bluuebunny/crossref_metadata_2025 huggingface dataset:
Wall oscillation and overdamped motion in magnetic bubble domains
Authors: MacNeal Bruce E. , Humphrey Floyd B.
Published: February 2003

Bubble-wall oscillation, in response to a step change in bias field, is reported in four bubble garnet samples with different compositions and characteristics. The wall velocity during oscillatory motion is found to be independent of the instantaneous drive on the domain wall, but does depend on the initial drive on the wall. The experimental relationship between the wall velocity vs and the initial drive Ha is given by vs=0.86 m/sec+(2.4 m/sec Oe) Ha for expanding motion and by vs =1.6+2.6Ha for collapsing motion. The half-period of oscillation, typically between 100 and 300 nsec, increases linearly with initial drive for low drive fields (∼1 Oe) and approaches a constant value at higher fields (≳2 Oe). Wall motion is analyzed in terms of Slonczewski’s formulation of wall mechanics and a velocity-momentum relationship of the form ?=a+b? is found to agree with the observed motion for a=3.2 m/sec and b=1.5 m/sec. Underdamped motion is observed in two ranges of initial drive field separated by a region in which wall motion is overdamped. The lower boundary between underdamped and overdamped motion, near a drive field of 2.3 Oe, is sharply defined, while the upper boundary, near 3.5 Oe, represents a more gradual transition. The transition to overdamped motion is accompanied by a sharp drop in effective domain-wall mobility, and the mobility returns to its original value in the second underdamped region. A comparison between theoretical and experimental parameters indicates that wall oscillation is most likely to be observed in materials with saturation velocities [v0=7.1γA/ h (K)1/2] greater than 10 m/sec and with resonance-damping parameters less than 0.04.
Enhanced crystallinity of silicon films deposited by CVD on liquid layers (CVDOLL process): Silicon on tin layers in the presence of hydrogen chloride
Authors: Graef M. W. M. , Giling L. J. , Bloem J.
Published: February 2003

Chemical vapor deposition of silicon on a graphite substrate coated with a 5-μm-thick fluid tin layer provides a possibility for the production of large grained polycrystalline silicon layers. Using silane as a source material, crystallites can be produced with a mean grain size of about 20 μm, compared with 5 μm on a substrate without fluid layer. The grain size can be further enhanced by adding HCl as an etching agent to the gas phase. Mean crystallite sizes of 100 μm and larger can be obtained by the use of a fluid layer and a proper combination of SiH4 and HCl.
Volume hologram recording and charge transfer process in Bi12SiO20 and Bi12GeO20
Authors: Peltier M. , Micheron F.
Published: February 2003

Bi12SiO20 and Bi12GeO20 are photoconductive and electro-optic crystals in which hologram recording is performed using the photorefractive effect; their sensitivity and optical quality are comparable with the high-resolution photographic plate. Hologram formation and erasure are analyzed in terms of a simple two-level charge transfer model. The photocarrier’s displacement length, comparable with fringe spacing and the nearly unity quantum efficiency, allows the attainment of the ultimate photosensitivity. The trapping centers concentration being much smaller than the absorption centers concentration, the saturation recording time and diffraction efficiency are found limited only by the trap-filling mechanism.
On the climb of dislocations in boron-ion-implanted silicon
Authors: Wu Wei-Kuo , Washburn Jack
Published: February 2003

The climb of dislocations, both perfect [b= (1/2) 〈100〉] and imperfect [b= (1/3) 〈111〉] was studied in boron-implanted silicon thin foils by electron microscope observation of the shrinkage of interstitial-type dislocation loops. The temperature dependence of the climb rate gave an apparent activation energy of 5.6±0.5 eV for both types. The imperfect loops adopted a rounded shape during shrinkage but tended to acquire straight segments whenever the climb motion required nucleation of new jog pairs. Climb rate at a given temperature was shown to be a function of the climb force on the dislocation and on the distance to the nearest efficient sink or source. The surfaces of the foil were shown to be relatively poor sinks for interstitials or alternatively poor sources for vacancies.
Approximate solutions for maximum shock response in a dissipative lattice
Authors: Tasi James
Published: February 2003

The development of maximum shock response is considered for a dissipative semi-infinite lattice that is subjected to a step jump in velocity at one end. Transform solutions, developed in an earlier paper for a given dissipative lattice model, are asymptotically analyzed using high-frequency contributions to the dispersion relation. For linearized force interaction, the growth and decay of maximum shock response is explicitly found in terms of tabulated functions. In addition, the absolute maximum response that can arise is determined along with the distance into the lattice at which it occurs. When nonlinear elastic interaction is considered, the dispersive oscillations that initially develop were found in the earlier paper to (i) show a continued growth, (ii) remain steady for a considerable distance, or (iii) soon decay, depending on the magnitude of damping. Here, a simple explicit relation between damping and nonlinear elasticity is obtained that determines which of cases (i) – (iii) will exist in a given problem.
On the wrinkling of a free surface
Authors: Andreussi Federico , Gurtin Morton E.
Published: February 2003

