bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Temperature and Environment on the Structure of Thin Single-Crystal Nickel Films
Authors: Alessandrini E. I.
Published: April 2005

Annealing experiments under varying conditions of temperature and pressure have been carried out along with transmission electron diffraction from thin single-crystal films of nickel. The single-crystal films were epitaxially grown by vapor deposition on heated, freshly cleaved (100) faces of rocksalt, and the annealing experiments were carried out in the diffraction instrument after the films had been floated off the rocksalt and mounted on Ni grids. The diffraction patterns of the as-grown films indicated that the Ni was a {001}-oriented single crystal with faulting that resulted in streaking in all four [111] directions. The {111} faults were removed by annealing above 500°C for 1 h at less than 1×10−5 Torr. At 400°C and vacuum pressures controlled by leaking air into the diffraction unit, structural changes were observed. At 1×10−5 Torr, the film remained single crystal; at 3×10−5 Torr, the electron diffraction patterns indicated faults in the [111] directions; and as the pressure increased to 5×10−5 Torr, Ni plus the previously reported metastable Ni+O phase appeared. A new complex two-phase structure of Ni plus Ni+O occurred at 7×10−5 Torr; and at 1×10−4 Torr, only the equilibrium NiO phase was observed. At higher temperatures and a constant pressure of 3×10−5 Torr, there was an absence of any transition phases.

Experiments were repeated with argon under similar conditions and no structural changes were observed. The changes are attributed to an increasing oxygen content in the film during the annealing conditions. The transformations are interpreted to be dependent upon a complex type of precipitation in which the oxygen fault interpretation postulated by Heidenreich et al. may be the first stage in the precipitation of NiO in the film.
Low-Energy Electron-Diffraction Study of the Cleaved (110) Surfaces of InSb, InAs, GaAs, and GaSb
Authors: Rae A. U. Mac , Gobeli G. W.
Published: April 2005

The (110) surfaces of InSb, InAs, GaSb, and GaAs produced by the Gobeli-Allen cleavage technique, have been studied by low-energy electron diffraction. The unit mesh at this surface of these III-V compounds has the same dimensions as the substrate unit mesh. A strong asymmetry in the intensity of the hk and hk̄ diffraction beams reveals that the surface atoms preferentially shield the atoms in the second layer and that the arrangement of atoms at the surface is not the same as the arrangement of atoms in the bulk of the crystal. No change in the surface structures was observed by heating the crystals close to their melting points following the cleavage. These same structures could also be produced by argon ion bombardment and anneal. The sticking probability for oxygen on the (110) surface was established to be less than 10−5 for all of the materials investigated.
Laser Oscillations at 0.918, 1.057, and 1.401 Microns in Nd3+-Doped Borate Glasses
Authors: Pearson A. David , Porto S. P. S. , Northover W. R.
Published: April 2005

Borate glasses doped with Nd3+ have been prepared in small (70 g) batches, and rods of sufficiently high optical quality for laser oscillations have been pulled directly from the melts. Laser action occurs in three groups of wavelengths, the strongest emission being at 0.918, 1.057, and 1.401 μ. Plots of the threshold for oscillation at 1.057 μ are given as a function of both Nd2O3 concentration and base glass composition.
Calculation of High-Energy Secondary Electron Emission
Authors: Sawyer Jerry A. , Van Lint Victor A. J.
Published: April 2005

The emission of high-energy secondary electrons from thin targets of low atomic number has been calculated. The targets are assumed to be bombarded with 25-MeV electrons, 600-kVp x rays, and prompt fission gamma radiation. The results give maximum efficiency of high-energy secondary electron emission of 8% for 25-MeV electrons, 0.30% for prompt fission gamma radiation, and 0.05% for 600-kVp x rays.
X-Ray Diffraction from Small Crystallites
Authors: Tiensuu Victor H. , Ergun Sabri , Alexander Leroy E.
Published: April 2005

The classical crystallographic equations used in deducing structure from peak positions, peak widths, and integrated intensities of x-ray scattering are facile enough, but they involve assumptions that are not valid for extremely small crystallites. An alternate approach more generally valid is to use the Debye interference function. These two different approaches have been compared, using as examples a diamond crystallite containing three unit cells on a side (∼10.7 Å) and one containing ten unit cells on a side (∼35 Å).
General Exact Solutions for the Diffusion Equations of Momentum, Heat, and Mass in Spiral Viscous Flows
Authors: Yang Wen-Jei
Published: April 2005

The diffusion equations of momentum, heat, and mass are solved for spiral flows of incompressible viscous fluids. General exact solutions for the steady-state distributions of velocity, temperature, and concentration are obtained through the use of the similarity transformation technique. Also described are two typical boundary conditions which may be applied to determine the integration constants in the general exact solutions.
Mechanical Properties of Vacuum-Deposited Gold Films
Authors: Blakely J. M.
Published: April 2005

Experiments were performed to investigate the tensile properties of gold films of thickness ranging from 2000 to 50 000 Å, deposited on rocksalt cleavage surfaces at temperatures from 40°–300°C. The grain size, which varied from about 200 Å to single crystals, has little influence on the early stages of the stress-strain curve which is characterised by an extremely high work-hardening rate and small total strain at fracture. The extent of plastic deformation is greater in monocrystalline films than in fine-grained polycrystalline ones. It is inferred that surface defects play an important role in determining the observed fracture stresses of the films.
Effect of Crystallite Size and Orientation on the Magnetization Ripple in Permalloy Films
Authors: Baltz A. , Doyle W. D.
Published: April 2005

