bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoluminescent and electrical properties of InGaPAs mixed crystals liquid phase epitaxially grown on (100) GaAs
Authors: Mukai Seiji
Published: February 2003

The liquid phase epitaxial growth of InGaPAs layers on (100) GaAs is described for growth temperatures of 785 and 815 °C. Photoluminescence (PL) spectra and electron Hall mobility of the layers are investigated as a function of crystal composition. The width of PL spectra measured at 300 K is 40 meV, approximately the same value as that of GaAs, when the energy gap Eg of the layers is 1.9 eV or lower than 1.6 eV. The spectral width is around 80 meV when the energy gap of the layers is around 1.75 eV. The increase in the spectral width is attributed to variation of the local energy gap from analysis of dependence of the PL spectra on temperature and on excitation intensity. The indication that local energy gap varies in layers with Eg around 1.75 eV is consistent with the composition dependence of electron mobility. The mobility shows a sharp dip down to 1000 cm2/Vs around this composition, while it depends on composition only slightly for layers with Eg lower than 1.6 eV. The dip in composition dependence is attributed to space-charge scattering from analysis of temperature dependence of mobility. X-ray diffraction spectrum and surface morphology are also reported. The width of x-ray diffraction spectra is large for layers with Eg around 1.75 eV. This indicates that the local lattice constant varies significantly. Thick and uniform layers are particularly difficult to grow for such composition. These composition dependences of PL spectra, x-ray diffraction, and surface morphology are more significant in layers grown at 785 °C than in layers grown at 815 °C. The local variation of energy gap and lattice constant is attributed to variation of local composition caused by immiscibility of InGaPAs.
Ion knock-on broadening effects in Auger sputter profiling studies of ultrathin SiO2 layers on Si
Authors: Taubenblatt Marc A. , Helms C. R.
Published: February 2003

Ultrathin layers of SiO2 on Si (less than ∼100 to 200 Å) show a reduction in the measured width of the Si–SiO2 interface when profiled using ion sputtering. Although previously attributed to the intrinsic properties of thin oxides or surface roughening due to ion-beam etching, this effect is predominantly caused by ion knock-on broadening or knock-on enhanced diffusion. It is important to realize that this effect is an artifact of the sputtering process, and not a property of the system under study. A model is developed based on the spatial distribution of the energy deposited by the sputtering ions to explain the observed reduction in measured interface width. This model is compared with interface widths obtained using Auger electron spectroscopy from identically grown thermal SiO2 samples which have been thinned by chemical etching to eliminate oxidation kinetic effects.
Phenomenological theory of shock-induced polarization. I
Authors: de Icaza-Herrera M.
Published: February 2003

After reviewing the actual state of knowledge on Shock-Induced Polarization, we discuss the validity of Allison’s theory, specially concerning the physical meaning of his three parameters P0s, K′, and τ. We then propose another approach, splitting the electric field in the dielectric into two components: the electric field (uniform) produced by the charges in the plates, and the electric field (nonuniform) produced by the polarization charges. This enables us to relate the line integral of polarization across the dielectric with an easily measurable potential difference F(t ). Its time derivative Ḟ(t ) is then found to be related with the polarization discontinuity across the shock front, without making any assumptions on the space or time dependence of polarization. Later, we introduce the dielectric properties in a Lagrangian frame, which are finally inserted, in Eulerian form, in Ḟ(t ). Four equations for Ḟ(t ) are obtained, depending on the relaxing properties of the nonshocked medium and on the mechanism producing the polarization: the dipolar orientation or the bond scission model. We also present the Ḟ(t ) equation when there is no reflected shock at the second electrode, the entire dielectric being shocked.
Construction of a wide-range tabular equation of state for copper
Authors: Trainor Kathleen S.
Published: February 2003

A global equation of state (EOS) for copper has been constructed, ranging from densities of 10−3–103 Mg/m3 and from ambient temperatures to 5×104 eV (1 eV=11604.5 K). Six different theoretical models were used: a soft sphere liquid model at low temperatures below melt density; an ionization equilibrium model based on a modified Saha method at moderate temperatures in expansion; a nonideal plasma theory for high temperatures; a modified Thomas–Fermi–Kirzhnits model in compression; rigorous electron band theory for the zero degree isotherm; and a semiempirical model in the solid-liquid-vapor region. Assembly of the EOS will be described. Agreement with existing experimental data is good.
The effect of interposed silicide thickness on growth rate in bilayer silicide thin-film structures: The Si〈111〉/Pd2Si/Cr system
Authors: Zingu E. C. , Comrie C. , Pretorius R.
Published: February 2003

