bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of NiAl3 and Ni2Al3 phase growth on lateral diffusion couples
Authors: Liu Joyce C. , Mayer J. W. , Barbour J. C.
Published: July 2002

The phase formation of NiAl3 and Ni2Al3 is studied on lateral diffusion couples of an Al-rich source on a Ni thin film at temperatures from 375 to 500 °C. Analytical electron microscopy is used to determine the crystal structures, chemical compositions, and the widths of growing phases. Simultaneous growth of NiAl3 and Ni2Al3 is observed at 375 and 450 °C. Al atoms dominate the diffusion process in NiAl3 and Ni2Al3. The growth of Ni2Al3 has a parabolic dependence on annealing time, and the growth constant, X2/t, has an activation energy of 2.0±0.2 eV. The growth kinetics is further studied by comparing the growth rates of NiAl3 in one- and two-phase growth, and by applying the criteria proposed by Gösele and Tu to the simultaneous growth of NiAl3 and Ni2Al3.
TM-TE optical-mode conversion induced by a transversely propagating magnetostatic wave in a (BiLu)3Fe5O12 film
Authors: Tamada H. , Kaneko M. , Okamoto T.
Published: July 2002

Highly Bi-substituted garnet films (BiLu)3Fe5O12 (Bi=0.89/f.u.) have been grown on (111)-oriented Gd3Ga5O12 substrates by liquid-phase epitaxy with only Bi2O3 as a flux. The specific Faraday rotation θF attains −0.14 deg/μm at 1.3 μm. Guided-optical-wave propagation loss of 0.6 dB/cm at 1.3 μm is obtained by doping an appropriate amount of MgO in the melt. Magnetostatic backward volume wave (MSBVW) is launched efficiently into the film as expected from the measured small ferromagnetic resonance linewidth of 0.7 Oe, whereas magnetostatic surface wave and magnetostatic forward volume wave are subject to the severe attenuation due to their coupling to spin-wave modes. The interaction between guided optical wave and MSBVW is investigated in a transverse configuration where the input optical wave passes almost orthogonal to MSBVW. The TM-TE optical-mode conversion induced by MSBVW is observed over the frequency range of 3.5–7.5 GHz. Its efficiency, as high as 47%/0.8 W at 4 GHz, is obtained for the interaction length of 7 mm.
Quantum chemical study of adhesion at the SiC/Al interface
Authors: Li S. , Arsenault R. J. , Jena P.
Published: July 2002

Using the intermediate neglect of differential overlap approximation, the total energies of a number of clusters modelled to represent the SiC/Al interface have been calculated as a function of distance separating the two surfaces of SiC and Al. The adhesive energy of the interface is calculated by minimizing the total energies corresponding to various crystallographic orientations of the SiC and Al surfaces. The results are used to provide semiquantitative understanding of the bonding mechanism and the effect of reconstruction at the SiC/Al interface.
Mechanical properties of diamondlike carbon films
Authors: Hoshino Shigeki , Fujii Kazutaka , Shohata Nobuaki , Yamaguchi Hirotaka , Tsukamoto Yuji , Yanagisawa Masahiro
Published: July 2002

Diamondlike carbon (DLC) films have been deposited onto room-temperature silicon substrates, which are placed on a cathode, in a dc plasma of methane (CH4) and hydrogen (H2) gas mixture. Ultramicroindentation hardness and Young’s modulus for the films were measured. The mechanical properties of DLC films change greatly in two different anode positions relative to the cathode. In the case of an upward anode position (so-called parallel electrode), the maximum ultramicroindentation hardness value is 200 GPa(3700 Hv) and the maximum Young’s modulus value is 480 GPa. At a sideward anode position, the maximum ultramicroindentation hardness value and Young’s modulus value are 480 GPa(7500 Hv) and 850 GPa, respectively, which are much higher values than those at the upward anode position. The contact-start-stop test results indicate that DLC films have a possibility for use as a wear-resistant protective layer.
The etching of polymers in oxygen-based plasmas: A parametric study
Authors: Joubert O. , Pelletier J. , Arnal Y.
Published: July 2002

A parametric study of the etching of polymers has been performed in a 2.45-GHz microwave multipolar plasma using an electron-cyclotron-resonance excitation and an independent 13.56-MHz rf biasing. The etch rates achieved in N2O and N2/O2 discharges are measured as a function of different plasma parameters, i.e., the ion current density bombarding the wafer surface, the ion energy, and the relative atomic oxygen concentration as estimated by actinometry. In both types of plasmas, the etch rate evolutions with ion energy exhibit a two-step variation corresponding first to ion-induced adatom displacements on the polymer surface and second, above a threshold energy, to the rising of sputtering. Under given ion bombardment conditions the polymer etch rate, unchanged by the presence of molecular oxygen, appears to be only controlled by the atomic oxygen concentration in the plasma. The etching kinetics, which first increases proportionally to ion current density and atomic oxygen concentration before reaching saturation, clearly indicates a monolayerlike adsorption of oxygen on polymers. With this hypothesis, the etching behavior can be fully explained by a model recently proposed for plasma etching.
Defects and optical absorption bands induced by surplus oxygen in high-purity synthetic silica
Authors: Nishikawa Hiroyuki , Tohmon Ryoichi , Ohki Yoshimichi , Nagasawa Kaya , Hama Yoshimasa
Published: July 2002

