bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical and Optical Properties of Mercury Selenide (HgSe)
Authors: Gobrecht H. , Gerhardt U. , Peinemann B. , Tausend A.
Published: April 2005

HgSe single crystals are grown by zone melting. The compound crystallizes in the zinc-blende structure and splits into (100) planes. For temperatures ranging from 90° to 500°K conductivity, Hall effect and thermoelectric power are measured; above 500°K evaporation of HgSe begins. The lowest carrier concentration of the crystals at 300°K is 3.5×1017 cm−3. Only n-type conduction is found. The highest mobility at 300°K is 18 500 cm2/v sec. Magnetoresistance shows that the longitudinal effect is very small compared with the transverse. From the photo emf of the p-n junction Se/HgSe crystal and from the absorption edge of layers the energy gap of 0.5 to 0.75 ev is obtained. Using the temf and the absorption an estimation of the effective mass leads to 0.04 to 0.07 m0.
Some Electrical and Optical Properties of ZnSe
Authors: Aven M. , Marple D. T. F. , Segall B.
Published: April 2005

Single crystals of ZnSe have been prepared by the vapor growth technique and optical and electrical measurements on these crystals are reported. Analysis of the reststrahlen reflection peak gives 0.026 ev for the transverse optical phonon energy. The longitudinal optical phonon energy is 0.031 ev as calculated from the transverse phonon energy, the static dielectric constant, ε0=8.1±0.3, and the high-frequency dielectric constant, ε∞=5.75±0.1. The effective ionic charge calculated from the Szigetti formula is 0.7±0.1. Exciton absorption peaks associated with the valence and conduction bands in the vicinity of Γ were observed at liquid hydrogen temperature with the principal peak at 2.81±0.01 ev. The exciton reduced mass 0.1 m0 combined with the room temperature electron-to-hole mobility ratio of 12, obtained by preliminary transport measurements on n- and p-type ZnSe gives tentative values of 0.1 m0 and 0.6 m0 for the electron and hole masses, respectively.

Reflectance was determined by various methods in the range 0.025 to 14.5 ev photon energy and was analyzed by the Kronig-Kramers inversion method to obtain the optical constants in the 1 to 10 ev range. A number of peaks appear in the imaginary part of the dielectric constant.

The first set of peaks, 2.7 and 3.15 ev, are believed to be due to exciton and interband transitions at Γ with a spin-orbit valence band splitting of 0.45 ev. The second set of peaks, 4.75 and 5.1 ev, are tentatively assigned to transitions at L with a spin-orbit splitting of 0.35 ev. Other peaks are observed at higher energies.
Exciton States and Band Structure in CdS and CdSe
Authors: Hopfield J. J.
Published: April 2005

The theoretical effects of a finite slope condition band crossing on the direct exciton energy levels of wurtzite compounds is investigated. The lack of an experimental confirmation of these effects places an upper limit of about 10−10 ev-cm on the slope of the conduction band at k = 0 in CdS, and a slightly larger limit in CdSe. Theoretical estimates of these slopes are also calculated. Another possible method of observing the magnetic effects due to the nonzero wave vector of the excitons is noted. The striking increase of the exciton oscillator strength in CdSe in a magnetic field is attributed to the magnetic compression of the excitons. A brief comparison of experimental energy band parameters for CdS and CdSe is given.
Piezoelectric Scattering and Phonon Drag in ZnO and CdS
Authors: Hutson A. R.
Published: April 2005

Piezoelectric scattering of conduction electrons by acoustical phonons is discussed for ZnO and CdS, and approximate values of the mobilities determined by this mechanism alone are derived. The phonon drag contribution to the Seebeck effect in ZnO is assumed to arise from crystal-momentum exchange between electrons and acoustical phonons by way of the piezoelectric interaction alone. Comparison of the results of this assumption with the data has led to the discovery of strong piezoelectric phonon scattering from neutral donor states. These two piezoelectric scattering mechanisms and an effective electron mass of about 0.32m, derived from other experiments, provide a model for phonon drag in ZnO which agrees with the temperature dependence and ``impurity'' dependence of the data and gives the correct magnitude of the effect to within the uncertainties of the approximations employed.
Excitons and Band Splitting Produced by Uniaxial Stress in CdTe
Authors: Thomas D. G.
Published: April 2005

A single exciton peak may be seen in the reflection spectrum of CdTe, a semiconductor with the cubic zinc-blende structure. Some properties of this exciton and of the associated fluorescent phenomena are described. Under uniaxial compressive stress, the single exciton peak splits into two peaks corresponding to the splitting of the J=32 valence band. The movement of the peaks as a function of stress has been determined for four directions of stress in the (110) plane. Within experimental error, the splittings are identical for a given stress applied in any direction. Thus, although the material is elastically anisotropic, the splitting may be described by one rather than two deformation potentials. These conclusions are consistent with the polarization properties of the exciton transitions. The polarization properties also show that under compressive stress the MJ=±½ band moves ``up'' and the MJ=±32 band moves ``down.''
Method for Measuring Dynamic Mechanical Properties of Viscoelastic Liquids and Gels; the Gelation of Polyvinyl Chloride
Authors: Birnboim Meyer H. , Ferry John D.
Published: April 2005