Permalloy films of composition 83% Ni 17% Fe ranging from polycrystalline to monocrystalline were prepared by evaporation. Conventional electron micrographs, selected area diffraction patterns, and Lorentz electron micrographs were taken to study the average magnetic ripple wavelength (λ0) as a function of the average crystallite size (a) of the film. Below a critical crystallite size, polycrystalline films showed a linear increase of the ripple wavelength with increase in crystallite size. It was found that λ0=4a in agreement with the maximum probable wavelength predicted theoretically by Rother. Films with preferred orientation showed similar behavior with λ0=10a. A plateau was reached (λ0=9000 Å, a=2000 Å, λ0=12 000 Å, a=1160 Å, respectively) after which an increase in crystallite size had no effect on the ripple wavelength. Monocrystalline films did not exhibit ripple structure and it is concluded that in these films λ0=∞.
Energy Distribution of Sputtered Cu Atoms
Authors: Stuart R. V. , Wehner G. K.
Published: April 2005

Energy distributions have been obtained for atoms sputtered from Cu (100), (110), (111), and polycrystalline surfaces bombarded by 80- to 1200-eV Hg and noble gas ions. Energies of sputtered atoms are found to depend markedly on the angle of ejection. For a (110) surface bombarded by 1000-eV Kr ions, average energies of ejected atoms are 9.5 eV in the [110] direction (normal to the surface) and 14.2 eV in the [011] direction (60° to the surface normal). Ejection energies decrease for lighter ions in the order Kr+, Ar+, Ne+, and He+. For a (110) surface bombarded by 600-eV He ions, the average energy of atoms ejected in the [110] direction is 5.5 eV. Dependence on bombarding ion energy is very weak above 1000 eV where average energies of sputtered atoms are found to be in the range 5–15 eV. Ejection energies decrease at lower bombarding ion energies and decrease rapidly below 200 eV. For atoms ejected in the [110] direction from a (110) surface under Kr ion bombardment, the average energy decreases from 5.5 eV at an ion energy of 200 eV to 2.6 eV at an ion energy of 80 eV.
Uniaxial Anisotropy due to Magnetoelastic Energy in Constrained Polycrystalline Films
Authors: West Forrest G.
Published: April 2005

A possible mechanism for uniaxial anisotropy in ferromagnetic films is the magnetoelastic energy Wλ which results from the constraint imposed on the film by the substrate. Below some temperature T′ at which the mobility of the film atoms on the substrate is sufficiently low, the constraint prevents the film from deforming in magnetostriction. An increase in the magnetoelastic energy, therefore, occurs when the film is magnetized in a direction other than that in which the film was deposited.

This paper examines this constraint energy in detail and shows that earlier calculations which have been based on the average polycrystalline magnetostriction are not correct in principle, since the correct calculation requires averaging the magnetoelastic energy over a polycrystalline aggregate. For the maximum value of Wλ at room temperature the correct calculation gives 4.2, 1.8, and 42 (103 erg cm−3) in nickel, iron, and cobalt, respectively. The value for iron is an order of magnitude larger than that given by earlier calculations. These values are found to be consistent with the experimental results of several groups of workers for films of nickel, iron, and cobalt deposited on amorphous substrates in vacua of less than about 10−5 Torr and for electrodeposited films of nickel and cobalt. The particular case of the temperature dependence of Wλ in nickel films is found to be in agreement with the reported experimental behavior when annealing of the constraint is allowed for. The annealing kinetics are discussed qualitatively in the light of observations by Benjamin and Weaver on film-substrate adhesion. This discussion predicts, in agreement with experiment, the possibility of room-temperature magnetic annealing in films deposited on unheated glass substrates in good vacua.

Evidence is also presented for the presence of constraint energy in evaporated films of the nickel-iron alloys, particularly near the 50% Ni composition. The calculations for the maximum room-temperature values of Wλ give a maximum of 3×103 erg cm−3 at 50% Ni and a minimum of about 20 erg cm−3 at 82% Ni.
Direct Observation of Double Bragg Reflections in X-Ray Diffraction Patterns of Pyrolytic Graphites
Authors: Guentert O. J.
Published: April 2005

Several spurious peaks observed in the x-ray diffraction patterns of bulk specimens of pyrolytic graphites (PG) have been identified as double Bragg peaks. Their angular position is described by 2θhkl+2θh′k′l′, where θhkl and θh′k′l′ are the Bragg angles of the participating single reflections. The intensity dependence of the peaks on the specimen shape and the specimen orientation is distinctly different from that of single Bragg reflections, but agrees well with predictions based on double Bragg reflections. The concentrations of doubly reflected power which give rise to the unexpected peaks are due to the highly preferential alignment of crystallites. It has been known for some time that double Bragg reflections from polycrystalline samples may be sufficiently strong to contribute significantly to the small-angle scattering of x rays. The present study demonstrates that in favorably textured specimens they may even become strong enough to show up as peaks in normally recorded diffraction patterns. Techniques are described by which such peaks can be distinguished from single Bragg reflections.
Voltage Decay Measurement of Photoexcitation and Trapping of Carriers in Selenium
Authors: Regensburger Paul J.
Published: April 2005

