disilane should be enhanced up to 70 for n type, and even 300 for p type, to obtain such a highly conductive and wide gap film. The crystallinity of the photodeposited μc‐Si films appeared to be improved in comparison with that of films by conventional plasma glow discharge technique. View full abstract»

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  • Incoherent emission of an electron beam in a free electron laser rectangular waveguide

    Page(s): 1432 - 1438
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    A calculation is presented of the incoherent radiation emitted by an electron beam of finite radius passing through a linearly polarized magnetic undulator in a rectangular waveguide with perfect conducting walls. This analysis is based on the Fourier component of the Lienard–Wiechert fields. The metallic boundary conditions are exactly incorporated in the formalism by means of the ‘‘image currents’’ method. In the Fresnel approximation, we show that the double infinite sum over ‘‘images’’ is transformed into one over ‘‘vertical modes,’’ consisting of trigonometric functions. The discrete frequency spectrum and angular distribution of the radiation are studied for several energy spread and electron beam radius cases. The predicted radiation patterns provide useful diagnostics to determine the electron beam properties (trajectories, energy and angular spread, betatron oscillation). The amount of relative power emitted on each mode is a gaussian function exp(-an2). View full abstract»

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  • Phase modulation technique for eliminating phase noise in picosecond T2 measurements based on stimulated Raman gain

    Page(s): 1439 - 1449
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    The pump and probe variant of the stimulated Raman gain technique permits the measurement of picosecond dephasing times with low‐power, continuous‐wave mode‐locked lasers, but it suffers by its susceptibility to inevitable randomly induced fluctuations in the relative phases of the interacting laser fields. The resulting severe requirements on optical stability can be circumvented through application of a double‐modulation–detection scheme that we have developed. It is based on rms detection of the T2 signal as generated through application of a low‐frequency phase modulation of precise amplitude, additional to the commonly applied rf modulation with corresponding lock‐in detection. A detailed description of the method and its experimental realization is presented. T2 measurements on the 656 cm-1 vibration of liquid CS2 illustrate its performance. In comparison with previous techniques, precision is improved by about a factor of 4. But more important is the fact that the technique permits to make a continuous recording of the T2 signal, while achieving at the same time a reduction in measurement time by an order of magnitude. Furthermore, optimization of the optical setup is possible, through direct monitoring of the dephasing signal at any delay. Automating the data taking and processing should be straightforward. View full abstract»

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  • Lamb wave interaction with light

    Page(s): 1450 - 1455
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    The interaction of light with Lamb waves propagating in transparent plates has been investigated. The analytical study has been done by considering a three‐step interaction, at the limiting surfaces and within the propagation medium. Experimental data are given, relative to isotropic crystal plates in the MHz frequency regions and compared with theory. View full abstract»

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  • Phase shift of photoacoustic signals from microparticles in liquids

    Page(s): 1456 - 1459
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    The wave equation in which the source term is coupled with the thermal energy migration was analyzed, and the physical meaning of the phase of photoacoustic signals generated in turbid solutions was clarified. These theoretical results, partially verified by experiments, showed the possibility for novel thermal characterizations and size measurement methods of microparticles. The theoretical limitation of the size measurement was 102 Å for samples with nonradiative relaxation times of 1 nsec. View full abstract»

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  • Behavior of high‐voltage gaps in the presence of large space‐charge fields

    Page(s): 1460 - 1465
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    It is shown in this paper that a high‐voltage gap exhibits a nonlinear capacitance behavior in the presence of large space‐charge fields. The existence of this nonlinear capacitor is quasi dc in nature and does not result from transit time effects, i.e., high‐frequency effects. This nonlinear behavior can be used to tailor the shape of bunched intense relativistic electron beams. View full abstract»

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  • Reduction of enhanced arcing by some electronegative gases

    Page(s): 1466 - 1469
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    Activation or enhanced arc durations due to the presence of minute quantities of organic contaminants in low‐current arcing atmospheres is becoming a problem in the reliability of the new generation of miniature relays sealed in plastic or metal containers. This article describes arc duration reduction by the addition of the electronegative gases, SF6 and C2Cl3F3 to the arcing atmosphere when part‐per‐million hydrocarbon impurities were present. The effects of hydrogen on the arc durations is also examined. View full abstract»