An apparatus has been developed to determine the components of the complex shear modulus of viscoelastic liquids and dilute gels over a continuous frequency range from 0.01 to 5 cps by amplitude-phase shift measurements and from 2.5 to 400 cps by single coil transducer impedance measurements. The temperature range is from −40° to 150°C. The sample is deformed in very small strains with annular pumping geometry, as in the earlier apparatus of Smith, Ferry, and Schremp. Preliminary results on 2.29 and 3.00% solutions of polyvinyl chloride in di-2-ethyl hexyl phthalate provide the dynamic storage and loss moduli and the relaxation spectrum as they change during the process of gelation. The moduli of the ungelled solutions, at an early stage of the aggregation process, follow the Zimm theory rather closely, and the local effective viscosity derived therefrom lies between the solvent viscosity and the solution viscosity. The loss compliance of the aged gels is approximately represented by the Bueche theory for cross-linked networks. However, it is evident that the gels contain a large proportion of sol fraction (polymer species unattached to the network).
Rate of Recrystallization of Polyethylene Single Crystals
Authors: Statton W. O.
Published: April 2005

Platelet crystals of linear polyethylene recrystallize extremely rapidly when immersed in a bath of a hot liquid such as ethylene glycol, glycerine, or Woods metal. This recrystallization rate is much faster and to greater extent than when the heating medium is air. For example, heating in the liquids at 127°C causes the length of the chains between folds to increase 50% in 1 sec; the ultimate increase of 200% occurs in about 10 sec. No definite explanation is presently apparent for this much faster rate and greater extent in liquids. No evidence is found for reversibility when annealed crystals are reheated at a lower temperature.
Hypothesis of Voids in Semicrystalline Polymers
Authors: Matsuoka Shiro
Published: April 2005

The expression V=xVc+(1−x)Va, for the specific volume of a semicrystalline polymer, is a highly successful approximation; here x is the degree of crystallinity, Vc is the specific volume for the crystalline regions, and Va is the specific volume for the amorphous regions. In specimens for which x is near unity, however, this equation demands values for the parameters which are inconsistent with other experimental evaluations. We suggest that the discrepancy arises because of the presence of voids. Thus in addition to crystalline and noncrystalline regions we propose regions of zero density. The average volume of such voids is not known, but their existence can be inferred from the significant, permanent density enhancement which can be brought about by pressure-induced crystallization.
Extension of the Eyring-Ree Theory of Non-Newtonian Flow
Authors: Faucher Joseph A.
Published: April 2005

The Eyring-Ree theory of non-Newtonian flow is extended to the case of a continuous distribution of flow units. This results in an integral equation of the form F(ṡ)= ∫ 0∞G(t) arc sinh (ṡt)dt. This equation can be solved by integral transform methods to yield the unknown distribution function G(t) when the flow curve F(ṡ) is known as an analytic function. For the case of limited empirical data, approximation methods can be used to obtain G(t). Experimental data are shown for polyethylene at two temperatures and the distribution functions calculated.
Light Scattering Study of the Annealing of Drawn Polyethylene
Authors: Rhodes Marion B. , Stein Richard S.
Published: April 2005

Low-angle light-scattering patterns are obtained for stretched polyethylene films which are annealed both with and without the constraint of constant length. The effects of stretching temperature, annealing temperature, temperature of measurement, and degree of elongation are studied. Morphological changes in superstructure are found which parallel changes in crystal orientation.
Dielectric Loss in Poly-(Hexamethylene Adipamide) and Poly-(Hexamethylene Sebacamide) at Low Temperatures
Authors: Stein M. N. , Lauttman R. G. , Sauer J. A. , Woodward A. E.
Published: April 2005

The dielectric behavior of samples of nylon 6–6 and nylon 6–10 has been studied in the temperature region from −160° to 60°C at frequencies of 0.1 to 100 kc/sec. The effects of thermal history, electron irradiation, and post irradiation annealing on the two dielectric loss peaks found in this frequency-temperature range have been explored. Electron irradiation of nylon 6–6 and 6–10 and thermal quenching of nylon 6–6 lowers the γ peak (−70°C at 1 kc/sec for 66 nylon) and raises the β peak (+15°C for 66 nylon at 1 kc/sec). Post irradiation annealing of nylon 6–6 or 6–10 irradiated to low doses (25 to 100 mrad) removes the effect of the irradiation on the dielectric behavior, but on irradiation to high dosages (900–1000 mrad) the dielectric loss values in the region of the β maximum at 0.1 and 1.0 kc/sec are greatly reduced. The frequency shifts of the dielectric loss maxima for all samples give activation energies in kcal/mole which fall in the 8–15 range for the β maximum and 9–19 for the γ maximum. These absorption peaks and the effect of various variables on them are discussed in terms of the molecular structure and possible molecular motions responsible for their occurrence.
Growth of Crystals from Molten Crosslinked Oriented Polyethylene
Authors: Judge Jane T. , Stein Richard S.
Published: April 2005

