bluuebunny/crossref_metadata_2025 huggingface dataset:
Anode discharge mode and cathodic plasma state in high-current vacuum arcs
Authors: Toya H. , Uchida Y. , Hayashi T. , Murai Y.
Published: July 2002

Anode surface states and traces of the cathode spots after arcing of various anode discharge modes in vacuum have been studied in the current range of 5–20 kA. Spectroscopic measurements of the radial electron temperature profile in the cathode region, which is related to the distribution of the current density, have also been performed to investigate the cathodic plasma state of the arcs in the various anode modes. The arc of a half-wave sinusoidal current of 60 Hz was burned between a 60-mm-diam anode and a 30-mm-diam cathode spaced 4 mm apart. The electrodes were made of oxygen-free, high-conductivity copper. The cathode spots spread uniformly over the entire cathode and a uniform current density profile was obtained in the diffuse-arc mode. It was found, however, that the cathode spots bunch together and the current density profiles peak at the center of the discharge in the anode-spot mode. The cathode-spot bunching and the nonuniformity in the current density profile become significant with a sufficient increase in arc current to cause severe erosion of the anode. Another finding was that the cathode spots spread almost uniformly over the cathode while a nonuniform current density profile appears in the diffuse arc associated with the presences of the arc-voltage fluctuation and a slight anode melting, i.e., in which the transition to the foot-point mode has begun. The occurrence of current constriction in the arc without cathode-spot bunching will be briefly discussed.
Effect of thermal relaxation and low-temperature irradiation on the chemical short-range order of amorphous Zr-Fe alloys
Authors: Wecker J. , Freyhardt H. C. , Adrian H. , Klaumünzer S.
Published: July 2002

Amorphous Zr100-xFex ribbons have been produced by melt spinning in the composition range 20≤x≤43. The superconducting transition temperature Tc is used as a probe for studying structural changes in the zirconium-rich alloys. Modifications of the short-range order are controlled by sample composition, by annealing at temperatures below the crystallization temperature (relaxation), and by low-temperature irradiation with heavy ions. In contrast to amorphous Zr-(Cu, Ni, Co) alloys, the critical temperature Tc in the Zr-Fe system increases with increasing annealing temperature. Low-temperature irradiations, on the other hand, lead to a decrease in Tc, which levels off at a value identical for as-quenched and relaxed samples. The results are discussed on the basis of an association model. In the amorphous state, the iron-poor alloy decomposes into iron-rich associates (possibly with Zr2Fe stoichiometry) embedded in a superconducting matrix, slightly improverished in iron, which is described as a regular solution of the components. The composition dependence of the electrical resistivity and the Vickers hardness, as well as previous Mössbauer experiments, indicate the existence of two different associates for x>30, with concentrations of approximately 33 and 50 at. % Fe, respectively.
Amorphous diffusion barriers in Al-Si and Au-Si contacts
Authors: Hung L. S. , Colgan E. G. , Mayer J. W.
Published: July 2002

Coevaporated amorphous Co50Ta50 and Co50Mo50 alloys were investigated for applications as diffusion barriers in Al-Si and Au-Si metallization. The high-temperature stability of diffusion barriers has been found to be correlated with the thermodynamical driving forces for chemical reaction between the barrier constituents and their surroundings. Amorphous Co50Ta50 films react with Al overlayers at temperatures around 450 °C, much lower than the crystallization temperature. A TaAl3 layer interposed between the amorphous film and the Al overlayer provides an ideal scheme against degradation during high-temperature annealing. Amorphous Co50Mo50 alloys possess low mutual solubilities and unfavorable free energies for compound formation with Au; it thus remains intact and prevents the interaction between the Si substrate and an overlay Au film during thermal annealing at 550 °C. Degradation of the layered structure at localized points is observed and attributed to the presence of pinholes and other macroscopic defects in the amorphous film.
A framework for the kinetics of film growth under simultaneous doping conditions
Authors: Stassinos Elias C. , Lee Hong H.
Published: July 2002

A general framework for the kinetics of film growth is given for the codeposition of both host (semiconductor) and dopant species on the basis of the electronic effects of adsorbed species on the adsorption of the host and dopant species onto the doped crystal surface. Independent experiments can be carried out for the determination of the growth kinetics in an a priori manner. Simple analysis procedures are involved. The general framework is applied to the polycrystalline silicon growth in the presence of As, P, and B that was reported in the literature.
Growth of Pr-, NdxCe1−x-, and NdxCr1−x-pentaphosphate crystals
Authors: Kubota K. , Murai H. , Kanata T.
Published: July 2002

Nd-pentaphosphate crystals with Ce and Cr as diluents and Pr-pentaphosphate crystals were grown. These crystals were investigated by several spectroscopic measurements: optical absorption, x-ray diffraction, Raman scattering, etc. All rare-earth pentaphosphates have exactly the same crystal structure, but replacing the rare-earth ion by a transition-metal ion causes lattice deformation. Energy transfer from optically excited Ce3+ to Nd3+ was observed.
Schottky barrier diode on a submicron-thick silicon membrane using a dual surface fabrication technique
Authors: Lee Kevin , Silcox J. , Lee C. A.
Published: July 2002

