bluuebunny/crossref_metadata_2025 huggingface dataset:
Ground state spin excitations in HoAl2
Authors: Rhyne J. J. , Koon N. C.
Published: February 2003

Inelastic neutron scattering has been used to examine the spin waves in a single crystal of the cubic Laves-phase compound HoAl2, which orders at a TC=28 K. Three pairs of acoustic (in-phase spin precession) and optic (out-of-phase precession) modes were observed in their respective Brillouin zones centered at (220) and (002). Due to the weak Ho–Ho exchange all modes show relatively little dispersion (e.g., the lowest acoustic mode which exhibits a band width of 1.5 meV and a q=0 gap of 1.4 meV). Measurements were made at 4 K for spin waves propagating in three directions [q,q,0], [q,0,0], and [q,q,q]. The spectra showed significant anisotropy in the second half of each zone. The observed inelastic scattering modes have been analyzed using an RPA pseudo-boson formalism with crystal field and exchange parameters consistent with those found for other RAl2 compounds.
Disappearance of the magnetic relaxation in spin glasses
Authors: Salamon* M. B. , Tholence J. L.
Published: February 2003

We have studied the relaxation of the magnetization in the spin-glass phase of Fe10Ni70P20 and CuMn0.243%. Following zero field cooling the magnetization M(H,T,t) of spin-glasses increases quasilogarithmically with time t after applying a field H at t=0: M(H,T,t)=M(H,T,t=0)+S(H,T) ln t. The quantity S(H,T) has been studied for 30 s≤t≤1200 s below Tg, temperature of the ac susceptibility peak. For both systems S(H) increases almost linearly with H for a given temperature, reaches a maximum value Sm for Hm, then decreases and tends to zero for a field HM at least four times larger than Hm. For a given field, S(T) exhibits a maximum near Tg in low field. This maximum becomes higher, sharper and is displaced to lower temperatures for increasing field values. A line Hm∝(Tg-T)γ with γ=1.5 and 1.8 for CuMn and Fe70Ni10P20, respectively, is obtained. This line has a form similar to the de Almeida-Thouless line Hc=(Tg-T)1.5. However, Hm or HM are smaller by a factor 16 or 4 than the corresponding Hc value. The data for each sample, when scaled according to S/M(t=30 s), collapse onto similar curves when plotted as a function of H/Hm. This suggests some universal behavior of the magnetic relaxation in quite different spin-glasses.
Structural study of alloyed gold metallization contacts on InGaAsP/InP layers
Authors: Vandenberg J. M. , Temkin H. , Hamm R. A. , DiGiuseppe M. A.
Published: February 2003

Specific contact resistance of gold metallization on In1−xGaxAsyP1−y has been measured as a function of composition from InP to In0.53Ga0.47As. The alloy formation of the contacts was investigated in the temperature range 130°–550°C, using temperature dependent in situ x-ray diffraction. The thermodynamics of the solid state reactions are discussed. The electrical contact behavior can be explained in terms of the alloys which form at various temperatures. In the ternary Au/InGaAs/InP contact polycrystalline GaAs and a thin layer of Au3In2 form at lower temperatures (150°–250 °C) and remain stable up to 550 °C. This is consistent with the measured low contact resistance which is comparable to that of the Au/GaAs contact.
Superconducting microphone for photoacoustic spectroscopya)
Authors: Costa Ribeiro P. , Labrunie M. , Von der Weid J. P. , Symko O. G.
Published: February 2003

A superconducting microphone has been developed for photoacoustic spectroscopy at low temperatures. The microphone consists of a thin mylar membrane coated with a film of lead whose motion is detected by SQUID magnetometer. For the simple set-up presented here, the limiting pressure sensitivity is 7.5×10−14 atmospheres/Hz1/2.
A CCD image sensor and a microcomputer make magnetic domain observation clear and convenient
Authors: Shirae K. , Sugiyama K.
Published: February 2003

Laborious surface polishing has been inevitably necessary for domain observations of bulk magnetic materials by Kerr effect. We have made it possible to observe the magnetic domain without any surface polishing for bulk magnetic materials. A CCD (charge coupled device) image sensor and a microcomputer did the contrast enhancement and noise reduction. Domains in rapidly quenched amorphous magnetic materials have been observed clearly without any surface polishing.
Characterization of magnetic transistors
Authors: Lopez J. L. , Licini J. C.
Published: February 2003

Planar bipolar transitor devices can be made to sense magnetic fields when the operating point is at the onset of collector saturation. This paper reports the results of characterization of five such devices responding to 60 Hz magnetic fields. Magnetic sensitivity was found to be proportional to emitter current and reached a maximum of 0.92 mV/gauss. Output was directly proportional to input over the range of 0.58 to 580 gauss. Signal to noise ratio was 3.1 per gauss. Frequency response was observed to 1 MHz.
Vector potential formulation for three-dimensional magnetostatics
Authors: Kotiuga P. R. , Silvester P. P.
Published: February 2003