A model has been developed, using Fick’s diffusion equations, to describe the effect of interposed silicide thickness on the growth rate of the outer silicide layer in bilayer metal–silicon thin film system. The model is based on diffusion-limited transport of silicon through the interposed silicide layer and predicts that the growth rate of the outer silicide layer will be inversely proportional to the thickness of the interposed layer, if the interposed thickness exceeds a certain critical value. To test the model, the growth rate of CrSi2 formation in the Si〈111〉/Pd2Si/Cr system was studied as a function of Pd2Si thickness. The CrSi2 thickness was always found to increase linearly with annealing time, indicating a reaction-limited process. For thin epitaxial Pd2Si layers the CrSi2 growth rate was equal to that of CrSi2 grown directly on Si. However, for epitaxial Pd2Si layers thicker than the critical thickness, CrSi2 growth was inhibited causing the growth rate to be inversely proportional to Pd2Si thickness, in contrast to that found for CrSi2 formation on nonepitaxial Pd2Si where no thickness effects were found. The thickness effect of the epitaxial Pd2Si layer is believed to be due to its microstructure, which inhibits silicon diffusion.
Study and application of the mass transport phenomenon in InP
Authors: Chen T. R. , Chiu L. C. , Hasson A. , Yu K. L. , Koren U. , Margalit S. , Yariv A.
Published: February 2003

A study of the mass transport phenomenon in InP is presented. Conditions and possible explanation for the transport process are discussed. Characteristics of the mass transported InP homojunctions are described and compared with those in the InP–InGaAsP heterojunctions. Effects of the mass transported junction on laser performance are discussed.
Pulsed thermal annealing of ion-implanted silicon
Authors: Scovell P. D. , Spurgin E. J.
Published: February 2003

The use of a graphite strip heater to anneal implanted silicon has been investigated. The good electrical activity of an arsenic implanted layer obtained after annealing in this way is shown to degrade after simulated low temperature processing and lead to highly resistive layers. The annealing system has been used to reactivate such layers by employing high temperature thermal pulses of short duration which avoids excessive in-diffusion. The same annealing schedule has been used successfully to activate highly doped antimony, boron, and phosphorus layers. The importance of controlling the annealing ambient has also been studied and it is concluded that annealing in nitrogen avoids out-diffusion of dopant from the surface.
Electron power loss in the (100) n channel of a Si metal-oxide-semiconductor field-effect transistor. II. Intersubband phonon scattering
Authors: Krowne Clifford M.
Published: February 2003

A simple matrix element is used to approximate electron-acoustic phonon scattering between different electron subbands i in the n channel of a (100) surface silicon MOSFET (metal-oxide-semiconductor field-effect transistor) device. This matrix element is used to determine the form of the electron power loss Pij in a i→j intersubband transition. P10 is calculated for TL =4.2 °K lattice temperature and electron temperatures Te between 4.4 °K and 18 °K when the electron inversion density Ninv =(3.76–10.0)×1011 cm−2 and an acceptor density NA =1014/cm3, and compared to Fang and Fowler’s experimental data (which is put into the form of an experimental power loss Pexp). This is justified since the total power loss P due to intrasubband scattering as well as other Pij terms besides P10 is small. It is found that good to excellent fits between P10 and Pexp occur by adjusting the separation Δε10 between the lowest two circular subband edges. Δε10 is between 5.2 and 9.4 meV, and the electron-phonon deformation coupling constant D≊3.5 eV. The values of Δε10 obtained in such a manner roughly agree with Stern’s theoretical self-consistent results. P10 is very sensitive to both Δε10 and to the effective mass for motion parallel to the surface m1 with the results implying that m1≊0.19m0 (m0=free electron rest mass). If one wants to find the contribution of intersubband scattering to P at higher TL, the formalism should still be applicable, although the approach could be much more complicated due to the addition of new Pij terms coming from both higher subbands and new scattering agents such as optical modes.
Minority-carrier diffusion-length measurement and lifetime in Pb0.8Sn0.2Te and indium-doped PbTe liquid phase epitaxy layers
Authors: Shahar A. , Oron M. , Zussman A.
Published: February 2003

Minority carrier diffusion length was measured between 10–110 K, using a laser light spot scanning technique in Pb0.8Sn0.2Te and In-doped PbTe layers, grown by liquid phase epitaxy. A new method for fabricating diodes with a beveled surface is described. Diffusion lengths L of about 10 and 1 μm were measured in Pb0.8Sn0.2Te epilayers grown at 500 and 600 °C, respectively. In indium-doped PbTe epilayers, L varies with temperature in the range 0.2 to 1.6 μm. The measured diffusion length was used with available mobility data to derive the minority-carrier lifetime in these epilayers. Comparison of the experimental results with theory shows that in undoped Pb0.8Sn0.2Te, carrier lifetime is dominated by band-to-band radiative and Auger recombination mechanisms, while in In-doped PbTe, recombination takes place via nonradiative centers. The implications of the observed diffusion length and the derived lifetime values on the performance of optoelectronic devices are discussed.
Interfacial stability of SnO2/n-Si and In2O3:Sn/n-Si heterojunction solar cells
Authors: Maruska H. Paul , Ghosh Amal K. , Eustace Daniel J. , Feng Tom
Published: February 2003

High efficiency SnO2/n-Si and In2O3:Sn/n-Si solar cells have been fabricated which when encapsulated in EVA (ethylene vinyl acetate copolymers) and kept at temperatures below 200 °C exhibit long-term stability. However, in the absence of proper encapsulation or at high temperatures, it is possible for the properties of heterojunction SnO2/n-Si and In2O3:Sn/n-Si solar cells to suffer degradation through two distinct mechanisms, one optical and the other thermal in nature. In either case, losses in Voc can be correlated with changes in the dark current-voltage characteristics: light stress increases the dark saturation current J0, while heat stress decreases the diode quality faction n. Both degradation mechanisms are related to changes in the stored charges in the SiOx interphase region between the conducting oxide and the silicon. The thermal process is only relevant for temperatures above 300 °C, while the optical process is only evidenced if ultraviolet light is incident on the cell. Thus, cells kept at T<200 °C behind a suitable UV-absorbing filter remain stable indefinitely.
1/f noise in polycrystalline silicon resistors
Authors: de Graaff H. C. , Huybers M. T. M.
Published: February 2003