The growth of crystals from the melt in oriented, crosslinked polyethylene was studied by x-ray diffraction and birefringence as a function of orientation. It was found that for samples elongated more than about 200%, the crystals grow with their c axes parallel to the stretching direction. At elongations less than 200%, there is a rather abrupt transition to a mode of growth in which the b axis is perpendicular to the stretching direction with a tendency for the a axis to be aligned parallel to this direction. An interpretation is made in terms of the folded-chain concept of crystal structure.
Drift Velocity of a Charged Particle in an Inhomogeneous Magnetic Field
Authors: Hurley James
Published: April 2005

Alfvén and Spitzer have obtained an expression for the drift velocity of a charged particle in an inhomogeneous magnetic field. The result is correct to first order in the ratio of the drift velocity to the particle velocity. We have presented here a class of fields for which the drift velocity may be calculated exactly.
Excess and Hump Current in Esaki Diodes
Authors: Claassen Richard S.
Published: April 2005

The origin of the excess and hump current in Esaki diodes is described in terms of discrete defect energy levels in the forbidden band. The hump current results from equi-energy transitions of electrons which originate in a defect level in the n side and tunnel to the valence band on the p side. Impurity conduction is required for appreciable hump currents. The position of the hump locates the defect level if the Fermi level is known for the n side. The excess current is explained in terms of energy dissipating transitions in which electrons start from a defect location within the junction, tunnel to a virtual state in a localized defect in the p region, and drop to the valence band by impact recombination. A crude derivation by the WKB method relates the logarithm of the excess current to the bias voltage where the proportionality factor contains the square root of the effective mass of the electron. From current-voltage curves for diodes fabricated from germanium, silicon, and gallium arsenide, the effective electron masses are estimated as 0.01, 0.1, and 0.05 m, respectively. Defect levels in germanium are estimated at 0.06 and 0.24 ev below the conduction band; levels in silicon are located at 0.04 and 0.42 ev; and in gallium arsenide 0.12 and 0.5 ev below the conduction band. The simultaneous existence of two defect levels can give rise to two distinct slopes of the logI vs V curve which have been observed in silicon and gallium arsenide diodes following irradiation with 2 Mev electrons.
Excess Noise in Germanium and Gallium-Arsenide Esaki Diodes in the Negative Resistance Region
Authors: Montgomery M. D.
Published: April 2005

Low-frequency noise measurements have been made throughout the entire useful bias range of germanium and GaAs Esaki diodes. Evidence is presented in agreement with Esaki and Yajima that a near square-law relationship exists between the mean-square, short-circuit noise current and excess current for bias voltages beyond the valley voltage in germanium diodes. Attempts to find a like relationship in GaAs were not conclusive. Measurements of the noise within the negative-resistance regions of the diodes showed a nearly continuous exponential relationship between excess noise and bias for the germanium units and a similar plot was obtained for the GaAs diodes, except a well-defined peak in the noise current was found at about 0.2 v forward bias. The evidence that the results indicate a rather continuous distribution of allowed states in the forbidden band of the germanium samples and a possible localized maximum in these states in the GaAs samples is discussed.
Transparency of Glass and Certain Plastics under Shock Attack
Authors: Mallory H. Dean , McEwan William S.
Published: April 2005

It is considered common knowledge by many workers in the field of detonation phenomena that transparent plastics quickly go opaque under strong shock wave attack. In this paper high-speed photographs are shown, and it is seen that Lucite and Plexiglas do not go opaque until shattered by tension waves. The behavior of plate glass is somewhat similar. By adjustment of dimensions and lighting, events can be observed with good photographic quality through the shock front for an undetermined length of time.
Magnetization Curve of an Infinite Cylinder
Authors: Muller M. W. , Wehlau A.
Published: April 2005

We have calculated the magnetization curves of an infinite ferromagnetic cylinder with negative uniaxial anisotropy. The cylinder axis is a hard magnetocrystalline direction and the basal plane is an easy plane. The applied field lies along the cylinder axis. The distribution of the magnetization corresponds to the azimuthally symmetric mode denoted as ``magnetization curling.'' With the present choice of anisotropy, stable solutions for the distribution can be obtained through partial reversal of the magnetization.
Interrelation of Electronic Properties and Defect Equilibria in PbTe
Authors: Miller E. , Komarek K. , Cadoff I.
Published: April 2005

The resistivity, Hall coefficient, and Seebeck coefficient of single crystals of PbTe were investigated in the range from 77° to 900°K using a capsuling arrangement which prevented tellurium loss from the specimens at elevated temperatures. The low temperature properties obtained agree with the data reported in the literature. The thermal energy gap obtained from the high temperature measurements cannot, however, be brought into agreement with the energy gap determined from room temperature absorption measurements by considering solely the excitation of electron-hole pairs across the energy gap at elevated temperatures. Rather, it is necessary to include the carriers generated by defect formation at elevated temperatures. Both Schottky-Wagner and Frenkel defects are present, the activation energies for formation of the two types of defects being related by the equation EF=½ES+0.55 ev≃0.7 ev.
Solid-State Perturbations of Nuclear Quadrupole Coupling Constants
Authors: Bersohn Richard
Published: April 2005