Three-dimensional magnetostatics problems, with no a priori assumptions about model geometry or topology, admit two vector potential formulations: the physical formulation which is a consequence of Maxwell’s equations, and an alternate formulation which includes the vector Laplacian formulation as a special case. The lack of uniqueness inherent in the physical formulation is computationally undesirable because numerical discretization may produce singular coefficient matrices. The alternate formulation, on the other hand, can yield a unique solenoidal vector potential and nonsingular finite element matrices. This alternate formulation also satisfies the physical formulation if the physical problem is well posed.
On the uniqueness of solution of magnetostatic vector-potential problems by three-dimensional finite-element methods
Authors: Mohammed O. A. , Davis W. A. , Popovic B. D. , Nehl T. W. , Demerdash N. A.
Published: February 2003

In this paper, particular attention is paid to the impact of finite-element approximation on uniqueness and to approximations implicit in finite element formulations from the uniqueness requirements standpoint. It is also shown that the flux density is unique without qualifications. The theoretical and numerical uniqueness of the magnetic vector potential in three-dimensional problems is also given. This analysis is restricted to linear, isotropic media with Dirichlet Boundary conditions. As an interesting consequence of this analysis it is shown that, under usual conditions adopted in obtaining three-dimensional finite-element solutions, it is not necessary to specify div Ā in order that Ā be uniquely defined.
Three-dimensional finite element solution of anisotropic complex potential problems
Authors: Konrad A.
Published: February 2003

Numerical solution methods for real conservative fields are abundant in the literature, but interest in complex potential problems has been very low. The author presents ideas that justify interest in complex scalar potentials. For instance, the ability to solve complex scalar potential problems is shown to be a prerequisite for the solution of general, three-dimensional, magnetic vector potential problems. As another example, the electromagnetic properties of dielectrics, semiconductors, and magnetic materials can be described by complex material property tensors. The electric or magnetic scalar potential distribution in such media may be obtained from the complex Laplace’s equation. The paper examines three-dimensional anisotropic complex potential problems and briefly describes a finite element formulation based on a brick-shaped, second-order, subparametric finite element. An example illustrates the method.
Three-dimensional solution of high-speed magnetic levitation problems
Authors: Nicolas A. , Sabonnadière J. C. , Silvester P. P.
Published: February 2003

The performance of magnetic levitation systems at cruising speeds may be approximated by their behavior at infinite speed. For the latter case, the field equations can be stated in terms of scalar potentials only, permitting decomposition of the three-dimensional boundary value problem into a set of two-dimensional problems. Each of the latter may be solved by a finite element method, leading to a cheap and flexible analysis.
A hybrid finite element–boundary element formulation of Poisson’s equation for axisymmetric vector potential problems
Authors: Salon S. J. , Peng J. P.
Published: February 2003

A previous paper1 has elaborated the virtues of combining the finite element method and the boundary element method, by allowing the user to select any region of the problem to be represented by finite elements or boundary elements. This ‘‘hybrid’’ method is now extended to axisymmetric geometries for vector potential problems. Examples are given for static field and for eddy current problems.
A simple interactive finite element processor for teaching purposes
Authors: Coulomb J-L.
Published: February 2003

The finite element method is now a standard numerical procedure for solving electric or magnetic fields. In this paper, we describe a simple interactive finite element processor used in a student environment to teach the finite element method, and its use in the design of electrical devices. This processor allows students to describe the main finite element concepts (mesh generation, region properties, boundary conditions) and to realise some numerical experiments in field computation. A particular attention is given to the influence of the finite elment discretization on the quality of the field solution. This processor is also a good introduction to CAD techniques. Students describe the device under study by means of interactive graphic procedures using a graphic display and digitizer. The canonical structure of the geometric and mesh data base is an example of the use of the modern concepts in data structures. The geometric structure chosen allows quick interactive modification of the representation of the device under study. Because this processor is especially built for teaching purposes, it is very easy to learn and to use. This point is very essential and will be developed in the full paper.
Near-zero magnetostrictive metallic glasses with very high saturation induction
Authors: Ramanan V. R. V.
Published: February 2003

The soft magnetic properties of a series of metallic glasses in the Co–Fe–Ni–Mn–B–Si system are described. These glasses have very low values for saturation magnetostriction (+5 to −1 ppm) and some of the highest values for saturation induction (1.1 to 1.3 T) reported for such glasses. Most importantly, the Curie temperture is lower than the crystallization temperature, thus allowing the use of easy, conventional annealing procedures for the optimization of the soft magnetic properties. Initial permeabilities in excess of 17 000 at 1 kHz may thus be achieved for optimal compositions within the system. These metallic glasses offer great promise for applications such as recording heads to be used in conjunction with high coercivity metal tapes.
Selectively thermalized sputtering for the direct synthesis of Sm–Co and Sm–Fe ferromagnetic phases
Authors: Cadieu* F. J. , Cheung T. D. , Aly S. H. , Wickramasekara L. , Pirich R. G.
Published: February 2003

Ferromagnetic films of the Sm–Co and Sm–Fe systems have been synthesized by sputtering onto substrates at temperatures above 600 °C so that the deposit is directly crystallized upon deposition. For the directly synthesized phases, high sputtering gas pressures were used so that the sputtered atoms transferred excess momentum to the sputtering gas atoms before arriving at the substrate. The object has been to promote the growth of possible metastable phases and to allow preferred orientation effects to be present in the films. Directly synthesized SmCo5 films grown by this method, showed a predominant (110) texture, for oxygen levels in the films of greater than about 6 at. %. As the oxygen incorporation level in the SmCo5 films was reduced to 1.4 at. % oxygen, only a (200) texture was observed. In Sm–Fe films with 6.5 at. % oxygen, a new metastable phase forms at the 1–5 composition. This oxygen stabilized metastable phase is not present in Sm–Fe films made with lower amounts of oxygen incorporation.
Effects of inhomogeneous regions on electric potentials and magnetic fields: Two special cases
Authors: Cuffin B. Neil
Published: February 2003