The nature of excess oxygen in as-manufactured and γ-irradiated high-purity synthetic silicas is investigated. Electron-spin-resonance measurements suggest that peroxy radicals ( 3/4 SiOO⋅) could be produced either by the cleavage of peroxy linkages ( 3/4 SiOOSi 3/4 ) or by the reaction of E’centers ( 3/4 Si⋅) with oxygen molecules. The excess oxygen is found to exist in the glass in two forms: as peroxy linkages and as interstitial molecular oxygen. The peroxy linkage is shown to be the cause of optical absorption at 3.8 eV. Heat treatment at 900–1000 °C results in the growth of the 3.8-eV band, that is, the peroxy linkages, through the reaction of oxygen vacancies and interstitial dioxygen molecules. These results indicate that the 5.0- and 3.8-eV bands (which are characteristic of ‘‘oxygen-deficient’’ and ‘‘oxygen-surplus’’ silica, respectively) can coexist in a glass, depending on the synthesis conditions.
Thermal conductivity of dielectric thin films
Authors: Lambropoulos J. C. , Jolly M. R. , Amsden C. A. , Gilman S. E. , Sinicropi M. J. , Diakomihalis D. , Jacobs S. D.
Published: July 2002

A direct reading thermal comparator has been used to measure the thermal conductivity of dielectric thin-film coatings. In the past, the thermal comparator has been used extensively to measure the thermal conductivity of bulk solids, liquids, and gases. The technique has been extended to thin-film materials by making experimental improvements and by the application of an analytical heat flow model. Our technique also allows an estimation of the thermal resistance of the film/substrate interface which is shown to depend on the method of film deposition. The thermal conductivity of most thin films was found to be several orders of magnitude lower than that of the material in bulk form. This difference is attributed to structural disorder of materials deposited in thin-film form. The experimentation to date has primarily centered on optical coating materials. These coatings, used to enhance the optical properties of components such as lenses and mirrors, are damaged by thermal loads applied in high-power laser applications. It has been widely postulated that there may be a correlation between the thermal conductivity and the damage threshold of these materials.
Generation of axial magnetic fields in laser-produced plasmas
Authors: Bhattacharyya B. , Sarkar Susmita
Published: July 2002

Axial magnetic fields earlier observed in laser-produced plasma experiments can be generated in the case of nonlinear interactions of lasers with under dense plasmas. It has been shown that for high-frequency laser (viz. Nd-glass laser having the wavelength (λ)=1.06 μm and the power flux (P)=1016 W/cm2) the background dc magnetic field would be important only when electron cyclotron frequency is comparable to the laser frequency.
Synthesis of pure titanium nitride layers by multipulse excimer laser irradiation of titanium foils in a nitrogen-containing atmosphere
Authors: D’Anna E. , Leggieri G. , Luches A. , Martino M. , Drigo A. V. , Mihailescu I. N. , Ganatsios S.
Published: July 2002

Experimental results are reported concerning the synthesis of pure, hard, and adherent titanium nitride layers by multipulse excimer (λ=308 nm) laser irradiation in a nitrogen or ammonia atmosphere. It is shown that the process is more efficient when the irradiation is performed in a nitrogen atmosphere. The general characteristics of synthesized surface compound layers are compatible with the requirements of utilization in microelectronics.
Entropy optimization in quantitative texture analysis.  II. Application to pole-to-orientation density inversion
Authors: Schaeben H.
Published: July 2002

Anisotropic behavior of single-phase polycrystalline material is controlled by its constituent crystal grains and their spatial orientation within the specimen. More specifically, a macroscopic physical property in a given direction is the mean value of the corresponding property of the individual crystallites with respect to the statistical distribution of their orientations. Thus, the statistical orientation distribution is a mathematical approach of describing and quantifying anisotropy. Unfortunately, the orientation density function (ODF) can generally not be measured directly. Therefore, it is common practice to measure pole density functions (PDFs) of several distinct reflections in x-ray- or neutron-diffraction experiments with a texture goniometer. Recovering an ODF from its corresponding PDFs is then the crucial prerequisite of quantitative texture analysis. This mathematical problem of texture goniometry is essentially a projection problem because the measured PDFs represent integral properties of the specimen along given lines; it may also be addressed as a tomographic problem specified by the crystal and statistical specimen symmetries and the properties of the diffraction experiment itself. Mathematically, it reads as a Fredholm integral equation of the first kind and was conventionally tackled by transform methods. Because of the specifics of the problem, these are unable to recover the part of the ODF represented by the odd terms of the (infinite) series expansion. In this situation, more sophisticated iterative methods, especially finite-series-expansion methods were developed within which the required non-negativity of the ODF to be recovered plays the prominent role. An efficient way to guarantee non-negativity is to employ entropy optimization.
X-ray induced hole trapping in electroradiographic plates
Authors: Kasap S. O. , Aiyah Viswanath , Baillie A. , Leiga A. G.
Published: July 2002

Changes in the electrical properties of pure a-Se and Cl-doped a-Se:0.35% As electroradiographic layers upon exposure to x-ray radiation has been examined using xerographic techniques based on the first residual potential VR1 and the cycled-up residual potential VR∞ Hole lifetime τ as determined from the Warter expression VR1=L2/2μτ has been found to decrease sharply with the x-ray dose, tending to saturate at higher dose levels in both pure a-Se and Cl-doped a-Se:0.35%As. The hole liftime following x-ray exposure recovers toward its equilibrium value at the anneal temperature. The recovery time is dependent on the dose and is accelerated appreciably by temperature, indicative of a thermally activated process. Cycled-up xerographic residual-potential measurements have indicated that the deep-hole-trap population increases with exposure to x rays.

