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1 Mar 1977

Volume 48, Issue 3, pp. 853-1387

Page 1 of 5 Pages Next Page | Jump to Page

Absolute linear thermal‐expansion measurements on copper and aluminum from 5 to 320 K 

F. R. Kroeger and C. A. Swenson

J. Appl. Phys. 48, 853 (1977); http://dx.doi.org/10.1063/1.323746 (12 pages) | Cited 111 times

Online Publication Date: 26 August 2008

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A linear absolute dilatometer based on a three‐terminal parallel‐plate capacitor design has been used to obtain thermal expansion data for high‐purity copper and aluminum from 5 to 320 K. These data have an absolute accuracy of ±0.1% above 20 K for copper and above 30 K for aluminum, and agree well with published data at the higher temperatures. The disagreement which exists with other data below 5 K for copper and below 15 K for aluminum is believed to be sample dependent, but the mechanism is not known. The aluminum results in this region depend on the state of annealing of the sample.
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06.20.F- Units and standards
65.40.De Thermal expansion; thermomechanical effects

Linear thermal expansion measurements on silicon from 6 to 340 K 

K. G. Lyon, G. L. Salinger, C. A. Swenson, and G. K. White

J. Appl. Phys. 48, 865 (1977); http://dx.doi.org/10.1063/1.323747 (4 pages) | Cited 78 times

Online Publication Date: 26 August 2008

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Linear thermal expansion measurements have been carried out from 6 to 340 K on a high‐purity silicon sample using a linear absolute capacitance dilatometer. The accuracy of the measurements varies from ±0.01×10−8 K−1 at the lowest temperatures to ±0.1×10−8 K−1 or 0.1%, whichever is greater, near room temperature, and is sufficient to establish silicon as a thermal expansion standard for these temperatures. The agreement with previous data is satisfactory at low temperatures and excellent above room temperature where laser‐interferometry data of comparable accuracy exist. Thermal expansions calculated from ultrasonic and heat‐capacity data are preferred below 13 K where experimental problems occurred.
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06.20.F- Units and standards
65.40.De Thermal expansion; thermomechanical effects

Observation of ultrasonic surface waves on plane and cylindrical solids by optical methods

Alain Faure, Gérard Maze, and Jean Ripoche

J. Appl. Phys. 48, 869 (1977); http://dx.doi.org/10.1063/1.323748 (7 pages) | Cited 3 times

Online Publication Date: 26 August 2008

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We present results of observation and velocity measurements of surface waves generated on plane and cylindrical metallic samples submitted to an ultrasonic beam oriented at a slightly greater angle than the second critical angle, which is called the Rayleigh angle. Two different techniques are applied in the experiments. One consists of the visualization of the surfaces of the constant phase of ultrasound in water. The second uses light diffraction by surface‐wave corrugations. In this case, the insonified zone is immersed while the observation zone is in contact with the air. This technique allows the determination of the velocity, either directly by measurement of the distance between the diffraction orders or by using the properties of superposition between two echoes. Stainless steel is studied at an ultrasonic frequency near 5 MHz. On the plane surface a unique surface Rayleigh wave is detected. On the cylindrical surface a cylindrical‐surface Rayleigh wave is detected in addition to another wave. In the two cases, the velocity of the Rayleigh waves agrees well with the theoretical results: 2875 m/s for a plane and 2900 m/s for a cylinder. The additional cylindrical wave, with a higher velocity (3550 m/s), is assumed to be a circumferential one, and it turns into a higher‐velocity wave (4360 m/s) at the transition between a plane and a cylindrical boundary.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties

Enhanced elastic modulus in composition‐modulated gold‐nickel and copper‐palladium foils