The effects of inhomogeneous regions on electric potentials and magnetic fields are compared for two special cases. The first case is for measurements far from the sources and inhomogeneous regions for which it is shown that the effects on both types of measurements are exactly the same. This means that both types of measurements contain the same information about the inhomogeneous regions. The second case is for the effects on measurements near a spherical inhomogeneous region. Equations are derived for the electric potentials and magnetic fields produced by dipolar sources near an inhomogeneous sphere. These equations show that the effects on the two types of measurements are generally the same. A sphere whose conductivity is less than the rest of the volume conductor decreases the potentials and fields of sources perpendicular to the sphere, but increases the potentials and fields of sources tangential to it; a sphere with greater conductivity has the opposite effects. The relative amplitudes of these changes are very nearly the same for potentials and fields. The spheres also produce very nearly the same shifts in the potential and field patterns. The only significant differences in the effects occur for a tangential dipole near a highly conductive sphere for which the field pattern is shifted more than the potential pattern, and the field pattern is distorted. These differences may be useful in obtaining more accurate information about sources in the body.
Raman backscattering in an electron beam-plasma system
Authors: Willett Joseph E.
Published: February 2003

The parametric decay of an electromagnetic pump wave into a backscattered electromagnetic wave and an electron electrostatic scatterer wave in a plasma traversed by an electron beam is investigated. A formula for the growth rate of the backscattered and scatterer waves is derived and studied numerically.
Polarization control of an antireflection-coated GaAlAs laser diode by an external optical feedback
Authors: Mitsuhashi Y.
Published: February 2003

A polarizer between an antireflection-coated GaAlAs laser diode and an external optical feedback system is used to control the polarization characteristics of the output light and to select the single or multilongitudinal modes (TE/TM) by adjusting the orientation of the polarizer.
Use of thermocapillary migration in a controllable heat valve
Authors: Schmid L. A.
Published: February 2003

In accordance with the Marangoni effect, immiscible droplets in a host fluid in which a temperature gradient exists move in the direction of increasing temperature. It is proposed that this thermocapillary migration could be used to construct a ‘‘liquid wick’’ that would return the condensed vapor at the condenser end of a heat pipe back to the evaporator, thus completing the fluid circuit. The droplets would be formed by capillary pressure forcing the condensate through a perforated diaphragm whose temperature would control the droplet flux, and hence the heat flux between the two ends of the heat pipe, thus making it a controllable heat valve.
Reexamination of the crystal structure of a high-pressure phase in praseodymium metal
Authors: Smith Gordon S. , Akella Jagan
Published: February 2003

H. K. Mao, R. M. Hazen, P. M. Bell, and J. Wittig [J. Appl. Phys. 52, 4572 (1981)] reported that praseodymium metal undergoes a crystallographic phase transformation from a distorted fcc structure to a distorted hcp structure at a pressure of ∼21 GPa. This phase change, further, is accompanied by a large volume decrease ∼19%. We have reexamined their powder diffraction data for the distorted hcp structure and find the data can be satisfactorily interpreted in terms of the well-known orthorhombic α-uranium type of structure. The volume decrease at the phase change is now estimated to be only ∼9.8%.
Metallic conductivity and air stability in copper chloride intercalated carbon fibers
Authors: Oshima Hisashi , Woollam John A. , Yavrouian Andre
Published: February 2003

We have formed carbon-copper chloride intercalation compounds using variously graphitized carbon fibers as host materials. The resultant conductors are air stable, thermally stable to 450 °K, have electrical resistivities as low as 12.9 μ Ω cm at room temperature, and have metallic conductivity temperature dependencies. These intercalated fibers have tensile strengths of 160 000 psi, and Young’s moduli of 25×106 psi. For aerospace use, (resistivity×density)−1 is a figure of merit. On this basis, a reduction in resistivity by a factor of two will make this conductor competitive with copper.
Depolarization of the edge emission of cadmium sulfide under intense laser excitation
Authors: Namiki Akira , Oka Tetsushi
Published: February 2003

The depolarization of the edge emission was observed in the highly excited cadmium sulfide (CdS) at 77 K. Assuming the Boltzmann distribution of the holes, the temperature estimated from the intensity ratio, I⊥/I∥, was higher by about 100–150 K than 77 K.
Optical conductivity of amorphous Ta and β-Ta films
Authors: Nestell J. E. , Scoles K. J. , Christy R. W.
Published: February 2003

