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1 Jun 1973

Volume 44, Issue 6, pp. 2447-2931

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Pressure dependence of elastic moduli of tungsten carbide cermet

J. Paul Day and Arthur L. Ruoff

J. Appl. Phys. 44, 2447 (1973); http://dx.doi.org/10.1063/1.1662593 (2 pages) | Cited 11 times

Online Publication Date: 9 October 2003

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The elastic constants of a commercial tungsten carbide cermet (3% cobalt binder) were measured as a function of pressure at room temperature. As pointed out in a recent publication by Ruoff, the pressure dependence of the elastic constants affects the maximum possible pressure which a vessel can contain. This dependence is discussed in light of the present data.

On the interaction of prismatic and glissile dislocations

J. Narayan

J. Appl. Phys. 44, 2449 (1973); http://dx.doi.org/10.1063/1.1662594 (3 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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A transmission electron microscopy study of the interaction between a prismatic dislocation loop and a straight dislocation moving in its glide plane in MgO is reported. The interactions are discussed in terms of Kroupa's theoretical estimates of interaction parameters.

Precipitation and solid solution effects in aluminum‐copper thin films and their influence on electromigration

G. A. Walker and C. C. Goldsmith

J. Appl. Phys. 44, 2452 (1973); http://dx.doi.org/10.1063/1.1662595 (4 pages) | Cited 8 times

Online Publication Date: 9 October 2003

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With the recent discovery that the addition of copper to thin aluminum films increases the lifetime to electrical failure of the films, a large effort has been made to understand the role of the copper in the process. The present paper describes experiments on various types of thin polycrystalline films designed to understand the solid solution and precipitation effects in the films. It is shown that precipitation is different from the bulk and in turn different from thin‐film work on unsupported single‐crystal films. Possible mechanisms relating copper additions to electromigration lifetime are considered and the effect of total copper distribution in the films is found to be important. Differences in residual gas pressure in the vacuum system can alter precipitation processes.

Thermal and elastic properties of silicate oxyapatite crystals

R. H. Hopkins, J. de Klerk, P. Piotrowski, M. S. Walker, and M. P. Mathur

J. Appl. Phys. 44, 2456 (1973); http://dx.doi.org/10.1063/1.1662596 (3 pages) | Cited 5 times

Online Publication Date: 9 October 2003

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The elastic constants, thermal expansion, thermal conductivity, and heat capacity are reported for a new class of laser hosts‐the silicate oxyapatites. For Ca2La8(SiO4)6O2 the five independent elastic constants obtained from sound velocity measurements are C11=1.71, C12=0.62, C33=1.71, C44=0.52, and C13=0.39×1012 dyn∕cm2, the thermal expansion coefficients at 300 K are 8.9×10−6 and 6.6×10−6 K−1 for the [1010] and [0001] directions, respectively, and the room‐temperature conductivity is about 0.019 W cm−1 K−1. Sound velocity and thermal expansion data suggest a Debye temperature between 400 and 500 K.

Charge buildup in electron‐irradiated dielectrics

Bernhard Gross, Julian Dow, and S. V. Nablo

J. Appl. Phys. 44, 2459 (1973); http://dx.doi.org/10.1063/1.1662597 (5 pages) | Cited 20 times

Online Publication Date: 9 October 2003

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Irradiation of dielectrics with nonpenetrating electron beams generates long‐lasting space charges. A simple experimental and mathematical method is developed for the investigation of charge buildup during irradiation. Time‐resolved charge measurements carried out with pulsed beams of 1‐MeV electrons, pulse duration of 4×10−5 sec, and an average current density of 10−2 A∕cm2 were used to analyze effects of charge leakage caused by radiation‐induced conductivity and electron range reduction caused by retardation of the incident electrons in the internal space‐charge field. Leakage is found to predominate in silica and borosilicate glass while range reduction predominates in polyethylene.