The successful fabrication of a Schottky barrier diode on a 150-nm-thick single-crystal silicon membrane using a new dual surface technique is described. The cut-off frequency of the diode was calculated from the zero-bias capacitance and series resistance to be approximately 2 THz, which compares favorably with currently achieved values in GaAs. The advantages of the dual surface device fabrication technique pioneered in this paper are noted.
All refractory Nb/Yb-YbOx/Nb Josephson junction
Authors: Morohashi Shin’ichi , Hasuo Shinya
Published: July 2002

A new all refractory Josephson junction, in which Yb oxide is used as a tunneling barrier, has been fabricated by the self-aligned contact process. The heat formation energy of Yb oxide is higher than that of Al oxide. It is expected that a junction with Yb oxide would be more stable than one with Al oxide. The obtained current-voltage characteristic is Vm=15 mV at the critical current density jJ=1500 A/cm2. Its dielectric constant and barrier height are compared with Al oxide.
Shape-dependent effects on an electromagnetic pulse propagating in a lossy plasma
Authors: Patterson J. M. , Robiscoe R. T.
Published: July 2002

We develop a theory describing the propagation of an electromagnetic pulse propagating in one dimension through a medium of essentially arbitrary conductivity and polarizability. An integral solution for the pulse amplitude is obtained by means of the slowly varying envelope approximation. Within the limits of this approximation (which requires linear coupling of the pulse to the medium, smooth variation of the pulse envelope, and pulse widths large enough to contain many cycles of the pulse carrier frequency), our solution is quite general, and it allows relatively easy comparison of the evolution of various pulse shapes as they travel through the medium. We apply the theory to an analysis of a pulse propagating in a lossy plasma, and show that among pulses with similar initial widths and energies, the initial pulse shape can have significant effects on the subsequent pulse distortion, broadening, and energy transport. Specifically, for a lossy plasma, we find that the pulse energy transport is enhanced for pulses which are initially well localized about a central maximum.
Photoluminescence determination of effects due to In in In-alloyed semi-insulating GaAs
Authors: Yu P. W. , Walters D. C. , Mitchel W. C.
Published: July 2002

Photoluminescence measurements at 2 and 2–40 K were made to study effects due to In alloying for InxGa1−xAs semi-insulating substrate materials grown by the liquid-encapsulated Czochralski method. The neutral CAs bound exciton is a good photoluminescence transition to determine a small variation of In composition in the range of 0≤x≤0.014. The band-gap reduction ΔEg (eV) can be expressed by −1.59x. The radial nonuniformity of In concentration and photoluminescence intensity were determined. The axial segregation of In was also analyzed with the help of the neutron activation analysis and spark-source mass spectrometry.
Measurement of interface states in palladium silicon diodes
Authors: Evans Howard L. , Wu Xu , Yang Edward S. , Ho Paul S.
Published: July 2002

In this paper we present the results of a forward-biased capacitance measurement on palladium silicon Schottky diodes. The data are interpreted in terms of the interface state density by taking into account the effect of series resistance and using Shockley–Read–Hall statistics. Exchange of charge between the metal and the interface states is included in the model. For the as-deposited sample, an effective state is postulated to lie opposite the metal Fermi level with a concentration of 1×1012/cm2. Upon annealing and formation of palladium silicide, the density of states decreases by a factor of 2 and changes occur in the capture and emission time constants.
Electrocathodoluminescence in insulator-bridged vacuum gaps under high-voltage stress
Authors: Jaitly N. C. , Sudarshan T. S.
Published: July 2002

The surface glow associated with Lucalox alumina insulator under high-voltage dc and ac stress in bridged vacuum gaps was determined to be a continuum radiation with band limits from about 220 to 500 nm with a peak around 320 nm. A second peak with very low intensity was observed at longer wavelengths. Such surface luminescence from other materials (including different types of alumina) bridging the vacuum gap was either absent or too weak to be analyzed. There is ample evidence to support the view that the observed glow with Lucalox (99.9 wt. % Al2O3) is associated with electronic transitions between quantum-mechanical states at defect sites (either interstitial atoms or vacancies) in the crystal structure of Al2O3. These defect sites are either the F+ centers (one electron trapped at an anion vacancy, i.e., Al2+ ion) or the F centers (two electrons trapped at an anion vacancy, i.e., Al+ ion). The results of this investigation indicate that the observed luminous front along an insulator surface in vacuum, prior to flashover, is not necessarily indicative of a streamer-type discharge development in the gas phase, desorbed from the insulator surface. Such a luminous front is indicative of electronic transitions at defect sites located at or near the insulator surface.
Remote plasma-enhanced chemical-vapor deposition of epitaxial Ge films
Authors: Rudder R. A. , Fountain G. G. , Markunas R. J.
Published: July 2002

Epitaxial Ge films have been deposited at 300 °C using a remote plasma-enhanced chemical-vapor deposition technique where metastable He atoms flow downstream from the plasma region to dissociate GeH4 molecules into deposition precursor species. Ge epitaxy is demonstrated on Ge(111), Si(100), and GaAs(111)Ga face substrates. An in situ cleaning process that involves a moderate thermal bake at 300 °C and a hydrogen plasma etch of the native oxides is integral to the process. Reflection high-energy electron diffraction is used to examine surface quality just prior to and after deposition. Uniform integral order diffraction streaks and fractional order reconstruction features observed from the Ge epilayers indicate that high quality Ge epitaxial layers can be grown using remote plasma-enhanced chemical-vapor deposition.
Influence of immiscibility in liquid-phase epitaxy growth of InGaPAs on GaAs
Authors: Kondo Masahiko , Shirakata Sho , Nishino Taneo , Hamakawa Yoshihiro
Published: July 2002