We consider an elastic half-space whose free surface is capable of supporting its own stress field. This stress is a linear function of surface strain and is related to the stress in the interior of the body by a nonclassical boundary condition. We study the wrinkling (buckling) of the surface and show that this type of behavior is possible whenever the surface has a compressive residual stress or a negative stress-strain modulus.
Constant radius magnetic acceleration of a strong non-neutral proton ring
Authors: Sprangle P. , Kapetanakos C.A.
Published: February 2003

The constrained or constant radius magnetic acceleration of a strong non-neutral proton ring by a modified betatron field is considered. The modified betatron field consists of an azimuthal magnetic field Bϑ superimposed on a betatron field Bz in which the 1 : 2 flux rule is satisfied. An important advantage of the constrained acceleration is that the energy of the nonrelativistic ions increases with the square of the magnetic field. It has been found that the orbits of the gyrating particles are stable when the self-field index ns{=ω2p[2γ0ϑ(t) Ω20(t)]−1} is much greater than unity, provided that ns< (Bϑ/2Bz)2 at the orbit. For Bϑ=0, the orbits are stable only if ns<1/2.
The relation between the shock-induced free-surface velocity and the postshock specific volume of solids
Authors: Lyzenga Gregory A. , Ahrens Thomas J.
Published: February 2003

The release of solids from a state of shock compression at a free surface is examined. For isentropic release, the postshock specific volume V′0 is shown to be constrained by V′0? (Ufs−Up)2/P1+V1, where (P1,V1) is the pressure-volume Hugoniot state of shock compression and Ufs and Up are the free-surface and shock particle velocities, respectively. When a sudden phase change occurs during the release process, this lower bound is increased, subject to simplifying assumptions about the phase transition.
Thermal expansion of amorphous metal alloys
Authors: Brooks H. A.
Published: February 2003

The thermal expansion of glassy metals of general composition (FexNi1−x)0.75P0.16B0.06Al0.03 has been determined. The thermal expansion α was found to vary smoothly between 1.07×10−5 deg−1 for x=0.2 to 0.75×10−5 deg−1 for x=1. The glassy metals considered here are only available in thin-ribbon form and, therefore, cannot be measured by techniques that require compressive loading of the sample. The method used here employs a linear-variable-differential transformer to monitor the elongation of a ribbon that is under slight tension.
Calculation of corona onset and breakdown voltage in short point-to-plane air gaps
Authors: Parekh H. , Salama M. M. A. , Srivastava K. D.
Published: February 2003

A method of calculation of corona-onset and breakdown voltage in short point-to-plane air gaps is proposed in this paper. This method is based on the assumption that for corona (for negative voltage on the point electrode) or breakdown (for positive voltage on the point electrode) to occur, the energy input into the gap due to the formation of an electron avalanche should reach a critical value. The critical value of the energy is calculated numerically from the known experimental value of the breakdown voltage in uniform field. The corona-onset and breakdown voltages calculated from the proposed method are compared with other existing methods as well as with experimental results.
Scaling a double-pulsed copper chloride laser to 10 mJ
Authors: Nerheim N. M. , Vetter A. A. , Russell G. R.
Published: February 2003

By use of low-inductance (0.5 μH) discharge circuits, pulses of 9.6 mJ were obtained from a double-pulsed CuCl laser. An oscillator-amplifier configuration produced a pulse energy of 11 mJ. Scaling studies indicate that additional increases in the laser energy could be obtained by increasing the discharge voltage above 20 kV and/or by increasing the laser-tube dimensions.
A perturbation analysis of the attenuation and dispersion of surface waves
Authors: Tiersten H. F. , Sinha B. K.
Published: February 2003

A perturbation formulation of the equations of linear piezoelectricity is obtained using a Green’s function approach. Although the resulting equation for the first perturbation of the eigenvalue strictly holds for real perturbations of real eigenvalues only, it is formally extended to the case of purely imaginary perturbations of real eigenvalues. The extended equation is applied in the calculation of the attenuation of surface waves due to the finite electrical conductivity of thin metal films plated on the surface and air loading. The influence of the viscosity of the air is included in the air-loading analysis, and the calculated attenuation increases accordingly. Since the metal films are thin compared with a wavelength, an approximate thin-plate conductivity equation is employed in the determination of the attenuation due to the electrical conductivity of the films. The resulting attenuation is obtained over a very large range of values of sheet conductivity. This is accomplished by using the equation for the first perturbation of the eigenvalue iteratively to determine the solution and attendant attenuation to any desired degree of accuracy. The phase velocity dispersion curve due to the mechanical effect of a thin film plated on a substrate is determined for relatively large wavelengths by employing the perturbation equation iteratively, and excellent agreement is obtained with the results of other more direct approaches. The calculations have been performed for an aluminum film on either ST-cut quartz or Y-Z lithium niobate.
Effect of electrolyte pH and bias voltage on the hardness of the (0001) ZnO surface
Authors: Ahearn J. S. , Mills J. J. , Westwood A. R. C.
Published: February 2003