Thin films of tantalum evaporated in high vacuum onto fused silica substrates at liquid-nitrogen temperature are amorphous, even after heating above room temperature. On room-temperature substrates, β-Ta, with a 30-atom tetragonal unit cell, is deposited. The electron-diffraction interference function of the amorphous a-Ta agreed best with dense random packing models, although a β-Ta microcrystalline model also gave fairly good agreement. The complex optical conductivity was determined from reflection and transmission measurements in the spectral range 0.5–6.5 eV at room temperature. The results for a-Ta and β-Ta were very similar to each other, differing significantly from bcc α-Ta (deposited onto heated substrates or crystallized from amorphous films), and they could be extrapolated to the measured dc conductivity at zero energy. After subtraction of a Drude contribution with an electron mean-free-path on the order of the interatomic distance, the remainder showed some features of the interband absorption in α-Ta, though somewhat smoothed and weakened. We conclude that the local arrangement of near neighbors is more important than whether long-range order exists.
Transient capacitance spectroscopy in polycrystalline silicon
Authors: Srivastava P. C. , Bourgoin J. C. , Rabajo F. , Mimila Arroyo J.
Published: February 2003

We have performed deep level transient spectroscopy (DLTS) on 5 Ω cm p-type polycrystalline silicon. Typical DLTS spectra exhibit three peaks centered at 250, 300, and 340 K. The density of states which is estimated from these spectra is found to extend from 0.18 eV of the valence band with a density ∼ 2×1015 eV−1 cm−2. Measurements of capture rates have shown a characteristic trap filling time of ∼10−3 s corresponding to an apparent capture cross section of the order of 10−21 cm2. Studies of the passivation (in a deuterium plasma) of these boundary states have also been made. In that case, the DLTS spectra present only one significant peak at 245 K; the density of states of the unpassivated material is reduced to localized states centered at 0.32 eV from the valence band with a concentration of 5.6×1014 cm−2. The capture cross section of these states is 3.7×10−20 cm2.
Investigation of thermally stimulated luminescence and its description by a tunneling model
Authors: Thioulouse P. , Giess E. A. , Chang I. F.
Published: February 2003

Using a tunneling pair recombination model with the assumption of spatially distributed ‘‘ionized’’ pairs of luminescent centers and traps, a general and analytical expression of thermally stimulated luminescence (TSL) intensity is derived. The Hoogenstraaten and Bube methods of determining the activation energy are still valid in the tunneling model, except they determine the activation energy of the trap tunneling state. Based on explicit expressions for TSL, it is shown that the study of TSL shape yields information on the dependence of the pair distribution on phosphor excitation conditions. Experimental results on Zn2SiO4:Mn single crystals with or without arsenic codoping are presented.
Deposition of thin films by beam induced polymerization of divinyl benzene
Authors: Fritzsche C. R.
Published: February 2003

Approaches to the mathematical description of thin film deposition from the gas phase by beam induced polymerization are discussed and compared to experimental results. As an example, deposition from divinyl benzene has been studied using electron as well as ion beams. A suitable combination of experiments under continuous and pulsed irradiation was found to enable the determination of reaction cross sections and time constants. For divinyl benzene the cross section for the activation of polymerization by electrons was found to be 2×10−14 cm2. The lifetime of the active centers was found to be about half a second. The charge necessary to deposit a 100-nm layer can be lower than 0.15 C/cm2. Ion beam induced polymerization proceeds with much higher efficiency, promising some prospects for its application in microlithography.
The effects of heat treatments on the transport properties of CuxS thin films
Authors: Hmurcik L. , Allen L. , Serway R. A.
Published: February 2003

We have studied the effects of heat treatments on three CuxS thin films (1.995≤x≤2). Our results suggest that initial heat treatments cause copper in grain boundaries to diffuse irreversibly into the CuxS crystallites. Subsequent heating in hydrogen causes a reduction in surface oxides while the reverse process occurs in an oxygen atmosphere. At a given elevated temperature, the resistivity ρ and charge density P vary with time according to the expressions P=P0e±(t/τ)1/2 and ρ=ρ0e∓(t/τ)1/2 . On the other hand, the mobility is found to be approximately constant at a given temperature during heat treatment.
Effects of annealing on the electrical properties of CdxHg1−xTe
Authors: Jones C. L. , Quelch M. J. T. , Capper P. , Gosney J. J.
Published: February 2003

CdxHg1−xTe with 0.17<x<0.31 has been annealed using closed-tube and open-tube methods. In both methods the mercury vapor pressure during an anneal was controlled by a mercury reservoir held at a temperature either the same as the CdxHg1−xTe (isothermal anneal), or lower than the CdxHg1−xTe (two-temperature anneal). Isothermal anneals carried out in closed-tube and open-tube systems convert material which is initially p type by native defects to n type. Two-temperature, closed-tube anneals can be used to convert n type to p type, the acceptor concentration being controlled by the CdxHg1−xTe temperature and the mercury vapor pressure. Two-temperature, open-tube anneals also result in conversion from n to p, however, the mercury vapor pressure (over the range studied) does not influence the final acceptor concentration but does affect the time required to reach equilibrium. The results are discussed in terms of the pressure-temperature diagram and the defect/impurity balance in CdxHg1−xTe .
Preparation and properties of V-substituted garnet films for ion-implanted 1.0-micron bubble devices with improved high-temperature propagation
Authors: Rana V. V. S. , Nelson T. J. , LeCraw R. C. , Blank S. L.
Published: February 2003