The liquid-phase epitaxy (LPE) growth of InGaPAs grown on (100) GaAs substrate has been studied under various growth conditions over the whole solid composition range. It has been found that the degree of supercooling less than 5 °C is necessary to successfully grow InGaPAs LPE layers in the composition region influenced by immiscibility, and that the extraordinary broadening of their photoluminescence spectra is attributed to a large number of defects and dislocations included in them. The role of the elastic energy induced from a substrate is discussed on a basis of the experimental results of the InGaPAs LPE growth on GaAs. The degree of immiscibility is also discussed using the regular solution approximation.
Interface state generation associated with hole transport in metal-oxide-semiconductor structures
Authors: Boesch H. E. , McLean F. B.
Published: July 2002

The buildup of interface states in Al–SiO2–Si metal-oxide-semiconductor capacitors following exposure to pulsed electron-beam irradiation has been previously shown to be a two-stage process. In the present work, we further examined the buildup by varying the field across the oxide during the early (10−6–1 s) stage. The number of interface states that eventually result from irradiation is found to depend primarily upon the electric field present in the oxide while the radiation-generated holes are transporting through the oxide and not upon the field present while the electron-hole pairs are being created (during the radiation pulse). The results indicate that the holes are primarily responsible for the interface state buildup and imply that they initiate interface state production during the transport stage by generating or activating a precursor state or species in the oxide.
Semiempirical stopping power equation for positrons
Authors: Pal P. B. , Varshney V. P. , Gupta D. K.
Published: July 2002

A semiempirical equation for the total stopping power for positrons in elements, compounds, and alloys has been found which is valid in the energy region from 0.01 to 1000 MeV. Values of the total stopping power obtained by the present approach are in good agreement with the theoretical values recently reported by Berger and Seltzer [National Bureau of Standards Internal Report No. 82-2550-A (1982)] within a 5% discrepancy.
Study of InP surface treatments by scanning photoluminescence microscopy
Authors: Krawczyk S. K. , Garrigues M. , Bouredoucen H.
Published: July 2002

Spatially resolved photoluminescence (PL) measurements are used to study the effect of etching (HF, HNO3, NH4OH, H2O2) and annealing of InP surface. We reveal a strong nonuniformity of the PL intensity on a microscopic scale and a large dependence of the morphology of the PL images on chemical treatment and annealing of InP samples.
Patterned implanted buried-oxide transistor structures
Authors: Kamins T. I. , Marcoux P. J. , Moll J. L. , Roylance L. M.
Published: July 2002

Metal-oxide-semiconductor field-effect transistors have been fabricated with a buried-oxide layer implanted under only the source and drain regions. Tungsten selectively chemically vapor deposited over the polycrystalline-silicon gate electrode limited the oxygen-implanted area and provided a self-aligned structure. The surface of the source and drain regions was raised above that of the channel by the implanted oxide. The buried oxide formed under the source and drain regions joined smoothly with the surrounding field oxide. Some additional oxide was formed beneath the thermally grown field oxide by the implanted oxygen, and significant field oxide appears to have been removed by sputtering during the implantation. A simplified, nonoptimum, transistor-fabrication process produced depletion-mode, n-channel devices which exhibited transistor action.
Nanosecond hydrogen flashlamp: Spectral and temporal characteristics from the vacuum ultraviolet to the visible red
Authors: Fuchs C. , Henck R.
Published: July 2002

A flashlamp of the relaxation type with dissymmetrical thoriated tungsten electrodes is described for generation of intense electrical and light pulses of width as short as 1 ns at high repetition rates. Comprehensive data on the dependence of emission spectra, intensity, and pulse shape on operating parameters as pressure, electrode gap distance, and polarity are presented. The results provide a useful guide for users as well as information on the physics of low ionized plasmas.
Auger electron spectroscopy study of GaAs layer growth on InP substrate
Authors: Matsui Y. , Hayashi H. , Yoshida K.
Published: July 2002

A new procedure for molecular-beam epitaxy growth is proposed in order to obtain a flat atomic layer without surface steps. The adsorption and desorption of Ga atoms on an InP substrate were studied by measuring the Auger electron peak intensities. It was found that the excess Ga atoms (surface steps) on the first monolayer of GaAs could be removed by annealing at an appropriate temperature. In addition, a new surface-cleaning procedure for an InP substrate is described.
Influence of defects on photoluminescence of InSe
Authors: Imai Kazuaki , Suzuki Kazuhiko , Haga Tetsuya , Abe Yutaka
Published: July 2002

Spatial distribution of defects near the cleaved surface of InSe is determined by means of the ion-channeling technique. The luminescence spectra of InSe crystals with low defect concentration show three lines above 1.330 eV at 14 K. The specimens with high defect concentration show broad emission peaks at around 1.32 eV.
Optics of twisted nematic and supertwisted nematic liquid-crystal displays
Authors: Leenhouts F. , Schadt M.
Published: July 2002