W. M. C. Yang, T. Tsakalakos, and J. E. Hilliard

J. Appl. Phys. 48, 876 (1977); http://dx.doi.org/10.1063/1.323749 (4 pages) | Cited 224 times

Online Publication Date: 26 August 2008

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The biaxial elastic modulus Y[111] has been measured by bulge testing in Au‐Ni and Cu‐Pd foils containing short‐wavelength one‐dimensional composition modulations produced by vapor deposition. As compared with homogeneous foils of the same average composition, the modulated foils exhibited an appreciable increase in modulus—from 0.21 to 0.46 TPa for Au‐Ni and from 0.27 to 1.31 TPa for Cu‐Pd. For the latter system, the increase was found to be proportional to the square of the amplitude of the modulation. The enhancement of the modulus decreased with increasing wavelength and for wavelengths greater than 3 nm the modulus was the same as that for homogeneous foils. It was also observed that the deformation was non‐Hookian; the slope of the stress‐strain curves decreased with increasing strain.
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81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
46.80.+j Measurement methods and techniques in continuum mechanics of solids

Effect of temperature on irradiation‐induced dislocation loops in copper

Bennett C. Larson and F. W. Young

J. Appl. Phys. 48, 880 (1977); http://dx.doi.org/10.1063/1.323750 (7 pages) | Cited 13 times

Online Publication Date: 26 August 2008

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The effect of irradiation temperature on irradiation‐induced dislocation loops in copper has been studied by x‐ray diffuse scattering. Dislocation loop size distributions and total defect concentrations were obtained for irradiations in the temperature range 316–483 °K for neutron doses in the range (1–10) ×1018 n/cm2. The average loop sizes were found to increase with increasing irradiation temperature and increasing neutron dose. The number of point defects stored in the loop distributions tended to saturate at the higher doses and were found to decrease with increasing irradiation temperature. Ambient‐temperature measurements made on 4 °K neutron‐ and electron‐irradiated copper indicated the dislocation loops formed during the anneal to room temperature were smaller than those produced by ambient‐temperature reactor irradiations.
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61.80.Hg Neutron radiation effects
61.80.Fe Electron and positron radiation effects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.05.C- X-ray diffraction and scattering

Berlinite, a temperature‐compensated material for surface acoustic wave applications

A. Jhunjhunwala, J. F. Vetelino, and J. C. Field

J. Appl. Phys. 48, 887 (1977); http://dx.doi.org/10.1063/1.323703 (6 pages) | Cited 9 times

Online Publication Date: 26 August 2008

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The surface and pseudosurface acoustic wave properties of berlinite (α‐AlPO4) have been theoretically predicted in order to evaluate the merit of using this material in related surface acoustic wave devices. The surface and pseudosurface acoustic wave velocities, an estimate of the electromagnetic to acoustic coupling, the temperature coefficient of delay, the powerflow angle, and the attenuation have been determined for several standard crystallographic cuts. These results supplement the results given by Carr and O’Connell. This material is shown to possess several temperature‐compensated cuts and about four times the coupling of α‐quartz. It is pointed out that α‐AlPO4 may be only one of many potentially temperature‐compensated materials with a silica derivative‐type structure.
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68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound

Range profiles of 100–400‐keV deuterons in nickel: Experiment and computer simulation

W. Möller

J. Appl. Phys. 48, 893 (1977); http://dx.doi.org/10.1063/1.323704 (5 pages) | Cited 5 times

Online Publication Date: 26 August 2008

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The range profiles of 100–400‐keV deuterons have been determined using the D(d,p)T nuclear reaction technique after implantations at normal and oblique incidence. The experimental profiles show a long tail to the surface due to diffusion and a peak which is identified with the original range distribution. From the profiles, the most probable projected range and the longitudinal and lateral range straggling are derived as functions of the implantation energy. Good agreement is obtained with range profiles calculated by computer simulations using the binary‐collision model if the depth resolution of the nuclear reaction method is taken into account. The mean projected ranges agree well with predictions from analytical theory.
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61.80.Jh Ion radiation effects
29.40.-n Radiation detectors

Location of positive charges in SiO2 films on Si generated by vuv photons, x rays, and high‐field stressing

