bluuebunny/crossref_metadata_2025 huggingface dataset:
High resistivity in InP by helium bombardment
Authors: Focht M. W. , Macrander A. T. , Schwartz B. , Feldman L. C.
Published: February 2003

Helium implants over a fluence range from 1011 to 1016 ions/cm2, reproducibly form high resistivity regions in both p- and n-type InP. Average resistivities of greater than 109 Ω cm for p-type InP and of 103 Ω cm for n-type InP are reported. Results are presented of a Monte Carlo simulation of helium bombardment into the compound target InP that yields the mean projected range and the range straggling.
Cryogenic temperature mechanical behavior of solid mercury
Authors: Purushothaman S. , Caulfield T.
Published: February 2003

Tensile mechanical behavior of as-cast solid mercury which is relevant to Josephson integrated circuit packaging applications has been studied at 77 K and between 4.2 and 20 K. It was found that solid mercury is ductile, particularly so at temperatures close to 4.2 K. Further, at and near 4.2 K solid mercury exhibits pronounced work hardening, high tensile strength, and markedly serrated flow behavior. A possible explanation of these observations is presented, based on existing information on deformation and transformation characteristics of mercury at cryogenic temperatures.
Diffusion of carbon atoms in hydrogenated amorphous silicon carbide into hydrogenated amorphous silicon through the interface
Authors: Komuro Shuji , Aoyagi Yoshinobu , Segawa Yusaburo , Namba Susumu , Masuyama Akio , Okamoto Hiroaki , Hamakawa Yoshihiro
Published: February 2003

It was found that carbon atoms in hydrogenated amorphous silicon carbide (a-SiC:H) films deposited on a-Si:H film were diffused into the a-Si:H film. We suggest that the carbon atoms in the a-Si:H region are the origin of the decrease of the lifetime and the diffusion coefficient of photoexcited carriers in the a-Si:H.
Photoluminescence in liquid phase epitaxially grown Hg0.3Cd0.7Te
Authors: Feldman Bernard J. , Bajaj J. , Shin S. H.
Published: February 2003

The photoluminescence spectra of liquid phase epitaxially (LPE) grown Hg0.3Cd0.7Te and its CdTe substrate have been measured. The CdTe spectra consist of two band-edge sets of lines, B and C, while the Hg0.3Cd0.7Te spectra consist of one set of lines, A. From the temperature dependence of both the integrated intensity and peak position, we determined that the A line is unrelated to the C line but is very possibly related to the B line. The B line in CdTe is due to recombination of electrons and holes bound to a neutral donor. This suggests that the same neutral donor may be present in both materials, whereas the impurity or defect responsible for the C line in CdTe is undetectable in LPE-grown Hg0.3Cd0.7Te.
Interfacial properties of Al2O3-InP metal-insulator-semiconductor structure prepared in excess organophosphorus atmosphere
Authors: Kobayashi Takeshi , Ichikawa Tohru , Sakuta Ken , Fujisawa Kazuo
Published: February 2003

The effects of the excess phosphorus vapor added in the chemical vapor deposition (CVD) ambient on Al2O3-InP metal-insulator-semiconductor (MIS) interfacial properties were investigated. The triethylphosphorus (TEP) was used as an excess phosphorus source gas suitable for the low temperature CVD. The change in the surface state density distribution (Nss) curves of the MIS diodes due to TEP introduction was clear: the Nss value of the broad peak at 1 eV, superimposed on the U-shaped background, was reduced to one order of magnitude lower than that of the TEP-free device.
Effect of oxygen on the photoluminescence of CdS/CdTe thin films
Authors: Tang C. W. , Vazan F.
Published: February 2003

Photoluminescence (PL) of CdS/CdTe thin films prepared with and without oxygen has been studied. A donor-acceptor transition (1.521 eV at 4.2 K) was observed only at the CdS/CdTe interface of samples prepared in an oxygen ambient. Together with the observed relative strength of the deep acceptor level, Ev+0.15 eV, it is possible to correlate the PL data with the type of conduction in CdTe films prepared in different atmospheres and the shallow- or deep-junction behavior of the CdS/CdTe solar cell.
Submillimeter detector operation of granular superconducting NbN films
Authors: Carr G. L. , Karecki D. R. , Perkowitz S.
Published: February 2003

Detection of submillimeter radiation between 10 and 40 cm−1 (300–1200 GHz) has been carried out with a high resistance granular NbN film (R⧠= 8440 Ω/⧠) below 6 K with evidence of Josephson-like operation. The nonoptimized detector sensitivity and noise equivalent power at 17.5 cm−1 (525 GHz) were about 20 V/W and 5×10−8 W/Hz1/2, respectively, comparable to values obtained with granular Sn and Pb.
Monte Carlo investigation of transient hole transport in GaAs
Authors: Brennan K. , Hess K. , Iafrate G. J.
Published: February 2003

Transient transport of holes in GaAs is studied under the conditions of high energy injection. This study is made using a Monte Carlo simulation with the unique inclusion of a realistic band structure based on the K*P method. The results reported herein show that a significant velocity overshoot occurs at low applied electric fields over distances greater than 1500 Å. As the applied field increases, the effect of the overshoot upon the transit time becomes less pronounced. There is no discernable gain in the drift velocity for holes injected at high energy, 0.1 eV, as compared to holes injected at zero launching energy for the distances considered here.
Correlation of photoluminescence and deep trapping in metalorganic chemical vapor deposited AlxGa1−xAs (0≤x≤0.40)
Authors: Bhattacharya P. K. , Subramanian S. , Ludowise M. J.
Published: February 2003