For the first time calculations of the off-state transmission of twisted nematic liquid-crystal displays (LCD’s) are presented which exhibit twist angles greater than the conventional 90 °. The transmission has been calculated using a treatment introduced by Priestley. In addition, the CIE (Commission Internationale d’Eclairage) color coordinates were evaluated which, together with the brightness, determine the optical appearance of an LCD. The finite efficiency of the polarizers was taken into account. The results are compared with those obtained for conventional 90 ° twisted nematic LCD’s. From the calculations follow the conditions required to obtain optimal contrast and steep electro-optical characteristics in 180 ° supertwisted LCD’s designed for high information content applications.
Temperature dependence of 1/f noise in silicon
Authors: Luo J. , Love W. F. , Miller S. C.
Published: July 2002

Results of 1/f noise measurements in n-Si and p-Si between room temperature and liquid-nitrogen temperature are presented. The temperature dependence of the noise in the n-Si samples appears fairly complex, and it does not appear that one can find a simple model to explain it. Two different heat treatments of p-type samples were used. In those treated at 950 °C the noise declines with increasing reciprocal temperature in a manner similar to that found by other investigators. For p-type samples treated at 550 °C the noise at room temperature is two orders of magnitude smaller than for the high-temperature samples and the temperature dependence is much smaller.
Aspects of thermal activation theory and applications to the Josephson effect
Authors: Cristiano R. , Silvestrini P.
Published: July 2002

The problem of the thermal induced escape of a Brownian particle from a metastable state is studied in the overdamped limit by the first-passage time technique. It provides an extension of Kramers’ results to the case of an energy barrier U0 close to the thermal energy kT. Differences between this approach and that of Kramers for low barrier energy are quantified in the specific example of a Josephson junction. In the case of periodic potential and stationary conditions, our calculations reproduce the results by Ambegaokar and Halperin. This approach can also be applied to the case of an rf SQUID.
Spin reorientation in NdDyFe14B
Authors: Yelon W. B. , Foley B. , Abache C. , Oesterreicher H.
Published: July 2002

NdDyFe14B shows a spin reorientation around TS =92 K which is lower than that obtained for Nd2Fe14B (150 K). Neutron diffraction on powder specimen indicates a preferential occupation for Dy atoms of the 4 f sites, but does not reveal the spin reorientation.
Schottky-barrier field-effect transistors of 3C-SiC
Authors: Yoshida S. , Daimon H. , Yamanaka M. , Sakuma E. , Misawa S. , Endo K.
Published: July 2002

Schottky-barrier field-effect transistors have been fabricated first from 3C-type SiC. Al-doped p-type and nondoped n-type 3C-SiC epilayers were successively grown on p-type Si substrates by chemical vapor deposition. Au and Al electrodes were used for Schottky-barrier gate contacts and ohmic (source and drain) contacts for n-type SiC. Transistor operation was observed for the first time for the field-effect transistors of 3C-SiC.
Raman spectroscopy of liposomes exposed to millimeter waves
Authors: Furia Luciano , Gandhi Om P. , Benner Robert E. , Hill Douglas W.
Published: July 2002

Several biological effects resulting from exposure to millimeter waves have been reported. In an attempt to determine if millimeter waves might affect the conformational state of membranes, sonicated liposomes have been irradiated with millimeter waves at 41.650 GHz, stabilized in frequency to ±50 Hz. Raman spectra from the lipid vesicles were then collected in the conformational and in the C-H stretching region. No changes in either the Raman peak locations or relative intensities were detected upon millimeter-wave irradiation, either below or above the transition temperature of the phospholipid (41 °C).
Preparation and characteristics of the TlBr-TlI fiber for a high power CO2 laser beam
Authors: Ikedo Masaru , Watari Masafumi , Tateishi Fumikazu , Ishiwatari Hiromasa
Published: July 2002

The TlBr-TlI (thallium bromoiodide) crystal and its fiber preparation method were studied in order to develop a high power CO2 laser beam fiber. As a result of this study, the most preferable composition for the fiber was determined to be 42 wt. % TlBr. The fiber (0.5 mm in diameter and 1.5 m in length) at that composition had the following excellent characteristics: (1) a high output power of 138 W (70 kW/cm2), (2) a high total transmissivity of more than 93%/1.5 m, and (3) a bending radius of ultimate 3.5 cm.
Confinement of a potassium plasma in a spindle cusp magnetic field
Authors: Bosch R. A. , Merlino R. L.
Published: July 2002

The confinement properties of a low-β (average) potassium plasma produced by contact ionization in a spindle cusp magnetic field were investigated. In this configuration, ne≊108–1010 cm−3, Te≊Ti≊0.2 eV, and the ions are weakly magnetized. Electron and ion densities, space potentials, and plasma flow velocities were measured in the ring and point cusps. The leak width of the escaping plasma was measured over a wide range of magnetic field strengths and neutral pressures. The dependence of the leak width on neutral pressure and magnetic field strength is accounted for by a simple model in which the plasma streams out of the cusps along the magnetic field lines while diffusing across the magnetic field due to the combined effects of neutral-particle collisions and Bohm diffusion. Measurements of broadband plasma noise suggest the presence of ion acoustic wave turbulence.
Electron density measurements in a photoinitiated, impulse-enhanced, electrically excited laser gas discharge
Authors: Seguin V. A. , Seguin H. J. J. , Capjack C. E. , Nikumb S. K.
Published: July 2002