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  • Cation vacancy formation energies in liquid‐phase‐epitaxial Hg1-xCdxTe

    Page(s): 1470 - 1473
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    Experimental measurements of the cation vacancy formation energies (Ef) of Hg1-xCdxTe were carried out by Hg‐annealing and rapid quenching to room temperature, followed by Hall measurements at 77 K. Our observations show that one charge state vacancy is dominant, so that the fractional number n of cation vacancies at temperature T is related exponentially to the energy Ef required to create one vacancy, n=A exp(-Ef/kT). No appreciable temperature dependence of Ef due to temperature variation of the ionization levels and the self‐consistent Fermi level is seen. Our measured value for the activation energy is found to be Ef=0.9±0.1 eV, for Hg1-xCdxTe with x=0.21, 0.3, and 0.43. This value is found to be nearly independent of Cd composition x. Theoretical calculations of the p‐type carrier concentrations due to cation vacancies in Hg0.8Cd0.2Te yield results which are in good agreement with experimental data. These modeling calculations predict the cation vacancies to be predominantly doubly ionized species at 77 K. View full abstract»

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  • Light scattering measurements of diffusional growth of precipitates in nickel‐ and cobalt‐doped MgO

    Page(s): 1474 - 1482
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    Changes in the sizes of second‐phase precipitates in nickel‐ and cobalt‐doped MgO single crystals have been examined in samples which were subjected to progressive thermal anneals at temperatures ranging from 600 to 1500 °C. Precipitate sizes and spatial locations were measured by means of light scattering before and after anneals in flowing argon. Absolute light scattering angular distribution measurements were used to obtain size distributions from a Mie theory deconvolution procedure. Comparison of the Ostwald ripening theory with the annealing time evolution of these precipitates indicates that the predominant growth can be described by a dislocation or grain boundary diffusion ripening mechanism. This mechanism is also consistent with ultramicroscope measurements taken before and after each anneal. The depletion region surrounding these ripening particles has been observed by means of backscattering in the measured angular distributions. Our results for diffusion within boundary regions are D’=(1.19±0.8×10-6 cm2/s)exp(-1.72 eV/kT) for nickel ions and D’=(1.60±0.9×10-7 cm2/s)exp(-1.36 eV/kT) for cobalt ions in MgO. These equations are in agreement with previous diffusion‐couple measurements of nonenhanced diffusion in grain‐boundary regions in these materials. View full abstract»

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  • Theory of lifetime measurement with the scanning electron microscope in a semiconductor containing a localized defect: Transient analysis

    Page(s): 1483 - 1488
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    This paper presents a transient analysis of electron‐beam induced current in a semi‐infinite semiconductor containing an individual pointlike defect. A focused electron beam positioned in the vicinity of the defect is cut off and the resulting current versus time decay is calculated. It is shown that the time constant of this decay is a complex function of geometrical aspects of the system, bulk properties of the material, and strength of the defect. Computational results are given for a dislocation line parallel to the charge collection plane. View full abstract»

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  • Optimal sample shape for internal friction measurements using a dual cantilevered beam

    Page(s): 1489 - 1492
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    An optimal shape for internal friction measurements using a dual cantilevered beam is described. The new shape is analyzed by a finite element method, in order (a) to optimize its parameters to reduce parasitic interactions with the sample holder, and (b) to calculate the stress distribution in the vibrating sample. The numerical analysis shows that the interactions between the sample and its holder are much weaker for the new shape than for the classical flexural vibration of a simple cantilevered beam. The predictions of the numerical analysis are compared to experimental results on a niobium sample at low temperature. View full abstract»

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  • Diffusion and second‐order reaction in a cylindrical fiber

    Page(s): 1493 - 1499
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    Many chemical reactions can only take place after a diffusion process involving one of the reagents. This work examines how a reagent A diffuses into a cylindrical fiber containing a uniform distribution of impurities B, when an irreversible second‐order reaction A+B→AB can take place. The reaction is considered to be the rate‐controlling process. The determination of the different concentration profiles requires the solution of a system of nonlinear partial differential equations for which an approximate solution is derived. It is shown how the diffusion profile of the reagent is modified by the reaction and how the formation of the reaction product depends on the diffusion process. This interdependence is illustrated by some specific examples. For small values of time the concentrations of the diffusing substance A lie below the values one would expect if no reaction took place. This difference depends on the reaction constant k and the number of impurities. The analysis of the differences between in‐ and out‐diffusion experiments is one way of measuring the influence of the reaction on the diffusion process. One possible application of the present model is the description of hydrogen diffusion and hydroxyl formation in optical fibers. View full abstract»

