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1 Dec 1972

Volume 43, Issue 12, pp. 4853-5209

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Scattering of a transverse elastic wave by an elastic sphere in a solid medium

Robert J. McBride and David W. Kraft

J. Appl. Phys. 43, 4853 (1972); http://dx.doi.org/10.1063/1.1661037 (9 pages) | Cited 5 times

Online Publication Date: 10 November 2003

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Cross sections are computed for the scattering of a plane transverse elastic wave by an elastic sphere in an infinite isotropic homogeneous elastic solid. Analytic expressions are derived for the matrix elements indicated by Einspruch, Witterholt, and Truell, and the resulting matrix equations are solved numerically. The dependence of the scattering cross section upon K1a (K1 is the transverse propagation constant, a is the obstacle radius) over the range 0.01–10 is computed for various combinations of host and scatterer materials. The sensitivity of the cross section and its component terms to the elastic properties of the host and scatterer materials, and their behavior in the Rayleigh limit approximation are discussed. The calculations include the case of a constant host with a varying obstacle, and a constant scatterer in a varying host medium. It is found that most of the examples tested can be grouped conveniently into four classes, with a fifth category containing unstable results; this classification scheme is based on the general shape and specific peaking behavior of the cross‐section curves. The peaking behavior is related to the occurrence of zeros in the spherical Bessel and Neumann functions.

Stability of dislocation loops near a free surface

J. Narayan and J. Washburn

J. Appl. Phys. 43, 4862 (1972); http://dx.doi.org/10.1063/1.1661038 (4 pages) | Cited 10 times

Online Publication Date: 10 November 2003

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The effect of surface forces on the stability of edge dislocation loops, b=(1∕2) [101], in MgO thin foils has been studied using transmission electron microscopy. The circular loops lying within a critical distance from the surfaces slip out without appreciable rotation. The critical distance in {100} foils, where the glide cylinders are at 45° to the foil surfaces, was found to increase with increasing loop size.

Effect of nitrogen on the electrical and structural properties of triode‐sputtered tantalum films

David J. Willmott

J. Appl. Phys. 43, 4865 (1972); http://dx.doi.org/10.1063/1.1661039 (7 pages) | Cited 16 times

Online Publication Date: 10 November 2003

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The structural and electrical properties of nitrogen‐doped tantalum films, sputtered in a dc triode system, have been investigated. For constant sputtering voltage and current, the tantalum deposition rate decreased with increasing nitrogen flow rate; at a flow rate of 12 cm3 min−1, the deposition rate was 75% of the rate obtained without the addition of nitrogen. The density of the films decreased from 15.4 to 9.8 g cm−3 as the nitrogen flow increased from 0 to 12 cm3 min−1. The net effect on the film thickness is an increase from 2700 to 3800 Å for films on glass substrates. Films were also deposited on ceramic substrates at the same time. Both x‐ray diffractometer and powder camera analysis showed that the films consisted of the bcc Ta phase at nitrogen flows up to 3 cm3 min−1 but the lattice was approximately 3% larger than for bulk Ta. The hcp Ta2N phase appeared at flow rates above 3 cm3 min−1 and the change from bcc Ta to hcp Ta2N was accompanied by an increase in the room‐temperature coefficient of resistance from positive to negative values. For films on glass, the resistivity was approximately 250 μΩ cm as the nitrogen flow increased from 4 to 8 cm3 min−1 but the resistivity had a monotonic increase for films on ceramic substrates. The hcp Ta2N phase was replaced by the fcc TaN phase as the flow rate increased in this range; the latter phase had a preferred (111) orientation on the substrate. As the flow rate increased from 8 to 12 cm3 min−1, the resistivity increased rapidly for both types of substrates and the temperature coefficients became rapidly more negative. It is suggested that this behavior is due to the presence of an insulating nitride phase in the film.