The 1/f noise in polycrystalline silicon resistors has been measured at room temperature. The resistors were manufactured in low-pressure chemical vapor deposition films, implanted with B, P, and As and processed in two different technologies with different temperature cycles. The spectral density was essentially independent of the type of implantation and of the processing. The results can be described with Hooge’s empirical law and Kleinpenning’s model for the 1/f noise in Schottky barriers. At low doping levels Hooge’s constant turned out to be ∼4×10−3 and it decreased with increasing doping concentration, more or less as (μ/μlattice)2.
Pressure pulse in an infrared pneumatic detector: Theory based on the Einstein coefficient for induced absorption
Authors: Gupta J. P. , Sachdev R. N. , Vohra K. G.
Published: February 2003

The kinetics of gases due to absorption of infrared radiation on closed cells has been discussed with the use of the Einstein coefficient for emission and absorption of radiation. The expression derived for the magnitude of pressure pulse in the cell explains satisfactorily the observed characteristics of the pneumatic detector.
Nonlinear self-consistent theory of the orotron
Authors: Leavitt Richard P. , Wortman Donald E.
Published: February 2003

We describe a simple, nonlinear, self-consistent theory of the orotron (a Smith–Purcell free-electron laser) in which the relationship between output power, beam current, and beam accelerating voltage is obtained in closed form. This model explains certain features of the orotron observed experimentally that were previously poorly understood. Quantitative predictions of the theory are in good agreement with experiment.
Effects of annealing and electromigration on surface morphology of polycrystalline films
Authors: Chang Chi-Yang , Huang Huei-Li
Published: February 2003

The capillarity-induced surface mass transport has been extended to cases where there is a notch and/or a ridge on a bicrystal system. Changes in the surface morphology caused by capillarity-induced and electromigration-induced surface diffusions and grain boundary diffusions have been analyzed. Thermal grooving is shown to develop only when the initial slope of a notch on the crystal surface is less than γb/2γs (γb and γs are, respectively, the grain boundary and the surface Gibbs free energy) or when the initial surface contains a ridge at the grain boundary. The slope of the grooving profile is invariant with time but its depth develops as the one fourth power of time. Surface fluxes due to the electromigration origin change the morphology in an asymmetric manner, biased in the direction of the electron flow. When combined with fluxes from grain boundary diffusion, severe mass depletion and accumulation can occur, giving rise to characteristic electromigration damage of open circuit failures. Finally, the concept of an optimum annealing time in relation to electromigration is explored.
Excitation of Be+ by electron impact
Authors: Ganas P. S. , Gately L. P.
Published: February 2003

A realistic analytic central potential is used to generate wave functions for the ground and excited states of singly-ionized beryllium. Generalized oscillator strengths and integrated cross sections from threshold to 5 keV are calculated in the Born approximation for 2s-ns, 2s-np and 2s-nd excitations. Comparison of the cross sections with experimental and theoretical data is discussed for the 2s-2p transition.
A new evaluation of the Goos–Hänchen shift and associated time delay
Authors: Yasumoto K. , Ōishi Y.
Published: February 2003

A wave packet reflected totally at an interface between two media may undergo the Goos–Hänchen shift and associated time delay. Two different theoretical approaches have been presented so far to evaluate this phenomenon. One is the stationary-phase method and the other is the conventional energy-flux method. In this paper, a certain deficiency existing in the conventional energy-flux method is pointed out and a new energy-flux method is derived based on an accurate argument of the conservation of energy flux. The new energy-flux method confirms the consistency of the predictions by the stationary-phase method from the point of view of the conservation of energy.
Temperature dependent density of states effective mass in nonparabolic p-type silicon
Authors: Lang Joseph E. , Madarasz Frank L. , Hemenger Patrick M.
Published: February 2003

Previously, an exact calculation was made for the temperature dependent density of states effective mass in p-type silicon. This calculation was made for the nondegenerate regime and included the full nonspherical-nonparabolic nature of the valence band structure. For those researchers interested in using this mass for the analysis of their transport data we offer a polynomial fitted expression. The values generated are within 1% of the theoretical values.
On the calculation of differential mobility
Authors: Price Peter J.
Published: February 2003

This note points out the advantage, in Monte Carlo computation of the differential mobility for semiconductor hot electrons, of calculating in terms of time interval between a perturbing field and the response, rather than for a given frequency of the perturbing field (time domain rather than frequency domain) and proposes a procedure for this. The extension to a hot-electron system not in a steady state is discussed.
Ferrite resonance cones
Authors: Bellan P. M.
Published: February 2003