Temperature dependence of the pyroelectric voltage response to step infrared signals in triglycine sulphate

M. Simhony, A. Shaulov, and A. Maman

J. Appl. Phys. 44, 2464 (1973); http://dx.doi.org/10.1063/1.1662598 (6 pages) | Cited 5 times

Online Publication Date: 9 October 2003

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An expression is derived for the pyroelectric (PE) voltage response to step radiation signals which can be applied up to temperatures close to the Curie point Tc under a ``small‐signal'' condition. Based on the Curie‐Weiss law and the thermodynamic theory of a second‐order ferroelectric transition, a discussion is given of the temperature dependence of the parameters of the PE voltage response: initial slope, peak value, rise time, and fall time as functions of sample parameters and load resistance. It is found that the PE voltage may reach a maximum close to Tc, and expressions are derived for this value as well as for the temperature at which it occurs. These results were checked in detail on 12 samples of single‐crystalline triglycine sulphate for temperatures from 20 °C to the Curie point, and good agreement between theory and experiment was observed. The application of the results to PE detection of ir is considered.

Correlation of density periodicity to pressure‐induced polymorphic transformations in solid elements

Lin‐gun Liu

J. Appl. Phys. 44, 2470 (1973); http://dx.doi.org/10.1063/1.1662599 (5 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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The densities of the elements have been found to be a periodic function of the atomic number in the same manner as the other properties of elements in the Periodic Table. The existence of pressure‐induced polymorphic transformations in solid elements at room temperature is found to be closely correlated to the periodicity of density, hence, the atomic number. With only the exception of Fe, no phase transformations have been found for 28 solid elements having densities greater than ρ=2.8+0.12Z. For elements having densities less than the above value, there might be only two exceptions out of 50 solid elements that do undergo pressure‐induced phase transformations within the range of presently available apparatus. This correlation seems to serve as a better indication for finding a high‐pressure phase than is predicted on the basis of crystal structure, and has led the author to find a high‐pressure phase in Se, Tm, and Lu.

Vapor epitaxy of CaF2 on NaCl

F. A. Koch and R. W. Vook

J. Appl. Phys. 44, 2475 (1973); http://dx.doi.org/10.1063/1.1662600 (8 pages) | Cited 4 times

Online Publication Date: 9 October 2003

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CaF2 films, 30–1500 Å thick, were vapor deposited at 25–380 °C onto air‐cleaved and vacuum‐cleaved NaCl in residual gas pressures of order 10−5, 10−7, and 10−9 Torr. The structures of the films were examined by in situ ultrahigh‐vacuum reflection high‐energy electron diffraction, conventional transmission electron microscopy, transmission electron diffraction, and surface replication techniques. The films consisted of many crystallites, the complex {110} and {001} orientations of which depended on the deposition parameters. The transition from the complex {110} orientation to the {001} orientation is described in detail in terms of its dependence on the deposition temperature, film thickness, vacuum, and substrate conditions. The {001} orientation was identified with two sets of thin needle‐shaped crystallites oriented at 90° to each other. The {110} orientation was identified with two sets of larger crystals also oriented at 90° to each other. At higher deposition temperatures the larger crystals formed predominantly at cleavage steps on the NaCl substrate, while the needlelike crystals tended to form on the surface of the films.