Acoustic radiation by interdigitated grids on LiNbO3

Michael R. Daniel and P. R. Emtage

J. Appl. Phys. 43, 4872 (1972); http://dx.doi.org/10.1063/1.1661040 (4 pages) | Cited 5 times

Online Publication Date: 10 November 2003

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Measurements are presented which show the acoustic power radiated as a function of frequency by an interdigitated transducer on the surface of a lithium‐niobate boule. Several peaks are seen which are identified as either surface waves or bulk longitudinal waves travelling close to the boule surface. The transducer is seen to cause radiation at all frequencies above that for fundamental surface‐wave generation. Additionally, the signal radiated to a nearby transducer is measured. This signal comprises just surface waves and a weaker bulk longitudinal wave. These are associated with the peaks in the launched power spectrum if reflections are suppressed. In finite regular‐shaped samples reflections cannot be entirely suppressed and cause many anomalous signals. Over‐all the results show that the average strength of bulk‐wave generation is at least an order of magnitude more than that of surface‐wave generation.

Kinetics and thermodynamics of thin‐film deposition by molecular beam methods. I. Adsorption and clustering of cadmium on germanium single crystals

R. J. H. Voorhoeve, J. N. Carides, and R. S. Wagner

J. Appl. Phys. 43, 4876 (1972); http://dx.doi.org/10.1063/1.1661041 (10 pages) | Cited 15 times

Online Publication Date: 10 November 2003

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The use of mass‐spectrometric molecular beam techniques allowed a detailed study to be made of the kinetics and thermodynamics of thin‐film deposition. Thermal accommodation, adsorption, nucleation, growth, and evaporation were measured for a single system. The deposits were characterized by their coverage‐dependent steady‐state evaporation rate, which is directly related to the thermodynamic potential of the evaporant in the film. The methods used and results obtained are exemplified by the present study of all stages of the ultrahigh‐vacuum (UHV) deposition of cadmium on the (100), (110), (111), (211), and (331) faces of germanium. In this paper, the initial stages of adsorption and clustering are described. The thermal accommodation coefficient was found to be between 0.8 and 1.0. On (111) substrates, adsorption of one monolayer of immobile cadmium atoms precedes nucleation of bulk cadmium. On the other substrates, 40% to 70% of a monolayer is adsorbed prior to nucleation. The extent of this adsorption is predictable from the structure of the germanium surfaces. Adsorption energies range from 25 to 32 kcal∕g atom, compared with a heat of sublimation of 26.7 kcal∕g atom. The kinetics of the desorption of cadmium during deposition is in agreement with an evaporation mechanism in which desorption of mobile single cadmium adatoms is the rate‐determining step. The desorption energy of mobile adatoms is approximately 12 kcal∕g atom in the nucleation stage. It is shown that the stability of the cadmium deposit increases only slowly after nucleation. Electrically active dopants in the germanium increase the extent of cadmium adsorption which precedes nucleation.

Kinetics and thermodynamics of thin‐film deposition by molecular beam methods. II. Nucleation, growth, and evaporation of cadmium on germanium single crystals

R. J. H. Voorhoeve, J. N. Carides, and R. S. Wagner

J. Appl. Phys. 43, 4886 (1972); http://dx.doi.org/10.1063/1.1661042 (15 pages) | Cited 8 times

Online Publication Date: 10 November 2003

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A study has been made of all stages of the deposition of thin films of cadmium on germanium single crystals with (100), (110), (111), (211), and (331) orientations. In the preceding paper, we examined adsorption phenomena in detail. This paper gives the results on the kinetics and thermodynamics of the nucleation and growth stages and of the evaporation of cadmium from the deposit. In addition, the morphology of the films is described. Nucleation occurs on a composite germanium‐cadmium substrate and proceeds until almost two monolayers have been deposited. The thermodynamic properties of the deposit during nucleation and growth have been obtained. The thin film can be characterized by a steady‐state evaporation rate ve. The critical incident flux necessary for nucleation of bulk cadmium is directly related to the maximum which ve attains during early deposition. Nucleation is easiest on planes which are rough on the atomic scale and becomes more difficult in the order (110)≲(331)<(211)<(100)≲(111). The ``liquid‐drop'' model of classical nucleation theory is inadequate to explain the results. A mechanism of nucleation and growth and of evaporation is given based on the kinetic data. The evaporation coefficient was found to be between 0.82 and 0.98. Defects and dopants in the substrate had only a minimal effect on nucleation and growth kinetics.