Past work has shown that surface-active environments can influence the hardness of such nonmetallic solids as silver chloride, magnesium oxide, alumina, quartz, and soda-lime glass. Specifically, a maximum in hardness can be produced when the ζ potential of these solids is zero. This ’’ζ correlation’’ has been taken to imply that surface charge can markedly influence near-surface hardness and, in particular, that solids are hardest when their surface charge is zero. To test this implied relationship between surface charge and hardness in a more direct fashion, the hardness of the (0001) surface of ZnO has been measured as a function of surface charge controlled using an electrolytic cell. The results of this study demonstrate that for ZnO a maximum in hardness is produced, but apparently not when the surface charge is zero. Rather, the hardness maximum is observed when the ZnO surface is positively charged (modest downward band bending). Moreover, previous suggestions attempting to explain the ’’ζ correlation’’ are shown to be inapplicable to the present results on ZnO, and an alternative mechanism involving charge exchange between donor levels and the conduction band is suggested.
The Compton profile of aluminum with silver Kα fluorescence radiation
Authors: Urban J. P. , Hosemann R.
Published: February 2003

In order to obtain more accurate information of Compton profiles a new technique, the Compton fluorescence scattering (CFS), was further developed. The most important advantage of the CFS compared with the conventional x-ray technique is that the background is small and well defined. With respect to γ radiation the resolution is much better and influences of multiple scattering are less serious. As an example the results on aluminum with Ag Kα radiation and a LiF 600 analyzer demonstrate that deviations between previous results with the Mo Kα conventional method and 412- and 59-keV γ measurements respectively could be interpreted. The best agreement was found with the 412-keV γ results.
Electrochromism in some thin-film transition-metal oxides characterized by x-ray electron spectroscopy
Authors: Colton Richard J. , Guzman Alberto M. , Rabalais J. Wayne
Published: February 2003

Qualitative results of an x-ray photoelectron and optical investigation of three thin-film transition-metal oxides, namely, WO3, MoO3, and V2O5 are reported. Data were obtained on films that were not colored and colored by an electrochromic process. The particular electrochromic coloration process used is electrolytic in nature and employs a sandwich-structure electrochromic cell and electrolyte pool. The optical spectra show increased absorption in the visible (red) and near-infrared spectral regions upon coloration. The photoelectron spectra for colored films exhibit a small band near the Fermi level and asymmetric band shapes for metal core-level bands which are absent in films that are not colored. The new band and the asymmetric band shapes are attributed to the presence of a reduced-state species caused by the presence of trapped electrons and metal bronze formation. Results from coloration with different electrolyte pools, i.e., H+, Li+, Na+, K+, Cs+, and Mg2+ electrolytes, are reported.
Sputtering of metal alloys containing second-phase precipitates
Authors: Greene J. E. , Natarajan B. R. , Sequeda-Osorio F.
Published: February 2003

Glow-discharge optical spectroscopy has been used as a real time monitor of the transient sputtering characteristics of alloy samples containing various amounts of second-phase precipitates. All alloys investigated reached a steady-state sputtering condition in which the chemical composition of the sputtered target material was equal to that of the bulk target. The transient sputtering time required to reach steady state was directly related to the time required to attain a steady-state rate of target surface cone formation and annihilation. Scanning Auger and electron microprobe analyses were used to show that cone formation in these alloys was due to masking of the matrix by slow sputtering second-phase precipitates and surface agglomerates. At steady state, the cone number density was found to be a function of bulk-alloy precipitate density, Ar sputtering pressure, and the sample sputtering rate. Increasing the Ar pressure resulted in increased scattering of sputtered atoms back to the target surface, while changes in overall target sputtering rate affected the surface migration and, hence, surface distribution of low-yield species. The average cone base diameter for Inconel 718, Incoloy 800, and Monel K-500 alloys was approximately 8 μm. The average depths removed during transient dc sputtering at an Ar pressure of 40 mTorr (5.3 Pa) and 2 kV were 1.5 μm for Inconel 718, 1.3 μm for Incoloy 800, and 0.1 μm for Monel K-500. For comparison, high-purity GaAs single-crystal samples sputtered under the same conditions reached steady-state sputtering after the removal of less than 100 Å. In all cases, films deposited on glass substrates at ambient temperature during steady-state sputtering had the same chemical composition as the bulk target. Inconel 718 and Incoloy 800 films also exhibited second-phase precipitates similar to those in the bulk targets.
The role of ion aggregates in Rebinder-Westwood environmental effects on wear as monitored by acoustic emission
Authors: Cuthrell Robert E.
Published: February 2003

The acoustic-emission rate is shown to be a direct measure of wear rate in a brittle solid and is used to study the strong dependence of drilling rates on the fluid environment. It is proposed that aggregation of ions in the drilling fluid produces charged or noncharged species which determine the surface zeta potential. The Rebinder-Westwood environmental effects on mechanical properties correlate well with the zeta potential and it is shown that the effects also correlate well with the state of charge of ions and ion aggregates in the fluid environment.
Optically pumped molecular lasers in the 11–17-μm region
Authors: Tiee Joe J. , Wittig C.
Published: February 2003

A large number of laser transitions in the 11–17-μm region have been obtained by optically pumping CF4, NOCl, CF3I, and NH3 with a single line-tunable CO2 TEA laser. These lasers have respectable conversion efficiency and can be scaled to high energies in a spectral region where the selective excitation of molecules is prerequisite to performing selective photodissociation and laser-induced chemistry experiments.
Thermoelectric properties of splat-cooled amorphous In20Te80, Ga20Te80, and Ge15Te85
Authors: Hsiung S. K. , Wang Rong
Published: February 2003