Comparison of cycled-up saturated residual potential and first-cycle residual-potential measurements have shown that as a result of x-ray exposure, the apparent capture coefficient increases, which can only be accounted for by introducing two x-ray-induced effects: (a) generation of deep hole traps and (b) formation of an equal number of trapped electrons and holes in the bulk due to irradiation. Recombination of holes with the trapped electrons in the bulk causes the apparent increase in the capture coefficient. A xerographic spectroscopy technique, based on the analysis of the rate of discharge of the saturated potential after the end of xerographic cycling, was used to map out the energy distribution of the occupied density of states in the mobility gap. It was found that the energy location of the peak of the occupied density of localized states remained unaffected by the exposure to x rays, but the peak value of the density of states increased with the exposure. The x-ray induced trap generation is thus simply an enhancement of the integrated concentration of inherent structural defects in the films located at their characteristic energies: 0.87 eV in pure a-Se and 0.90 eV in Cl-doped a-Se:0.35%As. The present results are consistent with the x-ray-sensitivity predictions of Kalade, Montrimas, and Rakauskas [Phys. Status Solidi A 25, 629 (1974)].
Formation of MnBi ferromagnetic phases through crystallization of the amorphous phase
Authors: Guo X. , Altounian Z. , Ström-Olsen J. O.
Published: July 2002

We have succeeded in forming single-phase MnBi in its two ferromagnetic phases, the low-temperature phase (LTP) and the quenched high-temperature phase (QHTP). The formation process involves rapid solidification into the amorphous state followed by thermal annealing. The crystallization of the amorphous material involves a series of transformations before single-phase LTP (≳95 wt. %) is finally achieved at a temperature of 543 K. Further heating transforms LTP into its high-temperature structure at 635 K, which upon quenching to room temperature gives the QHTP. Some magnetic properties of LTP and QHTP are presented.
Micromagnetic properties of ultrathin cobalt films
Authors: Kief M. T. , Mankey G. J. , Willis R. F.
Published: July 2002

The properties of the magnetic domain structures of ultrathin fcc cobalt films epitaxially grown on Cu (001) have been examined using an ultrahigh vacuum surface magneto-optic Kerr effect instrument. The evolution of magnetic behavior is observed for film thicknesses ranging from 1.4 to 7.5 monolayers. The coercivity is sensitive to film growth temperature and thermal cycling history. The coercivity decreases with diminishing film thickness and falls to very low values for the thinnest layers. The results are discussed in terms of Néel domain-wall micromagnetics for ultrathin films.
Fracture toughness behavior of the YBa2Cu3O7−x superconducting ceramic with silver oxide additions
Authors: Yeh F. , White K. W.
Published: July 2002

The influence of silver oxide additions on the fracture behavior of YBa2Cu3O7−x superconducting ceramic was studied. The KIC value has been found to increase from about 1 MPa√m to as much as 2.4 MPa√m with the blending of 30 wt.% Ag2O with the 1-2-3 powder. All compositions exhibited increasing resistance to fracture with crack extension. The addition of silver to the monolithic sintered structure not only raises the level of the KR curve, consistent with the rise in KIC, but also increases dKR/dΔa, indicative of an improvement in the cumulative toughening efficiency. Microstructural studies implicated crack face bridging by both the 1-2-3 grains, as well as the Ag component, as a major contribution to the observed improvement in toughening. The superconducting properties of these composites were not adversely affected by additions of up to 20% Ag2O.
Fermi-level movement at GaAs(001) surfaces passivated with sodium sulfide solutions
Authors: Berkovits V. L. , Bessolov V. N. , L’vova T. N. , Novikov E. B. , Safarov V. I. , Khasieva R. V. , Tsarenkov B. V.
Published: July 2002

Reflectance anisotropy spectrometry is used to study the electronic properties of sulfide-passivated GaAs. The optical technique allows measurement of the Fermi-level displacement at the surface in situ, while the sample is immersed into a sulfide solution. The kinetics of the process was found to be very sensitive to conductivity type and doping level in GaAs.
Formulation and solution of hyperbolic Stefan problem
Authors: Glass David E. , Necati Ozisik M. , McRae S. Scott , Kim W. S.
Published: July 2002

The interface condition for hyperbolic phase change problems, which includes sensible heat at the interface, is derived as an extension of the interface condition for standard parabolic phase change problems. The enthalpy formulation of the hyperbolic Stefan problem is presented and is used to numerically solve for the temperature distributions and the interface position. MacCormack’s predictor–corrector method is applied to solve the hyperbolic phase change problem and is validated by comparing the limiting case where the thermal relaxation parameter approaches zero to the parabolic phase change problem, in which the relaxation parameter is zero. Solutions with an applied surface temperature greater than the melt temperature are presented for two different Stefan numbers. It is noted that a discontinuity occurs at the phase change interface as well as at the thermal front.
Terawatt fiber pinch experiments
Authors: Kies W. , Decker G. , Mälzig M. , van Calker C. , Westheide J. , Ziethen G. , Bachmann H. , Baumung K. , Bluhm H. , Rusch D. , Ratajczak W. , Stoltz O. , Bayley J. M.
Published: July 2002