Diffusion measurements in thin films utilizing work function changes: Cr into Au

R. E. Thomas and G. A. Haas

J. Appl. Phys. 43, 4900 (1972); http://dx.doi.org/10.1063/1.1661043 (8 pages) | Cited 24 times

Online Publication Date: 10 November 2003

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The role of diffusion in limiting the reliability of substrate bonding for bimetallic Cr☒Au thin films was investigated using work function, Auger electron spectroscopy, and LEED measurements to characterize the structure and chemical composition of these films. The diffusion rates for Cr into Au films are measured by means of a new technique utilizing the change in electronic work function as a measure of the surface concentration change. It was found that the diffusion coefficient (D) depended on the deposition rate of the Au film, with a twofold increase in deposition rate giving rise to an order of magnitude increase in D. The presence of sulfur as an impurity in the Cr also had a significant effect on D. Comparison of these results with values of D obtained on Cr☒Au films by other workers give similar activation energies, but much lower values of D0 (temperature independent part of D) were obtained in this work. The effect on the lifetimes of devices using thin bimetallic films is discussed in terms of structure, variation in deposition rate, and the influence of contaminants.

Ferroelectric and optical properties of Pb5Ge3O11 and its isomorphous compound Pb5Ge2SiO11

Hiroshi Iwasaki, Shintaro Miyazawa, Hideo Koizumi, Kiyomasa Sugii, and Nobukazu Niizeki

J. Appl. Phys. 43, 4907 (1972); http://dx.doi.org/10.1063/1.1661044 (9 pages) | Cited 98 times

Online Publication Date: 10 November 2003

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The temperature characteristics of dielectric constants, spontaneous polarization, thermal‐expansion coefficients, indices of refraction, and optical rotatory power of Pb5Ge3O11 single crystals have been investigated in detail from room temperature up to above the Curie temperature, 177°C. From the results of these measurements, the following constants were obtained: linear thermal‐expansion coefficients (αa)F=7.75×10−6∕deg°C and (αc)F=7.79×10−6∕deg°C (ferroelectric phase), (αa)P=13.8×10−6∕deg°C and (αc)P=13.4×10−6∕deg°C (paraelectric phase); quadratic electro‐optic constants g33T = 0.47×108 cm4 /C2, g13T = 0.37×108 cm4 /C2; and electrogyration coefficient γ33 =8.7 cm2∕C. An isomorphous compound Pb5(Ge2O7)(SiO4) was synthesized and was found to be ferroelectric with T c=60°C and Ps=1.7 μC∕cm2 at room temperature. Ferroelectric properties and electrogyration coefficient were studied in the solid‐solution system Pb5(Ge2O7)(GeO4)1−x (SiO4)x.

Proton irradiation at 30°K and isochronal annealing of reactively sputtered Ta thin‐film resistors

J. Shewchun, W.R. Hardy, and P.P. Pronko

J. Appl. Phys. 43, 4915 (1972); http://dx.doi.org/10.1063/1.1661045 (7 pages)

Online Publication Date: 10 November 2003

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Tantalum thin‐film resistors reactively sputtered in oxygen and nitrogen simultaneously have been irradiated by 150‐keV protons at 30°K. The observed conductance increase of the films is ascribed to radiation‐produced defect levels within the inter‐island regions of Ta2O5 in these discontinuous films. The nonlinearity of the conductance increase with fluence may be accounted for by a nonlinear rate of defect production due to a combination of spontaneous recombination and close‐pair thermal annealing. The number of unstable sites surrounding each defect is found to be equal to or greater than four for crystalline Ta2O5. Thermal recovery of the damage proceeds in two main stages: Stage A (34–150°K) possesses some substructure and is attributed to close‐pair or correlated recombination; stage B (150–300°K) is very broad and structureless and is attributed to uncorrelated annihilation of defects at the gap‐island interface. Negative annealing stages (characterized by a conductance increase) indicate a metallic conduction process via connected metallic islands.