Optical study of lithium‐defect complexes in irradiated silicon

C. S. Chen and J. C. Corelli

J. Appl. Phys. 44, 2483 (1973); http://dx.doi.org/10.1063/1.1662601 (7 pages) | Cited 7 times

Online Publication Date: 9 October 2003

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Optical spectroscopy has been used to study the interaction of lithium impurity atoms with neutron‐produced defects in silicon. In addition to the divacancy‐associated defect absorption bands at 1.8, 3.46, and 3.61 μ, several additional radiation‐produced infrared absorption bands at 1.36, 1.50, 1.6, 1.94, 2.05, 2.09, 2.14, and 2.4 μ are observed in lithium‐doped silicon, irrespective of the oxygen concentration. In high oxygen concentration Si, a decrease of the (LiO)+ vibrational band (9.85 μ) accompanied by an increase of the oxygen interstitial vibrational band (9 μ) is observed after neutron irradiation (at ∼  300 ∘K) and heat treatment (to ∼  150 ∘C). This fact rules out the possibility of the formation of the Li☒O‐vacancy defect complex. The presence of Li decreases the production of the oxygen‐vacancy complex. The intensity and the annealing temperature of the divacancy‐associated bands strongly depend upon the Li concentration, and the intensity is found to be substantially lower than that observed for Si not containing Li. The Li defect bands exhibit a saturation in their intensity for (Li) ≈6×1016 cm−3. The bands increase in intensity after T ≳80 ∘C heat treatment. This is attributed to the dissociation of other simple Li‐associated defects. The results indicate that higher‐order defect complexes are responsible for the bands and the divacancy must be directly involved in the formation of at least one of them. Detailed annealing studies are presented.

Measurement of the anisotropy of resistivity due to screw dislocations in aluminium

A. J. Hamdani

J. Appl. Phys. 44, 2490 (1973); http://dx.doi.org/10.1063/1.1662602 (5 pages)

Online Publication Date: 9 October 2003

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The anisotrpic resistivity of dislocations produced by deformation is measured in high‐purity Al single crystals at liquid‐helium temperature. A network of screw dislocations is produced by twisting a single‐crystal cylindrical Al bar about the [111] direction which was along the axis of the bar. Resistivity parallel to the slip plane is measured by a mutual inductance method and along the crystal axis by a dc potentiometric method using Josephson junctions. Resistivities perpendicular to the specimen axis are found to be greater than those parallel to the specimen axis. The ratio Δρac∕Δρdc (where Δρac and Δρdc are the resistivity increments along the directions perpendicular and parallel to specimen axis, respectively) is approximately equal to 1.29.

Thickness dependence of conversion efficiency of ZnS film transducers for elastic surface waves

Ritsuo Inaba, Koji Kajimura, and Nobuo Mikoshiba

J. Appl. Phys. 44, 2495 (1973); http://dx.doi.org/10.1063/1.1662603 (9 pages) | Cited 5 times

Online Publication Date: 9 October 2003

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The conversion efficiency of ZnS transducers evaporated on a glass substrate for elastic surface waves has been measured as a function of the ZnS film thickness and analyzed by using a simple model. It is found that the thickness dependence of the conversion efficiency is affected by elliptic particle motion at the position of electrodes located at the interface between the ZnS film and the substrate (type I) or at the surface of the ZnS film (type II). Conversion efficiency calculated from the potential induced at the electrodes is in good agreement with the experiments. The analysis shows that the internal impedance of the thin‐film transducer is not simply proportional to Δ vs∕vs, where Δ vs is the perturbation in surface‐wave velocity when the electrodes are replaced by a thin‐film perfect conductor. Theory suggests that type I is most efficient when the thickness is about 0.4 times the surface wavelength.

Relationship between sputter cleaning parameters and surface contaminants

J. E. Houston and R. D. Bland

J. Appl. Phys. 44, 2504 (1973); http://dx.doi.org/10.1063/1.1662604 (5 pages) | Cited 10 times

Online Publication Date: 9 October 2003

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In an abnormal dc glow discharge sputtering system the current at a constant voltage and pressure is often found to decrease from an initially high value to a steady‐state level as the cathode surface is sputtered. We have investigated the relationship between this decrease in current and the level of cathode surface contamination by periodically analyzing the surface during sputter cleaning using the soft x‐ray appearance potential technique. We find that the excess initial current results from contaminating gas liberated from the chamber wall and cathode surface by the action of the discharge. The rate at which cathode surface contaminants are removed and the residual level that is indicated by the steady‐state discharge current are both strongly dependent on the over‐all cleanliness of the discharge system. With proper attention to cleanliness, however, it is found that the steady‐state discharge current can be used as a process control variable, indicating the attainment of a relatively clean cathode surface.