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  • Diffusion phenomena and defect generation in rapidly annealed GaAs

    Page(s): 1500 - 1504
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    A detailed study of transient thermal processing of S‐doped epitaxial GaAs wafers, both with and without ion‐implantation damage being present, has been performed. The average diffusivity of S is given for the temperature range 950–1050 °C, and is shown to be dependent on the position of any lattice damage present, the surface condition (capped or capless), and the annealing regime employed (thermal or rapid thermal). The mobility of the S‐doped region is degraded by rapid annealing, and the extent of this degradation is a function of the experimental conditions employed. Implantation of Si (which occupies a Ga site) into S‐doped n+ regions (S occupies an As site) failed to increase the electrical activity of the region above the often observed limit of 2×1018 cm-3. View full abstract»

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  • Redistribution of dopant arsenic during silicide formation

    Page(s): 1505 - 1514
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    A systematic study of arsenic redistribution in Ni, Cr, Ta silicide forming systems has been performed by implanting arsenic into metal layers or into single‐crystal silicon substrates. During silicide formation arsenic accumulates near the interface region, incorporates in the silicide, or diffuses out of the silicide into the surrounding ambient. Differences in the dopant redistribution are related to the arsenic initial location relative to the moving species in silicide formation and the diffusivity of dopant atoms at the metal‐silicon reaction temperature. View full abstract»

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  • Localized epitaxial growth of tetragonal and hexagonal WSi2 on (111)Si

    Page(s): 1515 - 1518
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    Both epitaxial tetragonal and hexagonal WSi2 (t‐WSi2 and h‐WSi2) were grown locally on (111)Si. The best epitaxy was obtained in 600–1100 °C two‐step annealed samples. The orientation relationships between t‐WSi2 and Si are [110]WSi2‖[111]Si and (004)WSi2‖(2¯02), whereas those between h‐WSi2 and Si are [0001]WSi2‖[111]Si and (202¯0)WSi2‖(202¯)Si. Interfacial dislocations, 80 Å in spacing, were identified to be of edge type with (1/6)〈112〉 Burgers vectors. Two step annealings were found to be effective in improving the epitaxy and relieving the island formation of WSi2 on Si. Significant intermixing of W and Si atoms during the preannealing is proposed to account for the effects. View full abstract»

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  • Reactions of Pd on (100) and (110) GaAs surfaces

    Page(s): 1519 - 1526
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    The reactions of Pd on atomically clean or air‐exposed (100) and (110) GaAs surfaces at temperatures between 20 to 500 °C in different ambients were investigated by transmission electron microscopy. Interfacial reactions quite different from previous x‐ray results were observed and two new Pd‐Ga‐As ternary phases were identified for the first time. At lower temperatures (T≲250 °C) the formation of a ternary phase PdGa∼0.3As∼0.2, which has a hexagonal structure very similar to that of Pd2Ge or Pd2Si with a0=b0=0.672 nm and c0=0.340 nm, was observed. This ternary phase is epitaxially oriented with (12¯0)ternary‖(100)GaAs and [001]ternary‖[011]GaAs on (100) GaAs substrates, and with (11¯0)ternary‖(110)GaAs and [001]ternary‖[11¯0]GaAs on (110) GaAs substrates. At temperatures between 350 and 500 °C only one phase, PdGa, was observed to form in a high vacuum environment, whereas in a forming gas ambient, either a mixture of PdAs2 and another ternary phase PdGa∼0.6As∼0.4 (at 350 °C) or a mixture of PdAs2 and PdGa (at 500 °C) was observed. The ternary phase PdGa∼0.6As∼0.4 is also hexagonal in structure with a0=b0=0.947 nm and c0=0.374 nm. The PdGa phase formed at high temperature is epitaxially oriented on (100) substrates with (110) PdGa‖(100)GaAs and [1¯11]PdGa‖[011]GaAs, but is randomly oriented on (110) substrates. All these observations indicate that the Pd‐GaAs reactions at T≳350 °C are very sensitive to the a- mbient conditions but not as sensitive to the GaAs surface cleanliness or substrate orientation. Correlation of these structural observations to ultraviolet and x‐ray photoelectron spectroscopy data obtained from the same reacted interfaces are also discussed. View full abstract»