The cause of the shifts in quadrupole coupling constants between the gas and solid phases and between equivalent positions in a symmetrical polysubstituted molecule is investigated. An assignment of quadrupole resonance frequencies to positions in the unit cell of 1,3,5-trichlorobenzene is made on the basis of the calculated electric field. There is agreement with the true assignment and with the magnitude of shifts due to external electric fields. It is concluded that shifts in the resonance frequencies of nuclei at equivalent positions are due mainly to crystalline electric fields. Part of the shift between gas and solid phases is ascribed to zero-point torsional oscillations of the molecule.
The Concept of Partial Ionic Character
Authors: Shull Harrison
Published: April 2005

The theoretical definition of partial ionic character is considered. The basic requirements which the author feels must be met before a satisfactory theoretical definition can be found are outlined. It is shown that current models for defining partial ionic character fall short of meeting these criteria. Suggestions are made as to the directions in which one must look for better models. In particular, it is emphasized that the dual requirements of orthogonal concepts based upon models which are invariant to arbitrary choices of basis functions must be met.
Lattice Vibrations in Solids
Authors: Krumhansl J. A.
Published: April 2005

This is a review of selected experimental and theoretical advances in the subject of lattice vibrations over the past several years. A general approach to the properties of phonon fields is presented, then the use of inelastic neutron scattering experiments and topologically consistent interpolation methods for phonon dispersion relations are reviewed. Localized modes of vibration are discussed, and a new method of ``effective moduli'' is presented.
Vacancy Pairs and Dislocations in Ionic Crystals
Authors: Kurosawa Tatsumi
Published: April 2005

(1) We have calculated the binding energy of vacancy pairs in NaCl and the other five alkali halide crystals. The calculations is improved at several points compared with that by Reitz and Gammel. The calculated values of the binding energy are considerably smaller than e2/ka and differ from the result by Reitz and Gammel; for instance, 0.44 ev in NaCl, 0.37 ev in NaBr, and 0.58 ev in KCl crystals.

(2) As the first step of the systematic investigations of dislocation problems, we have calculated the core energy and the Peierls-Nabarro critical yield stress of the edge dislocation for slip in the (110) plane in NaCl type crystal [the Burgers vector is a (110)]. If we write the energy of the dislocation at the center of a cylinder with radius R as K ln (R/R0), R0 is about 1 A in most of the alkali halide crystals. The results of the calculation concerning the Peierls-Nabarro yield stress permit us to understand the well-known fact that LiF has much larger critical yield stress compared with the other alkali halide crystals.
Spin Resonance of Point Defects in Magnesium Oxide
Authors: Wertz John E. , Orton John W. , Auzins P.
Published: April 2005

Transition metal impurity ions and intrinsic defects such as trapped electron and trapped hole centers are readily detected in magnesium oxide crystals by electron spin resonance. The valence state of impurity ions may readily be changed by heat treatment or by irradiation. For nickel and cobalt one may observe both the 2+ and 1+ states, while for iron, one additionally observes the 3+ state. The extra positive charge of trivalent ions is usually compensated by positive ion vacancies. Vacancies, either single or in clusters, alter the electric field symmetry about an impurity ion or intrinsic defect. Hence they may indicate their presence by altering the symmetry from cubic to tetragonal, rhombic or lower type. The impurities are generally substitutional, but one interstitial type has been found. Isolated positive ion vacancies can trap either one or two holes, in each case producing centers of axial electric field symmetry. Other hole centers are observed after extensive atomic displacements have been produced by neutron irradiation. Negative ion vacancies are difficult to produce except by such irradiation. Electrons trapped at negative ion vacancies are largely localized upon the vacancy, as is evident from the small hyperfine splitting of adjacent 25Mg ions. If crystals are heated in order to lead to association of vacancies, a second type of F center is formed. With protracted neutron irradiation, yet a third type of F center is produced. Optical studies are being undertaken to learn more about these paramagnetic centers.
Theory of Localized Electronic States at Point Imperfections
Authors: Gourary Barry S. , Fein Alvin E.
Published: April 2005

A review is given of the present status of the theory of s and p electrons in deep traps. The theory of the F center in LiF is reviewed in detail including recent work on ionic displacements in the vicinity of the center. This is followed by a discussion of the work of Cohen and Heine and the general justification of the point ion approximation for the interaction of a trapped electron with a matrix composed of closed-shell ions. Vacancies in diamond are discussed, and new results are reported for the three-electron configuration of a vacancy in silicon. Trapped-hole centers in the alkali halides are mentioned briefly.
Equilibrium Properties of Solid Solutions of Copper Ions in Large AgCl Crystals
Authors: Moser F.
Published: April 2005

Investigation of the optical and photolytic properties of large silver-halide crystals has shown that both cuprous and cupric ions can be incorporated in the AgCl lattice in true solid solution up to concentrations of the order of 1018 ions/cm3, and quantitatively measured by their characteristic optical absorption as well as by their role in the photolysis of such crystals. At elevated temperatures, the valence state of the copper is determined by the external chlorine pressure. The dependence, at equilibrium, of the cupric-ion concentration on the external chlorine pressure has been determined from measurements of the optical absorption of the cupric ion. This experimentally determined dependence has been compared to that expected from a consideration of the equilibrium number of filled copper levels and the known dependence of free-hole concentration on halogen pressure. Apart from the absorption bands associated with the copper, another absorption band, whose intensity is proportional to the free-hole concentration, has been observed in both pure and copper-containing crystals.
Electron Spin Resonance of Point Defects in CaF2
Authors: Bleaney B.
Published: April 2005