Glow‐discharge optical spectroscopy for the analysis of thin films

J. E. Greene and J. M. Whelan

J. Appl. Phys. 44, 2509 (1973); http://dx.doi.org/10.1063/1.1662605 (5 pages) | Cited 17 times

Online Publication Date: 9 October 2003

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Available techniques for the chemical analysis of epitaxial semiconductor films are limited because of typical sample thicknesses of 0.7–10 μm. The use of glow‐discharge optical spectroscopy was investigated as an analytical technique. GaAs was dc sputtered in Ar and the glow discharge monitored for the electroluminescence associated with one or more target elements. The present detection limit for Sn in GaAs is 3×1016 atoms cm−3 for a volume sputtering rate of 1.5×10−5 cm3∕min. The luminescent intensities combined with sputtering rates were used to estimate concentration profiles as a function of depth for GaAs1−x Sbx films grown on GaAs. Sputtering yields have been measured for GaAs over the range 0.5–3 kV and found to vary with orientation in the following order: (111)As, (111)Ga, (211), and (110).

Absorption current, dielectric constant, and dielectric loss by the tunnelling mechanism

H. J. Wintle

J. Appl. Phys. 44, 2514 (1973); http://dx.doi.org/10.1063/1.1662606 (6 pages) | Cited 31 times

Online Publication Date: 9 October 2003

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A calculation is made of the absorption current, dielectric constant, and dielectric loss expected from electron tunnelling into a single trapping level in a dielectric. Plots are given of current versus time, and of dielectric constant, dielectric loss, and loss tangent against frequency. This model reproduces the approximate t−n dependence of absorption current (t =time, n≃1) and nearly constant tanδ observed experimentally in many insulators. Numerical comparison with experiment shows that this model may apply to the case of high polymers, but is unable to account for the higher absorption currents occurring in oxides and similar inorganic dielectrics.

Blistering in helium‐ion‐implanted (111) niobium monocrystals

S. K. Das and M. Kaminsky

J. Appl. Phys. 44, 2520 (1973); http://dx.doi.org/10.1063/1.1662607 (10 pages) | Cited 16 times

Online Publication Date: 9 October 2003

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The formation of helium blisters on the (111) surface planes of monocrystalline niobium by implantation of 0.5–1.5‐MeV helium ions has been investigated for total doses ranging from 0.1 to 1.0 C∕cm2 for different target temperatures, angles of incidence of the projectiles, and channeling conditions. The results indicate that the blister shape is strongly dependent on target temperature. At 900 °C and for channeled projectiles, almost all the blisters have a threefold symmetry resembling a ``crow‐foot'' shape. The alignment of the crow‐foot blisters with respect to each other exhibits an asymmetry in that their prongs are aligned along only one set of 〈112〉 directions of the host niobium lattice such as [121], and [112], and [211] directions and not along the other equivalent set such as the [121], [112], and [211] directions. As the target temperature is lowered, the tendency to form dome‐shaped blisters increases; at room temperature only dome‐shaped blisters form. The average blister size appears to increase with decreasing target temperature, with increasing degree of channeling, and with increasing projectile energy; at room temperature the last of these variables is the one with the most pronounced effect on the size. The blister density is more than two orders of magnitude less for channeled projectiles than for unchanneled ones for irradiation at a target temperature of 900 °C. For the unchanneled projectiles, the angle of incidence of the projectiles does not appear to change the morphology of the blisters significantly.

Role of firing atmosphere on the rate of transformation of ZnS crystal

M. Sakaguchi and T. Hirabayashi

J. Appl. Phys. 44, 2530 (1973); http://dx.doi.org/10.1063/1.1662608 (3 pages) | Cited 2 times

Online Publication Date: 9 October 2003

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In order to investigate the role of firing atmosphere on the rate of transformation of a ZnS crystal, crystalline ZnS of hexagonal or cubic form was fired for 0.5–24 h at 800 and 1050 °C in each atmosphere of He, HCl, H2S, H2, O2, and their various mixtures, and the crystal structure of the fired ZnS was analyzed by x‐ray diffraction. At 800 °C, the transformation from hexagonal to cubic form occurred slightly in O2 and H2S, markedly in HCl, but hardly at all in He and H2 although NaCl was added. At 1050 °C, the transformation from cubic to hexagonal form occurred easily in all atmospheres except H2 and notably in HCl. The transformation occurred in H2 with added NaCl more easily than in pure HCl. Based on these results, it is concluded that the rate of transformation of a ZnS crystal is influenced both by the formation of defects, which result in the contact reaction between the atmosphere and the surface of the ZnS crystal, and by the bulk diffusion of anions (S2− and O2−).