Shallow and deep level photoluminescence (PL) in metalorganic chemical vapor deposition grown AlxGa1−xAs (0≤x≤0.40) are studied. Two sets of samples grown under different conditions are compared. The growth conditions are chosen to produce a large density of deep levels in one case and to minimize the deep level density in the other case. The 0.82-eV EL2 electron trap and four other dominant electron traps with activation energies ET ranging from 0.25 to 0.62 eV are identified. The concentrations of the four other traps are observed to increase with Al content in those samples grown under trap-producing conditions, and the traps are nearly absent in the other set of samples. The PL intensity is inversely proportional to trap concentrations. The trap densities are related to background contamination in the growth ambient, most likely H2O and O2, leading to the speculation that two traps with ET=0.35 eV and ET=0.25 eV involve Al and O complexes. Hole traps have also been observed but show no definite trends with x or the growth ambient. Radiative centers up to 400 meV deep exhibit more intense PL in samples grown under larger V/III ratios.
On the nonequilibrium statistics and small signal admittance of Si-SiO2 interface traps in the deep-depleted gated-diode structure
Authors: Agarwal A. K. , White M. H.
Published: February 2003

Nonequilibrium generation-recombination statistics are examined for the deep-depleted gated-diode structure. This structure eliminates the minority-carrier capture process and allows the competing emission process to dominate near the middle of the Si band gap. It is found that the steady-state occupancy function of the midgap interface traps deviates considerably from the Fermi–Dirac distribution which is applicable to the equilibrium situation. As a consequence of this deviation, rapid attenuation of the ac trap conductance with frequency for the midgap traps is predicted and experimentally verified. The ratio of electron to hole capture cross sections, R=σn/σp, has a pronounced influence on the trap energy associated with the onset of ‘‘pinning,’’ UTP=1/2(ln R).
Characterization of rf-sputtered BaTiO3 thin films using a liquid electrolyte for the top contact
Authors: Rose T. L. , Kelliher E. M. , Scoville A. N. , Stone S. E.
Published: February 2003

BaTiO3 films 0.5 to 2.5 μm thick have been deposited by rf sputtering onto Pt substrates held at temperatures from 340 to 930 °C. The effects on the structure and electrical properties of deposited films annealed in air at temperatures of 935 and 1200 °C were determined. Film structure was characterized by x-ray diffraction and scanning electron microscopy. The electrical properties were measured using a liquid electrolyte for the top contact. Well-defined crystalline films of BaTiO3 were obtained only when the film was annealed at 1200 °C. Milder conditions resulted in amorphous structures and/or other crystalline stoichiometric compounds of barium titanate. The amorphous films were more coherent than the annealed structures, giving lower leakage currents but smaller dielectric constants of <300. Annealing the films raised the effective dielectric constant to values as high as 7000, with an accompanying decrease in the insulation resistance. The results are interpreted on the basis of formation of a porous, incoherent crystalline structure in the annealed films which have exposed areas of the Pt substrate in contact with the electrolyte.
Pulsed laser treatment of La-implanted Ni single crystals
Authors: Battaglin G. , Carnera A. , Della Mea G. , Donà dalle Rose L. F. , Kulkarni V. N. , Mazzoldi P. , Miotello A. , Jannitti E. , Jain Animesh K. , Sood D. K. , Chaumont J.
Published: February 2003

La implanted Ni single crystals, irradiated with Q-switched ruby laser pulses up to 5.2 J/cm2, have been studied by 1.8-MeV 4He+ ion channeling. The laser induced damage is found higher in comparison with as-implanted damage. The as-implanted Ni(La) system shows nonsubstitutionality, which persists even after laser irradiations, whereas a substitutional solid solution would be expected. Irradiation in air above 1.5 J/cm2 shows a clear La surface peak, which is almost absent when irradiation is carried out in an ambient having reduced oxygen and water vapor content (10−2 Torr vacuum). The higher damage and La nonsubstitutionality after irradiation are shown to result from enhanced defect trapping during resolidification. The La surface peak formation is attributed to a mechanism involving oxidation and trapping of La at the surface. The experimental La profiles are then reproduced with a liquid phase diffusion analysis including such a mechanism.
Plasma polymerization and deposition of amorphous hydrogenated silicon from rf and dc silane plasmas
Authors: Ross R. C. , Jaklik J.
Published: February 2003