The growth and properties of films of a novel composition, (SmLuCa)3 (FeVSi)5O12, for 4-μm period Ion-Implanted Propagation Pattern devices, are described. The use of vanadium substitution to lower 4πMs yields films with high Curie temperatures (Tc =512–524 °K). Small amounts of silicon are added for lattice matching of the films to the substrate and also to increase the Q value. The presence of vanadium in films was also found to substantially increase the Faraday rotation. The bubble size in these films is nearly constant in the temperature range of −50° to +150 °C. The films also have a high mobility and low dynamic coercivity. Preliminary results of bubble propagation in these films in the temperature range −50° to +160 °C are described. It is expected that because of a combination of the desirable magnetic properties, these films will find a widespread use in bubble devices requiring operations to higher temperatures.
Evaluation of thermophotovoltaic conversion efficiency
Authors: Demichelis F. , Minetti-Mezzetti E. , Agnello M. , Tresso E.
Published: February 2003

The theory and the experiments on thermophotovoltaic (TPV) conversion are reported in this paper. The various parameters characterizing TPV systems are studied in order to provide design information for actual converters. Both the experimental results and theoretical calculations of TPV conversion efficiency are presented for comparison. They exhibit good agreement.
Diodes formed by laser drilling and diffusion
Authors: Anthony T. R.
Published: February 2003

Novel three-dimensional diode arrays have been produced in semiconductor wafers by a two-step process involving laser drilling and solid state diffusion. Holes are first produced through the wafer by laser drilling. Under suitable conditions, little or no damage to the wafer results from laser drilling. Then cylindrical p-n junctions around the laser-drilled holes are formed by diffusing an impurity into the wafer from a source in contact with the walls of the laser-drilled holes. Three applications of drilled diodes are discussed: microchannel interconnections through wafers, isolation grids, and radiation imagers.
Quantum mechanical reflection at triangular ‘‘planar-doped’’ potential barriers for transistors
Authors: Chandra Amitabh , Eastman Lester F.
Published: February 2003

The quantum mechanical reflection of electrons attempting to overcome the quasitriangular collector potential barrier in a planar-doped barrier transistor (PDBT) is an undesirable phenomenon that needs to be minimized. We describe a numerical technique for calculating the quantum mechanical reflection and transmission coefficients at triangular potential profiles that approximate the collector barrier of the PDBT. The results of these calculations, and the conclusions drawn, are presented.
Laser annealing study of the grain size effect in polycrystalline silicon Schottky diodes
Authors: Schaber H. , Cutter D. , Werner W. M.
Published: February 2003

Laser annealing is used to controllably vary the grain size of polycrystalline silicon films. The properties of Schottky diodes formed in such layers are studied experimentally by I-V and C-V measurements and interpreted in the framework of the grain boundary trapping model for polycrystalline silicon. For large grained material (grain size ≊10 μm) nearly ideal Schottky diode characteristics with a diode factor n close to unity are found. As deposited, fine grained material is fully depleted at the doping levels employed and yields a p-i-n diode behavior characterized by n=2. Observation of this regime without series resistance limitations is possible by using a buried n+ layer as the back contact of the diodes. Reverse currents of the diodes are inversely proportional to the grain size, as expected for generation at grain boundary traps.
Hall-effect studies on pyrrhotite
Authors: Pomoni Katerina , Theodossiou A.
Published: February 2003

We report here measurements on natural crystals of pyrrhotite from room temperature to beyond the Néel point. This material is known as a ferrimagnetic semiconductor, and also for its magnetic anisotropy. The isotherms of the Hall effect are given for samples cut in such a way that the magnetic field is applied along the c axis and perpendicular to it. The sign of the ordinary Hall effect proves that, in the measured temperature region, the conductivity is of p type. The energy gap can be derived from the ordinary Hall effect, and is ten times smaller along the c axis than in a direction perpendicular to it. The spontaneous coefficient Rs falls with increasing temperature, as happens in other antiferromagnetic and ferrimagnetic materials.
Platinum silicide ohmic contacts to shallow junctions in silicon
Authors: Cohen S. S. , Piacente P. A. , Gildenblat G. , Brown D. M.
Published: February 2003

Ohmic contact to shallow pn+ and np+ junctions in silicon were studied. Thin layers (∼200 Å) of platinum were sputter deposited and reacted with the silicon substrate at 590 °C to result in the stable PtSi silicide. In a self-registered process, aqua regia was used to etch the unreacted platinum. An Al-0.9% Si alloy has been used for final metallization. A small contact area of 3×3 μm2 was chosen so as to be in accordance with the current level of integration. A four-terminal Kelvin-resistor structure has been utilized to accurately measure the contact resistance. The effect due to the dopant concentration was studied at the implant dose range of 1–8×1015 cm−2. Van der Pauw sheet resistance measurements, secondary ion mass spectroscopy, and Rutherford backscattering experiments were all performed in order to characterize the shallow junctions and the silicide-silicon interface. Predeposition and in-situ etching resulted in considerable improvement in the measured specific contact resistance. Values well within the range required for very large scale integration applications were obtained.
Carrier conduction and trapping in metal-nitride-oxide-semiconductor structures
Authors: Suzuki Eiichi , Hayashi Yutaka
Published: February 2003