Electromigration and metalization lifetimes

R. A. Sigsbee

J. Appl. Phys. 44, 2533 (1973); http://dx.doi.org/10.1063/1.1662609 (8 pages) | Cited 29 times

Online Publication Date: 9 October 2003

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A model has been developed to predict the lifetime τf of integrated circuit metalizations which operate at high dc densities Je. Grain‐boundary electromigration, internal heat generation, and current crowding at growing voids dominate the rate processes that lead to failure. Joule heating of the stripe causes an initial temperature rise ΔT0 and heat flow into the substrate. If this rise is appreciable an instability exists in the stripe. When vacancies electromigrate down grain boundaries and precipitate on a suitable boundary, forming an elongated void, the electric current will be diverted. This is serious if the crack has a substantial length component perpendicular to the current flow which increases vacancy currents to the crack tip and the local heating. An analytical model considering these effects and the time for a crack to propagate across the stripe width yields a stripe lifetime integral which fits the form Pn =(1∕2)(1+0.265γΔT0). Here γ=ΔH∕kT2 is the temperature coefficient of the diffusion constant. Pn, the crack width, and the initial electromigration grain boundary flux then largely determine the stripe lifetime. The self‐heating contribution ΔT0 is shown to be an important term in the interpretation of accelerated test data and for proper extrapolation to lower temperature‐and‐current stress levels. The stripe temperature coefficient of resistance and melting point are shown to have only secondary effects on lifetime. Lifetimes have a Je−n dependence with n varying from unity at low ΔT0 levels to 15+ for high ΔT0 levels and are determined by the stripe and heat‐sink temperatures. For maximum stripe lifetimes, wide stripes with good thermal coupling to the heat sink are desirable.

Spontaneous polarization of Gd2 (MoO4)3

E. Sawaguchi and L. E. Cross

J. Appl. Phys. 44, 2541 (1973); http://dx.doi.org/10.1063/1.1662610 (4 pages) | Cited 16 times

Online Publication Date: 9 October 2003

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The spontaneous electric polarization Ps has been measured for Gd2(MoO4)3 over the temperature range from 4.2 °K to the Curie point. Near 4 °K the maximum Ps is slightly less than 0.29 μC∕cm2 with a very low temperature coefficient. An electric field enforced phase transition from paraelectric to ferroelectric at temperatures just above zero‐field Tc demonstrates the first‐order nature of the phase change. Better agreement was found near Tc between Ps and the relation (T − T1)1∕3 than between Ps and a Landau‐type function.

Microstructure, growth, resistivity, and stresses in thin tungsten films deposited by rf sputtering