Resonance cones, a phenomenon which has been observed in electrostatic plasma waves, should also exist in magnetostatic waves propagating in ferrites. Resonance cones, the spatial characteristics of the hyperbolic partial differential describing both plasma and ferrite waves, are aligned along the group velocity trajectory and are equivalent to the superposition of an infinity of normal modes. The existence of resonance cones has been overlooked in standard normal mode analyses of ferrite waves, where typically, only one mode is assumed to exist at a time.
Band-to-band Auger recombination in silicon based on a tunneling technique. II. Experiment
Authors: Krieger G. , Swanson R. M.
Published: February 2003

Using a new method based on hot-electron generation, band-to-band Auger recombination in n+ silicon is studied experimentally. Using the theory developed in Part I, a conservative analysis demonstrates that this Auger recombination is limited to an electron Auger coefficient smaller than 5×10−32 cm6/sec which is in disagreement with some earlier studies reporting Cn =2.8×10−31 cm6/sec.
Far-infrared photothermal ionization spectroscopy of semiconductors in the presence of intrinsic light
Authors: van de Steeg M. J. H. , Jongbloets H. W. H. M. , Gerritsen J. W. , Wyder P.
Published: February 2003

The equilibrium distribution of electrons and holes over shallow impurity states and energy bands of an ultrapure semiconductor is studied for the situation where the semiconductor is continuously illuminated with intrinsic light (i.e., radiation with energies of the order of the gap energy of the semiconductor). The response to additional injection of free minority or majority charge carriers into the energy bands—caused by photothermal ionization of minority or majority impurities, respectively—is separately investigated. The equilibrium and the response have theoretically been analyzed by means of a description with a set of rate of change equations. This analysis explains the usually observed behavior that photothermal ionization of minority impurities in ultrapure germanium under continuous illumination with intrinsic light gives rise to a decrease in electrical conductivity. The measured time evolution of the change in conductivity of an ultrapure germanium sample after the start of the photothermal process revealed a slow (∼5 ms) change, connected with minority impurities only, as well as a fast (<0.5 ms) change. The slow response time has been associated with the electron-hole recombination time, yielding a value 5×10−12 cm3 s−1 for the electron-hole recombination constant. It is demonstrated that in photothermal ionization spectroscopy, when using phase-sensitive detection techniques by means of a lock-in amplifier, such a simultaneous presence of a fast and a slow (i.e., of the order of magnitude of the chopping times applied) change in conductivity can cause artefacts in the spectra.
Substitutional placement of phosphorus in ion implanted silicon by recrystallizing amorphous/crystalline interface
Authors: Sadana D. K. , Washburn J. , Magee C. W.
Published: February 2003

Ion implantation of P into (111) Si has been investigated by cross-sectional transmission electron microscopy and secondary ion mass spectrometry. In the dose range 1×1015–2×1016 cm−2 at 120 keV the formation and width of the amorphous (a) layers were sensitively dependent on wafer temperature. The effect of dynamic annealing on the crystalline (c) to amorphous transformation, and the effect of amorphicity and roughness of the a/c interface on the formation of microtwins have been studied. It has been observed that the P atoms in the amorphous (a) region do not redistribute on subsequent annealing while the P atoms below the a/crystalline (c) interface diffuse rapidly into the Si substrate. The carrier concentration profiles from the annealed samples were found to follow the atomic profiles almost exactly over the depth range extending from the surface to where the original a/c interface existed. However, in the deeper regions, the electrical activity was found to be dependent on the annealing temperature used. The different behavior of atomic and carrier concentration redistributions in the amorphous and crystalline regions has been explained by a model that assumes incorporation of impurity atoms on substitutional sites by the moving a/c interface on recrystallization. The P atoms in the deeper regions are believed to redistribute via an interstitial diffusion mechanism at low temperatures (≤750 °C) and eventually occupy substitutional sites at higher temperatures (>800 °C).
Step coverage simulation and measurement in a dc planar magnetron sputtering system
Authors: Blech I. A. , Vander Plas H. A.
Published: February 2003

The step coverage of a dc planar magnetron sputtering system with a revolving substrate is analyzed by both computer simulation and measurement of the step coverage. The model assumes line of sight deposition, no reemission, and the cosine growth law. Good quantitative agreement has been obtained between the model and the experiments. The modeled system does not show the deep cracks typical of the point source planetary system. This is explained by comparing the vapor distribution functions of the planetary and the sputtering systems.
Properties of tin doped indium oxide thin films prepared by magnetron sputtering
Authors: Ray Swati , Banerjee Ratnabali , Basu N. , Batabyal A. K. , Barua A. K.
Published: February 2003

Indium tin oxide (ITO) films have been prepared by the magnetron sputtering technique from a target of a mixture of In2O3 and SnO2 in the proportion 9:1 by weight. By optimizing the deposition conditions it has been possible to produce highly transparent (transmission ∼90%) and conducting (resistivity ∼10−5 Ω cm) ITO films. A resistivity ∼10−4 Ω cm has been obtained for films of thickness ∼1000 Å at a comparatively low substrate temperature of 50 °C and without using oxygen in the sputtering chamber. To characterize the films, the following properties have been studied, viz., electrical conductivity, thermoelectric power, Hall effect, optical transmission, and band gap. The effect of annealing in air and vacuum on the properties of the films have also been studied.
Kinetics of anisothermal phase transformations
Authors: Markworth Alan J. , Glasser M. Lawrence
Published: February 2003