The trapping range of holes and electrons in amorphous selenium layers has been measured with a voltage decay technique. Values of 1.1 to 7.8×10−8 cm2/V were obtained for holes. This agreed well with values obtained by the pulse method. An electron range of 5.0 to 8.3×10−8 cm2/V was measured. Quantum efficiencies for photoexcitation of holes and electrons ranged from 7.5×10−4 to 1.0, depending on the wavelength of the incident light.
High-Frequency Properties of Epitaxial Silicon p-n Junctions at Low Temperatures
Authors: Fink H. J.
Published: April 2005

Variable reactance epitaxial silicon p-n junctions with approximately constant impurity gradients were investigated at 5.85 Gc/sec, 1 Mc/sec and dc between room temperature and 2°K. The p-n junctions were B-P and B-As doped. The units with breakdown voltages larger than 11V (at 300°K) showed an exponential freeze-out of the carriers at 5.85 Gc/sec when the temperature was lowered. The units with less than 7.7 V breakdown voltage showed clearly impurity band conduction at low temperatures. The maximum change of the reactive component between large forward currents and the breakdown voltage was temperature independent within ±10% for all the wafers. The cutoff frequencies of the wafers at 300°K were between 190 and 320 Gc/sec. The units with large breakdown voltages (>14 V) had a negative differential resistance in the dc forward voltage-current characteristics at low temperatures. From an extrapolation of the present experiments one would expect, when the impurity gradient at the junction is increased to such a value that the breakdown voltage is about 5.5 V, that epitaxial silicon variable reactance p-n junctions will operate at microwave frequencies and liquid-helium temperatures with approximately the same losses as at room temperature.
Sources of Error in X-Ray Measurements of Residual Stress
Authors: Cullity B. D.
Published: April 2005

Two sources of error are discussed. The first, due to previous plastic flow in one direction, causes an x-ray line shift whether or not a real macrostress is present, and is due to a particular distribution of microstress. The second source is stacking faults. The first error is unavoidable, but the second can be eliminated by the proper x-ray technique.
Comparison of Self-Irradiation Effects in Alpha Plutonium Enriched and Unenriched in 238Pu
Authors: Elliott R. O. , Olsen C. E.
Published: April 2005

Self-damage accumulation at 22.5°K has been studied in alpha plutonium enriched and unenriched in 238Pu. The enriched specimen was held at this low temperature for a period equivalent to about 14 000 h in terms of damage accumulated in the unenriched specimen. The resistivity of the enriched specimen increased to a maximum of 141.5 μΩ-cm and then decreased gradually with additional time. The increase has been attributed to self-irradiation damage consisting of interstitials and vacancies, and the decrease is discussed in terms of possible effects due to phase transformation, internal stresses, magnetic ordering, impurities, and clustering of defects. Annealing behavior differed widely in the two plutonium specimens studied and this is also discussed.
Single-Crystal Growth of LaF3
Authors: Weller P. F. , Kucza J. A.
Published: April 2005

Single crystals of LaF3 have been grown by the Čzochalski technique. Crystal clarity and perfection were strongly dependent on the amount of oxide impurity. Trivalent rare-earth doping was easily achieved, and divalent doping was possible with the easily reduced rare earths such as europium and samarium.
Growth of Bismuth-Antimony Single-Crystal Alloys
Authors: Brown Dale M. , Heumann Fred K.
Published: April 2005

Homogeneous crystals of Bi-Sb solid solutions are difficult to grow, but are important for the basic understanding of the electron transport properties and band structure of these materials. The problems arise from (1) the low melting temperature (approximately 300°C) which makes it difficult to achieve a large thermal gradient at the crystal growing interface; (2) the small liquid diffusion coefficient which was estimated to be between 2 and 3×10−5 cm2/sec at 300°C; and (3) a segregation coefficient so large (5–10) as to favor growth of undesirable cellular substructure. Under existing theories of crystal growth, the conditions necessary for producing crystals with Sb compositions from 5% to 14% free of macro- and micro-inhomogeneity are described. A zone-melting technique was used to grow the crystals with temperature gradients in the molten zone about 60°C/cm and growth rates between 1.6 and 0.4 mm/h. The degree of homogeneity was determined by etching studies, chemical analysis, and electron beam microprobing. Preliminary electrical measurements show considerable difference from previous measurements, particularly for the higher Sb contents.
Electron Diffraction Diffuse Streaks from Single-Crystal Tin Films
Authors: Vook R. W. , Baltz A.
Published: April 2005

Diffuse streaks in the electron diffraction patterns of single-crystal white tin films appear to be associated with nearby reflections, whether they are allowed or forbidden by the structure factor. Zero-order streaks, also observed, as well as the forbidden reflections and their accompanying streaks, are interpreted as resulting from multiple diffraction events. The disappearance of the streaks in x-ray patterns when the sample is cooled to −155°C suggests that they arise from an interaction between the incident radiation and very short wavelength elastic waves having highly anisotropic propagation.
Contact Charging of Micron-Sized Particles in Intense Electric Fields
Authors: Cho A. Y. H.
Published: April 2005