P. Petroff, T. T. Sheng, A. K. Sinha, G. A. Rozgonyi, and F. B. Alexander

J. Appl. Phys. 44, 2545 (1973); http://dx.doi.org/10.1063/1.1662611 (10 pages) | Cited 73 times

Online Publication Date: 9 October 2003

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The growth process and the microstructure of very thin W films (80–500 Å) deposited by rf sputtering on SiO2 and Si substrates have been observed by transmission electron microscopy (TEM). The resistivity and stress in these films have been related to the film microstructure, composition, and to the deposition conditions (substrate bias and rf deposition power). Thin W films deposited on silicon dioxide substrates under zero or positive bias have been found to grow in two distinct growth stages. Stage I corresponds to the formation of a thin continuous film (80–100 Å thick) of β‐W. The β‐W phase has the A‐15 crystal structure and has been identified as a faulted W3W compound. A small grain size (50–100 Å) is characteristic of the β‐W film. Stage II corresponds to the transformation of the β‐W film into a pure α‐W film with the bcc crystal structure. This thermally activated phase transformation takes place in the temperature range 100–200 °C. It is characterized by the growth of α‐W nuclei until complete coalescence of the α‐W islands; the resulting α‐W film consists of large grains (1500–2500 Å) which are free of dislocations. The end of stage II occurs for a critical film thickness tc beyond which the film is a continuous α‐W film. The value of tc is controlled by the rf deposition power and the substrate temperature. On the other hand, films deposited on negatively biased substrates do not contain the β‐W phase. These films consist of large α‐W grains (1500–2000 Å) with a high dislocation density. The resistivity of thin W films deposited under zero or positive bias is controlled by the amount of β‐W present in the film. The pure β‐W films have a high resistivity (100–300 μΩ cm); after the complete transformation β‐W→α‐W the large resistivity (30–40 μΩ cm) of these films is attributed to scattering by impurities. In particular, the lower resistivity of W films deposited under negative bias is related to their lower oxygen content. The sign and magnitude of the stress in these films are also controlled by the film microstructure, It is found that the stress in the films containing the β‐W phase is always tensile with a σ of (6–12) × 109 dyn∕cm2. The films consisting of α‐W are always compressively stressed in the range (2–12) × 109 dyn∕cm2.

Light scattering from an exploded lithium wire plasma

T. A. Leonard and D. R. Bach

J. Appl. Phys. 44, 2555 (1973); http://dx.doi.org/10.1063/1.1662612 (11 pages) | Cited 7 times

Online Publication Date: 9 October 2003

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A thin lithium wire was extruded and exploded in vacuum and the resulting plasma was studied during the first 2 μsec of the discharge. Included in the study were scattering of a Q‐switched ruby laser beam, high‐speed streak photographs showing the laser‐plasma interaction, and time‐resolved emission spectra. The low pressure in the discharge chamber of 5×10−5 Torr prevented current shunting and also resulted in a ``clean'' lithium emission spectrum. The electron density calculated from mass conservation and temperature varied from 1017 to 1019 cm−3 as the plasma column oscillated in diameter. These densities matched those obtained from a Fresnel reflection model very well. Broadening or shifting of the scattered light was less than 1 Å and the intensities yielded electron densities from 2×1019 to 1022 cm−3 when interpreted as cooperative electron scattering. The emission spectra from 3500 to 6900 Å showed three Li I, seven Li II, one Li III, and one unidentified line. The spectroscopic temperature obtained from various line ratios averaged about 4 eV, whereas the temperature found from a simple ``snowplow'' model analysis varied from 4 to 25 eV. The electron density measured by Stark broadening of emission lines compared well with the average density obtained through mass conservation.

Negative electron affinity surfaces on silicon using a rubidium∕oxygen dipole layer

Ramon U. Martinelli

J. Appl. Phys. 44, 2566 (1973); http://dx.doi.org/10.1063/1.1662613 (5 pages) | Cited 11 times

Online Publication Date: 9 October 2003

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Rubidium∕oxygen dipole layers have been used to generate negative electron affinity (NEA) surfaces on Si (100). Rb∕O layers behave exactly as Cs∕O layers with respect to the activation schedule and to the electron emission characteristics. Rb∕O layers show the same crystallographic anisotropy as Cs∕O layers in that only the Si (100) surface activates to NEA. The spectral photoresponse curves for each layer are identical. The characteristics of the Si∕Cs∕O and Si∕Rb∕O surfaces are compared to III‐V NEA emitters and to conventional emitters for which an Rb∕O surface layer produces a less efficient emitting surface. These results are explained by the fact that the dipole layer on NEA Si (100) is very well ordered with specific sites for the anions and the cations. The geometrical arrangement of the dipole layers most strongly determines their characteristics, as opposed to the chemical nature of the Cs∕O or Rb∕O compounds. Among other possible substitutes for Cs and O, neither Cs∕I, Cs∕F, and Cs∕S layers nor Na∕O and K∕O layers produced NEA on Si (100).