The electrical transport properties of splat-cooled amorphous semiconductors In20Te80, Ga20Te80, and Ge15Te85 were investigated by measuring the thermoelectric power S and dc resistivity ρ between 140 and 300 °K. For as-quenched samples, both S and logρ show linear relationships with 1/T, indicating a p-type intrinsiclike conduction ≳90% due to holes. To account for this intrinsiclike conduction, we propose a high degree of structural integrity in the splat-cooled amorphous samples, i.e., a structure having the homogeneity of the liquid and consisting of continuous Te chains with In, Ga, and Ge attached to broken bonds. However, annealed samples show extrinsiclike conduction from 0 to −130 °C, and both S and logρ show decrease linearly with respect to the decrease of temperature T. The effect of heat treatment interpreted as a structural disordering, appears due to atomic segregation at local areas.
Effects of heat treatment on the optical and electrical properties of indium–tin oxide films
Authors: Haines William G. , Bube Richard H.
Published: February 2003

The effect of heat treatment in various environments on the electrical and optical properties of indium–tin oxide (ITO) sputtered films has been investigated. As the resistivity is decreased by heat treatment in H2 from 8.3×10−3 to 4.3×10−4 Ω cm, the optical band gap increases from 3.05 to 3.42 eV consistent with a Burstein shift and intrinsic band gap of 2.98 eV, and for resistivities less than 8.3×10−4 Ω cm there is a rapid decrease in transmission at longer wavelengths due to free-carrier absorption and formation of dendritic precipitates. Careful control over all sputtering variables is essential to obtain reproducible properties.
Picosecond pulses on superconducting striplines
Authors: Kautz R. L.
Published: February 2003

The attenuation and phase velocity of a superconducting thin-film stripline are calculated at high frequencies using the theory of Mattis and Bardeen. These results are used to study the propagation of picosecond pulses which have frequency components approaching the superconducting energy-gap frequency.
Photovoltaic properties of CdTe p-n junctions produced by ion implantation
Authors: Chu Muren , Fahrenbruch Alan L. , Bube Richard H. , Gibbons James F.
Published: February 2003

A surface region about 0.22 μm thick of cadmium-annealed undoped n-type CdTe single crystal was converted to p type by implantation of 60-keV As+ ions followed by a cadmium annealing. The electrical properties of the p-type layer were measured as well as the photovoltaic properties of the p-n junction formed in this way. For illumination by sunlight an open-circuit voltage of 0.84 V was found in a cell with a solar efficiency of 3.0%. The parameters of the junction were determined using a model designed to describe the spectral response of the cell.
Diagnostics with series-connected Josephson tunnel junctions
Authors: Hebard A. F. , Eick R. H.
Published: February 2003

The prospect of incorporating Josephson tunnel junctions into future device technologies requires that fabrication procedures be developed which assure high junction yield, uniform quality, and reproducibility. Critical-current distributions which are extracted from the I-V characteristics of series-connected lead and lead-alloy junction arrays provide a quantitative measure of the yield, as revealed by a direct count of the 2Δ increments, and the quality or uniformity, as revealed by the width of the distribution. Examples of the effects of oxidation parameters, junction area, electrode thickness, magnetic fields, and thermal cycling on the critical-current distributions demonstrate the ease in which significant statistical information on simultaneously prepared junctions is obtained. As a further illustration of the use of this diagnostic method, we present results on flux-trapping experiments together with a preliminary survey of the effectiveness of a simple technique in which lead alloys are evaporated from a single source to completion and then oxidized in an acidic-oxygen environment.
Analysis of resonance phenomena in Josephson interferometer devices
Authors: Zappe H. H. , Landman B. S.
Published: February 2003

Approximate formulas that yield the resonance amplitude of symmetric two-junction interferometers have been derived using step-by-step linearizations and approximations based on physical arguments. The resonance amplitude is found to strongly depend on the device Q. It increases as Q increases, reaches a peak, and subsequently decreases again. In the low-Q region, the resonance step is very broad and largely independent of rapid changes in device current. This is not the case in the high-Q region where the resonance amplitude increases with decreasing device current rise time. In the range of validity of the approximations, the results were compared to computer solutions, and reasonable agreement was found for arbitrarily chosen test cases. Although derived for two-junction interferometers, the results can be extended directly to certain symmetric three-junction interferometers.
An investigation of a discharge-heated barium laser
Authors: Bricks B. G. , Karras T. W. , Anderson R. S.
Published: February 2003

Barium has been used as the working medium in a discharge-heated metal-vapor laser. The laser produced an average power of 12 W, principally at 1.5 μ, with an overall efficiency of 0.54% when operating at a pulsed repetition frequency (PRF) of 8 kHz. A parametric study of laser performance and a rollover in laser power at high barium number density are discussed.
Threshold conditions for the formation of surface plasmas by HF and DF laser radiation
Authors: Nichols D. B. , Hall R. B.
Published: February 2003