Micron-sized particles (0.3 to 15 μ in radius) of metals such as aluminum, carbonyl nickel, molybdenum; semiconductors such as magnetite and zirconium hydride; and insulators such as aluminum oxide, silicon oxide, and eccospheres are charged by contact electrification in electric fields up to 8000 V in a 0.3-cm gap. The charges are measured with a drift-tube detector and a quadrupole mass spectrometer and compared with a theoretical value which includes the contact potential and the electric field. Experimentally, the contact charge is quite important for particles less than one micron in radius, but relatively unimportant for larger particles. The experimental values are in good agreement with the calculated values for the range of materials and particle sizes studied.
Penetration of Krypton Ions into Molybdenum in a Glow Discharge
Authors: Bartholomew C. Y. , LaPadula A. R.
Published: April 2005

Previous work by the authors indicated that the penetration depth of krypton ions into the molybdenum cathode of a glow discharge tube operated at 150 V was the order of 104 Å after a 24-h bombardment (C. Y. Bartholomew and A. R. LaPadula, J. Appl. Phys. 31, 445 (1960)]. Additional results indicate that this penetration depth increases with time of operation of the discharge. A diffusion-like process appears to be dominant in the initial period of bombardment, but later the removal of surface layers by sputtering becomes dominant. The penetration reaches a steady-state condition after a sufficient period of bombardment.
Compositional and Thickness Dependence of the Ferromagnetic Anisotropy in Resistance of Iron-Nickel Films
Authors: Mitchell E. N. , Haukaas H. B. , Bale H. D. , Streeper J. B.
Published: April 2005

Experiments are reported in which (1) the resistivity has been measured as a function of the angle between the magnetic field direction and the current direction and as a function of the thickness in 82% Ni-18% Fe thin films, (2) the ferromagnetic resistance anisotropy in these films has been measured as a function of thickness, (3) the anisotropy in the fractional magnetoresistance has been measured as a function of thickness in these films, and (4) the anisotropy in the fractional magnetoresistance of films ranging in composition from 65% Ni-35% Fe to 92% Ni-8% Fe has been measured. The angular dependence of the resistivity agreed with theoretical predictions, provided suitable values are assumed for the mean free path and bulk resistivity of the films. The ferromagnetic resistance anisotropy appears to be independent of film thickness in the range from 75 to 2500 Å. The anisotropy in fractional magnetoresistance is lower than in bulk due to an abnormally high value for the resistivity of the zero magnetostrictive films studied. Nonzero magnetostrictive films also exhibit anomalies when the anisotropy in fractional magnetoresistance is compared with that in bulk material. A simple analytic expression relating these resistance anomalies to the magnetostriction parameter for the films is explained in terms of the magnetostriction of the films and the fact that they are attached to the substrate.
Conduction in Single Crystals of Ammonium Dihydrogen Phosphate
Authors: Murphy E. J.
Published: April 2005

Measurements of the temperature dependence of the conductivity of single crystals of ammonium dihydrogen phosphate are described. Impurities introduced in known amounts as substituents in the lattice enable the activation energy for mobility to be separated from the total energy in the Boltzmann factor for conduction. With Ba++ as impurity, the activation energy is 10.1 kcal/mole, with SO4−− 10.9; the average, 10.5 kcal/mole, is taken to be the activation energy for mobility in this crystal. It ls proposed that activation for mobility in this solid is due to the simultaneous breaking of two hydrogen bonds independently. The σ0 factors, both for intrinsic conduction and for impurity conduction, agree reasonably well with the values expected from the theory of ionic conduction. Measurements on crystals enclosed in an evacuated space show that hydrogen gas is generated by the electrolysis of the crystal. According to Faraday's law the theoretical yield for a univalent ion leading to a diatomic molecule (H2) as product is 0.5 mole/F; the observed yields ranged from 0.3 to 0.7 moles/F. It is inferred that the conduction is ionic and that the migrating particle is probably the proton. From the conduction data for the pure crystal, the energy required for the formation of ions within the crystal is calculated to be 19.8 kcal/mole. The mobility process in this crystal shows a strong resemblance to that in ice. Both appear to be referable to the breaking of two hydrogen bonds simultaneously and to the tunneling of protons between equivalent sites. Both crystals have hydrogen bonds as an important part of their structure.
Random Nucleation of New Domains in BaTiO3 Crystals at 20 kV/cm
Authors: Stadler Henry L. , Zachmanidis P. J.
Published: April 2005

The locations of domains appearing on the surface of a BaTiO3 crystal have been observed by repeated partial switching and etching to determine how frequently the domains appear at the same location on successive applied pulses. The ratio of the number of repeating locations to that of all locations is (10±1.6) % for a series of six pulses at 20 kV/cm on crystals with a positive internal bias and (28±5) % on crystals with a negative bias. The simplest interpretation of the results is that new domains can nucleate at points in the crystal remote from imperfections. This interpretation is in rough agreement with Landauer's calculation of the probability of thermally activated new domains for a 180° wall energy of 0.4 erg/cm2.
Order-Disorder Effects on Ferromagnetic Resonance
Authors: Spencer E. G. , Denton R. T.
Published: April 2005

The temperature dependence of ferromagnetic resonance losses was measured for single-crystal samples of lithium ferrite and yttrium iron garnet that were treated to increase or decrease the state of order of the atomic structure. The maximum linewidth, at low temperatures and caused by residual impurity ions, is much greater for the more ordered state as contrasted to the more disordered state. An explanation of these observations is given in terms of expected changes in the energy levels of the impurity ions with changes in the state of order.
Accurate Determination of the Ordinary-Ray Refractive Index in BaTiO3
Authors: Lawless W. N. , DeVries R. C.
Published: April 2005