D. J. DiMaria, Z. A. Weinberg, and J. M. Aitken

J. Appl. Phys. 48, 898 (1977); http://dx.doi.org/10.1063/1.323705 (9 pages) | Cited 82 times

Online Publication Date: 26 August 2008

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The location of positive trapped charge in the dry thermally grown films of SiO2 on Si in MOS structures has been investigated by combining the internal photoemission‐voltage dependence from both interfaces with the capacitance‐voltage technique. Trapped holes have been produced in the SiO2 by vacuum ultraviolet (vuv) photons, x rays, and high‐field stressing. After irradiation under positive gate bias, trapped holes have been found to reside near the Si‐SiO2 interface with an upper limit of about 50 Å determined for their centroid from this interface. After irradiation under negative bias, a similar situation was found to occur near the Al‐SiO2 interface; and in addition some positive charge was found approximately at the Si‐SiO2 interface. After high‐field stressing under negative bias, positive charge was found approximately at the Si‐SiO2 interface. The charge locating technique is described in detail as well as the implications of the results to radiation damage and insulator breakdown.
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73.40.Ns Metal-nonmetal contacts
73.61.Ng Insulators

Dependence of residual damage on temperature during Ar+ sputter cleaning of silicon

J. C. Bean, G. E. Becker, P. M. Petroff, and T. E. Seidel

J. Appl. Phys. 48, 907 (1977); http://dx.doi.org/10.1063/1.323706 (7 pages) | Cited 96 times

Online Publication Date: 26 August 2008

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It has been found that the kind and amount of damage produced in silicon following Ar+ ion bombardment at 1.0 keV and the annealing properties of the damage depend strongly on the temperature at which the sputtering is done in the range 25–800 °C. Some of these differences in damage are not evident with surface‐sensitive techniques such as LEED, RHEED, or AES, but have been revealed by transmission electron microscopy and by Rutherford ion backscattering. TEM examination of substrates annealed at 800 °C after being sputtered at temperatures in the range 25–800 °C shows an increase in the density and the size of crystal defects with increasing sputtering temperature. Rutherford ion backscattering shows an increase in silicon disorder and in retained argon with increasing sputtering temperature. These results are similar to observations reported for ion implantation at higher energies. Models for damage mechanisms are discussed briefly. It is concluded that for Ar+ ion sputter cleaning of silicon, the silicon should be kept at room temperature or below during sputtering to minimize residual surface damage after annealing.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

cw GaAs/GaAlAs DH lasers grown by Peltier‐induced LPE

J. J. Daniele, D. A. Cammack, and P. M. Asbeck

J. Appl. Phys. 48, 914 (1977); http://dx.doi.org/10.1063/1.323707 (3 pages) | Cited 15 times

Online Publication Date: 26 August 2008

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GaAs/GaAlAs DH lasers were grown for the first time by Peltier‐induced LPE. Peltier‐induced LPE is an LPE technique in which an electric current is passed through the semiconductor‐solution interface and cools it by the Peltier effect. The growth takes place at constant furnace temperature and the growth rate is proportional to the applied current. In this way, widely different growth rates were used for each of the four layers in the double heterostructure and the active layer was grown at average rates of 100–200 Å/min. Mesa stripe lasers were made from the resulting material and lased in cw mode at room temperature. Tests on pulsed devices showed Jth/d?5 kA/cm2 μm for devices from several wafers. Measurements of characteristic temperature, external slope efficiency, internal quantum efficiency, optical loss, and minority‐carrier lifetime yielded 150–160 °K, 22–30%, 50–66%, 20–45 cm−1, and 2.5–3.5 nsec, respectively. Thus, it was concluded that the Peltier‐induced LPE results in material and laser devices of quality comparable to those produced by normal LPE.
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68.55.-a Thin film structure and morphology
42.55.Px Semiconductor lasers; laser diodes
81.10.-h Methods of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Heterostructure by solid‐phase epitaxy in the Si 〈111〉/Pd/Si (amorphous) system