Carrier conduction and trapping in metal-nitride-oxide-semiconductor structures are investigated. It is clearly shown that holes dominate the carrier conduction in the nitride for both gate polarities, and electrons injected into the nitride from a cathode are almost completely annihilated by recombination in the nitride with holes injected from an anode, which is revealed by an induced junction technique. A model that the memory traps in the nitride act as the recombination centers in steady-state conditions is proposed. The recombination distance, the capture cross section, and the density of the memory traps or the recombination centers are estimated to be 81 Å, 2.86×10−13 cm2, and 4.32×1018/cm3, respectively, by fitting the experimental results with the theory based on the proposed model.
Generation annealing kinetics of interface states on oxidized silicon activated by 10.2-eV photohole injection
Authors: Sah Chih-Tang , Sun Jack Yuan-Chen , Tzou Joseph Jeng-Tao
Published: February 2003

Analysis of the generation and annealing kinetics of U-shaped and peaked donorlike interface density of states (DOS’s) are reported. The U-shaped interface DOS appears to be related to oxygen deficiency or silicon dangling bonds formed during oxidation and it does not anneal after 50 h at 25 C but anneals rapidly (minutes) above 300 C in hydrogen containing ambients, suggesting Si-H bond formation during anneal. The U-shaped DOS reappears following a first-order kinetics when 10.2-eV photogenerated holes are injected into the oxide, suggesting that these Si-H bonds are broken by hole capture and dissolved hydrogen molecules are formed. As many as three donorlike interface DOS peaks above Si midgap are also generated by the 10.2-eV photoholes following a first-order kinetics, and they appear to be related to excess oxygen or oxygen dangling bonds formed at the interface during oxidation. These donor DOS peaks anneal out in less than 50 h at 25 C following a second-order annealing kinetics, suggesting that the oxygen dangling bonds react with H2 to form SiO-H. Band edge tail states seem also evident whose density is not affected by the photoinjected holes suggesting an association with strained Si-Si bonds.
Current-waveform dependence of punchthrough probability in a Josephson tunnel junction
Authors: Enpuku K. , Irie F. , Nagatsuma T. , Yoshida K.
Published: February 2003

The so-called punchthrough phenomenon occurring in a logic gate using a Josephson tunnel junction is studied theoretically. An analytical solution of the Josephson equation describing the dynamic behavior of the Josephson gate in its resetting process is obtained with the modified averaged Lagrangian method. The solution leads to an expression for the punchthrough probability, which is capable of quantitative discussion and is applicable to arbitrary waveforms of the gate current. From the obtained expression, a study is made of the waveform dependence of the punchthrough probability, as well as its dependence on junction parameters. It is shown that the present analytical results agree well with those of computer simulations.
Effect of trapped magnetic flux on the threshold curves of three-junction superconducting quantum interference devices
Authors: Chang W. H.
Published: February 2003

Thin-film Josephson-junction quantum-interference devices require only a small amount of magnetic flux to switch them between the voltage state and the superconducting state. They are sensitive to any spurious magnetic flux present at the device. The magnetic flux may be trapped in the superconducting ground plane, particularly in ground plane holes. This paper analyzes the effects of the trapped magnetic flux on the threshold curves of three-junction Josephson interferometers. The threshold curves of the interferometer are calculated automatically by using a circuit optimization program. The automatic procedure of calculating the threshold curves of an interferometer can be applied to any Josephson-junction interferometer device. The threshold curves of both symmetric and asymmetric interferometers are calculated. We find that the threshold curves of a symmetric three-junction interferometer changes periodically as a function of the effective coupled trapped magnetic flux with a period of Φ0. The threshold curves are shifted and severely distorted in shape by the presence of the coupled trapped magnetic flux. The degeneracy of the threshold curves of a symmetric interferometer makes the unique quantitative determination of the trapped magnetic flux difficult. However, the degeneracy is removed in an asymmetric interferometer. The presence of the unbalanced trapped magnetic flux greatly shifts the entire threshold curve of an asymmetric interferometer.
Resistivity, superconductivity, and order-disorder transformations in transition metal carbides and hydrogen-doped carbides
Authors: Dy L. C. , Williams Wendell S.
Published: February 2003

Electron transport in transition metal carbides was investigated, with special attention to ordering effects in substoichiometric specimens and to the influence of hydrogen doping. Hydrided carbides specimens showed reduced resistivity values, a result attributed to the reduction of defect scattering as the carbon vacancies were filled with substitutional hydrogen ions. The effect of the order-disorder transformation NbC0.83 = Nb6C5 at 1030 °C was also to reduce defect scattering as the carbon vacancies became incorporated into the periodic potential of the ordered phase. As another illustration of vacancy scattering, the resistivities of non-stoichiometric HFCx and stiochiometric WC were compared. The superconducting transition temperatures of partially ordered Nb6C5 and hydrided NbCx decreased from those of the original specimens, disordered NbC0.83 and NbCx, respectively. The normal state resistivity of Nb6C5 displayed the  bulge  in its temperature dependence characteristic of high Tc superconducters. New data on the normal state resistivity and superconducting transition of single crystal NbC0.98 and TaC0.98 are presented, and a theorectical relation linking normal state resistivity and superconductivity is developed.
Microwave resonance and propagation in nonsaturated ferromagnetic media. I. Magnetic resonance in single crystal ferrite platelets
Authors: Rachford F. J. , Lubitz P. , Vittoria C.
Published: February 2003