Spall fracture in aluminum monocrystals: a dislocation‐dynamics approach

A. L. Stevens, Lee Davison, and W. E. Warren

J. Appl. Phys. 43, 4922 (1972); http://dx.doi.org/10.1063/1.1661046 (6 pages) | Cited 27 times

Online Publication Date: 10 November 2003

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High‐purity monocrystalline aluminum disks of three crystallographic orientations were subjected to carefully controlled planar impact producing low levels of spall damage. This damage was observed by optical and scanning electron microscopy of sections through the recovered disks, and was found to consist of voids of essentially octahedral form having {111} planes as faces. To describe the growth of these voids we propose a kinematical model based on the motion of edge dislocations. Dynamical equations describing the rate of growth of an individual void are obtained by applying established concepts of dislocation mechanics to the kinematical model. Finally, the dynamical void growth model is combined with an empirically established nucleation model to yield equations for calculating the total volume growth rate in a spalling sample. Extension of these results to other ductile fracture phenomena is suggested.

Expansion, crazing and exfoliation of lithium niobate on ion bombardment and comparison results for sapphire

William Primak

J. Appl. Phys. 43, 4927 (1972); http://dx.doi.org/10.1063/1.1661047 (7 pages) | Cited 7 times

Online Publication Date: 10 November 2003

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Surface deformation and destruction resulting from bombardment with respective 140‐keV ions H+, D+, He+, and Ne+ were observed. Following bombardment, spontaneous secular changes occurred over a period of many months at room temperature. Optical absorption curves of the specimens showed interference effects. Calculations of optical interference patterns caused by blistering are given. Some bombarded lithium niobate surfaces became crazed. The patterns consisted of fractures parallel to the ZY plane, despite no evidence of cleavage. Exfoliation occurred by material from the areas between the fractures breaking away. The surface deformation of a proton‐bombarded specimen annealed below 300°C simultaneously with the intense optical absorption caused by the hydrogen. Calculations of effects to be expected from neutron irradiation are given. The depths of the effects are compared with the particle ranges and appear to be close to their median projected ranges. The depths are greatly in excess of the ranges calculated from Lindhard's theories, which overestimate the electronic stopping power at these energies. The radiation effects along the range are important in determining the blistering behavior. The piezoelectric effect may be the cause of the crazing paralle to Y.

Electro‐optic properties of ferroelectric 5PbO ⋅ 3GeO2 single crystal

Naoya Uchida, Tadashi Saku, Hiroshi Iwasaki, and Kota Onuki

J. Appl. Phys. 43, 4933 (1972); http://dx.doi.org/10.1063/1.1661048 (4 pages) | Cited 9 times

Online Publication Date: 10 November 2003

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Linear electro‐optic coefficients of 5PbO ⋅ 3GeO2 have been measured at 6328 Å. The values obtained at room temperature are r11=0.27, r22=2.3, r13=10.5, r33=15.3, r41=0.6, r51=6, and rc=5.3 (in 10−12 m∕V). The relatively small values make the material unattractive for practical applications. Temperature dependence of r22, r13, and r33 have been measured up to above Tc, and the behavior supports the previous deduction that the high‐temperature phase is 6. It is found that the quadratic EO coefficients g13 and g33 are large compared with those for BO6 ferroelectrics and the values depend on the spontaneous polarization. The anomalous decrease of g13 and g33 has been observed in the vicinity of Tc.