S. S. Lau, Z. L. Liau, M‐A. Nicolet, and J. W. Mayer

J. Appl. Phys. 48, 917 (1977); http://dx.doi.org/10.1063/1.323708 (3 pages) | Cited 1 time

Online Publication Date: 26 August 2008

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When a thin film of Pd reacts with a 〈111〉 Si substrate, a layer of epitaxial Pd2Si is formed. It is shown that Si can grow epitaxially on such a layer by solid‐phase reaction.
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68.55.-a Thin film structure and morphology

Trapping of hydrogen isotopes in molybdenum and niobium predamaged by ion implantation

J. Bøttiger, S. T. Picraux, N. Rud, and T. Laursen

J. Appl. Phys. 48, 920 (1977); http://dx.doi.org/10.1063/1.323709 (7 pages) | Cited 47 times

Online Publication Date: 26 August 2008

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The trapping of hydrogen isotopes at defects in Mo and Nb have been studied. Ion beams of 11‐ and 18‐keV He+, 55‐keV O+ and Ne+, and 500‐keV Bi+ were used to create defects. Subsequently H or D was injected at room temperature by use of molecular beams of 16‐keV H+2 and D+2. Appreciable enhancements were observed in the amount of H and D retained within the near‐surface region of predamaged samples compared to samples with no prior damage. The total amount of D retained within the near‐surface region was measured by means of the nuclear reaction D(3He,p)4He, and H depth profiles were measured via a resonance in the nuclear reaction 1H(19F,αγ)16O. The H profiles correlate with the predicted predamaging ion profiles; however, appreciable tails to deeper depths for the hydrogen profiles are observed for the heavier predamaging ions. For a given predamage ion fluence, the amount of trapped deuterium increases linearly with incident deuterium fluence until a saturation in the enhancement is reached. The amount of deuterium trapped when saturation occurs increases with increasing predamage fluence. The experiments indicate that lighter ions, which create fewer primary displacements, are more effective per displacement in trapping hydrogen. An appreciable release of hydrogen is obtained upon annealing at 200 and 300 °C, and a preannealing experiment indicates this is due to detrapping rather than to any loss of traps. These temperatures suggest a much higher binding energy for the trapped hydrogen isotopes (∼1.5 eV) than the available evidence gives for simple H‐defect binding energies (≲0.3 eV). The detailed trapping mechanism is not known. However, it is suggested on the basis of the high binding energies and the high concentrations of hydrogen which can be trapped that clusters of hydrogen may be formed.
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61.80.Jh Ion radiation effects
29.40.-n Radiation detectors
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients

Size considerations in the design of cells for photoacoustic spectroscopy

L. C. Aamodt, J. C. Murphy, and J. G. Parker

J. Appl. Phys. 48, 927 (1977); http://dx.doi.org/10.1063/1.323710 (7 pages) | Cited 91 times

Online Publication Date: 26 August 2008

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The dependence of photoacoustic spectrometer sensitivity on the physical dimensions of the sample cell was investigated for sizes larger than and smaller than the gas thermal diffusion length. The results depend on the thermal properties of the gas and the sample in agreement with an extension of Parker’s theory of photoacoustic signal generation.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
43.20.+g General linear acoustics
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
51.90.+r Other topics in the physics of gases (restricted to new topics in section 51)

Nonlinear elastic interactions between acoustic bulk and surface waves

J. M. Rouvaen, R. Torguet, E. Bridoux, and C. Bruneel

J. Appl. Phys. 48, 934 (1977); http://dx.doi.org/10.1063/1.323711 (6 pages) | Cited 2 times

Online Publication Date: 26 August 2008

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A theoretical study of the nonlinear interaction between acoustic bulk and surface waves is presented in this paper. Starting from the nonlinear material elastic equations, a method for computing the scattering efficiency into acoustic bulk and surface waves is given. The wave‐vector conservation conditions for resonant interaction are then discussed. Possible applications to nonlinear scanning and signal processing are then studied.
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43.25.Ba Parameters of nonlinearity of the medium
43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties

Self‐masking selective epitaxy by molecular‐beam method

Seiichi Nagata and Tsuneo Tanaka

J. Appl. Phys. 48, 940 (1977); http://dx.doi.org/10.1063/1.323712 (3 pages) | Cited 50 times

Online Publication Date: 26 August 2008

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Using collimated Ga and As4 molecular beams from limited‐source apertures, epitaxial GaAs layers were grown selectively by self‐masking on preferentially etched GaAs surfaces with a lateral accuracy of 0.1 μm. From edge profile analysis, it is found that (1) the accuracy is limited by preferential growth of an obstruction layer, (2) the surface diffusion length of free Ga is dependent upon As4 arrival rate, and furthermore (3) the length is less than 200 Å in As‐rich growth conditions, while in Ga‐rich conditions the length is 1900 Å.
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68.55.-a Thin film structure and morphology
66.90.+r Other topics in nonelectronic transport properties of condensed matter (restricted to new topics in section 66)
81.20.-n Methods of materials synthesis and materials processing

The electric strength of hexane vapor and liquid in the critical region

A. H. Sharbaugh and P. K. Watson

J. Appl. Phys. 48, 943 (1977); http://dx.doi.org/10.1063/1.323713 (8 pages) | Cited 4 times

Online Publication Date: 26 August 2008

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The breakdown strength of hexane vapor has been measured above its critical temperature over a wide range of densities (0.001–0.45 g/cm3). Voltage pulses of 10‐μsec duration were used for the measurement. Above a density of 0.01 g/cm3 the strength of the vapor is appreciably less than the extrapolated low‐pressure results. This departure from Paschen’s Law is believed to be due to field emission from the cathode. Extrapolation of the high‐density vapor leads to a breakdown strength in excess of that measured in liquid. Measurements have also been made of breakdown strength under a range of conditions of temperature and pressure near the critical point in both liquid and vapor phases. The breakdown strengths of the liquid are somewhat lower than those of the vapor, but the values converge as one approaches the critical point, and it is suggested that the breakdown mechanisms in liquid and vapor are similar in the vicinity of the critical region.
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51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
52.80.Wq Discharge in liquids and solids
77.22.Jp Dielectric breakdown and space-charge effects

Preparation and properties of ferroelectric PLZT thin films by rf sputtering

M. Ishida, H. Matsunami, and T. Tanaka

J. Appl. Phys. 48, 951 (1977); http://dx.doi.org/10.1063/1.323714 (3 pages) | Cited 58 times

Online Publication Date: 26 August 2008

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Ferroelectric PLZT thin films were prepared onto Pt and fused‐quartz substrates by the rf sputtering method using powder targets with a few wt% of excess PbO. The structures of films were analyzed by x‐ray diffraction and classified into three types depending on substrate temperatures: the perovskite type (PLZT); the pyrochlore type, and the coexistence of both types. For the preparation of PLZT thin films, the substrate temperature was kept above 550 °C. Excess PbO seemed to act as a flux for crystal growth. The Curie temperature and hysteresis loops of thin films were investigated and it was confirmed that ferroelectric PLZT thin films could be obtained without annealing.
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68.55.-a Thin film structure and morphology
73.61.-r Electrical properties of specific thin films
77.80.-e Ferroelectricity and antiferroelectricity
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

A localized vibrational mode study of infrared absorption of CdTe : P

B. V. Dutt and W. G. Spitzer

J. Appl. Phys. 48, 954 (1977); http://dx.doi.org/10.1063/1.323715 (7 pages) | Cited 8 times

Online Publication Date: 26 August 2008

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Infrared localized vibrational modes of phosphorus‐related point defects are observed in a series of CdTe ingots doped only with P or with P and X, where X is In, Ga, or Al. The dopants were all added during growth by the horizontal Bridgman method. The proposed defects, their point‐group symmetries, and the local mode frequencies in cm−1 at 80 °K are as follows: PTe, Td, 322; a neutral P complex, C3v, 269, 308; PTe−InCd, C3v, 305, 331.5; PTe−GaCd, C3v, 301.5, 352.5, 357.5. CdTe : P, Al showed no PTe‐AlCd pair bands, which is probably related to the large force constant increases observed for both CdTe : P and CdTe : Al.
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78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors
63.20.Pw Localized modes
78.30.Hv Other nonmetallic inorganics