ESR of Nd3+ and U3+ in CaF2 (Bleaney, Llewellyn, and Jones, 1956) provided the first confirmation of the hypothesis of Zintl and Udgård (1939) that charge compensation for a trivalent lanthanum ion is provided by an interstitial fluorine ion. In some cases this is in the nearest interstitial site, as shown by observation of magnetic dipole interaction between it and Ce3+ (Baker, Hayes, and O'Brien, 1960). In other cases the charge compensating defect is absent or so far away that cubic symmetry is preserved at the lanthanum site. The effects of x-ray and ultraviolet irradiation at room and lower temperatures are being studied. Initial results show that Tm3+ ions can be converted readily to Tm2+, whose ESR spectrum has been measured (Hayes and Twidell, 1961). This has cubic symmetry, indicating that the Tm3+ ion is either accompanied by no defect or by a defect mobile at low temperatures. The spectra of Tm2+ and Yb3+ are compared. The work of Sierro (1961) on the hydrolysis of CaF2 is discussed.
Statistical Mechanics of Dilute Solid Solutions
Authors: Brebrick R. F.
Published: April 2005

An apparently quite general model for an essentially-ordered semiconductor compound containing impurity traces consists: (1) of atomic point defects randomly distributed over appropriate, equivalent sites and contributing to the internal energy of the crystal by terms linear in the concentration of each type of atomic point defect, and (2) an electronic energy band structure in which the concentration and type of ``impurity'' levels is determined by the concentration and type of atomic point defects. The assignment of donor or acceptor character to the native interstitials and vacancies is predicted in a specific case by analogy with the alkali halides. Otherwise the nature of the binding is irrelevant, provided the un-ionized impurity level associated with each substitutional atomic point defect bears the same charge as that on the substituted atom. From the appropriate quasi-grand partition function, one obtains the usual Fermi-Dirac distribution for electrons as well as distribution functions for the atomic point defects. In addition, one obtains expressions for the chemical potentials of the thermodynamic components. The latter are utilized in a discussion of those aspects of the M–N phase diagram pertinent to the semiconductor compound MN and in a discussion of amphoteric impurities.
Physical Chemistry of Compound Semiconductors
Authors: Prener Jerome S.
Published: April 2005

The problem of point-defect equilibria in compound semiconductors is considered. It is shown that the expected donor or acceptor properties of a defect in a compouud are entirely independent of the type of binding (ionic or covalent) in the compound. From general thermodynamic arguments it is shown that the number of degrees of freedom of a compound in internal equilibrium is one more than the number of chemical constituents of the compound independent of the number and nature of the defects it contains. The consequences of this are discussed and it is shown how mass action laws result, describing internal reactions among the defects. An example from the literature is presented to illustrate the methods of setting up and solving these mass action laws and how the solutions might be compared with experimental results. Finally, association between oppositely charged defects in solids is discussed.
Effects of Quenching and Annealing on Ionic Conductivity and on Dislocation Decorability in Silver Chloride
Authors: Layer H. , Miller M. G. , Slifkin L.
Published: April 2005

Pure silver chloride crystals, when cooled rapidly from high temperatures, show enhanced ionic conductivity which may be attributed to quenched-in Schottky defects. From the annealing out of this extra conductivity one deduces that for an associated vacancy pair the binding energy is 0.42 ev and the migration energy is ≥1.0 ev. The decorability of interior dislocations by swept-in photoelectrons is also discussed and is shown to be sensitive to the purity of the crystal.
Ionic Conduction in Zone-Refined KCl
Authors: Kanzaki H. , Kido K. , Ninomiya T.
Published: April 2005

Ionic conductivity in the extrinsic range of temperature (250° to 400°C) was measured for specimens taken from a single-crystalline ingot of KCl subjected to zone purification. The effect of dislocation density was studied in order to clarify the nature of ionic conduction in these highly purified crystals. Conductivity increased by a factor of 10 in the purest crystals by increasing dislocation density from 106 to 107 cm−2. Conductivity was decreased in the impurer crystals by increasing the density of dislocations. Comparing the results with predictions from charged dislocation theory, the value of 0.7 ev is obtained for the formation energy of positive ion vacancies.
Properties of Lithium Hydride-V Vacancy Formation, Cavitation, and Lithium Precipitation in Irradiated Lithium Hydride
Authors: Pretzel F. E. , Lewis W. B. , Szklarz E. G. , Vier D. T.
Published: April 2005