Axial channeling in ThO2

F. W. Clinard and W. M. Sanders

J. Appl. Phys. 43, 4937 (1972); http://dx.doi.org/10.1063/1.1661049 (6 pages) | Cited 2 times

Online Publication Date: 10 November 2003

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Axial channeling in single‐crystal ThO2 was investigated with 6.5‐MeV3He++ ions. The thorium sublattice was studied by evaluation of pulse‐height distributions from backscattered 3He ions, and the oxygen sublattice by evaluation of proton pulse‐height distributions from 16O(3He, p)18 F reactions. Critical channeling angles (ψ1∕2) and minimum yields (χmin) were determined for the 〈110〉 and 〈111〉 directions. Values for ψ1∕2 were generally consistent with those reported for the isomorphic compound UO2, whereas χmin values were considerably smaller than those reported for UO2. These results are compared with those predicted by current channeling theories, and are discussed in terms of the relative crystal perfection of ThO2 and UO2.

Superlattice of voids in neutron‐irradiated tungsten

V. K. Sikka and J. Moteff

J. Appl. Phys. 43, 4942 (1972); http://dx.doi.org/10.1063/1.1661050 (3 pages) | Cited 19 times

Online Publication Date: 10 November 2003

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Transmission electron microscopy of tungsten irradiated at about 550°C to a fast neutron fluence of approximately 1×1022 neutrons cm−2 reveal the formation of a superlattice of voids. The void lattice parameter is 195 Å and the lattice parameter to average void size is about six. Both the formation of the superlattice and the temperature dependence of the lattice parameter in tungsten, a material considered to have isotropic elastic properties, is in contradiction to present theories based on the elastic anisotropy of the host metal.

Martensitic pretransformation phenomena in the Au‐47.5 at.% Cd and the Fe‐29.7 at.% Ni alloys

H. Livingston and K. Mukherjee

J. Appl. Phys. 43, 4944 (1972); http://dx.doi.org/10.1063/1.1661051 (7 pages) | Cited 5 times

Online Publication Date: 10 November 2003

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Premartensitic transformation characteristics have been investigated in the Au‐47.5 at.% Cd and the Fe‐29.7 at.% Ni alloys by measuring electrical resistivity and magnetoresistance. Preliminary electron diffraction studies have also been made for the Au☒Cd alloy. An anomalous magnetoresistance peak was observed for both of these alloys prior to the martensitic transformation. In the Au☒Cd alloy this peak was about 2–3°C above the Ms, and for the Fe☒Ni alloy it was about 5–6°C above the Ms. Furthermore, when the Ms was lowered by isothermal stabilization, this peak moved in conjunction with the new Ms temperature. This indicates that the observed peak is truly associated with the premartensitic instability of the parent phase. The electron diffraction pattern of the parent phase of the Au☒Cd alloy shows extensive 〈110〉 and 〈112〉 streaking in the temperature range where anomalous magnetoresistance was observed. These experimental results could tentatively be interpreted in terms of anisotropic scattering centers resulting from localized strain inhomogeneities. Presumably these inhomogeneities are associated with the atomic shuffling prior to the actual phase transformation and could be identified with the so‐called ``strain embryos''.

Phenomenological theory of antiferroelectricity and ferroelectricity applied to NaNbO3 and the system KNbO3☒NaNbO3

C. N. W. Darlington

J. Appl. Phys. 43, 4951 (1972); http://dx.doi.org/10.1063/1.1661052 (6 pages) | Cited 3 times

Online Publication Date: 10 November 2003

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Cross has applied the Kittel‐Devonshire phenomenological treatment of ferroelectricity and antiferroelectricity to NaNbO3 and the system NaNbO3☒KNbO3. Recent experimental work has shown that the low‐temperature form has rhombohedral symmetry with space group R3c, and that therefore this phase is a ``line ferroelectric'', rather than a ``cone ferroelectric'' with canted polarization, as had been supposed by Cross. The amendments to the phenomenology are discussed, and it is shown that the agreement with observation is improved using the correct low‐temperature form.