Films of amorphous hydrogenated silicon were deposited from silane and disilane plasmas in a planar diode reactor using rf and dc excitation. Substrate temperature (Ts), total pressure (pT), interelectrode spacing (d), and excitation power (P) were systemically varied. Films were characterized in terms of H content and bonding, optical gap (Eo), ambipolar diffusion length (ld), and performance in p-i-n solar cell structures. The extent of silane polymerization to disilane and higher homologs by homogeneous plasma reactions is indicated as a dominant factor in controlling the composition and properties of a-Si:H deposited form rf- and dc-excited silane plasmas. The optimization of film properties at Ts=230 °C is found to be independently controlled by P, pT, and d inasmuch as they determine the degree of plasma polymerization. Films prepared under conditions promoting plasma polymerization resemble films made from SiH4–Si2H6 mixture feedstocks with nonpolymerizing conditions, exhibiting increased H content, dihydride density, and Eo as well as poorer electronic properties. The similarity of film properties for a variety of rf and dc nonpolymerizing plasmas suggests that the identity of the reactive monomeric film-forming specie(s) is either invariant or noncritical. These films have Eo≂1.7 eV, ld≂0.3 μm, and produce p-i-n solar cells with efficiencies≂7.5%. The roles of homogeneous and heterogeneous processes were investigated. Implications for maximum achievable deposition rates and silane utilization are discussed.
Depth distributions of sulfur implanted into silicon as a function of ion energy, ion fluence, and anneal temperature
Authors: Wilson R. G.
Published: February 2003

Depth distributions for sulfur (S) implanted in (100) and (111) silicon (Si) measured by secondary ion mass spectrometry are reported for S ion energies from 40 to 600 keV and ion fluences from 4×1012 to 4×1016 cm−2. The results of Pearson IV fits are tabulated for the energy and fluence series; the range parameters given are peak depth (Rm) and μ(Rp), σ(ΔRp), γ1, β2, and β′2 for both the peak of the distribution and the full curve (including the influence of the channeling tail). The S densities are measured from a maximum of 1021 down to <1015 cm−3 where the detection limit is probably caused by background oxygen (mass 32). Sulfur profiles are shown for annealing temperatures from 100 to 950 °C in (100) and (111) Si orientations. Sulfur is retained in the region of damage for densities above about 1018 cm−3, until an annealing temperature of 900 or 950 °C is reached, when the S is largely rejected from the Si crystal; the remaining S density is <1015 cm−3, in agreement with solid solubility.
Shallow junction cobalt silicide contacts with enhanced electromigration resistance
Authors: Vaidya S. , Schutz R. J. , Sinha A. K.
Published: February 2003

Aluminum contacts to shallow junctions in high-performance silicon integrated circuits suffer from an inhomogeneous Al/Si interaction, which culminates in a destruction of contact and junction integrity. Certain silicides such as CoSi2, on the other hand, are thermodynamically stable over Si. However, these still require an additional barrier layer between the top Al and the silicide to inhibit thermally induced reactions with Al. This work addresses the question of electromigration at one such proposed contact metallization scheme consisting of Al/TiN/CoSi2. Results indicate that the TiN provides a suitable barrier to Al/Si interdiffusion under standard device operating conditions. At extremely high currents and temperature, however, the contacts degrade by a localized Al/TiN interaction, which destroy the TiN barrier integrity, followed by Al/CoSi2 reaction and Si electromigration from the substrate. In contrast, Al/CoSi2 contacts are highly susceptible to junction leakage, with junction lifetimes controlled by the kinetics of Si diffusion through CoSi2.
Dopant diffusion in silicon: A consistent view involving nonequilibrium defects
Authors: Mathiot D. , Pfister J. C.
Published: February 2003

A numerical solution of the problem of diffusion via a dual mechanism is obtained for P, As, and B diffusion in Si by solving the full system of impurity, vacancy, and self-interstitial continuity equations. The suitable constants are derived by fitting on experimental results for diffusions in both inert and oxidizing ambients, and lead to interesting information on silicon point defects at high temperature. In particular, it is found that dopant diffusion is essentially vacancy assisted, whereas self-diffusion proceeds primarily via self-interstitials.
Epitaxial growth of Si films on CaF2/Si structures with thin Si layers predeposited at room temperature
Authors: Asano Tanemasa , Ishiwara Hiroshi
Published: February 2003

Heteroepitaxial growth of vacuum-evaporated Si films on CaF2/Si structures has been investigated. In order to prevent surface reaction between deposited Si and the underlying CaF2 films at high temperatures, a thin Si layer is in situ deposited at room temperature onto the CaF2 surface prior to deposition of Si at 800 °C. It has been shown from morphological and ion channeling studies that the thin predeposited Si layer, less than 10 nm in thickness, is useful to prevent the surface reaction without destroying the epitaxial growth, and that this technique is applicable to both (111) and (100) oriented substrates. The early stage of the growth is also studied. It has been found that the majority of the predeposited Si layer is not aligned to the substrate orientation even after a thick film has grown epitaxially. A possible model for the epitaxial growth is discussed.
Determination of the gap density of states in amorphous silicon by phase shift analysis of the modulated photocurrent
Authors: Aktaş G. , Skarlatos Y.
Published: February 2003

The density of localized states in the mobility gap of evaporated amorphous silicon films has been measured over a range of 250 meV between the conduction band and the Fermi level. The method employed is based on the analysis of the phase shift between an intensity modulated exciting light and the associated photocurrent induced in the semiconductor. The density of states falls off almost exponentially with energy away from the conduction band. It suggests an overlap of the conduction and valence band tails, a result consistent with the Cohen, Fritzsche, and Ovshinsky model.
Existence of ≂64-meV deep acceptor in Se-implanted GaAs after close-contact annealing
Authors: Dansas P. , Charlec J-P.
Published: February 2003