We present calculations of the magnetic resonance frequencies of multidomain single crystal ferrite platelets. The theoretical results are compared to our microwave ferromagnetic resonance (FMR) experiments performed at frequencies between 8 and 40 GHz and magnetic fields between 0 and 20 kOe. Good agreement is found between theory and experiment with no adjustable parameters. In the calculation we have included the effect of a change in the periodicity of regularly patterned domain structures on the FMR frequencies. The variation in periodicity is seen to influence the measured FMR frequencies f for magnetic fields H applied normal to the platelet plane in agreement with our calculations. The predicted variation in periodicity agrees with our visual observation of domain structures in the sample. The in-plane FMR data is also in reasonable agreement with calculations. Although the measured frequency and field FMR linewidths agree well with our calculations in magnetically saturating fields, the agreement is less satisfactory in the nonsaturated region.
Thin germanium nitride films grown by thermal reaction process
Authors: Hua Qingheng , Rosenberg James , Ye Jinguan , Yang Edward S.
Published: February 2003

Thin films have been grown on 〈111〉 germanium by thermal nitridation. The surface morphology, composition, thickness, and refractive index of the films have been investigated. Compositional analysis was performed by electron beam x-ray microanalysis which indicates that the films contain oxygen as well as nitrogen and have a nitrogen to oxygen ratio on the order of 2.5:1. Film thickness and refractive index were determined by ellipsometry. The thicknesses ranged from 60 to 150 Å, and the refractive indices ranged from 1.5 to 2.3 depending on growth parameters. A universal chart for evaluating the thickness and refractive index of dielectric films on germanium from the ellipsometric parameters ψ and Δ is also presented.
Steric origin of the silicon-oxygen-silicon angle distribution in silica
Authors: Thathachari Y. T. , Tiller W. A.
Published: February 2003

The oxygen-oxygen separation distance between adjacent tetrahedra in silica has been considered as a restrictive criterion for the formation of accepted structures. The single stipulation of a minimum O-O separation of say 2.9 Å leads to a distribution of the Si-O-Si angle with a maximum at about 145° and cutoffs near 120° on the low end and 180° on the high end of the scale, all in excellent agreement with the experimental observations for silica. No detailed energetic considerations are involved.
Defect formation chemistry of EL2 center at E
c−0.83 eV in ion-implanted gallium arsenide
Authors: Li G. P. , Wang K. L.
Published: February 2003

Deep level defects after annealing were investigated for horizontal Bridgman GaAs implanted with donor species (Si, S, Se) and with a combination of these donors and oxygen. It was demonstrated that the EL2 defect level at Ec−0.83 eV and its concentration were identical for both cases, implanted with and without oxygen, and that oxygen could not be involved in the formation of EL2. Based upon the assumption of stoichiometry balance, a possible model for defect formation mechanism was constructed by considering diffusion and chemical reactions during ion implantation and annealing process. Using this model, the EL2 center may be assigned to a simple antisite defect—As in a Ga site if no complexes of higher orders were assumed to form. The model predicts that the donor impurities act as a catalyst during the formation of the EL2 defect but are not involved in the actual coordination of the defect or complex formation. Finally, the defect concentration profiles were shown to be controlled by the resulted stoichiometry deviation due to implantation and by different diffusivity of the implanted species as predicted by our model.
The mechanism of the enhancement in divacancy production by oxgyen during electron irradiation of silicon. I. Experimental
Authors: Lindström L. J. , Oehrlein G. S. , Jaworowski A. E. , Corbett J. W.
Published: February 2003

Czochralski silicon samples containing different amounts of interstitial oxygen were irradiated with 2-MeV electrons at room temperature to a fixed dose of 1.0×1018 electrons/cm2. Prior to irradiation the interstitial oxygen content of similar specimens had been varied in a controlled way by precipitating different amounts of the dispersed oxygen by suitable heat treatments. The introduced divacancy density correlates linearly to the concentration of the interstitial oxygen. A certain concentration of divacancies is always introduced, independent of the amount of interstitial oxygen present. Our data show that the divacancy concentration correlates much better to the density of introduced vacancy-oxygen complexes than to the initially present dissolved oxygen concentration. Different models for the oxygen enhancement of divacancy production are discussed.
Surface structure of silicon carbide irradiated with helium ions with monoenergy and continuous energy distributions
Authors: Miyagawa S. , Ato Y. , Miyagawa Y.
Published: February 2003

Silicon carbide was irradiated at room temperature and 600 °C with helium ions with monoenergy (3–100 keV) and continuous energy distribution ranging from 0.5 keV to 20 keV up to a total dose of 1×1019 ions/cm2 using an ion accelerator controlled by a microcomputer. For room temperature irradiation, porous structures appear on the surface of samples irradiated to dose of ∼5×1018 ions/cm2, and the damaged layer is easily removed from underlying undamaged layer by ultrasonic vibrations. On the other hand, for target temperature of 600 °C, such porous surface structures are not observed, which is due to thermal annealing. It has been shown that the surface deformation depends strongly not only on the implantation profile, but also on irradiation modes of helium ions. Flaking is completely avoided by prebombardment of helium ions with continuous energy distribution, which deliberately produces a pathway for gas release. In order to simulate wall erosion due to helium bombardment, silicon carbide was also irradiated with a Maxwellian distribution. No blistering or flaking is observed for an average energy of 3 keV.
Theoretical strength of a perfect nickel crystal under simple stresses
Authors: Thakur K. P.
Published: February 2003