Acoustoelectric interaction in degenerately doped piezoelectric semiconductors

E. Mosekilde

J. Appl. Phys. 43, 4957 (1972); http://dx.doi.org/10.1063/1.1661053 (7 pages) | Cited 3 times

Online Publication Date: 10 November 2003

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The acoustoelectric gain constant is calculated quantum mechanically for arbitrary degeneracy of the electron gas. The requirements of energy and momentum conservation in individual electron‐phonon interactions result in a rather sharp reduction of the gain factor when the acoustic wave number exceeds the characteristic linear extension of the electron distribution in reciprocal space. A simple two‐band model is developed to describe effects of impurity banding upon the acoustoelectric interaction. According to this model, impurity banding enhances the acoustoelectric coupling and widens the active acoustic spectrum. These effects are associated with the increased density of states near the conduction‐band edge and with the presence of electrons of higher momentum effective mass than the conduction‐band electrons. At low temperatures it becomes possible for the linear gain factor as a function of acoustic frequency to have two maxima.

Positive‐ion bombardment of substrates in rf diode glow discharge sputtering

J. W. Coburn and Eric Kay

J. Appl. Phys. 43, 4965 (1972); http://dx.doi.org/10.1063/1.1661054 (7 pages) | Cited 224 times

Online Publication Date: 10 November 2003

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The plasma potential and the potential of an electrically isolated surface are measured in an rf diode sputtering glow discharge. The influence on these potentials of both the geometry enclosing the discharge volume and of a positively biased auxiliary electrode in contact with the discharge is investigated. It is shown that confining the discharge increases the plasma potential and the energy of positive ions incident on electrically isolated substrates, whereas applying a positive voltage to an auxiliary electrode also increases the plasma potential but does not significantly increase the energy of ions incident on electrically isolated substrates. The effect of rf modulation on the ionic energy distributions is demonstrated. This occurs as the ions pass through the plasma‐substrate sheath and results in a large broadening of the energy distributions of low‐mass species.

Effect of oxidation on the resistivity of Ni☒P films

S. T. Pai and J. P. Marton

J. Appl. Phys. 43, 4972 (1972); http://dx.doi.org/10.1063/1.1661055 (6 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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The oxidation and the resulting changes in the dc resistivity of chemically deposited Ni☒P films were studied. The oxidation was found to be a two‐stage process. At temperatures below 550°K mainly oxygen diffusion along the grain boundaries takes place, while above this temperature a surface‐oxide layer forms. The rates of these processes are similar to those for certain bulk metals. A model to explain the resistivity changes, containing two separate terms with different activation energies, is used to analyze the experimental results. The two terms correspond to the two stages of oxidation. The agreement between calculated and measured resistance values for near‐ideal films is satisfactory. We suggest that the model may be applicable to other thin‐metal films.

CO2 laser‐induced gas breakdown in hydrogen

A. A. Offenberger and N. H. Burnett

J. Appl. Phys. 43, 4977 (1972); http://dx.doi.org/10.1063/1.1661056 (4 pages) | Cited 9 times

Online Publication Date: 10 November 2003

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A single‐mode CO2 laser pulse of approximately 10 MW peak power has been used to induce breakdown at pressures from 50 to 700 Torr in hydrogen. Measurements of the reflected and transmitted laser intensity were obtained and the properties of the resulting spark were studied by means of image converter camera and spectroscopic techniques. At pressures in excess of 100 Torr the spark was observed to grow preferentially towards the focusing lens, while at lower pressures a symmetric expansion was observed. The observed motion was consistent with the existence of a breakdown wave during the rising portion of the laser pulse followed by a laser‐supported detonation. At pressures greater than 100 Torr, significant reflection (> 2%) was observed during the detonation phase.

Growth of electromagnetic waves on the surface of a negative differential conductance material

D. B. Matthews and Jeffrey Frey

J. Appl. Phys. 43, 4981 (1972); http://dx.doi.org/10.1063/1.1661057 (8 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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In order to determine the usefulness in device applications of semiconducting materials which exhibit a bulk differential negative conductivity, but which may be fabricated most easily in the form of thin sheets, a study is performed of the propagation of electromagnetic surface waves along the interface between such materials and free space. The dispersion relation of the system is determined for waves traveling with phase velocities comparable to the velocity of light, so that the quasistatic approximation is not made. rf charge concentration at the surface is accounted for in a manner similar to that used in the study of scalloped electron beams. Numerical solution of the dispersion relation is made for possible values of parameters for one relevant class of semiconducting materials, viz., compound semiconductors in which crystalline superlattices have been formed. Growth rates up to several decades of dB∕cm at frequencies up to 1012 Hz are seen to occur for reasonable superlattice parameters for gallium arsenide and indium antimonide.