Photoluminescence studies revealed the presence of a ≂64-meV deep acceptor in unimplanted and Se-implanted GaAs after close-contact annealing. Carbon has been identified as the major acceptor impurity in all implanted and unimplanted samples. No correlation has been found between implanted doses and the concentration of the ≂64-meV deep acceptors. The homogeneity of the carrier concentration and drift mobility profiles has been studied in terms of variations in the characteristics of metal-semiconductor field-effect transistors. Measurements of drain current transients (resulting from backgating effects under infrared illumination) have shown the existence of four deep levels. EL12 was found to be the principal electron trap, though was not detected within the implanted layer. EL2 was not detected at all. Specific influence of implantation and annealing are discussed. After annealing, it was noticed that migration of residual Mn and Cu towards the surface had occurred only in the implanted samples.
Theory of the retarding potential method of cathode temperature measurement
Authors: Adler E. A. , Longo R. T.
Published: February 2003

Retarding potential measurements can be used to determine the temperature of the cathode in a traveling wave tube. General expressions are derived for the current in a thermionic diode as a function of cathode temperature and applied voltage. An enumeration is made of the conditions under which such expressions can be reduced to a form that enables application of the retarding potential method of temperature measurement. An integral form is given for the factor needed to generalize the Richardson equation to more general geometry, and it is evaluated for a special case. Finally, there is a discussion of the case when, because of surface or other effects, the distribution function of emitted electrons is not given by the Fermi–Dirac distribution.
Spatial frequencies generation in an optical nonlinear medium
Authors: Adolf A. , Chatrefou D. , Euzenne D. , Morbieu B.
Published: February 2003

We present an experiment which shows the generation of spatial harmonic frequencies due to the refractive index nonlinearity in CS2. This experiment allows to test the validity of the formalism using the break-up integral and can lead to a new measurement method of the nonlinear index in optical materials.
Xerographic measurements in compensated hydrogenated amorphous silicon
Authors: Jansen F. , Mort J. , Grammatica S. , Morgan M.
Published: February 2003

Xerographic discharge measurements are reported on 10-μm-thick compensated hydrogenated amorphous silicon samples for doping levels as high as 5000 ppm by weight. Excellent xerographic characteristics including photosensitivity, charge acceptance, and hole range are maintained up to doping levels ∼ 100 ppm by weight. Beyond this both charge acceptance and hole range degrade due to associated increases in mid-gap-state densities.
dc conduction and dielectric absorption in PVF2
Authors: Faria Roberto M. , Gross Bernhard , Ferreira G. F. Leal
Published: February 2003

Charging and discharging currents in PVF2 are found to depend on the nature of the gas (argon or air) in which the samples are kept during measuring and on the pressure and humidity of the air.
Optical properties of diffusion-produced AuSn
Authors: Neel S. , Arakawa E. T. , Inagaki T.
Published: February 2003

Optical properties of the intermetallic compound AuSn were determined for photon energies between 0.6 and 2.9 eV by ellipsometry. The samples were made by interdiffusion in evaporated Au/Sn thin films at room temperature. The results obtained agree well with the results previously obtained for AuSn made by direct evaporation of a stoichiometric mixture of gold and tin.
A new approach of the dose-rate measurements in thermoluminescence dating
Authors: Michael Ch. , Andronikos P. , Haikalis D.
Published: February 2003

A method is described in which the dose rates of β and γ irradiation that are due to radioactivity in both the pottery and its environment are measured simultaneously. The main advantage of this method is that the CaF2 grains are irradiated under conditions similar to those existing during the irradiation of the quartz grains of the pottery, while buried in the soil. The calculations for the determination of the annual dose and subsequently of the pottery’s archaeological age, considering that the natural dose is known, are also described.
Catastrophic and latent damage in GaAlAs lasers caused by electrical transients
Authors: Sim S. P. , Robertson M. J. , Plumb R. G.
Published: February 2003

A study has been made of the susceptibility of 20-μm oxide stripe GaAlAs lasers to current transients. The current amplitude (as a function of duration) required to cause increased threshold currents or degradation rates has been found. Damage caused by forward bias transients was found to occur at the facets and was probably due to high surface recombination, leading to local absorption and excessive heating. Even when the immediate damage was insufficient to cause a detectable increase in threshold current, increased degradation rates resulted. Damage during reverse bias transients resulted from local avalanche breakdown which, though usually observed at the facets, was occasionally found outside the stripe. Such damage did not always lead to increased degradation rates. The reverse bias breakdown voltage of the lasers was found to be a more sensitive indicator of transient damage than the threshold current. The results provide substantial evidence to confirm that precautions must be taken against electrostatic discharge whenever lasers are handled. In addition, all laser bias circuitry, including that in test and measurement equipment as well as in optical fiber systems, must be checked to ensure that dangerous transients cannot occur.
On the reflection of lateral electromagnetic waves from perpendicular boundaries
Authors: King Ronold W. P.
Published: February 2003

Lateral electromagnetic waves propagate along the boundary between an electrically dense half space (z≥0) with the wave number k1 (earth, water) and a less dense half space (z≤0) with the wave number k2 (‖k2‖2≪‖k1‖2). The scattering of such waves by vertical discontinuities in the denser half space (k1 changes to k3) is analyzed. It is shown that the reflected field is very small even when k3→∞. Also analyzed are the reflections from thin vertical walls of height L of the denser medium projecting vertically into the less dense medium. These are studied specifically when the walls are made of metal. It is shown that reflections are small when k2L≪1, but very significant when k2L>1. The standing-wave patterns due to incident and reflected lateral waves are determined and shown graphically.
Intense relativistic electron beam propagation in evacuated drift tubes
Authors: O’Shea P. G. , Welsh D. , Destler W. W. , Striffler C. D.
Published: February 2003