Pinch formation in fiber pinch experiments has been investigated in the lower terawatt regime. The main results are: (1) there are upper limits of breakdown voltage (∼700 kV) and current rise rate (∼20 kA/ns) beyond which leak discharges develop within the vacuum feed of the pulseline KALIF; (2) there is a lower limit of fiber radius (∼10 μm) below which pinch disruptions take place at a pinch current of ≳300 kA; (3) the hot (Te≤1 keV) inhomogeneous pinch plasma develops typically 10 ns after local collapses (micropinches) at a pinch current ≳400 kA and lives for more than 50 ns; (4) neutron emission (yield of CD2 fibers ∼1010) appears mostly isotropic; (5) all fiber pinches show global expansion with velocities reaching from typically 10 μm/ns (initial expansion) to ≳100 μm/ns; and (6) the power requirements for the fiber ablation process are contradictory to those for the final pinch phase.
Shock and release wave properties of yttria-doped tetragonal and cubic zirconia
Authors: Grady D. E. , Mashimo T.
Published: July 2002

Velocity interferometry diagnostics are used to monitor transmitted compressive shock and release waves in yttria (Y2O3)-stabilized tetragonal and cubic zirconia. In tetragonal zirconia compressive yielding due to lattice slip or lattice instability is observed at 13–17 GPa and again at 30–31 GPa. This represents an additional fine structure to the dynamic compression of zirconia that has not previously been observed. A correlation with initial sample density is seen for the lower-amplitude yield. A single yield over the range of the data occurs at 5–6 GPa for cubic zirconia. Approximately 4%–6% porosity in the cubic zirconia accounts for initial yield somewhat lower than earlier studies. From unloading wave profile measurements, initial release wave velocities at the Hugoniot state and stress derivatives of these data are determined. Release moduli data increase monotonically over a Hugoniot stress range of 11–45 GPa. A stress derivative of this data of K′l = 1.85 is obtained. Stress derivatives determined directly from the initial release slope of individual profiles are significantly higher and suggest deformation or phase transformation kinetics on release. Release waves from Hugoniot states of 11–13 GPa suggest formation of a rarefaction shock and may imply a dynamic stress-induced transformation not indicated by the shock profile. A tensile spall strength of 1.6 GPa was determined for the tetragonal zirconia. This high value may be related to the large fracture toughness of this transformation-toughened ceramic.
Scattering loss characteristics of selenide-based chalcogenide glass optical fibers
Authors: Katsuyama Toshio , Satoh Shin , Matsumura Hiroyoshi
Published: July 2002

Scattering loss characteristics of Ge-Se binary chalcogenide glass optical fibers are investigated. It is found that there is a strong correlation between the wavelength-independent scattering loss and the absorption caused by H2O impurities. Therefore, the amount of H2O impurity mainly determines the wavelength-independent loss of these optical fibers. After removing the H2O impurity and adjusting the fabrication conditions, the transmission loss is less than 1 dB/m over a wide infrared wavelength region of 2–8.5 μm, except for a small peak at 4.5 μm.
Calorimetric and morphological studies of mechanically alloyed Al-50 at. % transition metal prepared by the rod-milling technique
Authors: Sherif El-Eskandarany M. , Aoki Kiyoshi , Suzuki Kenji
Published: July 2002

The mode of amorphization and crystallization of mechanically alloyed Al-TM (TM; Zr, Nb, and Ta) has been studied by means of differential thermal analysis, differential scanning calorimetry, optical metallography, scanning electron microscopy, and transmission electron microscopy. The mechanical alloying process via the rod-milling technique is classified into three stages of milling. At the early stage of milling, the elemental powders of Al and TM are grown to form layered-composite particles of a larger diameter as a result of cold welding. At the intermediate stage, a complete crystalline-to-amorphous transformation occurs at around 700 K, by heating the well-arranged layered particles in a differential thermal analyzer under an Ar atmosphere. This transformation occurs due to a thermally assisted solid-state amorphization between the layers of the elemental starting material in the composite particles. At the final stage of milling, an amorphous phase is formed by the mechanical driving force which is generated by the rods. The amorphization and crystallization properties of Al-50 at. % TM alloys are presented.
Using reverse bias currents to differentiate between bulk degradation and interfacial degradation in hydrogenated amorphous silicon p-i-n structures
Authors: Arch J. K. , Fonash S. J.
Published: July 2002

The ‘‘analysis of microelectronic and photonic structures’’ (amps) transport-simulation computer program has been used to show that a distinction can be made between the effects of light-induced bulk and interfacial degradation in hydrogenated amorphous silicon (a-Si:H) p-i-n detector and solar cell structures. Using reverse bias leakage (dark) currents, amps simulations show that, for p and n layers that do not allow significant injection of electrons and holes into the intrinsic layer of the p-i-n structure, a light-induced increase in the density of interfacial states will result in significantly different changes in the voltage behavior of the reverse bias dark currents than will a corresponding increase in the density of bulk defect states. This communication demonstrates that a careful study of the reverse bias dark currents can provide an excellent means of determining if light soaking of a-Si:H p-i-n devices results in bulk degradation, interfacial degradation, or both.
Degradation of mobility in neutron irradiated GaAs by the increased scattering from multiply charged ionized defects
Authors: Patel J. U. , Williams J. G. , Stillman G. E.
Published: July 2002