Energy thresholds for the formation of HF and DF laser-supported absorption waves at target surfaces have been measured for several target materials. Chemical laser pulses with a FWHM of 4 μsec and energies up to 150 J were focused to an effective target spot diameter of 0.94 cm. Thresholds were determined by observing the cutoff of incident laser radiation transmitted through a pinhole in the target. The observed variation of the plasma ignition time with incident pulse energy Ei showed that neither the threshold fluence es nor the threshold irradiance qm is invariant under variation of Ei. The measured dependence of es and qm on Ei is compared to calculations based on two simple threshold models. The minimum values of fluence es (in J/cm2) for which surface plasmas are formed are as follows: in the format ’’material [es (HF), es (DF)]’’: aluminum (65, 71); titanium (51, 43); stainless steel (65, 51); nickel (94, 43); copper (110, 46); Grafoil (94, 43); Lucite (100, 100).
Dynamic simulation of solution hardening
Authors: Schwarz R. B. , Labusch R.
Published: February 2003

The flow stress for the motion of a dislocation through a random array of weak obstacles of finite interaction range, and in the presence of viscous forces, has been calculated by integrating numerically the equation of motion in a digital computer. Through a normalization of the coordinates and time it is shown that the normalized critical stress S is a function of only two parameters: a normalized obstacle depth η0 and a normalized viscous damping γ. Numerical values of S were obtained for stepwise changes in η0 and γ and for a set of boundary conditions compatible with real experiments. For γ≳3, S becomes independent of γ and of the initial conditions for the dislocation motion. The results reproduce the analytical dependences of the theories that have been developed for extreme values of η0, providing furthermore the proportionality constants and the extent of η0 for which these theories are applicable. For γ<3, S is a function of η0 and γ and of the initial conditions for the dislocation motion: For a dislocation starting from rest there is an upper critical stress to initiate the motion, lower in value than S (γ≳3), while for a dislocation already in motion there is an even lower critical stress at which the dislocation stops moving. The latter corresponds to that calculated by the previous inertial theories, while the former had not been accounted for previously.
Epitaxial regrowth of Ar-implanted amorphous silicon
Authors: Revesz P. , Wittmer M. , Roth J. , Mayer J. W.
Published: February 2003

The influence of Ar on the recrystallization of implanted amorphous silicon layers has been studied. Investigation of the growth kinetics at temperatures up to 575 °C showed that epitaxial regrowth of silicon is halted if the Ar concentration at the amorphous–single-crystal interface reaches about 1.5×1020 cm−3. Further regrowth could be obtained by higher-temperature annealings, during which the Ar concentration profile was changed and part of the Ar diffused out. TEM analysis showed, that in samples with a dose of 6×1015 Ar ions/cm2, the formation of Ar bubbles occurred during implantation. During annealing the Ar bubbles grew about a factor of 6 in diameter. The epitaxially regrown silicon layers contained a large amount of microtwins. We present a model which relates the occurrence of microtwins to the existence of Ar bubbles.
Epitaxial regrowth of Ne- and Kr-implanted amorphous silicon
Authors: Wittmer M. , Roth J. , Revesz P. , Mayer J. W.
Published: February 2003

The recrystallization of Ne- and Kr-implanted amorphous silicon layers has been studied. Investigation of the growth kinetics at temperatures between 525 and 575 °C showed that the amorphous layer regrows completely. During annealing, 75% of the Ne diffused out while Kr out-diffusion could only be obtained by annealing the samples at 900 to 1000 °C after complete regrowth had already been established. TEM analysis revealed Ne bubbles in the as-implanted samples. Bubbles and microtwins in the epitaxially regrown layers were found in the Ne-implanted samples and in some of the Kr-implanted samples. Microtwins were only detected when bubbles were simultaneously present.
Transformation of observed crack traces on a section to true crack density for fracture calculations
Authors: Seaman L. , Curran D. R. , Crewdson R. C.
Published: February 2003

A statistical procedure has been derived for transforming apparent crack orientations, lengths, and numbers that are observed on a polished section to true orientations, lengths, and numbers. The cracks are assumed to have circular cross sections, and the orientation distribution is assumed to have axial symmetry, but no form is imposed on the observed or computed orientation and length distributions. The transformation has been incorporated into a computer code which has been tested for an analytical case and has been used to transform observed crack data for Armco iron. Comparisons are made with transformations by two approximate methods to guide in detemining whether to use the complete transformation in specific applications. The transformation should also be applicable to other observed metallographic surface features, such as ellipsoidal grains, twins, inclusions, and platelets of a new material phase.
Thermal time constants of thin-film resistors using pulse nonlinearity measurements
Authors: Hebard A. F. , Steverson W. M.
Published: February 2003

A technique of extracting quantitatve information about the thermal relaxation times of thin-film resistors is described. The procedure is based on a simple method in which a pulse string is applied to an ac-coupled circuit, and the resulting dc base-line shift is a direct measure of the resistive nonlinearity. The temperature rise in the resistor, as manifested by the measured nonlinearity, is found to be a function of the ratio of the pulse period and the thermal relaxation time. A linear dependence of the thermal relaxation time on film thickness for a variety of gold films evaporated onto oxidized silicon wafers is demonstrated, and the independent contributions of the effective thermal mass and the the thermal boundary resistance are quantitatively identified. We also discuss an alternative mode of instrumentation in which a symmetrically chopped string of fast and slow pulses, occurring on a time scale comparable to the relaxation time, is used with a synchronous detector to measure the nonlinearity.
The doping concentrations of indium-doped silicon measured by Hall, C-V, and junction-breakdown techniques
Authors: Schroder D. K. , Braggins T. T. , Hobgood H. M.
Published: February 2003