The propagation of a magnetically confined intense relativistic electron beam (IREB) (1 MeV, 27 kA, 20 ns FWHM) in vacuum drift tubes has been studied experimentally and theoretically. Experimental results for current propagation as a function of uniform applied magnetic field (0–1.2 T) are presented for various drift tube diameters, cathode geometries, and anode aperture sizes. An analytic model of laminar beam flow is presented which predicts the space-charge-limited current of a solid IREB propagating in a grounded drift tube. A steady-state equilibrium is examined and is compared with the experimental results.
Nonlinear surface wave generation in a planar waveguide structure
Authors: Hwang Whei-Lin
Published: February 2003

Electromagnetic (em) wave generation using nonlinear mixing schemes in planar structures is examined. These structures, consisting of interspersed layers of dielectrics and semiconductors, are assumed to have a finite length in the direction of wave propagation. Field expressions for the generated em waves are derived using two alternate approaches: the Green’s functions method and the application of Lorentz reciprocity theorem. All expressions are readily extended if losses are taken into consideration.
Ultrasonic propagation in close-packed disordered suspensions
Authors: Schwartz L. , Plona T. J.
Published: February 2003

Measurements on two systems (each with porosity φ=0.38) show that the ultrasonic response of fluid saturated granular composites is not easily predicted in terms of the acoustic properties of the individual constituents. In particular, systems comprised of unconsolidated glass and Plexiglas grains exhibit anomolous behavior in both the low and high frequency regimes. We find, however, that a satisfactory description of these composites can be developed using the same multiple scattering techniques employed in the analysis of electronic states in liquid and amorphous metals.
Surface-residual-stress evaluation using horizontally polarized shear waves
Authors: King R. B. , Fortunko C. M.
Published: February 2003

In this paper a new theory and experimental method are described for evaluation of surface residual stresses in inhomogeneous, anisotropic materials. The method is based on the use of horizontally polarized shear waves (SH waves) that propagate at a grazing angle with respect to the surface of a sample. In addition, a new theory is presented for grazing SH waves propagating through a body in which the stress distribution varies with depth. It is shown that to first order the average velocity of the grazing SH waves is dependent only on the surface values of residual stress. Based on the use of electromagnetic-acoustic transducers to generate and detect grazing SH waves, preliminary experimental verification of the theory is presented.
Fractoemission from cyclotrimethylenetrinitramine (RDX) explosive single crystals
Authors: Dickinson J. T. , Miles M. H. , Elban W. L. , Rosemeier R. G.
Published: February 2003

Production-grade Class D and laboratory-grown cyclotrimethylenetrinitramine (RDX) explosive crystals were fractured in a vacuum (10−5 Pa) while viewed by particle detectors biased to separate positive and negative charge. Fracture was achieved by compressive loading (both production and laboratory crystals) and by three-point bending (laboratory crystals only). ‘‘Cleavage’’-type fracture resulted for several crystals subjected to three-point bending and yielded a sharp emission peak followed by rapid decay. Longer and more intense emission was observed for a few crystals broken in flexure which may correspond to more ‘‘energetic’’ fracture. Multiple fracture, involving surface frictional grinding, occurred for crystals that were compressed; in this case, relatively intense emission resulted which continued for several minutes after fracturing the crystals. These results are discussed in terms of possible mechanisms.
Effect of probe size on electrical noise due to conductivity fluctuations
Authors: Miller S. C.
Published: February 2003

Increases in spectral noise density associated with small probe size are investigated. It is shown that conductivity fluctuations give fluctuating dipole fields. The dipoles near the electrodes lead to large noise for small electrodes. This dependence of noise on probe size is investigated for several geometries including the case where noise is produced at the surface of a three-dimensional medium. Also the effect of boundary conditions is considered. It is found that with a finite size sample one may simply treat a conductivity fluctuation as causing some average resistance change when probe size is comparable to sample sizes, but the dipole effect is important for small probes.
Tunnel barrier shape for rf-oxidized Nb/Pb-alloy junctions
Authors: Magerlein J. H.
Published: February 2003

Tunnel barriers produced by rf oxidation of Nb films were characterized by measuring the tunneling current density as a function of voltage j(V) and the junction specific capacitance Cs. The j(V) curves of high resistance junctions for voltages up to and exceeding the barrier heights showed that the tunnel barriers were approximately trapezoidal. The barrier heights at the base electrode and counterelectrode interfaces, which were both about 0.85 eV for Nb/Pb junctions, were reduced to about 0.57 and 0.44 eV, respectively, for Nb/PbInAu junctions. Deviations of the j(V) curves from those calculated for a trapezoidal barrier included evidence of barrier rounding at the base electrode interface as well as substantial zero-bias anomalies, which suggest the presence of traps in the barrier. The large increase in resistance on thermal annealing observed for Nb/Pb junctions appeared to result primarily from an increase in barrier height.
Hysteresis losses and magnetic phenomena in ribbons of type II superconductors in the noncollinear regime
Authors: LeBlanc M. A. R. , Lorrain J. P.
Published: February 2003