Mobility changes were measured at temperatures from 15 to 305 K in n-GaAs van der Pauw samples irradiated by fast reactor neutrons. The inverse mobility values, obtained from the variable temperature Hall measurements were fitted using the relation μ−1=AT−3/2+BT3/2. The inverse mobility was found to increase as a result of neutron irradiations over the whole range of temperature; the increase is attributed to the increased scattering from neutron induced charged defects. The values of A found by the least square fitting were used to estimate the increased scattering effect from neutron-induced ionized defects after each step of irradiation. It is concluded that in order to explain the experimental results presented here, the creation of multiply charged defects must be considered.
Probe diagnostics of non-Maxwellian plasmas
Authors: Godyak V. A. , Piejak R. B. , Alexandrovich B. M.
Published: July 2002

Various probe diagnostic methods have been applied to rf plasmas with non-Maxwellian electron energy distribution functions (EEDF) and the results of these diagnostic methods have been compared. Plasma density and electron temperature were obtained using standard procedures from the electron retardation region (classic Langmuir method), the ion saturation region, and the electron saturation region of the measured probe I/V characteristic. Measurements were made in a 13.56-MHz capacitive argon rf discharge at two gas pressures: p=0.03 Torr, where stochastic electron heating is dominant, and p=0.3 Torr, where collisional electron heating dominates. Thus, the measured EEDF at each gas pressure manifests a distinct departure from thermodynamic equilibrium being bi-Maxwellian at 0.03 Torr and Druyvesteyn-like at 0.3 Torr. Considerable differences in electron density and temperature were obtained from the different parts of the probe characteristic and these values differ dramatically in many cases from those found from integration of the measured EEDF’s, thus demonstrating that using standard procedures in non-Maxwellian plasma can give misleading results.
Spectrally dispersed amplified spontaneous emission for improving irradiation uniformity into high power Nd:glass laser system
Authors: Nakano H. , Tsubakimoto K. , Miyanaga N. , Nakatsuka M. , Kanabe T. , Azechi H. , Jitsuno T. , Nakai S.
Published: July 2002

An amplified spontaneous emission (ASE) from Nd:glass has been introduced into the high power twelve beam Nd:glass laser system, Gekko XII for obtaining smooth intensity distribution of a focused beam. The angular dispersion of an ASE spectrum with large beam divergence was adopted for efficient beam smoothing without significant reduction of the harmonic conversion efficiency. Temporal evolution of the beam smoothing was evaluated as a function of the beam divergence by using a statistical model of speckle. In Gekko XII, the spectral width and beam divergence of ASE were controlled in a range of 0.4 to 0.6 nm and 6 to 22 times diffraction limited, respectively. Final output energy of 1.3 kJ/beam in a 2.2 ns duration was demonstrated without significant gain reduction and spectral narrowing. The doubling efficiency of 50% was obtained at a low intensity region of around 0.3 GW/cm2 by matching the angular dispersion of spectrum to that of phase matching condition of a frequency conversion crystal. The speckle structures in the focused beam pattern measured at the equivalent target plane were greatly smoothed out due to the introduced angular dispersion of spectrum and the large beam divergence. The standard deviation of the intensity distribution of the focused beam pattern was estimated to be 3.3%.
Excitation efficiency in thin-film electroluminescent devices: Probe layer measurements
Authors: Benoit J. , Barthou C. , Benalloul P.
Published: July 2002

The study of the excitation efficiency ηexc on thin-film electroluminescent devices with special semiconductor layer—a very thin probe-doped layer located at different part of the pure ZnS layer—has proved that ηexc is not homogeneous across the active layer. Moreover, this variation of ηexc depends on the amount of the transferred charge. At high excitation range, ηexc decreases continuously from the cathode toward the anode of the active layer. This behavior of ηexc is related to a space charge located in some part of the ZnS layer and generated by the energetic electrons. This space charge reduces the total efficiency of a conventional device when operating at high excitation range.
A new vector Preisach-type model of hysteresis
Authors: Adly A. A. , Mayergoyz I. D.
Published: July 2002

New isotropic vector Preisach-type models of hysteresis are introduced. These new models contain additional unknown functions. This presents the opportunity to incorporate more experimental data in the identification process than in the case of previously suggested vector Preisach models, thus leading to more accurate models. The solution of the identification problem is discussed and some results of experimental testing of these models are reported.
Annealing of ion implanted silver colloids in glass
Authors: Wood R. A. , Townsend P. D. , Skelland N. D. , Hole D. E. , Barton J. , Afonso C. N.
Published: July 2002

Silver colloids have been formed by ion implantation in float glass. Subsequent annealing methods alter the size distribution and optical reflectivity of the colloids. Furnace anneals and rapid flame heating convert large colloids into smaller units but excimer laser annealing appears to cause a dissolution of silver into the glass network.
Analysis of stress-induced void growth mechanisms in passivated interconnect lines
Authors: Bower A. F. , Freund L. B.
Published: July 2002