Hall-effect measurements are routinely used to determine the doping concentrations in semiconductor material. We show that for Si : In such measurements give erroneously high results. The Hall concentrations, determined by curve fitting, are typically twice those determined from C-V and junction-breakdown measurements, which measure the doping concentrations directly. We consider the latter data more reliable.
The MOM tunneling diode: Theoretical estimate of its performance at microwave and infrared frequencies
Authors: Sanchez A. , Davis C. F. , Liu K. C. , Javan A.
Published: February 2003

A theoretical analysis of the metal-oxide-metal (MOM) antenna/diode as a detector of microwave and infrared radiation is presented with the experimental verification conducted in the far infrared. It is shown that the detectivity at room temperature can be as high as 1010 W−1 Hz1/2 at frequencies of 1014 Hz in the infrared. As a result, design guidelines are obtained for the lithographic fabrication of thin-film MOM structures that are to operate in the 10-μ region of the infrared spectrum.
Sputtering of PtSi
Authors: Liau Z. L. , Mayer J. W. , Brown W. L. , Poate J. M.
Published: February 2003

The sputtering of PtSi by Ar ions of 10 to 160 keV has been studied by Rutherford backscattering techniques with depth resolutions of 200 Å at normal incidence and 40 Å at extreme glancing angles. The surface layers of the sputtered samples become Pt enriched over depths ranging from 100 to 1600 Å. For a given Ar energy, the Pt enrichment extends approximately over a constant depth and the enrichment increases with increasing Ar dose until steady state is reached. The steady-state composition ratio of Pt to Si at the surface is ∼2.0 for all energies. The sputtering yields of Si before steady state are found to be larger than those of Pt, consistent with Pt enrichment. A phenomenological model, based on preferential ejection of Si from the surface and enhanced diffusion over the range of Ar, explains the present data.
Sub-T
g annealing studies of rubber-modified and unmodified epoxy systems
Authors: Ophir Zohar H. , Emerson John A. , Wilkes Garth L.
Published: February 2003

Epoxy network systems based on DGEBA (bisphenol-A-diglycidyl ether) and NMA (nadic methyl anhydride) systems modified with the low molecular weight CTBN (carboxyl-terminated butudiene-acrylonitrile copolymer) rubbers were prepared and studied. It was found that below the glass transition of the epoxy matrix these materials displayed time-dependent changes in their mechanical properties; specifically, the strain to break as well as the rate of stress relaxation were observed to decrease in a near-linear behavior with the logarithm of time at sub-Tg annealing. Calorimetric methods clearly showed a simultaneous decrease in enthalpy with time that behaved in a similar fashion as the time-dependent mechanical properties. All the calorimetric and mechanical data are qualitatively related. The importance of this phenomena is considered in view of the widespread use of epoxys. Similar behavior is expected for other network glasses thermally quenched into a nonequilibrium state.
Adhesion and hydrophilicity of glow-discharge-polymerized propylene coatings
Authors: Sharma Ashok K. , Millich Frank , Hellmuth Eckhard W.
Published: February 2003

The glow-discharge polymerization of propylene has been studied using an electrodeless electromagnetically coupled (inductive coupling perpendicular to the reactor) tubular reactor operating at a radio frequency of 27.1 MHz. The effects of monomer flow rate (or reactor pressure at constant pump speed), polymerization time, and substrate position on the adhesion of polymeric film to glass and aluminum have been determined. Conditions have been found for excellent adhesion to a substrate. Improvement of the hydrophilicity of the glow-discharge-polymer surface has been achieved by oxygen etching.
Water sorption of polycarbonate and its effect on the polymer’s dielectric behavior
Authors: Bair H. E. , Johnson G. E. , Merriweather R.
Published: February 2003

Polycarbonate absorbs water in two stages: in the initial period of absorption at an elevated temperature all of the water was found in an unassociated state when cooled to room temperature; and, in the second stage, most of the additional water absorbed by the polymer was identified in a separate liquid phase (clustered water). From water sorption studies on polycarbonate bars, we advance the following model for the formation of clusters. After the polymer is saturated with water at an elevated temperature and cooled, its solubility is lowered and water condenses in the form of microscopic water-filled cavities, providing the internal pressure which is generated by the excess water exceeds the strength of the polymer. Below Tg the clusters are formed only after the polycarbonate (Mw=26 600) has been hydrolytically degraded; whereas, above Tg, clusters can be formed without degradation. Cluster regions were found by SEM to be spherical cavities, usually measuring from 0.1 to 1.0 μ across. In addition, the glass temperature of polycarbonate was lowered as the molecular weight decreased due to hydrolysis and the amount of water in the polymer increased. Unassociated water was found to enhance the low-temperature dielectric loss of polycarbonate. Frozen clustered water produced an additional secondary loss peak about 40 °C below the β transition. In addition, the liquid clustered water produced a loss mechanism in the kHz region that was interpreted as a Maxwell-Wagner effect.
Crystallographic factors affecting the structure of polymeric spherulites. I. Morphology of directionally solidified polyamides
Authors: Lovinger Andrew J.
Published: February 2003