We have measured hysteresis losses, W(h0, hb, Hb0), in ribbons of VTi and Nb subjected to oscillating magnetic fields of various amplitudes h0 directed transverse to a static bias magnetic field Hb0, hence the name, noncollinear regime. A second bias field hb along h0 may also be introduced. Hb0 and h0 are directed along the length and width of the ribbon respectively or vice versa (90° rotation). The families of data curves are compared with the predictions of double critical state models where (i) dB/dx=±FP(B)/B governs the critical gradients of the magnetic induction and (ii) dθ/dx=±FP(B)F(θ)/B2, the spatial variation of the orientation of the sheets of flux lines, with θ=0 along Hb0. The effect on W(h0,hb,Hb0) of choosing F(θ)=1/tan θ, k and k/(1+‖θ‖)2 is illustrated and the latter is seen to yield the best agreement. The locus of the magnetization along the length and width of the samples, 〈M∥〉 and 〈M⊥〉, have been monitored separately and simultaneously during the cycles of h0(t) for various h0 and Hb0 with hb=0 or h0. These observations, in particular the curves of the magnetization along Hb0, constitute severe tests of any model. The corresponding curves generated by the model using F(θ)=k/(1+‖θ‖)2 are presented. The physical origin of F(θ) is explored.
Laser-induced phenomena at liquid-glass interfaces: Particle deposition and holographic bubble grating formation
Authors: Eyring Gregory , Fayer M. D.
Published: February 2003

Intense diffraction from a periodic array of microscopic bubbles is reported. These bubble gratings are generated by 100-ps, 1.06-μm pulses of intensity 108–109 W/cm2 which are crossed at a liquid-dielectric interface. The time dependence of the diffraction yields information on the surface bubble expansion, contraction, and migration. It is demonstrated that there is a mechanism by which optical radiation can transfer impurity particles from the liquid to the glass surface. These surface particles are strongly heated by subsequent laser pulses, causing them to produce bubbles. Laser-induced particle deposition also lowers the threshold for surface damage. Once attached, the particles can be removed from the surface using a double pulse sequence with pulse separations ≤30 ns. This desorption process is related to the temperatures and cooling rates of the surface particles, which can be estimated by analyzing the spectral and temporal characteristics of the emitted blackbody radiation. The dependence of these phenomena on the laser intensity and the chemical properties of the liquid is described, and a variety of possible applications are discussed.
Thermal oxidation of silicon: Chemisorption and linear rate constant
Authors: Hu S. M.
Published: February 2003

This is the first of a series of three papers which, by introducing new concepts and new formulations that are consistent with experimental observations, attempt to treat a number of topics related to the kinetics and the mechanisms of the thermal oxidation of silicon. The present paper deals with the surface reaction aspect of oxidation. A new oxide growth law has been formulated to be consistent with the observed power-law pressure dependence of interface reaction kinetics. Then the subject of chemisorption, proposed here as an intermediate step of the thermal oxidation of silicon, is treated at length. It is shown, from a first-principles analysis, that the energy of chemisorption should vary approximately logarithmically with the amount of chemisorption, that this leads to an adsorption isotherm which is related to the oxygen pressure by a power law, and that the exponent of the power law should vary linearly with temperature within a reasonable span. The effects of substrate doping and of substrate damage are also analyzed.
Space-time correlation properties of the magnetization process and eddy current losses: Applications. I. Fine wall spacing
Authors: Bertotti G.
Published: February 2003

The physical origin of eddy current losses in materials characterized by a very fine and complex domain structure is discussed, on the basis of a general statistical theory of losses developed in preceding papers. It is shown that the same process which is at the basis of the Barkhausen effect, namely the space-time clustering of elementary domain wall jumps, also gives rise to a detectable dynamic loss contribution in excess to the classical one, in spite of the fact that the ratio between the average wall spacing and the sample thickness is much smaller than unity. A quantitative evaluation of this effect is carried out, obtaining a loss equation which is then compared with some experimental data. Since, according to this interpretation, the same microscopic mechanism is responsible for both the Barkhausen effect and the loss anomaly, it is found that a quantitative relation exists between the parameters of the obtained loss expression and the Barkhausen noise statistical properties. Through this relation, a comparison of loss and Barkhausen noise measurements can provide a valuable test of the consistency of the proposed loss model.
Space-time correlation properties of the magnetization process and eddy current losses: Applications. II. Large wall spacing
Authors: Bertotti G.
Published: February 2003

The physical processes controlling the behavior of dynamic losses in oriented materials are analyzed on the basis of a general statistical theory of losses developed in preceding papers. In contrast to the Pry and Bean model, the case of a system of statistically independent walls, in which dynamic wall-wall interactions are neglected, is considered. In this approximation, the basic parameter controlling the loss behavior turns out to be the surface Q̃ of active walls participating in the magnetization process at different magnetizing frequencies fm. A simple model is developed, starting from the observation that it is the applied magnetic field that essentially controls the increase of Q̃ with increasing fm. Since the applied field governs, at the same time, the velocity of the moving walls, a competition between wall velocity and active wall surface changes is predicted, which leads to a nonlinear dynamic loss behavior. The obtained loss expression represents a simple generalization of the Pry and Bean model, capable of taking into account, in an approximate but unified way, the various mechanisms, such as the presence of irregularities in the wall motion, domain refinement, and wall bowing, which strongly affect the behavior of dynamic losses in oriented materials.
Observation of a new chromium-related complex in GaAs:Cr
Authors: Deveaud B. , Lambert B. , Picoli G. , Martinez G.
Published: February 2003