Measurements of the electron density within a photo-initiated, impulse-enhanced, electrically excited (PIE) laser gas discharge are presented. Ion current measurements were made using a single Langmuir electrostatic probe positioned within the laser discharge volume. Calculations of the electron density were made utilizing a thick-sheath analysis. The results indicate that the electron density increases by two orders of magnitude as the pulser power level is increased. In addition, the electron density was observed to decrease markedly as the dc discharge current was increased.
Selected-area liquid-phase epitaxy of iron garnet films applying local ion implantation of the substrate
Authors: Strocka B.
Published: July 2002

Selected-area liquid-phase epitaxy of garnet films has been achieved through local substrate damage caused by ion implantation before film deposition. Thus, patterning with a geometrical resolution of a few microns of some micron-thick epitaxial garnet films is possible. Film patterns are defined by ‘‘perfect’’ epitaxial film regions grown on unimplanted substrate areas and defective film regions where the substrate has been implanted before film deposition. The films produced consist either of imperfect monocrystalline film areas, film areas resulting from island growth, or of substrate areas without overgrowth. Application of the method to the growth of epitaxial (Gd,Bi)3(Fe, Ga,Al)5 O12 films permits local magnetic switching of the magnetization direction confined to ‘‘perfect’’ film regions without switching of the adjacent imperfect film area.
Electrical and metallurgical investigations of the metallization system: Si/PtSi/V/Al
Authors: Salomonsen G. , Olsen A. , Lo/nsjo/ O. , Finstad T. G.
Published: July 2002

Schottky-barrier diodes have been fabricated by evaporation of Pt on Si substrates followed by annealing at 500 °C to yield PtSi. Then V and Al were evaporated. The amount of oxygen intentionally incorporated in the V film during deposition was varied and the resulting effect on the diffusion barrier action of the vanadium film has been studied by I-V and C-V measurements of the diodes and by backscattering spectrometry of simultaneously prepared test samples. It is found that for V films with low oxygen concentrations annealing in the range 400–600 °C leads to the formation of VAl3 and subsequent barrier height change. For vanadium films containing 50-at. % oxygen there is no observable reaction between V and Al and the barrier height is preserved for annealing between 400 and 600 °C.
A note on the analysis of space-charge-limited current data
Authors: Jarman Richard H.
Published: July 2002

By reference to recent data on amorphous silicon, it is shown that the measurement of the temperature dependence of the current in the space-charge-limited regime leads to a determination of the trap density and distribution, and the product of the free-carrier mobility and density of extended states.
Deposition of the reactive metals Al and In onto sputtered and cleaved Hg1−xCdxTe surfaces
Authors: Davis G. D. , Beck W. A. , Niles D. W. , Colavita E. , Margaritondo G.
Published: July 2002

The interactions of the reactive metals Al and In with both cleaved and sputtered p-type Hg1−xCdxTe surfaces have been investigated using synchrotron radiation-induced ultraviolet photoelectron spectroscopy. The sputtered surfaces are depleted of a fraction of their Hg (∼25% and ∼40% for x=0.21 and x=0.28 material, respectively, relative to the Hg found on the corresponding cleaved surfaces) and are more inverted than the cleaved surfaces with the Fermi level higher in the conduction band. During metal deposition, the cleaved and sputtered surfaces behave similarly: in the initial stages, the metal reacts with the HgTe alloy component to form a metal telluride and Hg, which leaves the surface region. At the same time, the inverted surface becomes more degenerate. After the metal has reacted with all the available HgTe within a certain surface region, an unreacted metallic film grows on the surface. Such identical behavior of the two types of surfaces is explained by the large difference in thermodynamic stability between HgTe and the metal tellurides.
Perpendicular and longitudinal magnetic properties and crystallographic orientation of Co-Cr film
Authors: Tsumita N. , Shiroishi Y. , Suzuki H. , Ohno T. , Uesaka Y.
Published: July 2002

The magnetic properties and the c axis orientation of Co-Cr thin films deposited on various substrates with concentrations of 0–20 at. % Cr are investigated. The intermediate layer of C,5 nm thick, between the substrate and Co-Cr layer is found to bring a great improvement in the c-axis orientation toward the normal of the film plane, a situation suitable for perpendicular recording. On the other hand, the thicker the underlayer of Cr, the better the c-axis orientation and a higher coercivity in the film plane is realized; this is suitable for longitudinal recording.
Thermomagnetic analysis, annealing effects, and Cr distribution in CoCr sputtered films
Authors: Snyder J. E. , Mountfield K. R. , Kryder M. H.
Published: July 2002

Thermomagnetic analyses (TMA) of rf-sputtered CoCr films have shown unusual magnetization versus temperature behavior. On heating, magnetization persists to around 700 °C. After cooling from 800 °C, however, magnetization does not appear again until around 300 °C. On all subsequent heatings and coolings, such films retain a Curie temperature of around 300 °C. At the same time, room-temperature Ms values decrease considerably. TMA of bulk samples of the same composition show a Curie temperature around 300 °C and no subsequent change of Curie temperature upon heating and cooling. These data cannot be explained on the basis of Cr-rich oxide formation. Additional experiments have ruled out Cr segregation in a planar transition layer. X-ray and electron diffraction measurements have shown no evidence of long-range order-disorder phenomenon. However, the data are consistent with explanations involving either Cr grain-boundary segregation or atomic-scale redistribution of the Cr. A simple model of grain-boundary segregation has been developed which predicts the expected relationship of average composition and Cr-rich grain boundary width. Minimum widths and minimum composition differences can be calculated.
Quantum effects in magnetic pickup at high-areal storage densities
Authors: Wohlleben D. , Pott R. , Eiling A.
Published: July 2002