Expansion of crystals and compresses of LiH containing up to 40% LiT was observed during exposure to tritium β particles at temperatures from −196° to 400°C. Lithium metal precipitation was observed by electron paramagnetic resonance in small samples of similar composition. The results of auxiliary measurements of optical absorption, electrical conductivity and diffusion, nuclear magnetic resonance, and x-ray lattice parameter were used to interpret the data. Expansion was primarily related to the introduction of vacancies into the LiH crystal lattice to accommodate the products of radiation damage and tritium decay, to permit the formation of bcc Li metal, and to produce cavities in the crystals at high temperatures. Radiation damage was quickly reversed at the lowest temperatures, and the primary defects observed were interstitial He3 atoms and F centers. Warming to room temperature caused aggregation of the F centers and introduced vacancies which destroyed the interstitials Periodic warming for observation further increased the net expansion to allow the formation of bcc Li metal. At higher storage temperatures, vacancy diffusion stabilized a portion of the defects produced by radiation damage with the net result that increased expansion, increased Li formation, and H2 molecular species were observed in the crystals. The expansion rates in the temperature range of increasing radiation damage gave an activation energy consistent with that obtained for vacancy diffusion. An intercomparison of expansion and bcc Li formation at 23°C gave results consistent with the radiation-damage yield and with the formation of Li metal by a diffusion-controlled process. Above a 300°C minimum a second increase in expansion related to cavitation was observed.
Optical Detection of Domain Structure and Current Flow in Superconducting Lead Films
Authors: DeSorbo W. , Newhouse V. L.
Published: April 2005

This report presents a survey of domain structures observed on some lead films under various conditions of applied magnetic field, made visible using the magneto-optic technique. Fields due to a current are also observed. The static appearance and the dynamic behavior of the patterns are similar to the appearance and the behavior observed earlier in bulk samples of ``hard'' superconductors.
Contact Potential in Thin Metal Films
Authors: Bryla Stanley M. , Feldman Charles
Published: April 2005

Attempts were made to observe a work function variation with thickness of thin gold, platinum, and silver films. The films were vacuum deposited onto fused silica substrates at pressures of about 10−8 torr. The vibrating capacitor method was used to measure the contact potential difference between the films and a platinum reference surface as a function of film resistance. The measurements were carried out at pressures of 10−8−10−10 torr. The contact potential difference was found to be independent of film resistance in the range of 5 ohms/sq to 108 ohms/sq.
A Quantitative Theory for the Dislocation Multiplication during the Early Stages of the Formation of Glide Bands
Authors: Wiedersich H.
Published: April 2005

A quantitative theory of dislocation multiplication in the early stages of glide band formation is proposed. It is based on the model of double cross slip suggested by W. G. Johnston and J. J. Gilman [J. Appl. Phys, 31, 632 (1960)]. Moving screw dislocations are believed to undergo cross slip but return in a random fashion into slip planes parallel to the original slip planes. The edge dislocation parts created between the two cross slip events cannot follow the screw dislocations, thus creating dipole dislocation trails. If the distance between the dipole dislocations is large enough that they pass each other under the applied stress, a new dislocation loop is formed in the parallel plane and the original dislocation is restored completely in its glide plane. On this basis, expressions for the number of trails and for the number of new loops created directly and indirectly by a moving dislocation are derived. The results of the theory are found to be in good agreement with the limited available data, namely the measurements on dislocation multiplication in LiF by W. G. Johnston and J. J. Gilman [J. Appl. Phys. 30, 129 (1959)].
Flow and Recovery Properties of Nearly Stoichiometric Polycrystalline Uranium Carbide and the Mechanism of Work Hardening of Crystalline Solids
Authors: Chang Roger
Published: April 2005

The flow and recovery properties of nearly stoichiometric polycrystalline uranium carbide were studied in the temperature range 1500° to 1900°C at strain rates varying between 2×10−5/sec to 2×10−3/sec. The flow data seem to follow a relationshipε̇≅Kσ5exp(−37 500/RT), whereε̇ is the strain rate, K a proportionality constant, R the gas constant, T the absolute temperature, and σ the flow stress at strain =0.001. A mathematical evaluation from recovery data of the activation volume associated with dislocation motion is presented and its potential to yield basic information on the mechanism of work hardening is discussed.
Ions Sputtered from Copper
Authors: Bradley R. C. , Ruedl E.
Published: April 2005

Positive ions sputtered from copper under a variety of different bombardment and surface conditions have been mass analyzed and found to include species characteristic of the incident ions (``reflected'' ions), of copper and some of its compounds, and of alkali metal impurities. A model is described which accounts for most of the properties of the ``reflected'' ions, not in terms of reflection but in terms of the amount of gas trapped and released by the surface. The ionizing agent is unknown but is thought to be the bombarding ions (or their secondary electrons) rather than the surface. The Cu+ ions, on the other hand, seem to be surface ionized sputtered particles originating from patches of high local work function. Yield data seem to correlate qualitatively with probable changes in work function caused by adsorption of impurities, sputtering, or vacuum annealing. The CuO+ peak is believed to be caused by dissociation and ionization of cuprous oxide molecules under the action of the ion bombardment. The rates of formation and disappearance of this peak were studied under various circumstances. An unusually high sputtering rate was found to occur at an argon bombarding energy of 75 ev. Na and K impurities sputtered from and ionized by the copper surface showed some interesting transient effects which can be interpreted in terms of a low sputtering probability compared to the base metal. The relevance of these experiments to sputtering theories, ion pumping, oxidation, cleanup, and surface ionization theory is discussed.
Precision Orientation of Germanium Crystals in the [111] Direction Using Alloy Pits
Authors: Dreiner R. , Garnache R.
Published: April 2005