An analytical study of anisothermal phase-transformation kinetics is described. In particular, the familiar Johnson–Mehl–Avrami equation is generalized to the situation for which temperature increases linearly with time. An exact analysis of the problem is carried out, with the general solution being obtained in terms of one of Horn’s confluent hypergeometric functions. In order to facilitate practical application of the analysis, a number of approximate solutions are also obtained, one which is applicable for small relative changes of temperature and two of which are described in terms of certain asymptotic expansions. Two specific numerical examples are considered which serve to illustrate conditions affecting the relative accuracy of the approximate solutions.
Time-dependent etching of GaAs and InP with CCl4 or HCl plasmas: Electrode material and oxidant addition effects
Authors: Smolinsky Gerald , Gottscho Richard A. , Abys Susan M.
Published: February 2003

In the dry etching of microelectronic devices, a common side effect is the deposition of material which can inhibit etching and catastrophically contaminate devices. However, simultaneous deposition and etching may be necessary to achieve a desired selectivity and anisotropy. Carbon tetrachloride is one plasma reagent which has been used to etch Al, Si, GaAs, and InP and has shown a propensity to deposit polychlorocarbons. Two variables known to affect both plasma etching and deposition rates are electrode material and oxidant concentration. To understand these effects, we utilize optical emission spectroscopy to measure instantaneous CCl4 plasma etching rates of GaAs and InP as a function of O2 or Cl2 concentration with graphite or stainless steel electrodes. For comparison, HCl plasma etching of InP is also examined. Post-etch surface analysis by Auger electron spectroscopy in conjunction with time-resolved, etching-rate measurements enable a separate assessment to be made of the effects of gas-phase composition and deposition on etching rates. When stainless steel electrodes are used, oxidant addition to the CCl4 feedstock liberates chlorine and enhances the initial etching rate but does not reduce etch inhibition by plasma-generated deposits. The use of graphite electrodes reduces deposition but does not eliminate it. If an HCl plasma is used with stainless steel electrodes to etch InP, deposition and etch inhibition by iron and nickel chlorides occur. In general, deposition can be minimized by using graphite electrodes and HCl gas. However, faster etching rates can be achieved by using graphite and CCl4. In this case oxidant addition should not only enhance etching rates but also reduce polychlorocarbon formation. The use of stainless steel electrodes with chlorine containing plasmas should generally be avoided.
Laser-enhanced nucleation of oxidation-induced stacking faults in silicon
Authors: Hayafuji Y. , Ogawa J. , Aoki Y. , Shibata A. , Usui S.
Published: February 2003

We have studied the laser-enhanced nucleation of oxidation-induced stacking faults in ion-implanted silicon. Silicon ions of 100 keV were implanted onto the silicon surface in the dosages ranging from 1.0×1013 to 1.0×1014 cm−2. The laser beam used was 1.06 μm in wavelength with a diameter of 40 μm, and was generated from a Q-switched Nd:YAG laser at a repetition rate of 12 kHz and a 150-ns pulse width. It was found that the laser irradiation enhanced the generation of oxidation-induced stacking faults or their generation nuclei through the implantation-induced lattice defects at the boundary between the laser scanned and nonscanned regions. Laser-enhanced nucleation is caused by the supersaturation of the silicon self-interstitials generated by the rapid heating-cooling cycle induced by laser irradiation reacting with the self-interstitials induced during oxidation.
Properties of electroless gold contacts on p-type cadmium telluride
Authors: Musa A. , Ponpon J. P. , Grob J. J. , Hage–Ali M. , Stuck R. , Siffert P.
Published: February 2003

The electrical and structural properties of contact obtained on p-type cadmium telluride by electroless deposition of gold from a chloride solution have been investigated by means of current-voltage measurements and ion beam analysis (Secondary Ion Mass Spectrometry and Rutherford Backscattering). On high resistivity material, the ohmic behavior of these contacts has been found strongly dependent on the time of reaction between AuCl3 and CdTe and can be interpreted in terms of a current flow enhanced by tunnelling through the Au–CdTe barrier. This enhancement results from the diffusion of dopant gold atoms into the semiconductor, a distance of a few tens of nanometers below the interface.
Interaction of hydrogenated amorphous silicon films with transparent conductive films
Authors: Kitagawa M. , Mori K. , Ishihara S. , Ohno M. , Hirao T. , Yoshioka Y. , Kohiki S.
Published: February 2003

The effects of the deposition temperature on the interaction of the hydrogenated amorphous silicon films with indium–tin–oxide and tin–oxide films have been investigated in the temperature range 150–300 °C, using Auger electron spectroscopy, secondary ion mass spectrometry, and scanning electron microscopy. It was found that the constituent atoms such as indium and tin are detected in the thin amorphous silicon films deposited. Around the interface between the transparent conductive films and amorphous silicon films the formation of oxidized silicon was also observed. The depth distributions of indium in the amorphous silicon films are strongly dependent upon the deposition temperature while those of tin are almost independent. From results on the observation of the surface morphology of the amorphous silicon films, it has been shown that those depth distributions may be much affected by the initial covering over substrates with the amorphous silicon films.
Damage induced in Si by ion milling or reactive ion etching
Authors: Pang S. W. , Rathman D. D. , Silversmith D. J. , Mountain R. W. , DeGraff P. D.
Published: February 2003