Approximations involving the transport equation for ions in drift tubes

T. V. Vorburger, S. B. Woo, and J. H. Whealton

J. Appl. Phys. 44, 2571 (1973); http://dx.doi.org/10.1063/1.1662614 (4 pages) | Cited 4 times

Online Publication Date: 9 October 2003

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Questions have been raised on the validity of the transport equation for ions in drift tubes at high E∕N, the ratio of the electric field to the gas number density. We investigate the approximations surrounding the derivation of the transport equation from the Boltzmann equation. The nature of these approximations, the range of their validity, and the magnitude of error introduced by them are discussed. A model for ion‐molecule reactions is included in the collision integral of the Boltzmann equation.

Auger electron emission micrographic studies of the cleavage surface of graphite single crystal

Kazunobu Hayakawa, Hiroshi Okano, Susumu Kawase, and Shigehiko Yamamoto

J. Appl. Phys. 44, 2575 (1973); http://dx.doi.org/10.1063/1.1662615 (5 pages) | Cited 3 times

Online Publication Date: 9 October 2003

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A new primary beam scanning Auger electron energy analyzer was constructed. The diameter of the primary beam is about 3 μm at 9 keV. Using this apparatus, Auger electron emission microanalysis was carried out on the cleavage surface of a natural graphite single crystal by selecting analyzing points in the sample current image of the specimen surface. In addition, by synchronizing the scanning of the primary beam on the specimen surface with the flying spot of the cathode ray tube, Auger emission micrographs were obtained as the brightness modulation due to a particular Auger spectral line emitted from the specimen. By analyzing the microanalysis spectra, the micrographs, and the sample current images, the chemical composition and the texture of the specimen surface were determined with a spatial resolution of 3 μm.

Observation of aspherical particle rotation in Poiseuille flow via the resistance pulse technique. II. Application to fused sphere ``dumbbells''

D. C. Golibersuch

J. Appl. Phys. 44, 2580 (1973); http://dx.doi.org/10.1063/1.1662616 (5 pages) | Cited 6 times

Online Publication Date: 9 October 2003

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The presence of an insulating particle in an electrolyte‐filled pore causes a fractional resistance change, ΔR ∕ R = fv ∕ V, where v ∕ V is the ratio of particle to pore volume. The shape factor f is a function of particle shape and orientation. While traversing the pore, the particles will rotate in the shear of Poiseuille flow. As a result aspherical particles will exhibit periodic resistance variations and this effect has been observed directly using fused sphere ``dumbbells'' as test particles. The particle dynamics are found to be in agreement with simple hydrodynamic theory. The resistance effects for the dumbbells can be described in terms of an equivalent ellipsoid with an axis of symmetry to equatorial axis ratio of 1.25. On the other hand, the dumbbells are hydrodynamically well described in terms of an ellipsoid with an axis ratio of 2.4. The data indicate that strong orientation effects occur in the convergent entrance flow.

High‐energy oxygen jet propagation

H. David Glenn

J. Appl. Phys. 44, 2585 (1973); http://dx.doi.org/10.1063/1.1662617 (6 pages)

Online Publication Date: 9 October 2003

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This paper reports jet time of arrival, brightness‐temperature profiles, and pressure histories over a greater distance and for longer observation times than have been previously reported. A Voitenko compressor was used to produce a high‐energy jet of oxygen through a 2‐cm‐i.d. 350‐cm‐long steel pipe containing air initially at 2.5 μ of mercury. Velocities for the various identified jet components varied from 2.46 to 7.95 cm∕μsec. Brightness temperature, and pressure profiles were obtained at specific locations along the pipe. A maximum brightness temperature of 136000°K was measured for the plasma jet as it started down the exit pipe. The results suggest that delayed entrainment of ablated wall material was the predominant factor in reducing pressure and temperature in the slower components of the jet.
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