A method is described for orienting germanium crystals in the [111] direction with an accuracy within six minutes of arc. N-type germaniun is alloyed by liquid indium. The indium is then etched off and the resulting alloy pits are inspected by means of interference fringes. The information obtained from these pictures is used to determine the orientation with the accuracy noted above. An alternate method is described using information obtained from delineated P-N junctions on two angle lapped bevels.
Effects of Thermal-Mechanical Treatments on Faulting in Some fcc Alloys
Authors: Mikkola D. E. , Cohen J. B.
Published: April 2005

An increase in stacking fault probability associated with a solute with the same atomic size but a higher valence than the solvent was found by comparing filed Ag and Ag-6 at. % Al. The stacking fault and twin fault probabilities in ordered Cu3Au, where the atoms differ in size only, were higher than for either pure Cu or Au after deformation at and below room temperature. The stacking fault probability was lower in filings of quenched Cu3Au and Cu-14.3 at. % Al alloys, than in slowly cooled specimens. There is a close correlation between measured fault probabilities and available data on fault energies and Fermi surface configurations.

Twin faults were found in Cu-base alloys deformed at room temperature as well as at low temperatures.

Stacking faults in filings of Cu-14.3 at. % Al annealed out in two stages. The second stage was associated with recrystallization, with an activation energy similar to that for interdiffusion in this system. Twin faults were more stable than stacking faults.
Effects of Electron Random Motion on Microwave Propagation through a Plasma Parallel to a Magnetic Field
Authors: Willett Joseph E.
Published: April 2005

Expressions for the propagation of a circularly polarized microwave through a plasma parallel to a uniform and static magnetic field are derived from the Boltzmann equation and, alternately, from the equation of motion of an individual electron. Both methods yield identically the same formulation in which effects of the random motion of the electrons are predicted to result from (i) the Doppler shift due to electron motion parallel to the direction of propagation, (ii) electron free paths extending over distances significant compared to the attenuation length, and (iii) variation of collision frequency with electron velocity. The results of a numerical study of the propagation of a right-handed wave indicate that the first two of these effects are important in the region of cyclotron resonance even at moderate temperatures (e.g., in re-entry plasmas) provided that the collision frequency is small compared to the signal radian frequency. Substantial reduction of the attenuation of a right-handed wave in a plasma may be achieved by means of a magnetic field aligned parallel to the direction of propagation. The cyclotron frequency must be of the order of the signal radian frequency or larger and such that the enhanced attenuation arising from the electron random motion is avoided. The effectiveness of a given magnetic field in reducing the attenuation increases with decreasing ratio of collision frequency to signal radian frequency.
Shock-Wave Compression of Quartz
Authors: Wackerle Jerry
Published: April 2005

High explosive driving systems and high-speed optical techniques have been used to investigate the compressional behavior of x-cut, y-cut, and z-cut quartz crystals and fused quartz up to about 750 kbar pressure. In both forms of silica two-wave structures over a wide pressure range are identified as resulting from unusually high Hugoniot elastic limits. In crystalline quartz a dependence of the pressure of these elastic limits on driving shock pressure and sample thickness is associated with a relaxation-time phenomenon connected with the transition from elastic to fluid-like flow. Recovery experiments are reported which confirm a previous observation that sufficiently high shock pressures result in the transition of crystalline quartz to the fused state, and the implications of the compression data in this regard are discussed. Observations on fused quartz deomonstrate that shock-wave loading results in both the anomalous compression at low pressures and the compaction phenomena above 100 kbar which have been reported from hydrostatic experiments.
Beryllium Oxide Whiskers and Platelets
Authors: Edwards P. L. , Happel R. J.
Published: April 2005

Beryllium oxide platelets and whiskers have been grown by heating beryllium metal in a silica furnace tube and boat with a hydrogen atmosphere for 16 hr at 1500°C. Three distinct types of whiskers formed: one type was parallel to the crystallographic c axis, another in the basal plane ([1̄010] direction), and the third in an intermediate direction (approximately the [3̄032] direction). The first type are called ``flagpole'' whiskers because they are topped by small balls of metallic appearance; they grew at the site of the original metal charge. These whiskers have pores along their axes, except in rare instances in which, instead of a pore, a whisker may have disconnected voids along its axis. Their axial growth rate was not observed directly, but was at least 0.02 μ/sec. The other two types have the more normal whisker appearance and grew at a distance of from 2 mm to 2 cm from the original metal charge. They have no pores or voids. Their growth rate was at least 0.2 μ/sec. The larger platelets, which grew in the vicinity of the normal whiskers, were long in [1̄010] direction and wide in the [0001] direction. Some of the very smallest platelets grew in the basal plane. A mechanism of growth for the flagpole whiskers is proposed. It is assumed that molten beryllium balls are splashed onto a BeO substrate, and then react with water vapor to form whiskers which push the balls away from the substrate. The normal whiskers and platelets grew at a distance from the beryllium metal, and therefore their growth involves a vapor transport mechanism.
Fiber Texture and Magnetic Anisotropy in Evaporated Iron Films
Authors: Yelon A. , Asik J. R. , Hoffman R. W.
Published: April 2005

The fiber texture and magnetic anisotropy of evaporated iron films have been studied as a function of film thickness. It is found that there are three textures present: [110], [111], and [221]. In thin films, the [111] texture is dominant. It is also found that the magnetic anisotropy is of the order of 2×104 ergs/cm3 for 350-A films and decreases with increasing thickness.