The ordinary-ray index of refraction at 5893 Å in BaTiO3 was measured in the range 20°–160°C by a refined Chaulnes' method with an average error of 0.35%. Two BaTiO3 crystals were studied and the results indicate a constant index of 2.368 from 20° to 105°C; above the Curie point the ordinary index increased by 1.3% to 2.398 and remained constant to 160°C.
Ultrasonic Attenuation in Al2O3 at Ultrahigh Frequencies and Low Temperatures
Authors: Fitzgerald Thomas M. , Chick Bruce B. , Truell Rohn
Published: April 2005

Ultrasonic propagation in Al2O3 at low temperatures and high frequencies (to 3000 Mc/sec) is discussed in terms of the relations given by Woodruff and Ehrenreich. Phonon relaxation times calculated from thermal conductivity measurements are used. The measured low-temperature attenuation values at 1315 Mc/sec agree with the calculated values. A comparison of attenuation as a function of frequency is made among Al2O3, Ge, Si, and quartz. On comparing experimental values of attenuation for pure Al2O3 and impure Al2O3 (ruby) it is found that impurities lead to an increase in the attenuation as would be predicted from the corresponding effect of impurities on the thermal phonon relaxation time.
Alternating Current Power Losses in Superconducting Nb-Zr Alloys
Authors: Wisseman W. R. , Boatner L. A. , Low F. J.
Published: April 2005

A calorimetric technique, involving measurement of the thermal conductivity, was used to measure non-Ohmic ac power losses in short, 0.25-mm-diam samples of superconducting Nb-25% Zr and Nb-33% Zr wire as a function of frequency, current amplitude and waveform, and temperature. The observed power losses at 4.2°K ranged from 6×10−11 to 10−7 W/cm. The losses depended linearly on frequency in the range 60–40 000 cps and decreased approximately as T2.5 for temperatures T in the range 2.0°–4.2°K. Peak currents from 1 to 8 A were used to determine that the power loss was a function of the peak current Im rather than the rms current and also was proportional to Imn, where n varied from 2.6 to 4.5. These results indicate a hysteresis loss mechanism with no detectable relaxation effects for the entire frequency range covered. Models which have been proposed to account for hysteresis losses in hard superconductors are discussed. The results of this experiment are compared with earlier measurements on Nb-Zr alloys. There is considerable disagreement between the present results and the published results of Zar in magnitude and in the frequency and current dependences of the ac power losses.
Comparative Anatomy of Models for Double Injection of Electrons and Holes into Solids
Authors: Rose Albert
Published: April 2005

The several models for double injection of electrons and holes into solids are shown to fall into three groups: field-dominated, diffusion-dominated, and hybrid models. The current-voltage relation for the field-dominated models can be written out of hand, within a factor of two, using the criterion: ambipolar drift transit time of free pairs=lifetime of free pairs. Current-voltage dependencies J ∝ Vn, with n ranging from 1.5 to 3, depend on whether the material is insulating or semiconducting and the recombination monomolecular or bimolecular. In the diffusion-dominated models the current increases indefinitely while the voltage across the body of the sample remains constant at a value 2kT/e exp (L/2LD), where L and LD are the sample length and diffusion length, respectively. In the hybrid models, a field-dominated current in one part of the sample is matched to a diffusion-dominated current in the remainder of the sample. For all of the models reviewed, solutions for the current-voltage relations are obtained within a factor of two by relatively simple physical arguments.
Pressure Theory of the Thermoelectric and Photovoltaic Effects
Authors: Green Milton
Published: April 2005

The theory is based upon the hypothesis that free charge carriers—electrons and holes—and phonons exert pressures inside a solid. Gradients of such pressures exert motive forces on the carriers. On this basis, the hole current density Ip, in the absence of a magnetic field, is assumed to be Ip=σpE−μpgrad Pp−μp[open phi]gradP[open phi],where σp, μp, and Pp are, respectively, the conductivity, mobility, and pressure of holes; μpφ is the interaction mobility between holes and phonons; Pφ is phonon pressure; and E is the electrostatic field. A similar expression is obtained for electrons by exchanging the subscript p for n. (The two mobilities associated with electrons, however, are negative.)

The theory is applied to the nondegenerate semiconductor, with the assumption that the equation of the ideal gas law applies. (Thus, Pp=pkT, Pn=nkT, where k is the Boltzmann constant, T is temperature Kelvin, and p and n are concentrations of holes and electrons, respectively.) It is also assumed— for small currents—that deviation from the equilibrium pressures can be neglected.