Thermoelectric power of gold‐silver alloy films

W. F. Leonard and S. C. Lee

J. Appl. Phys. 48, 961 (1977); http://dx.doi.org/10.1063/1.323716 (3 pages) | Cited 2 times

Online Publication Date: 26 August 2008

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Thermoelectric power, resistivity, and temperature coefficient of resistance of annealed Au−Ag alloy films, covering the entire composition range, have been measured. Using size effects in the electron transport theory, the energy dependence of the mean free path U and the Fermi surface area V have been determined.
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73.61.At Metal and metallic alloys
72.15.Jf Thermoelectric and thermomagnetic effects
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Rare‐earth dihydride compounds: Lattice thermal expansion and investigation of the thermal dissociation

J. E. Bonnet and J. N. Daou

J. Appl. Phys. 48, 964 (1977); http://dx.doi.org/10.1063/1.323717 (5 pages) | Cited 12 times

Online Publication Date: 26 August 2008

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The lattice parameters of seven rare‐earth (La, Nd, Gd, Dy, Er, Tm, Lu) dihydrides are determined between room temperature and a temperature ranging from 500 to 800 °C. The parameter‐vs‐temperature curves, presenting a ’’knee’’ at temperatures which vary with the rare‐earth compound, are fitted by a least‐squares method in two separate regions. In the first region, the crystalline properties of dihydrides are compared to those of the parent rare earths. In the second region where a thermal dissociation occurs, we have calculated the formation energy Ef of a point defect. Ef increases with the rare‐earth atomic number from 0.25 to 0.7 eV. A law of corresponding states between these rare‐earth dihydride compounds is established. The participation of the rare‐earth sublattice in the process of hydrogen diffusion and thermal dissociation is predicted.
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61.05.C- X-ray diffraction and scattering
65.40.De Thermal expansion; thermomechanical effects
61.72.jd Vacancies
61.72.jj Interstitials

Surface acoutic wave velocity dispersion induced by radiative absorption

J. H. Parks and D. A. Rockwell

J. Appl. Phys. 48, 969 (1977); http://dx.doi.org/10.1063/1.323718 (9 pages) | Cited 1 time

Online Publication Date: 26 August 2008

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An analysis of the dispersive propagation of surface acoustic waves through a time‐dependent thermal gradient induced by radiative absorption is presented. The dispersive phase change of the acoustic wave is shown to depend on the details of the surface absorptive properties of the material. In particular, measurement of such induced phase changes can determine the parameters which characterize the surface depth dependence of the radiarrive absorption coefficient. This analysis is applied to two cases: (i) a strongly absorbing surface layer. The relative sensitivity to bulk and total surface absorption is discussed, as well as the radiative pulse conditions for which the absorption coefficient depth profile can be determined. This technique is applied to published results for 10.6‐μm radiative absorption on KCl surfaces for which the total surface layer absorption and the bulk absorption coefficient are individually measured. Additional applicatons to related surface measurements are discussed.
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78.30.-j Infrared and Raman spectra
78.40.-q Absorption and reflection spectra: visible and ultraviolet
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
81.70.-q Methods of materials testing and analysis

Strength of MgO and NaCl polycrystals to confining pressures of 250 kbar at 25 °C