This paper reports on a search for physical limitations of the inductive playback mechanism of magnetic recording at high-areal storage densities and high reading frequencies. Such a limitation is set by Johnson noise in the head wire material at about 108–109 bit/cm2 at room temperature. Cooling the head leads to a reduction of the head resistance, which goes far beyond classical expectation because of a quantum-size effect which becomes important when the mean free path of the wire material becomes larger than the wire diameter. At the same time the inductive pickup signal becomes a periodic function of the flux linked by the head with period Φ0/2, where Φ0=h/e is the quantum of flux. No (irreversible) inductive pickup signal can be expected at any temperature when the flux of a magnetic bit unit is less than Φ0/2, or at storage densities larger than 109–1010 bit/cm2.
Analysis of the field of the ferroelectric domain layer mode
Authors: Li Xingjiao
Published: July 2002

Theoretical analysis is made of the ferroelectric domain layer mode of the 180° ferroelectric domain structure. By starting from the general piezoelectric equation, a general dispersion relation of the ferroelectric domain layer mode is obtained and the dispersion curve of the ferroelectric domain layer surface wave for poled BaTiO3 ceramics is plotted. Analysis is done on why the wave velocity decreases with the increase in hk and it is suggested that the decrease of the wave velocity with the increase in hk in the same medium is due to ‘‘the combination-piezoelectric loading.’’ Still further analytic solution of ferroelectric domain layer mode is obtained. It is a combination of the hyperbola and exponential functions. When hk approaches zero or infinity, it degenerates into the equations of Bleustein–Gulyaev or Maerfeld–Tournois, i.e., the domain wall wave. The relationship of its amplitude of displacement versus hk, the space distribution of its amplitude of displacement, the relation of the amplitude of electric potential versus hk, and the space distribution of the amplitude of electric potential and the electric field are discussed in detail. The studying wave mode is not a mixture of the Bluestein–Gyulaev and Maerfeld–Tournois waves, but a new mode.
Observations of the thermalization of the neutralizing electrons in intense ion beams
Authors: Kraft R. , Kusse B. R.
Published: July 2002

Vacuum propagation of intense, pulsed ion beams relies on the existence of charge and current neutralization by electrons drawn into the beam channel by the electrostatic forces of the ions. We report here a set of measurements of the temperature of the neutralizing electrons and of the beam potential which support existing theories of the time and spatial development of the neutralizing space charge and current.
Conduction in illuminated GaAs/AlxGa1−xAs heterostructures. II. Calculation
Authors: McKinnon W. R. , Hurd C. M.
Published: July 2002

We describe a calculation of the effects of light on the dc conduction in n-type GaAs/AlxGa1−xAs heterojunctions. We treat the realistic case of a heterojunction with parallel conduction through both the 2D electron gas and the undepleted AlxGa1−xAs layer. We attribute persistent photoconductivity to thermally activated deep donors in the AlxGa1−xAs alloy, and we treat quantitatively the effects of continuous illumination of these deep donors. To obtain the corresponding effects on the 2D electron gas, we extend a calculation of Lee et al. [J. Appl. Phys. 54, 2093 (1983)]. We then combine these developments to produce for a general magnetic field state ( μB) a comprehensive model of the magnetoconductivity. This shows how varying the temperature, light intensity, magnetic field, or device parameters affects the carrier density and mobility for the heterojunction. In the companion paper [C. M. Hurd, S. P. McAlister, W. R. McKinnon, C. E. Falt, D. J. Day, C. J. Miner, and A. J. SpringThorpe, J. Appl. Phys. 61, 2244 (1987)], we use the model to interpret new results for GaAs/AlxGa1−xAs heterojunctions with x=0.2 and 0.3, and for Al0.3Ga0.7As alloys.
Energy levels of finite-depth quantum wells in an electric field
Authors: Fritz I. J.
Published: July 2002

Numerical calculations of energy levels and wavefunctions for a particle in a finite quantum well subject to an electric field are described. The calculations are restricted to the regime where the tunneling rate out of the well is small. In this regime the results are in good agreement with results of an approximate calculation wherein the finite well is replaced by an infinitely deep well whose width has been adjusted (separately for each level) to obtain the correct zero-field eigenvalue, as recently proposed for the ground state by Miller et al. [D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard, W. Wiegmann, T. H. Wood, and C. A. Burrus, Phys. Rev. B 32, 1043 (1985)]. Over a significant range of well depths and fields (which are the only variables, provided that appropriately normalized units are used), it is found that the difference between the approximate and exact eigenvalues can be accurately estimated from a simple empirical formula. These results should be useful in studies of electro-optic effects in semiconductor quantum-well structures.
Origin of anomalous increase in anisotropy field change for heavily ion-implanted magnetic bubble garnets
Authors: Imura R. , Sugita Y. , Suzuki R.
Published: July 2002