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  • Marker experiments in growth studies of Ni2Si, Pd2Si, and CrSi2 formed both by thermal annealing and by ion mixing

    Page(s): 1527 - 1536
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    Inert markers (evaporated tungsten and silver) were used in growth studies of silicides formed both by thermal annealing and by ion mixing in the Ni/Si, Pd/Si, and Cr/Si systems. The markers were initially imbedded inside silicides and backscattering spectrometry was used to determine the marker displacement after different processing conditions. The results obtained in thermal annealing are quite consistent with that found in previous investigations. Ni is the dominant diffusing species in Ni2Si, while Si is the diffusing species in CrSi2. In Pd2Si, both Pd and Si are moving species with Pd the faster of the two. In contrast, in growth of silicides by ion irradiation Si is the faster diffusing species in all three systems. View full abstract»

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  • Liquid‐phase‐epitaxial growth of In0.49Ga0.51P on (100) GaAs by a supercooling method

    Page(s): 1537 - 1541
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    In1-xGaxP epitaxial layers were grown on (100) GaAs substrates by liquid‐phase epitaxy using supercooling technique. The lattice mismatch normal to the wafer surface between In1-xGaxP layer and GaAs substrate varies linearly with the supercooled temperature of the growth solution. The composition‐pulling phenomenon was not observed in this study. The growth rate, the intensity, and the full width at half maximum of the photoluminescent spectrum are also dependent on the supercooling temperature. It is shown that the narrowest full widths at half maximum of photoluminescent peak are 10.6 and 35 meV at 14 and 300 K, respectively, when ΔT is 6 °C, and the strongest intensity is occurred at ΔT=12–18 °C. Carrier concentrations of undoped epitaxial layers are in the range of 1016 cm-3 measured by capacitance‐voltage method at 300 K and Hall method at 77 and 300 K. The optimum growth condition was then determined. View full abstract»

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  • Thermoelectric properties of lanthanum sulfide

    Page(s): 1542 - 1547
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    The Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect have been studied in γ‐phase La3-xS4 (LaSy) in the composition range 0.04≤x≤0.3 (1.35≤y≤1.48) in order to ascertain its suitability for high‐temperature (300 to 1400 K) thermoelectric energy conversion. In this temperature and composition range the material behaves as an extrinsic semiconductor whose degenerate carrier concentration is controlled by the stoichiometric ratio of La to S. A maximum figure‐of‐merit (Z) of ∼5×10-4 K-1 at a composition x=0.3, y=1.48 (LaS1.48) was obtained. View full abstract»

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  • Crystal orientation dependence of the electrical transport and lattice structure of zinc selenide films grown by metalorganic chemical vapor deposition

    Page(s): 1548 - 1553
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    ZnSe films have been grown on 〈100〉, 〈110〉, and 〈111〉B GaAs surfaces, using the metalorganic chemical vapor deposition technique. The electrical transport properties and lattice structure characteristics of these films have been studied using a van der Pauw technique and high‐resolution transmission electron microscopy. The electrical and structural properties of these films vary significantly with growth direction. In (100) layers, the observed defects are similar in nature to isolated compensated centers. For other orientations, observed properties are best described in terms of extended defects and grain boundaries. View full abstract»

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  • A comparison of single‐ and double‐carrier injection in amorphous silicon alloys

    Page(s): 1554 - 1561
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    We present results from both experimental and theoretical studies of single and double carrier injection into amorphous silicon alloys. For biases above approximately half the built‐in potential double carrier injection in forward biased p‐i‐n diodes leads to higher currents than are obtained for single carrier injection in n‐i‐n diodes. Single carrier injection was found to depend mainly on the density and distribution of localized states in the gap, whereas double injection currents are also very dependent on the recombination kinetics and the carrier band mobilities. Analysis of experimental results suggests that for an electron band mobility of 20 cm2/V sec the hole band mobility is approximately 4 cm2/V sec. View full abstract»