Assumptions concerning the phonon effect are quite general; the contribution from this source to the hole current density Ip is given by Ip[open phi]=−σp(kT/e)δp grad ln T,where e is magnitude of electronic charge. The dimensionless quantity δp, the phonon-dragging coefficient for holes (a temperature- and material-dependent parameter), is not amenable to calculation by the theory, in its present form, and must be determined experimentally. Again, a similar expression exists for electrons.
Redistribution of Acceptor and Donor Impurities during Thermal Oxidation of Silicon
Authors: Grove A. S. , Leistiko O. , Sah C. T.
Published: April 2005

The redistribution of impurities during thermal oxidation of silicon was studied both theoretically and experimentally. Experiments with specific impurities indicate that gallium, boron, and indium deplete from silicon, while phosphorus, antimony, and arsenic pile up during thermal oxidation. It is shown that the redistribution process can be significantly influenced by the escape of impurities through the oxide layer as well as by the segregation of the impurity at the oxide-silicon interface.
Energy Dependence of Proton Irradiation Damage in Silicon
Authors: Rosenzweig W. , Smits F. M. , Brown W. L.
Published: April 2005

The energy dependence of radiation damage in silicon for proton energies in the range 1.35 to 130 MeV has been measured by observing the degradation of the bulk minority carrier diffusion length in silicon solar cells. Variability in proton flux determination at four different accelerators was minimized by employing prebombarded solar cells with known minority carrier diffusion lengths as calibrated solid-state ionization chambers. Where beam intensity measurement comparisons with Faraday cups could be made, agreement to better than 5% was obtained.

The quantity characterizing the damage rate is the rate of change of the inverse square diffusion length with flux K≡d(1/L2)/dΦ. The 1-Ω-cm p-type silicon degraded, on the average at a rate six times less rapid than 1-Ω-cm n type, independent of energy. Room temperature annealing gave 30% to 50% decrease in K whenever the diffusion length was measured during and after irradiation. The energy variation of K agrees with the variation predicted by Rutherford scattering below 8 MeV, but decreases less rapidly at higher energies.

The measured diffusion lengths increased with excess carrier density n from 2% per decade at n=109cm−3 to 20% per decade at n=1014cm−3. The reported results, obtained at low excess carrier density, can be used to predict solar cell degradation under conditions of outer space illumination if the appropriate excess carrier density is used. Failure to take into account the diffusion length variation will result in an underestimate of the solar cell output of less than 7%.
Redistribution of Solute During Phase Transformations
Authors: Tiller W. A. , Sekerka R. F.
Published: April 2005

The redistribution of solute during phase transformations where solute partitioning occurs at the two-phase interface has been mathematically treated for (i) the special case of equal diffusion rate in both the liquid and solid and (ii) diffusion only in the liquid under the additional force of a constant electric field. This one-dimensional analysis shows that (i) diffusion in the solid has a small effect on the grown-in solute distribution for k0<1 but an appreciable effect for k0>1 and (ii) the presence of an electric field can significantly alter the grown-in solute distribution. Further, one can deduce from the latter analysis a new experimental method for determining the effective ionic mobility of the solute species in the liquid phase.
Microstrain Yield Stress in Neutron-Irradiated Copper Single Crystals
Authors: Koppenaal T. J.
Published: April 2005

τ0, the stress necessary to produce a plastic strain of 2×10−6, has been measured with the use of electrical resistance strain gauges in neutron-irradiated copper single crystals as a function of neutron dose (∼1016 to 1020 neutrons/cm2) and testing temperature (77° and 300°K). τ0 increases from about 0.3 kg/mm2 for ∼1016 neutrons/cm2 to over 5 kg/mm2 for ∼1020 neutrons/cm2; in annealed copper crystals, τ0 is ∼0.02 kg/mm2 (previously determined by other researchers). At all neutron doses, τ0 is about 75% of the macroscopic flow stress. τ0 is observed to increase with the cube root of the neutron dose; the macroscopic flow stress shows the same dose dependence.

The results are explained on the basis of dislocation generation and obstacle cutting mechanisms controlling the yielding. These mechanisms are thought to be simultaneously operative.
Fission-Fragment Tracks and Directional Effects in the Surface of LiF Crystals
Authors: Knorr T. G.
Published: April 2005

Elongated damage structures resulting from fission fragments traveling nearly parallel to the surface have been observed in (100) cleavage faces of bulk LiF crystals. These tracks have lengths up to 2.3 μ and are about 100 Å wide. The direction in which the fission fragment has entered the LiF crystal can be determined from the characteristics of tracks which cross typical fracture steps in the crystal surface. When the fragment enters the surface it registers a surface disturbance in the form of a trough defined by two ridges. Deeper in the crystal the fragment produces a single ridge and finally ceases to register a surface disturbance when it has penetrated more than about 30 Å into the crystal. Track length distributions have been determined from a large number of tracks for two specimens. These show good agreement with a theoretical distribution based on straightforward geometrical considerations. Details of the theoretical development are outlined in an appendix. There are, however, a disproportionately large number of tracks visible in <100> crystallographic directions. This would be explained if fragments registered surface disturbances from a greater depth in these particular directions.
High-Temperature Electrical Resistivity and Allotropic Transformation Temperature of Hafnium
Authors: Bedford Ray G.
Published: April 2005

The electrical resistivity of a Hf filament containing 4.9 at. % Zr was measured in the temperature interval from 1155° to 2250°K. The resistivity increases from 37 μΩ-cm at room-temperature to 187 μΩ-cm at 2025°K where the alloy undergoes a transition from an hcp to a bcc structure with a corresponding decrease in resistivity to 173 μΩ-cm. From data in the literature the transition temperature of pure Hf is estimated to be 2030°±30°K. Graphs of total emissivity versus temperature indicate that changes in the surface characteristics of the sample occurred during the measurements. After surface conditions became constant, the total hemispherical emissivity increased linearly with temperature from about 0.26 at 1200°K to 0.31 at 2000°K.
Magnetoelastic Waves in Yttrium Iron Garnet
Authors: Strauss W.
Published: April 2005