Surface damage in Si substrates created by Ar-ion milling or by reactive-ion etching in CF4, CHF3, Cl2, SiCl4, or SiF4 has been investigated. Metal-oxide-semiconductor capacitors were fabricated on the etched Si substrates, and the interface-state densities were obtained from capacitance-voltage measurements. Interface states generated by the dry etching processes were strongly dependent on the etching gas and the bias voltage. Carbon-based gases (CF4, CHF3) induced more interface states than those without carbon. For the carbon-based gases, Si samples etched in CHF3 showed lower densities of interface states than samples etched in CF4 under the same conditions. Generation lifetime measurements indicated that samples with large densities of interface states also had short lifetimes. Measurements of oxidation-induced stacking faults caused by dry etching were consistent with both the interface-state and lifetime measurements. Thermal annealing of the etched wafers was not effective in reducing the surface damage. The measured interface states on the dry etched Si substrates could be lowered to their pre-etched levels by removing at least 500 Å of the etched surface by wet chemical etching.
The microstructure of programmed n+p
n+ polycrystalline silicon antifuses
Authors: Lunnon M. E. , Greve D. W.
Published: February 2003

The microstructure and programming mechanism of an electrically programmable antifuse is described. The device consists of n+pn+ junctions in polycrystalline silicon programmed by applying voltage pulses to the two n+ terminals. High voltage electron microscopy and optical microscopy reveal the micro-structure of programmed antifuses. Devices with Al metallization can be programmed with a single long pulse. The final resistance is about 20Ω and a metallic aluminum spike is formed between the two contacts. With Al and TiW (barrier) metallization, programming occurs after a series of short pulses by migration of n+ dopant. This results in an ohmic contact between the two n+ regions with a final resistance of approximately 300Ω.
Interaction between microwaves and a single vortex in a long Josephson tunnel junction
Authors: Scheuermann M. , Chen J. T. , Chang Jhy-Jiun
Published: February 2003

The effects of microwave radiation on the vortex modes of Josephson tunnel junctions have been examined. Current steps are induced on the resistive branches at voltages V=(n/m)(hν/2e) where n and m are integers and ν is the frequency of the incident radiation. The system we have studied is a well-defined one in which vortices undergoing periodic motion interact with the periodic perturbation of the microwave radiation. Vertical steps are induced when resonance occurs.
Properties of Nb3Ge variable-thickness bridges
Authors: Goto T. , Tanihara H.
Published: February 2003

Variable-thickness bridges (VTB’s) using Nb3Ge film have been investigated. In order to form a very short length bridge in the direction of the current flow and cause little damage to the superconducting properties, slant evaporation and anodization technique was used. The current–voltage characteristics, temperature dependence of critical current response to microwave irradiation were measured. One of the VTB’s whose length is estimated to be less than 100 nm showed microwave induced steps over a wide temperature range, from 6 to 18.3 K. The resistively shunted Josephson junction model is found to explain the behavior of the device well.
Stable performance Nb variable thickness microbridge type Josephson junctions: A reproducible fabrication technique
Authors: Kodama Jun-ichi , Hontsu Shigeki , Hirai Heihachiro , Oka Hisao , Kato Tadao , Watakabe Yaichiro , Kato Taka-aki
Published: February 2003

A novel method of fabrication, as described in the following, was developed that ensures a good reproducibility of the junction. Namely, poly-Si was deposited over a Si substrate whose surface had been previously thermally oxidized. The poly-Si overlaid surface was then thermally oxidized. The bridge configuration of the junction was microprocessed by means of electron beam lithography. The fabricated configuration served as a mask in depositing the Nb layer on the substrate by means of rf sputtering to conclude the fabrication of a microbridge Josephson junction. The final process of the formation of the variable thickness microbridge configuration was readily carried out by placing another properly shaped mask over the masking bridge or by forming an SiO2 layer over the poly-Si layer. The SiO2 layer was processed by selective plasma etching so that it would act as a mask over the bridge portion. The stabilization of the characteristics of the junction has been achieved due to the passivation which takes place during the heat treatment in atmosphere by forced oxidation of the Nb film surface and to the annealing of the film itself.
Effects of additives on the superconducting properties of powder-metallurgically produced C
u-Nb3Sn composite wires
Authors: Wecker J. , Bormann R. , Freyhardt H. C.
Published: February 2003

C u-Nb3Sn microcomposite wires with additions of In, Ga, and Ge to the bronze and of Ta to the niobium have been produced by the hot-powder-metallurgical preparation method. The characteristic influences of the additives on the superconducting properties are discussed on the basis of measurements of critical current densities (up to fields of 19–22 T), critical temperatures as well as x-ray microprobe analyses. Although all alloying additions are incorporated into the Nb3Sn filaments, significant enhancements of the upper critical field by 2 and 4 T, respectively, can only be achieved for Ta and Ga. With an appropriate choice of the preparation parameters the current-carrying capability is considerably improved in the field range above 12 T. The optimized current densities reach values of 108 and 2×107 A/m2 at 16 and 19 T, respectively.
Magnetic properties of iron oxide photolytically produced from Fe(CO)5 impregnated porous glass
Authors: Borelli N. F. , Morse D. L. , Schreurs J. W. H.
Published: February 2003