A field‐emission illumination system using a new optical configuration

Lee H. Veneklasen and Benjamin M. Siegel

J. Appl. Phys. 43, 4989 (1972); http://dx.doi.org/10.1063/1.1661058 (8 pages) | Cited 12 times

Online Publication Date: 10 November 2003

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A field‐emission electron‐beam illumination system employing an ``oxygen processed'' field emitter and a specially adapted optical configuration is described and experimentally evaluated. A preaccelerator lens, acting directly upon the beam emerging from the field‐emission diode, allows the accelerator section to be used in a field‐lens mode where the gun crossover remains stationary within the accelerating lens for a wide range of operating conditions. The gun is particularly insensitive to accelerator aberrations and to changes in the high voltage, tip voltage, and beam current, making it particularly suitable for high‐voltage microscopy. Operating at 50 kV under conditions favorable for conventional transmission electron microscopy, measurements indicate a brightness of over 108 A∕cm2∕sr at a beam current of 10−8 A with 10 μA total emission current in satisfactory agreement with theoretical predictions. The discussion includes some general design considerations and performance predictions necessary for optimizing the field‐emission system for application in conventional transmission electron microscopy.

Diffraction of electromagnetic plane wave by an infinite slit embedded in an anisotropic plasma

Kohei Hongo

J. Appl. Phys. 43, 4996 (1972); http://dx.doi.org/10.1063/1.1661059 (6 pages) | Cited 1 time

Online Publication Date: 10 November 2003

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Two‐dimensional diffraction of an H‐polarized electromagnetic plane wave by a slit embedded in an anisotropic medium is studied. The problem is formulated using the discontinuity characteristic of the Weber‐Schafheitlin integral (WSI), and expressions for the diffracted fields and the surface wave trapped in the vicinity of the conducting screen are derived. The numerical results for the radiation pattern of a diffracted field are presented. The pattern is found to show an asymmetry for normal incidence. The solutions are valid for arbitrary small slit width and arbitrary anisotropy.

Anode current density in high‐current pulsed arcs

K. T. Shih

J. Appl. Phys. 43, 5002 (1972); http://dx.doi.org/10.1063/1.1661060 (4 pages) | Cited 3 times

Online Publication Date: 10 November 2003

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A method has been developed using a split anode to measure the anode current density distribution in high‐current pulsed arcs. Rogowski coils were used to detect the current to each half of the split anode as a function of arc position relative to the splitting plane. Transformation equations were derived to obtain local values of current density from the measured lateral distributions. The data were taken using a copper anode in air at one atmosphere with arc current from 750 to 2250 A. The peak anode current densities were found to be between 3.4×105 and 5.5×105 A∕cm2.

Electrical measurements in silicon under shock‐wave compression

N. L. Coleburn, J. W. Forbes, and H. D. Jones

J. Appl. Phys. 43, 5007 (1972); http://dx.doi.org/10.1063/1.1661061 (6 pages) | Cited 7 times

Online Publication Date: 10 November 2003

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The electrical behavior of p‐type silicon in the (111) orientation was studied under shock stresses from 8 to 160 kbar. Positive electrical signals are induced in the crystals during passage of elastic shock waves. Maximum signal amplitude was detected below the Hugoniot elastic limit (55 kbar). Resistance‐vs‐stress measurements were made when the polarization signal was zero, i.e., no elastic waves were in the crystals. The resistance becomes very small near the elastic limit, indicating that a metallic state is reached. The relative resistance, R∕Ro, then increases significantly at 133 kbar where a phase transition is indicated.
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