Magnetoeleastic pulses with variable echo time were observed in a rod of yttrium iron garnet. Data were taken at room temperature in the frequency interval 0.5 to 3.3 Gc/sec with input power in the milliwatt range. At a fixed carrier frequency, pulses were observed for external magnetic fields ranging over several hundred oersted; characteristically the echo time increased with decreasing field. The carrier frequency-magnetic field-echo time behavior can be explained in terms of a θ=0 magnetoelastic disturbance traveling along the rod axis. It is launched at the position where ωc=γHi. The disturbance propagates along the rod axis to the nearer end-face where it is reflected. On arrival back at the launch site, a fraction of the energy is detected and the remainder reflected for another round trip. The process is repeated several times to give rise to a pulse sequence. The experimental results can be understood in terms of a magnetoelastic wave packet with calculated travel time T=∫um−1dz≈∫us−1dz+∫ue−1dz, where the group velocities, u, refer to magnetoelastic, spin, and elastic waves, respectively. Spin-wave loss has been included and gives improved agreement between theory and experiment.
Temperature Dependence of Paramagnetic Relaxation at Point Defects in Vitreous Silica
Authors: Castle J. G. , Feldman D. W.
Published: April 2005

Spin relaxation has been measured at 3 kOe and at lattice temperatures from 1.24° to 250°K for the E′ centers generated in one type of vitreous silica by 2-MeV gamma rays. An unusual temperature dependence was found in which the spin-lattice relaxation time varies roughly as T−2,5 over most of the range. All of the data are accurately fitted by analytical functions derived from a coupling of the individual defect centers to the vitreous host involving excess local strain due to mechanical resonances of about 4.1×1011 and 6.0×1012 cps at each E′ center. The strength of the coupling and the characteristic frequencies of mechanical resonance are similar to those in crystalline SiO2.
A Protected 100-kG Superconducting Magnet
Authors: Coffey H. T. , Hulm J. K. , Reynolds W. T. , Fox D. K. , Span R. E.
Published: April 2005

Superconducting wire made from heavily cold-worked ductile niobium-titanium wire shows much less degradation in solenoids than does the corresponding widely used niobium-zirconium alloy. The origin of this behavior is discussed in terms of flux jumping and the differences in metallurgical properties of the two alloy systems. The superior niobium-titanium alloy has been used in the inner sections of a 100 000-G solenoid which has been driven normal repeatedly without damage. Details of design, construction, and operation of this solenoid are discussed with particular reference to critical rate of excitation under flux creep conditions. The normalization properties of the solenoid are analyzed in terms of the thermal propagation model, and the voltage rise and temperature maximum are estimated from this model.
An Analysis of Direct Energy Converters by the Methods of Irreversible Thermodynamics
Authors: Robinson Lawrence Baylor , Beaty Robert Carroll
Published: April 2005

Methods of thermodynamics of irreversible processes are presented within the framework of the Burgers-Pipkin solution of the Boltzmann transport equation. The thermionic energy converter is treated as a thermocouple and analyzed by the nonequilibrium thermodynamic methods which are developed.

Following a general treatment, the cesium diode is treated as a specific example. Detailed calculations are made of the thermal conductivity and the electrical conductivity, as well as the ratio. In making the calculations, contributions from the electrons, positive ions, and neutral particles, are considered as well as interactions among the various types of particles. Binary interactions between the neutral particles, collective (Coulomb) interactions among charged particles, and (quantum-mechanical) collisions between electrons and neutral particles are taken into account. Each type of interaction has its appropriate effect on the thermal and electrical conductivities.

A brief discussion of the results and implications of the analysis is given, along with a reiteration of the assumptions and the limitations of the calculation.
Young's Modulus, Shear Modulus, and Poisson's Ratio in Silicon and Germanium
Authors: Wortman J. J. , Evans R. A.
Published: April 2005

The elastic coefficients for an arbitrary rectangular coordinate system are calculated as a function of direction cosines in the crystal. Young's modulus, shear modulus, and Poisson's ratio are defined in general and values tabulated for some of the more important directions in the crystal. Graphs of these moduli are also plotted as a function of crystal direction for orientations in the (100) and (110) planes as well as planes determined by the [110] direction and any perpendicular direction.
Equation of State of NaCl and Its Use as a Pressure Gauge in High-Pressure Research
Authors: Decker Daniel L.
Published: April 2005

The pressure as a function of lattice parameter and temperature has been calculated for NaCl over a pressure range of 0 to 500 kbar for temperatures between 0° and 1500°C. The calculation used the Mie-Grüneisen equation of state with Born-Mayer type repulsion terms between first and second nearest neighbors. The Grüneisen constant was expanded about its value at room temperature and atmospheric pressure; the first coefficient in the expansion being evaluated by forcing the calculated thermal expansion at atmospheric pressure to fit the experimental results of Enck. The two empirical parameters in the repulsion terms were evaluated using the experimental lattice parameter and isothermal compressibility at atmospheric pressure. The calculated pressure vs volume agrees with Bridgman's room-temperature measurements in NaCl below 100 kbar to within 3% and with high-pressure high-temperature shock data to better than 2%. It is proposed to use the numerical results to calibrate the pressure in high-pressure high-temperature apparatus.
Biquadratic Exchange and the Temperature Dependence of Sublattice Magnetization in Lithium Ferrite
Authors: Prince E.
Published: April 2005