Simple theoretical models have been used to investigate four possible mechanisms of void growth in interconnect lines with a bamboo grain structure. The mechanisms considered are: creep deformation by dislocation motion; grain-boundary diffusion; diffusion along the interface between the line and the surrounding passivation; and void growth by lattice diffusion. The results show that all four mechanisms may cause the void to grow, but any one mechanism operating alone gives rise to slow or negligible rates of growth; however, plastic creep flow and grain-boundary diffusion may act in a cooperative manner, which causes rapid void growth. It is shown that the extent of coupling between diffusion and creep increases as the linewidth is reduced. Finally, the numerical calculations are used to estimate the time required for the line to fail, as a function of temperature and linewidth. The predictions are shown to be consistent with observations reported in the literature.
Interactions of wide band-gap single crystals with 248 nm excimer laser radiation. I. MgO
Authors: Webb R. L. , Jensen L. C. , Langford S. C. , Dickinson J. T.
Published: July 2002

The emission of charged and neutral particles from single-crystal MgO irradiated with pulsed 248 nm excimer laser light is studied by means of quadrupole mass spectrometry, time-resolved emission spectroscopy, luminescence spectroscopy, and scanning electron microscopy (SEM) observations. The role of the initial distribution of near-surface defects plus defects which result from repeated application of laser pulses is explored. This increase in defect density eventually leads to formation of a visible plume and rapid material vaporization. SEM observations after irradiation indicate that substantial surface fracture is present prior to the onset of rapid vaporization. Defect production during irradiation is attributed to mechanical processes involving deformation and fracture with accompanying dislocation motion. The accumulation of these defects increases laser absorption in the near-surface region resulting in rapid thermal etching and cluster emission.
Formation and decomposition of DO3 ordered structure in sputtered Fe-Al magnetic thin films
Authors: Miyazaki Masahiro , Sakemi Yoshikazu , Komatsu Takayuki , Matusita Kazumasa
Published: July 2002

Fe77.2Al22.8 and Fe70.5Al29.5 magnetic thin films with a thickness of 1 μm were prepared by a rf magnetron sputtering method, and the formation and decomposition of DO3 ordered structure, Fe3Al, were examined through x-ray diffraction analysis and conversion electron Mössbauer spectroscopy. The formation of DO3 ordered structure was confirmed in both films obtained by annealing at 500 or 600 °C. The DO3 ordered structure in the Fe77.2Al22.8 was unstable at temperatures above 700 °C, leading to the decomposition into α-Fe and FeAl.
The functions of Al in MnBiAlSi magneto-optical films
Authors: Huang D. , Zhang X. W. , Luo C. P. , Yang H. S. , Wang Y. J.
Published: July 2002

This article reports the effect of Al doping into MnBiSi films on the structure and magneto-optical properties of the parent. Under suitable Al doping, the x-ray diffraction peaks of (002) and (004) move to a larger 2Θ value related to that of MnBiSi. Moreover, two satellite peaks appear beside the main (002) and (004) peaks of MnBiAlSi. Such structural distortion due to Al doping results in an increased Kerr rotation angle, an effective perpendicular anisotropy constant Ku, as well as improvement of the thermal stability of MnBiSi.
Forward volume wave microwave envelope solitons in yttrium iron garnet films: Propagation, decay, and collision
Authors: Tsankov Mincho A. , Chen Ming , Patton Carl E.
Published: July 2002

Magnetostatic forward volume wave (FVW) microwave magnetic envelope solitons in 7.2 μm thick, single-crystal yttrium iron garnet films have been studied at 5.6–6.0 GHz. Rectangular input pulses with peak powers up to 3 W and pulse widths 5–50 ns were used. Single soliton output pulses with a characteristic increase in amplitude and pulse narrowing are observed when the power or width of the rectangular input microwave pulse exceeds threshold levels. Above these levels, output pulse peak power versus input power or pulse width exhibits a nonlinear increase and shows saturation effects. Multiple peak output profiles are observed for pulse powers and widths well above threshold. Solitons could be formed for all frequencies within the usable, low transmission loss portion of the magnetostatic FVW band. The use of reflected pulses from the film edge made it possible to study soliton decay and soliton collisions. The soliton decay rate was found to be approximately twice the linear rate, as expected from theory. The collision of solitons was found to occur with no significant change in shape and velocity. The various characteristic times from theory for pulse decay, pulse dispersion, nonlinear response, and propagation are found to be consistent with the experimental results.
Control of electrical conductivity in laser deposited SrTiO3 thin films with Nb doping
Authors: Tomio Takeshi , Miki Hidejiro , Tabata Hitoshi , Kawai Tomoji , Kawai Shichio
Published: July 2002

Nb-doped SrTiO3 (STO) thin films (Nb, 0<x<100 mol%) with a-axis orientation have been prepared on nondoped STO (100) and LaAlO3 (100) single crystals using a pulsed laser deposition technique. Solid-solution films are formed between STO and SrNbO3 without any impurity phases. Electrical conductivities of Nb-doped STO films can be controlled from 10−7 to 104 S/cm by changing the concentration of the doped Nb. Carrier concentration of the Nb-doped STO films also increases by increasing the Nb concentration.
Efficiency of photoluminescence and excess carrier confinement in InGaAsP/GaAs structures prepared by metal-organic chemical-vapor deposition
Authors: Diaz J. , Yi H. J. , Erdtmann M. , He X. , Kolev E. , Garbuzov D. , Bigan E. , Razeghi M.
Published: July 2002