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  • Observation of single‐carrier space‐charge‐limited flow in nitrogen‐doped α‐silicon carbide. I. I‐V characteristics and impedance

    Page(s): 1562 - 1570
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    This paper first reviews the properties of silicon carbide, in which polytypism is a salient feature. If a highly compensated insulating polytype is sandwiched between low resistive polytypes, space‐charge injection will occur. The theory of space‐charge‐limited current flow in the presence of traps is reviewed and a somewhat different version of the standard theory is presented, which shows more clearly the ohmic and space‐charge‐limiting regimes. Close analytical parametric forms for I and V are obtained. Experimental data on I‐V characteristics and impedance are presented for 52–300 K. Except at the highest temperature, four regimes are clearly visible in the I‐V curves. A quantitative comparison with the theory is made and various transport quantities for α‐SiC are deduced. View full abstract»

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  • Observation of single‐carrier space‐charge‐limited flow in nitrogen‐doped α‐silicon carbide. II. Electrical noise

    Page(s): 1571 - 1577
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    Noise spectra of α‐SiC in the presence of space‐charge‐limited flow are attributed to trapping noise. In the ohmic regime, SΔI∝ I20 and in the ohmic and low‐voltage quadratic regime SΔI∝I0∥V0∥ as required by the theory. The trapping levels are determined from the slope of the time constants versus 1/T; the results are in fair agreement with those obtained from the current‐voltage characteristic. The magnitude of the noise requires a modulation mechanism, such as caused by mobility fluctuations in the temperature range where ionized impurity scattering dominates. View full abstract»

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  • Dark current transport mechanism of p‐i‐n hydrogenated amorphous silicon diodes

    Page(s): 1578 - 1583
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    The dark current‐voltage characteristics of p‐i‐n hydrogenated amorphous silicon diodes with various thicknesses of the intrinsic layer (i‐layer) (770–9300 Å) are systematically investigated. The magnitude of the forward current is found to be independent of thickness of the i layer, which is obviously against the simple conventional junction theory. It has been demonstrated through various experiments that the forward current of amorphous p‐i‐n diodes is limited by a layer thinner than 770 Å, possibly being the p/i interface or a narrow zone of the i layer. View full abstract»

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  • Properties of amorphous germanium tunnel barriers

    Page(s): 1584 - 1596
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    The properties of tunnel barriers made with amorphous Ge (a‐Ge) deposited at approximately 80 K were studied in Al/a‐Ge/Al tunnel junctions and also in junctions where one electrode was Ni or Fe. The conduction process was shown to be tunneling for barriers less than about 100 A at liquid He temperature and consistent with Mott variable‐range hopping for higher temperatures and thicknesses. Measurements were made of current density J and dynamic conductance dJ/dV as a function of voltage V, thickness s, and temperature T. The measurements were compared with available theoretical expressions for rectangular tunnel barriers based on the WKB approximation. The applicability of these expressions for barrier heights less than 100 meV was examined and a modified equation for J(V) was derived which eliminated assumptions which are inaccurate for such low barriers. The measurements were also compared to this modified equation and to numerical solutions. Values for the effective tunnel barrier height ranging from 20 to 80 meV were obtained. Theoretical expressions for J(V) could be fitted to the measurements fairly well, but not perfectly; for J(T) the fit was poor. Values of s obtained using the modified expression for J(V) tended to be 10%–20% less than those measured by a quartz‐crystal thickness gauge using the bulk crystal density. The conductance peaks corresponding to the peaks in the superconducting density of states were considerably broadened over Al/Al2O3/Al junctions either because of depairing of the Al films in contact with a‐Ge or from an inelastic process in the barrier. No spin polarization of the tunnel currents was observed when one of the electrodes was Ni or Fe. Some measurements were made of a‐Ge barriers treated with glow discharges in N2, O2, and H2. The properties of a‐Ge were very similar to those previously found for a‐Si. - Evidently the basic conduction process in these junctions is tunneling, but the simple tunneling model cannot entirely explain the results. Various proposals to account for these divergences from the simple tunneling model are discussed. View full abstract»

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Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

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Meet Our Editors

Editor
P. James Viccaro
Argonne National Laboratory