Neutron diffraction measurements have shown that the sublattice magnetizations in lithium ferrite are significantly higher, in the temperature range from 0.4 Tc to 0.9 Tc, where Tc is the Curie temperature, than predicted by molecular field calculations. An approximate analysis of the effect of adding a biquadratic term to the exchange interaction suggests that the principal effect is to distort the temperature scale in such a way as to make T/Tc = (T′/Tc) (1+β〈SA·SB〉), where T′ is the temperature calculated from a molecular field model and β is of the order of the ratio of the biquadratic to bilinear exchange coefficients. If the A-A B-B interactions are neglected, but a biquadratic term is included in the A-B interaction with β=0.04, the calculated curves are in good agreement with experiment.
Electron Mobility Studies in Surface Space-Charge Layers in Vapor-Deposited CdS Films
Authors: Waxman A. , Henrich V. E. , Shallcross F. V. , Borkan H. , Weimer P. K.
Published: April 2005

Hall and field-effect surface mobility has been measured in polycrystalline films of CdS of thickness 1000–4000 Å. At low surface potential, the mobility increases with surface potential. The Hall mobility was observed to increase exponentially with temperature from −80° to 120°C. These effects can be explained using a polycrystalline film model. The effects of diffuse surface scattering were not observed at low surface potential due to the small mean free path of electrons. However, when the channel thickness was comparable to the electron mean free path a decrease in mobility was observed.
Nernst Effect in Indium Antimonide
Authors: El-Saden M. R. , Thomas F. W.
Published: April 2005

The Nernst coefficient Q was measured for n-type InSb in the temperature range 260° to 340°K and magnetic field range 4 to 12 kG. For indium antimonide the difference between the adiabatic and isothermal Nernst coefficients is negligible. The method of measurement of the true Nernst voltage is similar to that for the Hall effect. In addition to variation with temperature, Q also varies appreciably with magnetic field. The Hall coefficient, electrical conductivity, and Righi-Leduc temperature difference were also measured. The experimental values of Q show poor correlation with those based on the Lorentz-Sommerfeld theory.
Opto-Electric Effects in Ge-GaAs p-n Heterojunctions
Authors: Agusta B. , Anderson R. L.
Published: April 2005

In an abrupt Ge-GaAs p-n heterojunction, a plot of conduction band edge vs position shows a discontinuity at the material interface. As a result, a ``notch'' occurs in the band-edge profile which strongly affects the opto-electric characteristics of such a junction. The conversion efficiency is much less than that of a homojunction of similar doping levels. At room temperature the photocurrent is limited by the rate at which electrons can be thermally excited from the notch into the GaAs. At 78°K this contribution to current is negligible. For reverse bias, the photocurrent results from electron tunneling from the notch into the GaAs. In forward bias, the space charge resulting from the presence of the optically excited electrons in the notch changes the potential profile in such a way so as to reduce the forward current, and to cut it off entirely for sufficiently high light intensity. Because of the low conversion efficiency, it is concluded that such a heterojunction collector in an optical transistor is not practical.
Light Modulation Experiments at 16 Gc/sec
Authors: Myers R. A. , Pershan P. S.
Published: April 2005

An experimental study of light modulation at 16 Gc/sec, using the linear electro-optic (Pockels) effect, has been performed. The principal result has been the demonstration of a new type of traveling-wave-like light modulator, which takes advantage of the fact that in crystals which have a 4̄ axis (such as KDP— potassium dihydrogen phosphate) an electric field parallel to this axis is equivalent to a field in the opposite direction if the crystal is rotated 90° about the axis. The modulator is made of a stack of crystals alternately rotated 90° with respect to one another and of a height such that the electric field changes phase by 180° in the time light takes to pass through one crystal. In this way, the electrically induced birefringence increases with optical path even though the microwave modulating field is a standing wave with no spatial variation in the direction of light propagation. For the experiments to be described, the microwave field is obtained with a multimode solid dielectric cavity efficiently driven in its TE101 mode. Results on simple devices containing two and three crystals are reported, and a discussion of the general properties of this type of device is presented. In addition, the magnitude of the electro-optic effect in KDP and ADP (ammonium dihydrogen phosphate) has been found to be the same at 16 Gc/sec, within experimental errors of 25% in ADP and 12% in KDP, as the low-frequency clamped effect in these materials, in agreement with previous observations at 9 Gc/sec. Results concerning the variation with optical wavelength of the electro-optic effect in these materials at 16 Gc/sec are also reported.
Dose Dependence of the Dislocation Breakaway Stress in Neutron-Irradiated Copper as Measured by Amplitude-Dependent Internal Friction
Authors: Thompson D. O. , Paré V. K.
Published: April 2005

Measurements of the strain-amplitude dependence of the internal friction in copper have been made at 100°C as a function of fast neutron dose. Although it is found that the Granato-Lücke theory of amplitude-dependent internal friction does not describe the results obtained, the dose dependence of the dislocation breakaway stress can be deduced by other means. After taking into account the variation with neutron dose of the mean free dislocation length, it is found that the breakaway stress is proportional to the cube root of the integrated flux in the dose range from 1011 to 1014 neutrons/cm2 (E>0.6 MeV). Extrapolation of the breakaway stress results to doses greater than 1019 neutrons/cm2 shows essential agreement with earlier neutron-hardening results. The results are discussed in terms of a source-hardening mechanism.