This article discusses the magnetic properties observed in porous glasses impregnated with metal carbonyls after exposure to light. In the photolyzed and consolidated glasses both superparamagnetic and single domain ferrimagnetic particles were found to be present, with the single domain particles having an exceedingly high coercive force. The concentration ratio between superparamagnetic and single domain particles depends strongly on temperature. An analysis of the observed phenomena is given.
Corner clusters in thin soft magnetic layers. I. Space-charge-density and field singularities
Authors: van den Berg H. A. M.
Published: February 2003

The magnetization distributions in the neighborhood of the corners of soft ferromagnetic geometries are both theoretically and experimentally investigated. We have previously introduced the wall cluster—a collection of domain walls having one intersection line, the so-called cluster knot, in common—as a novel concept to get a better grip on the complex process of domain-structure conversions. These wall clusters can be classified according to the positions of the cluster knots into the free, the edge, and the corner clusters. The edge and free clusters, whose cluster knots coincide with one single edge and with no any edge of the geometry, respectively, have been discussed elsewhere. Here the micromagnetic characteristics of a corner cluster in thin layers are discussed, while the systems approach to corner clusters, in which the cluster is treated as a system of walls, is left to Part II. Bear in mind that the torque equilibrium is dominated by the total Maxwell field, composed of the external and demagnetizing field near the domain walls and the edges of the geometry. From this starting point, it is shown that no domain wall is present in a region in which the total field is not zero. Similarly, it is demonstrated that no line space-charge-density singularities can appear at a cluster knot. As a consequence, the magnetization in the domains can be divided into so-called rotation segments and uniform sectors, in which the magnetization rotates circularly around the cluster knot or is quasiuniform, respectively. Space-charge-density singularities occur at the bounding surfaces of the geometry. This surface-charge density generates a singularity in the total field in case this density does not reduce to zero in the corner. No domain wall can be present in the corner in these circumstances, so that the cluster knot is either shoved along one of the bounding edges of the corner or it disengages itself from the edges and the corner cluster is tranformed into a free cluster. It is experimentally demonstrated that these singularities in the field often, but not always, occur in the corner when an external field is applied. These and other above-mentioned statements are also supported by experimental evidence.
Wall oscillations of domain lattices in underdamped garnet films
Authors: Argyle B. E. , Jantz W. , Slonczewski J. C.
Published: February 2003

This report describes a recently developed domain-wall-oscillation spectrum analyzer and the results of some sensitive quantitative measurements of domain wall motion response in underdamped garnet films. Objects of study include periodic bubble domain lattices and periodic stripe patterns. Wall displacements as small as 5 Å (only a few percent of the wall width) are detectable, thus allowing observation of resonance multiplets due to wall flexure not seen by other techniques. The data presented here are taken in the linear region at low drive (well below onset of velocity saturation) in thin film samples of Gd, Ga:YIG grown epitaxially on Gd3Ga5O12. The domain wall resonance linewidth determination of the Gilbert damping parameter agrees with monodomain ferromagnetic resonance, resolving previous discrepancies with respect to effective mass and damping coefficient found in free oscillations following pulsed excitations in thin films and in complex susceptibility spectra in thick single crystal plates. Losses and nonlinearities due to coercivity appear suppressed in dense domain configurations by the presence of strong restoring forces. Comparison of our theory and experiments show that the rigid-wall model accounts well for the first resonance, including its dependence on lattice period and external field applied normal to the film. The Döring mass, however, needs correction by numerical calculations for effects of stray fields. Empirical and a priori restoring-force coefficients agree very well with our observed resonance frequencies.
Investigation of the velocity of energy circulation of magnetostatic modes in ferrites
Authors: Fishman D. A. , Morgenthaler F. R.
Published: February 2003

The velocity of energy circulation associated with the uniform precession mode in a ferrite sphere is studied. Specifically, the effect of the boundary conditions imposed by a concentric conducting spherical cavity is considered for the uniform precession magnetic resonance mode of a yttrium-iron-garnet (YIG) sphere. Theoretical analyses show that there is a critical ratio between the radius of the ferrite sphere and the conducting cavity where the energy velocity of the uniform precesion mode approaches zero. Spin wave instabilities, as a result of the nonlinear coupling of the uniform precession mode to spin wave excitations, are brought on if the rf-energy density inside the ferrite exceeds a specific threshold value. Thus a decrease in the energy velocity is expected to decrease the amount of incident power required for the onset of spin wave instabilities. We report that decreases in threshold power for the Suhl first order spin wave instability have been observed as a function of the cavity radius. The experimental cavity consists of two conducting partial hemispheres, one on each side of the YIG sphere.
Absolute optical absorption coefficient measurements using transverse photothermal deflection spectroscopy
Authors: Mandelis Andreas
Published: February 2003