A new zero-phonon line in GaAs:Cr is observed at 0.844 eV. This line is attributed to an internal transition of a Cr2+-Te complex. Photoluminescence excitation experiments are reported for the first time on the 0.839-eV line (Cr2+–X). Comparison of the results on these two centers with those obtained on isolated Cr2+ gives interesting details about the trigonal field at Cr2+–X and Cr2+-Te. Other complexes are not suspected to be observed in luminescence.
Exciton transport in optically excited AlxGa1−xAs-GaAs single quantum well
Authors: Le H. Q. , Lax B. , Maki P. A. , Palmateer S. C. , Eastman L. F.
Published: February 2003

Evidence of exciton transport in optically excited Al0.2Ga0.8As-GaAs quantum well structures at low temperature and low excitation intensity is demonstrated. Photoluminescence studies of single quantum wells showed an increase in the luminescence intensity of free excitons in the GaAs quantum well with a corresponding decrease in the exciton luminescence of Al0.2Ga0.8As barriers as temperature is varied from 1.9 to 16 K. Magnetic fields up to 100 kOe were applied in order to hinder ambipolar transport. It was found that magnetic fields caused no effect on exciton luminescences. These results indicate that excitons are formed in the barrier domains and migrate to the quantum well. Further analysis leads to the interpretation that excitons undergo relaxation without being dissociated in a quantum well. It was found that a thermal activation energy E∼3.5±0.5 meV is involved in the transport of excitons. The origin of this activation energy is considered.
A simple model for impurity photoabsorption in silicon
Authors: Bambakidis G.
Published: February 2003

A simple model for absorption of infrared radiation by impurity atoms in silicon crystals has been developed and applied to electronic excitations of the Group V donors Bi, Sb, As, and P, and the Group III acceptors B, Al, Ga, and In. The model is based on the quantum-defect method for approximating bound donor or acceptor wave functions outside the core region of the impurity. For each donor species, the relative oscillator strengths have been calculated for the transitions from the ground state to the first four excited levels. For each acceptor species, the relative oscillator strengths were calculated for transitions from the P3/2 ground state to the first three P1/2 excited levels. Comparison with high-resolution absorption spectra show qualitative agreement for the low-lying transitions.
Phenomenological model for pisosecond-pulse laser annealing of semiconductors
Authors: Agassi D.
Published: February 2003

A system of three coupled diffusion equations describing the equilibration process in the premelt phase of laser annealing is solved and analyzed for a short pulse—20,30 psec—on a thin (d=150 Å) and thick Si,Ge slabs. We find the carrier temperature to be a very sensitive gauge for the electron-phonon relaxation time constant τ0. The existing data (Si, λL =0.533 μm and EL =0.25 J/cm2) are consistent with τ0≂0.4–1.0 psec, and the carrier peak temperature is predicted to be in the range 2000–4300 °K.
Mechanisms for lateral solute segregation in edge-defined film-fed crystal growth
Authors: Ettouney Hisham M. , Brown Robert A.
Published: February 2003

The extent of lateral dopant segregation across a crystal sheet produced by the edge-defined film-fed growth technique is set by the shape of the die and molten zone and by the intensity of the convection in the melt. Finite element calculations of the velocity and concentration fields for model melt shapes are used to separate the influences of growth rate, die geometry, melt height, tapering of the melt/gas interface, and curvature of the melt/solid phase boundary on lateral segregation. Curvature of the solidification front is most important when the melt height is large enough that the diffusion layer does not reach the die top. Surface-tension-driven convection induced by the axial temperature gradient dominates over the growth velocity and leads to qualitatively different lateral segregation patterns.
Stress effect in Au-Si Schottky diode doped with Cu
Authors: Tōyama Naotake
Published: February 2003

The stress effect in Au-Si Schottky diodes doped with copper was examined by photoelectric measurement under localized anisotropic stress of the order of 109 dyn/cm2. It was found out that the current increase with stress was due to the changes of both the shunt resistance and the effective Richardson constant of a Schottky diode. The changes of these diode parameters with stress are attributed to the multiplication of the residual lattice strain in silicon due to copper introduction. The lattice strain produces a strain-induced level at 0.160 eV from the conduction band edge. We can infer that a tunneling current component through the potential barrier via this strain-induced level increases with stress. To obtain a highly stress-sensitive diode, the lattice strain of the order of 0.9–1.2×10−4 must be introduced previously into the surface of silicon by the choice of a proper copper diffusion condition.
An investigation of the two-dimensional shape of ion-implanted regions
Authors: Roitman P. , Albers J. , Myers D. R.
Published: February 2003