The morphology of even-even nylons has been reexamined in order to determine whether crystallographic factors can exert a dominant influence on the morphology and growth behavior of polymeric spherulites. Directional solidification of these polyamides produces long oriented spherulites at zone velocities below ∼5 μm/min, while at higher rates unusual patterns are obtained by interaction with small positive spherulites. In most cases, the stable form is that of oriented negative spherulites presenting an extremely fine fibrillar texture. Fluctuations in temperature gradient or in sample motion cause initiation of divergent fronts of spherulitic aggregates, which, however, exhibit interrupted growth patterns and variable growth rates; this exceptional growth behavior is not imposed by the characteristics of zone solidification. In addition, the aggregates appear to posess an unusually coarse texture, whereas that of positive spherulites is intermediate between the textures of the other two spherulitic species. Most aggregates have a totally mixed birefringence; however, the positive birefringence of others is inconsistent with their orientation and polarizabilities.
Crystallographic factors affecting the structure of polymeric spherulites. II. X-ray diffraction analysis of directionally solidified polyamides and general conclusions
Authors: Lovinger Andrew J.
Published: February 2003

The morphological diversity in even-even nylons described in Paper I was found to be the result of crystallographic factors related to the high extent of hydrogen bonding. Among all spherulitic species in these polyamides, only positive spherulites crystallize in accordance with the phenomenological theory of Keith and Padden. However, as a result of their unit cell orientation which renders the hydrogen-bonded sheets radial and the molecular chains almost tangential, folding occurs predominantly into the melt rather than in the usual tangential manner. The microstructure of negative spherulites departs from the norm in that long ribbonlike lamellae are absent; instead, negative fibrils are composed of short segments containing tangentially arranged stacks of hydrogen-bonded sheets. In spherulitic aggregates the molecular chains are crystallized at the unusually acute angle of 49° to the direction of solidification. The preferred direction of fibrillar growth in these aggregates is oblique to the spherulitic radius; this could account for their variable and interrupted growth rate, their apparent coarseness of texture, as well as their extinction at 45° to the crossed polars. All spherulitic species crystallize with the α-unit cell. A possible explanation for this is offered, relating the unilateral shear of hydrogen-bonded planes to dipole interactions between adjacent layers. Such interaction would also help explain the positive birefringence of spherulitic aggregates which is inconsistent with their polarizabilities.
A systematic study of the effect of casting solvent on the bulk properties of linear SBS block copolymers
Authors: Wilkes Garth L. , Bagrodia Shiriam , Ophir Zohar , Emerson John A.
Published: February 2003

Using a well-characterized series of styrene-butadiene triblock copolymers, a systematic study was carried out to determine the influence of casting solvent, used for film preparation, on the final mechanical properties. The results clearly indicate that in the range of styrene contents of 30–40 mole%, the modulus behavior varies greatly as the solubility parameter δ of the casting solvent is varied. Specifically, the modulus increases as δ increases. At lower or higher styrene content, the properties are influenced but to a much lesser degree. Interpretation of the measured mechanical behavior is given in light of morphological data obtained by rheo-optical methods.
Experimental and theoretical study of the xenon laser and associated high-gain phenomena
Authors: Sandoval R. P. , Moreno J. B.
Published: February 2003

A pulsed infrared xenon laser system, constructed to study phenomena associated with high gain, is described. Extracted-power measurements from both an amplifier and an oscillator are presented. Comparison with semianalytical solutions of simple-model equations is made to obtain estimates for small-signal gain (2.0 cm−1) and saturation intensity (0.2 W/cm2). The effects of aperturing and wall reflectivity on oscillator output are also studied. A simple model together with measurements show that aperturing enhances parasitic oscillations.
Design of a D-shaped toroidal field coil
Authors: Kuroda Kunishige
Published: February 2003

A method for making a multilayer toroidal field coil free from the bending moment is studied by applying File’s theory to each layer of the coil. According to this method, the shape of a multilayer toroidal field coil is determined so that the layers in the winding are in pure tension and, therefore, are not subject to any bending moment. The winding thickness of the resultant coil is not uniform along the winding. Successive layers are no longer in contact, leaving some empty space between them. Tension on a conductor varies in magnitude from layer to layer and is constant in the same layer, as in a solenoidal coil. A toroidal field coil with a magnetomotive force of 18.8 MA T, a vertical bore of 1.51 m, and a horizontal bore of 1.07 m is designed with this method.
Ionic conductivity of silver bromide microcrystals by dielectric-loss measurements
Authors: Travot G. , Divetain P. , Sirand-Rey G.
Published: February 2003

The photographic emulsion which consists of the conductive silver halide microcrystals embedded in the insulating gelatin can be regarded as a heterogeneous medium showing the dielectric dispersion called the Maxwell-Wagner effect. From the dielectric-loss measurement versus the frequency, the conductivity is measured for various-size AgBr cubic microcrystals. A new method of calculation based upon the Cole-Cole diagram properties is proposed, and the results are presented.
The annealing of an abrupt planar surface discontinuity by surface diffusion
Authors: Brailsford A. D.
Published: February 2003