Information about the optical absorption coefficient of solid materials in contact with a fluid phase can be obtained from photothermal deflection (PDS) measurements using both the signal amplitude and phase channels of the PDS response of a system to an optical excitation. This paper presents a theoretical model of photothermal processes in the transverse (TPDS) experimental configuration. The theory is used to determine the dependence of both signal channels on the optical absorption coefficient of the solid material and to define absorption coefficient ranges within which TPDS can be used as a spectroscopic technique. A method concerning the use of the combined amplitude and phase data for the absolute measurement of the absorption coefficient is presented for the experimentally important thermally thick limit.
Theoretical aspects of photoacoustic spectroscopy with light scattering samples
Authors: Helander Per
Published: February 2003

A theoretical model for photoacoustic spectroscopy with light scattering samples is discussed. Some special cases are derived and the nature of the measured signal and the underlying physics are analyzed. Comparisons with transmission and diffuse reflectance spectroscopy are made.
Measurement of boron diffusivity in hydrogenated amorphous silicon by using nuclear reaction 10B(n,α)7Li
Authors: Matsumura H. , Sakai K. , Maeda M. , Furukawa S. , Horiuchi K.
Published: February 2003

The method to measure boron profile by using the nuclear reaction 10B(n,α)7Li is applied to estimate the diffusivity of boron in the glow-discharged hydrogenated amorphous–silicon (a–Si:H). It is found that the diffusivity of boron in a–Si:H is much larger than that in crystalline silicon (c–Si). For instance, it is about 2×1016 cm2/s at 330 °C and larger than in c–Si by twelve orders of magnitude. The activation energy of the diffusivity is also estimated to be 1.5 eV. These values are nearly equal to those of hydrogen in a–Si:H. The minimum duration, in which the characteristics of p–i–n type a–Si:H solar cells may start to change due to this boron diffusion, is roughly estimated using both boron diffusivity and its activation energy.
Crystallization characteristics of Ni-Zr metallic glasses from Ni20Zr80 to Ni70Zr30
Authors: Altounian Z. , Guo-hua Tu , Strom-Olsen J. O.
Published: February 2003

We present the results of a crystallization study in glassy Ni-Zr. The alloys were prepared by melt spinning over the continuous range Ni20Zr80 to Ni70Zr30 including for the first time the region between Ni40Zr60 and Ni60Zr40. As expected we find that the glasses are most stable at and around the eutectic compositions, except that at the extreme Zr-rich eutectic the glasses are destabilized by the premature precipitation of ω-Zr. The products of crystallization indicate that the current crystalline phase diagram is incomplete: a new peritectoid phase must be added at the composition Ni2Zr.
Electron paramagnetic resonance determination of the generation rate of As antisites in fast neutron irradiated GaAs
Authors: Goltzene A. , Meyer B. , Schwab C.
Published: February 2003

The generation rate of paramagnetic defects has been measured by means of Electron Paramagnetic Resonance over the 1015–1017-10n  cm−2 fluence range, using a low flux (7×1010 10n  cm−2 s−1) of fast neutrons; much higher yields are achievable than reported up to now. A comparison of 4.2-  and 295-K spectra evidences a narrowing of the hyperfine structure separation of the components of the AsGa quadruplet with increasing temperature.
Structure of ion-implanted and annealed Hg1−xCdxTe
Authors: Bahir G. , Kalish R.
Published: February 2003

The structural and compositional changes in ion-implanted and annealed Hg1−xCdxTe (x=0.21; 0.29) were studied by means of ion-beam probing techniques. Rutherford backscattering (RBS) and particle-induced x-ray (PIXE) experiments were carried out under channeling the nonchanneling conditions. The following results were found. (i) The damage caused by room-temperature implantation of a variety of ions (Al, P, Ar, In, Hg) reaches saturation when an energy density of 2–4×1024 eV/cm3 goes into nuclear collisions. (ii) The damage profile for light ion implantation (150-keV, P, Ar) is more shallow than the implant range, while for heavy implants (300-keV, In, Hg) it extends substantially deeper than the range. (iii) The damage consists of extended defects, probably stacking faults. The results of furnace, Q-switched ruby, and cw CO2 laser annealing were investigated. Best annealing was obtained when the implanted surface was irradiated with photons from a cw CO2 laser for 0.3 sec at a power of 250 W/cm2. Under such conditions the crystallinity is restored and no changes in stoichiometry are evident. The theoretical considerations for the choice of RBS or PIXE analyses for compound crystals are reviewed.
The energy spectra and the quantum efficiencies of electrons emitted from the metallic elements irradiated by 60Co gamma rays
Authors: Nakamura Masamoto
Published: February 2003

The energy spectra, angular distributions, and the absolute quantum efficiencies of forward emission electrons from 60Co γ-ray irradiated metallic elements have been measured using a double focusing β-ray spectrometer. Samples measured were C, Al, Cu, Mo, Sn, W, and Pb. Their thicknesses were chosen about equal to the maximum range of a 1.33 Mev photoelectron so as to ensure electron equilibrium. Similar spectral shapes were observed for samples with similar atomic numbers, but energy spectrum for the large atomic number sample was different from the small atomic number one. Photoelectron peaks were observed in the spectra for W and Pb. An empirical equation which gives the quantum efficiency as the function of atomic number was obtained. The efficiencies computed from this equation were in good agreement with experimental results and numerical calculations.