Special double- and separate-confinement InGaAsP/GaAs heterostructures intended for photoluminescence measurements have been grown by low-pressure metal-organic chemical-vapor deposition. The band gap of the active region quaternary material was close to 1.5 eV, and the waveguide of the separate-confinement structures was near 1.8 eV. Measurement of the integrated luminescence efficiency at 300 K has shown that over a wide range of excitation level (10–103 W/cm2) radiative transitions are the dominant mechanism for excess carrier recombination in the active region of the structures studied. As determined by spectral measurements, the excess carrier concentration in the waveguide of the separate-confinement heterostructures and the intensity of the waveguide emission band correspond to a condition of thermal equilibrium of the excess carrier populations in the active region and the waveguide. The ratio of the intensity of the waveguide emission to the active region emission fits a model which assumes that the barrier height for minority carriers (holes) is equal to the difference in band gaps between the active region and the waveguide region.
Interface structure and perpendicular magnetic anisotropy in Pt/Co multilayers
Authors: Bertero G. A. , Sinclair R. , Park C.-H. , Shen Z. X.
Published: July 2002

Pt/Co multilayers sputter-deposited in Ar and Xe ambients, and periodic multilayers composed of specific combinations of Pt, Pd, and Co layers, were grown to study the effects of energetic backscattered Ar neutrals on the interface structure. The effects were correlated with the magnetic and magneto-optical properties with emphasis on the perpendicular magnetic anisotropy, K⊥. Films were characterized by high-resolution transmission electron microscopy, x-ray diffraction including grazing incidence geometry, and magnetic circular x-ray dichroism techniques as well as by standard magnetic and magneto-optic methods. It is found that the perpendicular magnetic anisotropy is extremely sensitive to the degree of intermixing, sharp interfaces yielding the largest anisotropy. The three to fourfold difference in K⊥ found between Ar and Xe sputtered films can be directly correlated to the magnitude of the orbital moment contribution 〈LZ〉 in the Co. This orbital contribution is found to be strongly sensitive to the interface sharpness in the films.
Effect of H2 dilution on the growth of low temperature as-deposited poly-Si films using SiF4/SiH4/H2 plasma
Authors: Kim Sung Ki , Park Kyu Chang , Jang Jin
Published: July 2002

We have studied the effect of H2 dilution on the growth of polycrystalline silicon (poly-Si) using SiF4/SiH4/H2 by a remote plasma chemical vapor deposition. With an increase of H2 dilution ratio the grain size decreases and the polycrystalline fraction increases, probably due to enhancement of the nucleation rate with H2 flow rate. We have deposited polycrystalline silicon films with a crystalline fraction of 89% at a substrate temperature of 330 °C. The peak of the deconvoluted Raman spectrum contributed from the microcrystalline (or amorphous) Si portion in the deposited poly-Si film increases and the full width at half maximum decreases with increasing H2 flow rate.
In situ scanning electron microscope comparison studies on electromigration of Cu and Cu(Sn) alloys for advanced chip interconnects
Authors: Lee K. L. , Hu C. K. , Tu K. N.
Published: July 2002

A high-resolution in situ SEM (scanning electron microscope) has been configured for real time comparison studies of the electromigration characteristics of Cu and Cu(Sn) alloys. Drift velocity test structures were fabricated and used to simulate the Cu line/W via structure in the multilevel interconnects. Electromigration comparison testings were carried out over a temperature range of 250 to 450 °C and current density of 5×105 to 2.1×106 A/cm2. Under these test conditions, the measured electromigration activation energy for Cu, Cu(0.5 wt %Sn), Cu(1.0 wt % Sn), and Cu(2 wt % Sn) are 0.73, 0.95, 1.25, and 1.14 eV, respectively. The measured critical length for Cu and Cu(Sn) alloys are ≂2.5 μm at a current density of 2.1×106 A/cm2. The observed average drift velocity of Cu mass transport in Cu(Sn) alloys changes with the depletion of Sn atoms which were also found to move in the direction of electron current. Eventually, the Cu mass transport rate reaches a value comparable to that in pure copper test stripes. The measured resistivity values of the Cu(0.5 wt % Sn) and Cu(1 wt % Sn) using Van der Pauw test structures are 2.4 and 2.9 μΩ cm, respectively. In comparison with Cu and Al(Cu) device interconnects, Cu(Sn) alloys exhibits higher electromigration activation energy, good resistance to hillocks and void formation and comparable resistivity. These characteristics clearly indicate the fact that Cu(Sn) alloys are potentially good candidate for advanced device interconnect applications where high-current density and good electromigration resistance are required.
Photoluminescence study of electron tunneling transfer in coupled-quantum-well structures
Authors: Shimizu Naofumi , Furuta Tomofumi , Waho Takao , Tomizawa Masaaki , Mizutani Takashi
Published: July 2002

We have investigated the processes of electron tunneling between the first two states in asymmetric coupled-quantum-well structures using time-resolved photoluminescence spectroscopy. The rates of electron tunneling transfer from a wide to a narrow well are derived from the decay times of the photoluminescence from the wide well at various electric fields. It is confirmed that the transfer is enhanced at the electric-field value where the exciton energy in the wide well is equal to the electron energy in the narrow well. By analyzing the energy difference between the initial and final states in the transfer process, which can be measured as the energy difference between the direct and indirect recombinations at the maximum electron tunneling transfer rate, it is shown that this tunneling transfer process is closely related to interface roughness. The electron tunneling transfer rates obtained experimentally are compared with the intersubband scattering rates calculated taking various scattering processes into account and it is found that the tunneling rates are predominantly determined by interface roughness. Furthermore, the rate of tunneling transfer is found to decrease as the temperature increases from 3 to 40 K. This temperature dependence is discussed in terms of the exciton/electron population ratio in the wide well.
High field magnetic force microscopy
Authors: Proksch Roger , Runge Erik , Hansma Paul K. , Foss Sheryl , Walsh Brian
Published: July 2002