On the basis of this experiment and information from earlier experiments, several theories of the origin of magnetic anisotropy in films are examined, and shown to be inadequate for iron films. A theory for the origin of the anisotropy is proposed, based primarily on the magnetic energy associated with an array of vacancy needles. These vacancy needles can also qualitatively explain the resistivity anisotropy and dichroism observed by other workers.
Elastic Deformation, Plastic Flow, and Dislocations in Single Crystals of Titanium Carbide
Authors: Williams Wendell S. , Schaal R. D.
Published: April 2005

Single crystals of the brittle refractory-hard-metal TiC have been plastically deformed at temperatures from 800° to 2200°C. Dislocation etch-pit studies on {100} cleavage surfaces after bending showed that the slip plane is {111} in the rocksalt structure. The slip direction is taken to be that of the shortest Burgers vector, 〈110〉. The slip system is then the same as that of fcc metals and diamond cubic semiconductors. The resolved shear stress for slip in TiC at 1100°C was found to be large: ∼10 kg/mm2. TiC crystals loaded at room temperature did not deform plastically, but did accommodate elastic strain up to 1.2% if the surfaces were electropolished. A shear stress of 0.4 of the theoretical strength was obtained. These results are consistent with the long-held hypothesis that the binding in hard metal carbides is partially covalent and not exclusively metallic. The Peierls stress resisting dislocation motion should then be large, as in the covalent crystals Ge and Si, and thermal activation would be required for plastic flow. The observed formation of debris by jogs in moving dislocations might alternatively be responsible for the large flow stress. The effects of impurities, precipitates, and composition differences are being investigated.
Bismuth Whisker Growth
Authors: Mayer Ludwig , Rickett Robert , Stenemann Heinrich
Published: April 2005

Profuse and rapid bismuth-whisker growth from thin bismuth films occurring only in the presence of manganese is reported. This growth was observed during the heat treatment of thin bismuth-manganese double layers in the vacuum hot stage on a metallurgical microscope. Optimal conditions for whisker growth are described. The presence of manganese required for whisker growth strongly suggested that the whiskers might be composed of a bismuth-manganese compound. However, chemical microanalytical tests, melting point determinations, magnetic and magnetoresistivity measurements definitely proved that the whiskers grown were bismuth whiskers. Measurements of magnetoresistance as a function of the orientation of the whiskers in the magnetic field showed that the whiskers were essentially bismuth single crystals with their long axes normal to the principal crystallographic axis The results of exploratory measurements of such additional physical properties of the whiskers as electrical resistivity, temperature coefficient, maximal fracture strength, and strain sensitivity factor are also reported.
Analysis of Semiconductor p-n Junctions and Junction Devices by a Flux Method
Authors: McKelvey J. P.
Published: April 2005

A novel technique of analysis of excess carrier behavior in semiconductors, based upon conservation of carrier fluxes, after allowing for generation and recombination, is applied to semiconductor p-n junctions and simple junction devices. It is assumed that the junction acts as a source of excess minority carriers with respect to the bulk material on either side of the junction, and that the flux strength associated with the junction is proportional to exp (eV/kT), where V is the bias voltage appearing across the junction. In the case of the planar p-n junction in an infinite semiconductor, the usual exponential current-voltage dependence is obtained, but a more general expression for the saturation current than that obtained from the conventional diffusion calculation is exhibited. In particular, it is shown that for sufficiently low-carrier lifetime in the bulk material adjacent to the junction, the saturation current is less than that predicted by the conventional diffusion calculation, and becomes independent of lifetime in the low-lifetime limit. The application of the method to simple device structures is also discussed, and a simple p-n photovoltaic cell is considered as an example. Here again the current-voltage dependence (which is related to the boundary condition at the junction rather than to diffusion and recombination phenomena in the bulk) is unaltered, but modified expressions for saturation and generation currents are obtained. Applicability of the method is currently limited to one-dimensional, field-free, steady-state situations.
Effect of Dielectric Breakdown on the Charging of ZnO Xerographic Layers
Authors: Hoesterey D. C.
Published: April 2005

The invariance of the initial potential of ZnO xerographic layers with respect to the potential of the corona source, and the increase of the initial potential with increasing layer thickness appear to be a consequence of the dielectric breakdown of small regions of the layer during charging. The variation of initial potential with the layer thickness seems to be a result of a positive space charge in the volume of the layer. This space charge probably comes from normally full electron traps within kT of the dark Fermi level which are ionized during charging. Typical space-charge densities are about 1014/cm3.
Complex Representation and Computation of Two-Dimensional Magnetic Fields
Authors: Beth Richard A.
Published: April 2005

The method of evaluating two-dimensional fields as analytic functions of a complex variable without resort to absolute values and complex conjugates is described and applied to the magnetic field produced by straight currents. Explicit formulas are derived suitable for numerical computation of vector and scalar potentials, of field components, and of field gradients for round and polygonal (including rectangular) conductors, current ribbons, and arrays thereof.