Gary L. Kinsland and William A. Bassett

J. Appl. Phys. 48, 978 (1977); http://dx.doi.org/10.1063/1.323719 (8 pages) | Cited 41 times

Online Publication Date: 26 August 2008

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The strengths of MgO and NaCl polycrystals under confining pressures to 250 kbar have been determined in a diamond‐anvil high‐pressure cell. The stresses in the samples are inferred from the strains determined by x‐ray diffraction. The strength of MgO polycrystals is found to rise from a 1‐bar confining pressure value of about 4 kbar to a maximum of 30±10 kbar at a pressure of 50±20 kbar and to remain constant at that value to a pressure of 250 kbar. The strength of NaCl polycrystals is found to rise from a 1‐bar confining pressure value of about 0.3 kbar to a maximum of 4.0±1.5 kbar at a confining pressure of 250 kbar. The interpretation of the form of strength versus pressure for these two compounds is discussed in terms of a brittle‐ductile transition. Preliminary transmission electron microscope data are presented.
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62.50.-p High-pressure effects in solids and liquids
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties

Instability of cracks under impulse loads

J. F. Kalthoff and D. A. Shockey

J. Appl. Phys. 48, 986 (1977); http://dx.doi.org/10.1063/1.323720 (8 pages) | Cited 34 times

Online Publication Date: 26 August 2008

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A plate impact method was used to produce internal penny‐shaped cracks in polycarbonate and to study the response of these cracks to short tensile pulse loads. The observed crack instability behavior could not be explained by classical static fracture mechanics. A short‐pulse fracture mechanics was developed from static fracture mechanics concepts. The instability criterion was obtained from considerations of the early time stress intensity histories experienced by cracks struck by short‐pulse loads. This criterion, which requires that the dynamic stress intensity exceed the dynamic fracture toughness for a certain minimum time, gave results in accord with the experimental data. Short‐pulse fracture mechanics defines the conditions for which simple static expressions can be used to determine dynamic fracture toughness. The dynamic fracture toughness of polycarbonate at a stress intensification rate of 107 MN m−3/2 sec−1 was measured to be 2.2±0.2 MN m−3/2, about 60% of the quasistatic value. This result supports the view that material toughness does not increase sharply at high loading rates, but rather decreases monotonically with increasing stress intensification rate until a constant minimum value is reached.
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46.50.+a Fracture mechanics, fatigue and cracks
62.20.M- Structural failure of materials

Reflection and bulk‐wave conversion of Rayleigh wave at a single shallow groove

J. P. Parekh and H‐S. Tuan

J. Appl. Phys. 48, 994 (1977); http://dx.doi.org/10.1063/1.323721 (10 pages) | Cited 12 times

Online Publication Date: 26 August 2008

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The reflection and surface‐to‐bulk wave conversion of a Rayleigh wave incident at a single shallow groove on an elastically isotropic substrate have been studied for various rectangularlike and troughlike groove profiles. It is found that the maximum value of the amplitude reflection coefficient is insensitive to the groove profile, and that the groove width producing maximum reflection or zero reflection of the incident surface wave is independent of the profile for all rectangularlike grooves. In all cases, both P and SV bulk waves are excited, with the latter carrying most of the bulk‐wave power. While the angular distribution of the bulk‐wave power patterns is strongly dependent on the groove width for a given profile, it is surprisingly insensitive to the profile for a given width. The fraction of the total incident power which is converted to bulk waves has been calculated.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
68.35.Gy Mechanical properties; surface strains
68.35.Iv Acoustical properties
62.50.-p High-pressure effects in solids and liquids

A fast‐opening switch for use in REB diode experiments

C. W. Mendel and S. A. Goldstein

J. Appl. Phys. 48, 1004 (1977); http://dx.doi.org/10.1063/1.323797 (3 pages) | Cited 91 times

Online Publication Date: 26 August 2008

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The operating characteristics of a plasma‐filled fast‐opening switch and its performance in pinching experiments on Sandia’s Proto I accelerator (double sided, 2 MV, 7.2 Ω, 24 nsec each side) are described. The growth of a sheath between the plasma and the cathode of the switch is the mechanism responsible for the switch impedance rising from 0.1 to 50 Ω in 10 nsec. The effect of this switch on diode prepulse and machine turn‐on transient suppression is discussed.
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52.75.Kq Plasma switches (e.g., spark gaps)
52.75.Di Ion and plasma propulsion
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