The two-dimensional shape of arsenic ion-implanted regions in single-crystal silicon was investigated both experimentally and theoretically. Experimentally, two techniques were shown to have the necessary submicron resolution: a junction etch process and a scanning electron microscope-induced current collection method. A comparison of junction depths determined by the etch technique and the electron beam induced current technique with the depths calculated using several amorphous target codes was made. For the case of low temperature (600 °C) anneals, the etch technique agrees very well with the junction depths predicted by the amorphous target code due to Winterbon. The lateral junction locations obtained from the etch technique are in good agreement with the predictions of a two-dimensional Monte Carlo code which indicates that the arsenic does not show any significant lateral scattering under mask edges. For the high temperature (1000 °C) anneals, the etch and electron beam induced current techniques agree with each other. Comparison with arsenic-diffusion models shows that concentration-dependent effects are important.
Ion-beam-induced atomic mixing and amorphization in Ti/Ni bilayered thin films
Authors: Saito K. , Iwaki M.
Published: February 2003

Ion-beam-induced atomic mixing of Ti/Ni bilayers was studied by transmission electron microscopy. The depth of the Ti/Ni interfaces was controlled to be approximately equal to the mean damage depth of 150-keV Ar ions. At a critical dose of 1×1015 ions/cm2, diffuse halo rings appear in the electron diffraction pattern, and increase in their intensity with Ar dose. This indicates that an amorphous phase is formed by ion mixing of the bilayers. After a high dose of 1×1017 ions/cm2, a high density of Ar bubbles is observed near the interface boundary. These results are understood in terms of the simultaneous operation of ion-beam-induced mixing and radiation-induced lattice instability.
A numerical study of manganese redistribution in GaAs employing an interstitial-substitutional model
Authors: Jordan A. S. , Nikolakopoulou G. A.
Published: February 2003

A finite element simulation of the anomalous out-diffusion of Mn in GaAs employing an interstitial-substitutional model combined with defect-chemical kinetics has been performed. The major species considered were Ga vacancies (VGa ), Mn substitutionals (MnGa), and interstitials (Mni) augmented by shallow donors (DAs ) and Ga vacancy-donor pairs (VGa-DAs). Mathematically, the model can be represented by two ordinary differential equations which are the kinetic relations describing the formation of MnGa and VGa-DAs coupled with three partial differential equations, including sink and source terms, for the diffusion of VGa, Mni, and DAs . The analysis required advanced numerical techniques using dynamic spatial and time meshes. We have achieved a very good theoretical description of Mn out-diffusion data for both 90 min and 24 h annealing cycles up to a depth of 0.5 μm from the surface [P.B. Klein, P. R. Nordquist, and P. G. Siebenmann, J. Appl. Phys. 51, 4861 (1980)]. Moreover, eventual depletion of the Mn contamination has been demonstrated. However, an inflection beyond 0.5 μm observed in the experimental results cannot be explained by the present treatment.
Formation of thin films of NiSi: Metastable structure, diffusion mechanisms in intermetallic compounds
Authors: d’Heurle F. , Petersson C. S. , Baglin J. E. E. , La Placa S. J. , Wong C. Y.
Published: February 2003

The formation of NiSi films from the reaction of Ni2Si with (100) and (111) silicon substrates was found to be controlled by a lattice diffusion process with an activation energy of 1.70 eV. In order to correlate kinetic information obtained by Rutherford backscattering with x-ray diffraction data, ‘‘standard’’ diffraction powder patterns for both Ni2Si and NiSi have been established. The existence of a metastable hexagonal form of NiSi has been confirmed. Observations on the formation of Ni2Si confirm previous investigations. The diffusion process at work during the formation of NiSi is discussed in terms of the crystalline anisotropy of this compound and compared to what is known about diffusion in other silicides.
Relation between growth conditions and reconstruction on InAs during molecular beam epitaxy using an As2 source
Authors: Hancock Bruce R. , Kroemer Herbert
Published: February 2003

We have studied the growth of InAs by molecular beam epitaxy using an As2 source and have determined the growth conditions at which the surface changes from arsenic stable to indium stable. We conclude that the governing parameter is not the flux ratio, but rather the flux difference, i.e., the absolute amount of excess arsenic supplied. We propose a model to explain this behavior.
Ultramicroindentation apparatus for the mechanical characterization of thin films
Authors: Wierenga P. E. , Franken A. J. J.
Published: February 2003

An apparatus is described which is suitable for the mechanical characterization of all kinds of extremely thin films by indentation experiments at very low loads. The penetration depth can be measured as a function of time or load with a resolution of 5 nm. The indentor force can be varied from 10 μN to 5 mN. On the basis of some examples it is demonstrated that the instrument is applicable for ultramicrohardness measurements on metal films as well as for the determination of the viscoelastic properties of polymer coatings. Moreover, it is shown that the apparatus can be used for surface profilometry and ultramicroscratching experiments on relatively soft layers.
Determination of the minority carrier mobility of n-type cadmium-mercury-telluride using the Haynes–Shockley method
Authors: Lacklison D. E. , Duggan G.
Published: February 2003

The measurement of the minority carrier mobility of n-type cadmium mercury telluride using Haynes–Shockley method is described. The practical and theoretical aspects of the measurement are presented and compared with the flying light spot method. Observed pulse widths were found to be larger than expected from diffusion broadening alone, a fact which is explained by the existence of an accumulating contact in the vicinity of the minority carrier detection region. The drift velocities determined from the rate of change of delay with distance were found to be relatively insensitive to this pulse distortion. Mobilities of 180 cm2/V s for Cd0.29Hg0.71Te at 185 K and 460 cm2/V s for Cd0.22Hg0.78Te at 90 K have been observed.