Effect of the growth-induced anisotropy field HKG has been investigated for the anomalous increase of the effective anisotropy field change Δ(Hk−4πMs) caused by annealing in heavily ion-implanted magnetic bubble garnets. In heavily implanted garnets, Δ(Hk−4πMs) increases with decreasing strain during annealing and does not follow the same curve that is obtained during implantation. The maximum difference in Δ(Hk−4πMs) between annealed and as-implanted samples corresponds to the value of Δ(Hk−4πMs) when the strain is reduced to zero by annealing. The anomalous increase is small in HKG-suppressed samples and is not observed in garnet films (YIG) without HKG. It is considered that the anomalous increase is due to suppression of the growth-induced anisotropy by heavy implantation. However, in the case of H+2 implantation the increase of Δ(Hk−4πMs) during the annealing process cannot be explained by the HKG suppression effect.
WSi0.11 Schottky gates for GaAs metal semiconductor field-effect transistors
Authors: Callegari A. , Spiers G. D. , Magerlein J. H. , Guthrie H. C.
Published: July 2002

Schottky gates for self-aligned GaAs metal semiconductor field-effect transistors (MESFETs) have been formed by dc magnetron sputtering of WSi0.11 onto sputter-cleaned GaAs surfaces. The WSi0.11/GaAs diodes showed good current-voltage and capacitance-voltage characteristics after annealing at 800 °C. Schottky barrier heights measured by current-voltage were φI-VB ≂0.73 eV with an ideality factor n≂1.14 for large diodes and φI-VB ≂0.67 eV with n≂1.3 for 1×10 μm gates without a self-aligned n+ implant. The n+ self-aligned implant was found to cause leakage current, which was interpreted as a parallel small-area, low-barrier diode at the gate edge. FETs formed with this gate material showed good threshold voltage uniformity with a standard deviation as low as 31 mV for 1 μm enhancement-mode FETs and 49 mV for 1 μm depletion-mode FETs on a 51-mm wafer.
Photoluminescence in strained InGaAs/GaAs superlattices
Authors: Dahl D. A. , Dries L. J. , Junga F. A. , Opyd W. G. , Chu P.
Published: July 2002

We present measurements and analysis of high-quality photoluminescence (PL) data from strained In0.13Ga0.87As quantum wells confined by unstrained GaAs barriers. Data were obtained from low temperature to room temperature on peak positions, intensities, and linewidth. The latter exhibits an unusual minimum at 31 K consistent with defect binding of excitons and one monolayer fluctuations in well size. The high-temperature linewidth agrees with that expected for phonon scattering. Peak positions show excellent agreement with a Kronig–Penny model augmented by a variational calculation of the n=1 bound-state energy of the heavy-hole exciton.
The origin of a highly resistive layer at a growth-interrupted interface of GaAs grown by molecular-beam epitaxy
Authors: Iimura Y. , Shiraishi T. , Takasugi H. , Kawabe M.
Published: July 2002

The origin of the formation of a highly resistive layer around a growth-interrupted interface in GaAs has been studied by capacitance-voltage carrier profiling and deep-level transient spectroscopy. It is concluded that the origin of the highly resistive layer is attributable to the formation of interface states created by exposure of the GaAs surface to air. The Fermi level at the interface is pinned in n-type GaAs, but is not in p-type GaAs.
Common parametrizations of electron transport, collision cross section, and dielectric strength data for binary gas mixtures
Authors: Van Brunt R. J.
Published: July 2002

Previously used parametrizations of dielectric strengths (electrical breakdown data) for gas mixtures in terms of electron collision and transport parameters are reviewed. A new method of fitting experimental data on dielectric strengths for binary electronegative gas mixtures is proposed based upon the principal assumption that the electron kinetic energy distributions in the gas are Maxwellian. The method provides physical insight into such behavior as pressure-dependent or pressure-independent synergisms, and is useful in checking the consistency between dielectric strength data and available information on electron transport and ionization, attachment, and momentum transfer collision cross sections. The method is applied here to the mixtures SF6/N2, CCl2F2/N2, and SF6/CCl2F2.
Improvement of two-dimensional electron gas concentration in selectively doped GaAs/N-AlGaAs heterostructures by atomic planar doping
Authors: Ishikawa Tomonori , Ogasawara Kazuto , Nakamura Tomohiro , Kuroda Shigeru , Kondo Kazuo
Published: July 2002

Atomic planar doping of Si into an AlGaAs layer was successfully applied to molecular-beam-epitaxially grown selectively doped GaAs/N-AlGaAs heterostructures in an attempt to improve the two-dimensional electron gas concentration. The dependence of the electron gas characteristics on the atomic-planar-doping conditions such as sheet doping density, spacer thickness, and substrate temperature was investigated. A thirty percent improvement in electron gas concentration, up to a value of 1.2×1012 cm−2, was achieved with almost the same mobility of 3.5×104 cm2/V s as in a conventional structure. Correspondingly, the characteristics of high electron mobility transistors, fabricated on such planar-doped GaAs/N-AlGaAs heterostructures, were also improved.
Improvement of amorphous silicon solar cells by electrochemical treatments
Authors: Matsumura Michio , Sakai Yuichi , Yae Shinji , Nakato Yoshihiro , Tsubomura Hiroshi
Published: July 2002