A theoretical study is made of the lattice stability or theoretical strength of nickel subjected to various kinds of simple stresses. Calculations are carried out using a Morse potential model and the criterion of stability introduced by Born. The region of G, M, and S stability for the Morse nickel in the a2=a3 plane of the a1, a2, a3 space is investigated. Cases of (i) unidirectional stress, (ii) two-directional stresses, (iii) application of hydrostatic pressure in the fcc and bcc phases, (iv) unidirectional deformation, and (v) two-directional deformation are shown to arise as specific cases of the generalized calculations presented here. Wealth of data for various elastic moduli, stresses throughout a wide range of lattice deformation are presented here for the Morse nickel. The possibility of phase transformation from fcc phase to bcc phase is discussed. The present results compare well with the literature data, which are available only for a few simple modes of loading.
Experimental investigation of the amorphous silicon melting temperature by fast heating processes
Authors: Baeri P. , Campisano S. U. , Grimaldi M. G. , Rimini E.
Published: February 2003

The recrystallization of amorphous Si layers on Si crystal substrates after laser irradiation was investigated to test previous experimental evidence that both the melting point and the melting enthalpy of the amorphous are lower than the corresponding crystalline values. The irradiation was performed in some cases from the back side of 100-μm-thick Si wafers to obtain a temperature distribution in the amorphous layer with a small spatial gradient. In the case of front irradiation the threshold energy density was measured as a function of the amorphous layer thickness, for the polycrystalline formation, crystallization with residual disorder, and good annealing, respectively. The experimental data agree quite well with heat flow calculations assuming a reduction of about 30% in the melting point and enthalpy of amorphous silicon with respect to crystalline silicon.
Trapping and surface permeation of deuterium in He-implanted Fe
Authors: Myers S. M. , Follstaedt D. M. , Besenbacher F. , Bo/ttiger J.
Published: February 2003

Iron was ion implanted with He and deuterium (D) and then heated at a constant rate of 2 K/min. The evolving depth distribution of the D was monitored using the nuclear reaction 2D(3He,p)4He, and resulting data were analyzed by applying the diffusion equation with appropriate trapping terms. Two defect traps for D were identified, the respective binding enthalpies being 0.53±0.07 and 0.71±0.07 eV when referenced to a solution site. The weaker of these traps is believed to be a monovacancy, while the stronger may be a vacancy cluster. A third type of trap, with strength 0.78±0.08 eV, was found to be associated with He. It is proposed that the responsible entities are ∼1 nm He bubbles which were observed by transmission electron microscopy, and that the D is bound to the walls of these bubbles by a mechanism similar to chemisorption. The analysis also yielded an estimate of the D recombination coefficient at the electropolished and air-exposed Fe surface, ∼5×10−19 cm4/s at a temperature of 500 K.
Excitation of ultrasonic Rayleigh leaky waves at liquid-solid interface for general angle incidence
Authors: Adler Laszlo , de Billy Michel , Quentin Gérard J.
Published: February 2003

Experimental results are presented to demonstrate the existence of ultrasonic leaky wave radiation from liquid-solid interface. This leaky wave is generated by a finite ultrasonic beam incident at any angle (not only at Rayleigh angle) to a liquid-solid interface and observed at the Rayleigh angle both forward and backward. It is suggested that the phenomena occurring at the Rayleigh angle incidence and producing (1) a complex reflected field and (2) a backscattered field are just two special cases of this general phenomenon.
Growth ‘‘kinetics’’ and growth mechanisms for disilicide layers obtained through implantation
Authors: d’Heurle F. M. , Petersson C. S. , Tsai M. Y.
Published: February 2003

Layers of NbSi2 and MoSi2 were grown by means of the implantation of germanium and arsenic ions through films of the respective metals, previously deposited on single crystal silicon substrates. The doses used varied from 1 to 15×1015 ions/cm2 with energies of 150, 200, and 250 keV. The thickness of the silicide layers increases in proportion to the square root of the implanted doses. This observation and other evidence indicate that the process is dominated by the atomic mechanisms encountered in radiation-enhanced diffusion, whereas ballistic mixing effects remain unimportant. The growth of disilicide layers during implantation is discussed with respect to (1) what is known about the growth of these disilicide layers during simple annealing, and (2) what is anticipated for diffusion-controlled solid state processes.
Optical and electrical characterization of multiply doped silicon: A study of the Si:(In,Al) system
Authors: Brown D. H. , Ohmer M. C. , Beasley K. D. , Rome J. J. , Brown G. J. , Fischer D. W.
Published: February 2003

Photoluminescence, infrared absorption, high-resolution photoconductivity, and Hall effect transport measurements have been used to study the optical and electrical properties of silicon single crystals grown by the float-zone method, which were intentionally doped with indium and aluminum. Indium-bound exciton luminescence, as well as strong U2 luminescence from isoelectronic traps, were observed in the as-grown material. However, despite a high concentration of Al in these samples, no aluminum bound exciton luminescence was observed. Exciton tunneling from Al to In bound states is believed responsible for the quenching of the Al luminescence. No photoluminescence from Al-related isoelectronic centers was detected, suggesting that In-related centers form preferentially. No X-levels were detected by Hall, absorption, or photoconductivity measurements before nor after electron irradiation and thermal annealing.