Most prior applications of Mullins’s formalism for the capillarity-induced time development of surface morphology have been restricted to cases where the deviations from a perfectly flat profile are small. An analytical technique is developed here for following the evolution of the surface profile of a body containing an initially abrupt discontinuity. The annealing, by surface diffusion, of a concave surface corner and grain boundary grooving are discussed as examples of the general method.
Equation of state of fluid T2 deduced from P-V-T and ultrasonic-velocity measurements on H2 and D2 to 20 kbar
Authors: Mills R. L. , Liebenberg D. H. , Bronson J. C.
Published: February 2003

From our previous measurements of P, V, T, and ultrasonic velocity u made on fluid n-H2 and n-D2 in the region 75<T<300 K and 2<P<20 kbar, we extrapolated values of V, u (P, T) for the radioactive isotope T2 by applying several scaling laws corrected for quantum effects. The data were used in a double-process least-squares fit to evaluate the parameters in a Benedict-type equation of state from which thermodynamic properties were derived.
ESR studies of hydrogen hyperfine spectra in irradiated vitreous silica
Authors: Vitko John
Published: February 2003

Various means of deuteration have been used to establish the hydrogenic origin of both the 119-G and 74-G hyperfine doublets observed in a variety of irradiated vitreous silica samples. The g values of both these defects appear inconsistent with an earlier model in which these lines were attributed to a hole localized on a hydroxyl group. Of the alternative models suggested by this experimental study, the most satisfactory attributes the 119-G doublet to an electron trapped at a hydrogen-compensated substitutional germanium impurity and the 74-G doublet to an electron trapped at a silicon atom adjacent to an oxygen vacancy and in the immediate neighborhood of a hydrogen, a defect termed the [E2′/H].
Studies on electrical conductivity of insulator-conductor composites
Authors: Rajagopal C. , Satyam M.
Published: February 2003

The variation of electrical resistivity of an insulator-conductor composite, namely, wax-graphite composite, with parameters such as volume fraction, grain size, and temperature has been studied. A model is proposed to explain the observed variations, which assumes that the texture of the composite consists of insulator granules coated with conducting particles. The resistivity of these materials is controlled mainly by the contact resistance between the conducting particles and the number of contacts each particle has with its neighbors. The variation of resistivity with temperature has also been explained with the help of this model and it is attributed to the change in contact area.
Transport properties of polycrystalline silicon films
Authors: Baccarani G. , Riccò B. , Spadini G.
Published: February 2003

The transport properties of polycrystalline silicon films are examined and interpreted in terms of a modified grain-boundary trapping model. The theory has been developed on the assumption of both a δ-shaped and a uniform energy distribution of interface states. A comparison with experiments indicates that the interface states are nearly monovalent and peaked at midgap. Their density is 3.8×1012 cm−2, in accordance with carrier-lifetime measurements performed on CVD films.
Heating and flux flow in niobium variable-thickness bridges
Authors: Wang Li-Kong , Hyun Dae-Jin , Deaver Bascom S.
Published: February 2003

The properties of niobium superconducting microbridges consisting of a thin-film bridge 300 Å thick, 1 μm wide, and 0.5 μm long joining two bulk films 5000 Å thick have been studied by measurements of I-V and dV/dI versus V as functions of temperature and microwave power and by microwave mixing experiments. Near Tc these bridges behave as nearly ideal Josephson junctions but at lower temperature their characteristics appear to be determined by flux flow. Hysteresis of the I-V curves, depression of the energy gap, a feature interpreted as the onset of a self-sustaining hot spot, and bolometric mixing can all be described very well by a simple heating model.
Theory of light scattering by surface acoustic waves on reflection and transmission
Authors: Stegeman G. I.
Published: February 2003

A general approach to the theory of light scattering by surface acoustic waves on reflection from and transmission through a surface is described. The appropriate polarization-driven-wave equation is solved exactly, and total solutions are found which also satisfy all the electromagnetic boundary conditions across the acoustically corrugated interface. This formalism is vectorial in character and is valid for all scattering angles. The scattering of both ’’s’’- and ’’p’’-polarized incident light is treated analytically and numerically for Rayleigh waves on an isotropic medium (fused quartz) and Y-Z lithium niobate and for Bleustein-Gulyaev waves on Y-X cadmium sulphide. The results deviate significantly from the predictions of previous scalar theories for scattering angles greater than a few degrees.
Degradation of discontinuous gold films under MeV heavy-ion bombardment
Authors: Andersen H. H. , Knudsen H. , Petersen P. Mo/ller
Published: February 2003

Thin discontinuous gold films evaporated onto 150–230-Å-thick C substrates were irradiated with perpendicularly impinging MeV N, O, F, Cl, and Br ions up to fluences of 5×1015 ions/cm2 and fluxes up to 8×1011 ions/cm2 sec. Surprisingly rapid degradation of the gold films was found; in some cases, up to 2000 gold atoms per impinging ion were removed, as measured by Rutherford scattering. The degradation was also investigated by transmission-electron microscopy. The angular distribution of the ejected gold atoms was indicated by a simple collector experiment and found incompatible with chunk emission. The degradation is concluded to be caused by the same ionization mechanism as that occurring when fission fragments form tracks in discontinuous metal films. During irradiation, the remaining part of the film is found to be stabilized against further degradation by ionization-induced cracking of hydrocarbons.