Magnetic force microscope (MFM) studies of high-density thin-film recording media have been performed in the presence of an applied magnetic field. In particular, the erasure behavior of bit transitions in the media have been investigated. For these studies a compact, high-field dc magnet has been constructed that fits the laser head of a Nanoscope III multimode microscope. Because of space constraints and concern over thermal drifts which could affect the stability of the MFM, a rotating permanent magnet was used instead of an electromagnet. The magnet is mounted in a yoke which guides varying amounts of flux to the sample. This was used to observe the erasure of bits in a magnetic hard disk. The applied field also magnetized the MFM cantilever, making it possible to magnetically characterize both the sample and the probe.
Harmonic response of near-contact scanning force microscopy
Authors: Chen G. Y. , Warmack R. J. , Huang A. , Thundat T.
Published: July 2002

One-dimensional harmonic oscillator theory was used to model tapping-mode atomic force microscope (TMAFM) operation in the near-contact region in the presence of gases and liquids. The force derivative of the tip-sample interaction changes the vibration amplitude and frequency at maximum amplitude of the cantilever. Additionally, the interaction is hydrodynamically damped by fluid motion around the tip and between the tip and the surface. Good agreement was found between theoretical and experimental amplitude as a function of height. For a sample-driven TMAFM operating in fluids, the cantilever can be very soft (spring constant ≪1 N/m) and operated at frequencies well above the fundamental. Under these conditions the cantilever and sample appear to act with a high spring constant, much like that used in a gaseous operation. The tip–sample interaction in the fluid is still mediated through the force derivative of the sample.
Carbon growth in diamond deposition on nickel studied in situ by soft x-ray emission spectroscopy
Authors: Johansson E. , Skytt P. , Carlsson J.-O. , Wassdahl N. , Nordgren J.
Published: July 2002

The initial stages of diamond growth on nickel have been studied by in situ electron-excited soft x-ray emission spectroscopy. The study has been able to clarify that the codeposition of ordered graphite at the substrate/film interface is due to carbon precipitation during the cooling-down period after the deposition. The possibility to follow a deposition process from the initial stages to the end with soft x-ray emission spectroscopy is also demonstrated.
Nanostructure fabrication via laser-focused atomic deposition (invited)
Authors: Celotta R. J. , Gupta R. , Scholten R. E. , McClelland J. J.
Published: July 2002

Nanostructured materials and devices will play an important role in a variety of future technologies, including magnetics. We describe a method for nanostructure fabrication based on the use of laser light to focus neutral atoms. The method uses neither a mask nor a resist, but relies on the direct deposition of atoms to form permanent structures. Since the atomic de Broglie wavelength is of picometer order, the size of structures produced is not significantly limited by diffraction, as in optical lithography. Lines as narrow as 38 nm full width at half maximum spaced by 213 nm have been produced and we have demonstrated the production of a two-dimensional array of dots. The highly parallel process of nanostructure formation and the intrinsic accuracy of the optical wavelength that determines structure spacing suggest a number of interesting applications, including calibration standards for various types of microscopy, lithography, and micromeasurement systems. Possible magnetic applications include the production of arrays of magnetic elements, laterally structured giant magnetoresistive devices, and the patterning of magnetic media.
Electrical conductivity in high-frequency plasmas
Authors: Lister G. G. , Li Y.-M. , Godyak V. A.
Published: July 2002

The electrical conductivity is an important parameter in understanding the mechanism by which power is coupled to a radio-frequency (rf) discharge plasma, as well as in determining the external electrical characteristics of the discharge. We present the results of computations of the resistive and reactive components of the collisional impedance of an argon plasma at 13.56 MHz. The plasma conductivity is computed from the two-term solution to the Boltzmann equation, and includes the velocity dependence of the electron collision frequency, as well as non-Maxwellian electron energy distribution functions. We compare these results with those obtained from the widely used classical expression for plasma impedance, in which the electron collision frequency is computed either in the dc or high frequency limit. Our results show that neither of the classical limiting expressions are adequate for discharge pressures in the range of few mTorr to a few Torr, which includes the region of operation for many rf discharges used in many applications of plasma technology. Further, the classical formula assumes that in the high-frequency limit the plasma reactance is due entirely to electron inertia. We demonstrate that the plasma reactance may be strongly influenced, and in some cases dominated, by electron collisions. Results are presented in graphical form, which are useful in evaluating the importance of these effects on the interpretation of experimental results and the modeling of rf discharges.
Generalized methodology for thermal diffusivity depth profile reconstruction in semi-infinite and finitely thick inhomogeneous solids
Authors: Mandelis Andreas , Funak Frank , Munidasa Mahendra
Published: July 2002

The formulation of a generalized expression for the thermal-wave field in an inhomogeneous finite-thickness solid on a homogeneous semi-infinite substrate is discussed. This is based on the Hamilton–Jacobi formulation of the thermal-wave problem [A. Mandelis, J. Math. Phys. 26, 2676 (1985)]. An algorithm to invert simulated photothermal frequency scan data in obtaining thermal diffusivity profiles using this expression is reported. The tolerance of this inversion procedure to noise in both simulated and experimental data is also discussed.