In the manufacturing process of amorphous silicon (a-Si:H) solar cells, leakage currents through the pinholes in the a-Si:H film often spoils its performance. We have demonstrated that two electrochemical treatments are effective for stopping the leakage through pinholes. One method is an electrochemical dissolution of the transparent conductive oxide exposed to the pinholes, and another is an electrochemical deposition of insulating materials in the pinholes. These effects have been confirmed by use of intentionally fissured a-Si:H electrodes as well as solar cells showing large leakage currents.
Effect of stress relaxation on polarization of InGaAsP buried heterostructure lasers by a repetitive temperature change
Authors: Yano M. , Kanno Y. , Ishikawa H. , Imai H.
Published: July 2002

This paper describes the effect of stress relaxation on the polarization of InGaAsP buried heterostructure lasers by means of a repetitive temperature change. We examine the change in the polarization ratio, TE mode power to TM mode power, under the repetitive temperature change. We find that the polarization ratio increases significantly for some lasers. This may be attributable to the relaxation of an external stress caused by bonding of the laser chip.
Optimizing hot-ion production from a gas-injected washer gun
Authors: McCarrick M. J. , Ellis R. F. , Booske J. H. , Koepke M.
Published: July 2002

This paper reports the results of a study to maximize the ion temperature of the plasma generated by a gas-injected washer gun. We characterize the gun discharge and the plasma output as a function of the controllable gun parameters. For hydrogen we find a maximum ion temperature of 100 eV with typical densities ranging from 2×1011 to 5×1012 cm−3. A primary feature of the pulsed gun discharge is the observation of large amplitude rf fluctuations on the cathode voltage. The fluctuation amplitude varies with discharge current and with the quantity of injected gas. We show that the scaling of the fluctuation level with gun parameters is in agreement with that expected of an unstable beam-plasma system. We find a linear relation between the square of the fluctuation amplitude and the product of the plasma density times the ion temperature of the plasma output nTi, suggesting a stochastic wave-induced heating mechanism.
Electrothermal breakdown: Solutions for the case of thermal resistance in the electrodes
Authors: O’Dwyer J. J. , Klemens P. G.
Published: July 2002

An exact solution is found for the critical voltage at a thermal instability corresponding to a particular model of a dielectric under high applied voltage and with thermal resistance in the electrodes. Other models that require approximate or computed solutions yield results that are very close to the analytic solution when appropriate dimensionless variables are chosen. The dimensionless critical voltage as a function of dimensionless critical thickness is shown to be almost independent of electrical and thermal conductivity parameters. It is also found that the solution for the thick limit applies in most cases of physical importance.
Cathodoluminescence, gain, and stimulated emission in electron-beam-pumped ZnCdSe
Authors: Khurgin J. , Fitzpatrick B. J. , Seemungal W.
Published: July 2002

Cathodoluminescence and lasing properties of ZnCdSe were studied over a wide range of temperatures and excitation conditions in a demountable CRT. Lasing was obtained in the range of wavelengths from yellow to red. Based on the results of the experiments, gain and absorption spectra under different conditions were calculated. The band-gap dependence on excitation density was studied and the results offered an explanation for the differences between dependencies of the threshold-excitation densities on penetration depth at different temperatures.
Electron irradiation effect on antimony doping of silicon 〈111〉 grown by molecular-beam epitaxy
Authors: Delage S. , Campidelli Y. , Arnaud d’Avitaya F. , Tatarenko S.
Published: July 2002

The effect of electron irradiation on the antimony doping levels in silicon molecular-beam epitaxy has been studied. For substrate temperatures in the 620–800 °C range, electron irradiation enhances the doping efficiency significantly. Sharp, well-defined profiles, high doping levels (up to 3×1019 cm−3) and high-quality epitaxial layers are obtained. Using a semiempirical model, a chart of the doping levels as a function of both the substrate temperature and antimony flux is developed. The influence of electron irradiation on the antimony adlayer is also discussed.
Surface acoustic wave parametric generation with pumping of light
Authors: Nakagawa Yasuhiko , Kawanago Satoru
Published: July 2002

The parametric interaction between the surface-acoustic wave (SAW) and semiconductor carriers performed by the pumping of light has been studied theoretically and experimentally. As a result, it was shown that, in the separated media-coupled semiconductor/piezoelectric structure, the coupling between the SAW and semiconductor carrier can be varied using the irradiation of light from the outside. It was also confirmed that, using the pumping of light, the SAW parametric generation can readily be excited. Furthermore, we have studied the applications of these phenomena to engineering, and have shown that by utilizing the SAW parametric generation the Fourier transform of the light beam pattern can be obtained.
Velocity of twinning partial dislocations in silicon
Authors: Yasutake Kiyoshi , Shimizu Shinji , Umeno Masataka , Kawabe Hideaki
Published: July 2002

The growth velocities of deformation twins in the tangential direction are measured in silicon single crystals by the four-point bending method for temperatures between 350 and 500 °C and for shear stresses τ between 80 and 550 MPa. Stress and temperature dependences of the twin growth are found to satisfy the same empirical power-law equation as that for the motion of slip dislocations. Comparing the velocity of twin growth with that of slip dislocations, it is found that the activation energy is not much different between them, but the stress dependence of the twin growth is larger than that of the slip dislocation. The latter fact relates to the twinning dominantly observed under the high-stress condition (τ>260 MPa). Referring to the subsequent paper [J. Appl. Phys. 61, ▪▪▪ (1987)], the velocity data in this report are representative of the velocity of individual twinning partial dislocations which move on the coherent twin boundary.