bluuebunny/crossref_metadata_2025 huggingface dataset:
Ranges of solid solubility and optical energy gap values in CuIn(SxSeyTe1−x−y)2 alloys
Authors: Quintero Miguel , Woolley John C.
Published: February 2003

Equilibrium conditions for the alloy system CuIn(SxSeyTe1−x−y)2 were determined throughout the complete composition range. Polycrystalline samples of 60 different compositions were prepared by a melt and anneal technique, annealing times of up to three months at 600 °C being required. Debye–Scherrer x-ray powder photographs were used to investigate the equilibrium conditions. Single phase behavior was found over approximately two-thirds of the composition range, a broad miscibility gap being found on the CuIn(SxTe1−x)2 edge and extending into the center of the diagram. All phases were found to have the chalcopyrite structure with c/a=2. Values of a were determined in all cases and hence contours of constant a were plotted. Optical absorption measurements were carried out on all single phase samples to determine values of energy gap E0 at 70 and 300 K. For each temperature, the variation of E0 was fitted to a power series in x and z(=1−x−y) and hence contours of constant E0 plotted. The experimental values were compared with the predictions of the interpolation equation of Williams et al. [J. Electronic Mater. 7, 639 (1978)].
Comparison of predictions of interpolation equations with experimental values of lattice parameter and energy gap for some multicomponent alloys
Authors: Avon Julie E. , Donofrio Tom , Woolley John C.
Published: February 2003

The interpolation equations which may be used to predict properties of two composition variable semiconductor alloys such as (A1−xBx)(C1−yDy) and (AxByC1−x−y)D are reviewed and the former developed to cover the case of three variable alloys of the form (A1−xBx)(C1−yDy) (E1−zFz). The predictions of these various equations are then compared with experimental values of lattice parameters and energy gaps in the alloy systems (Cu1−xAg)(Ga1−yIny)(Se1−zTez)2 and (CdxZnyMn1−x−y)Te. The fit and appropriateness of each equation is discussed.
Direct measurement of the recombination velocity on a grain boundary
Authors: Mimila-Arroyo J. , Bourgoin J. C.
Published: February 2003

We present a new method for directly measuring the recombination velocity of minority carriers at grain boundaries or other defects in a semiconductor. It is a direct method because it allows the determination of both the recombination velocities and the diffusion length L independently and not, as in the conventional techniques, through a fit with a curve calculated as a function of both L and s. It is based on the measurement of the abrupt change of the current induced in a junction when the excitation beam is scanned through the grain boundary. The technique has been applied to a grain boundary in p-type polysilicon, leading to the result that a grain boundary, optically, observable might exhibit no recombination properties while another, practically unobservable optically, presented strong recombination properties.
Characteristics of acoustic emission signals of Hertzian and unloading cracks in glass
Authors: Kim Kwang Yul , Sachse Wolfgang
Published: February 2003

Reproducible acoustic emission (AE) signals can be observed when a spherical diamond indenter is used to generate cone- or ring-shaped Hertzian cracks on the surface of a glass specimen. The signals which are emitted during the loading of the specimen have features virtually indentical to those resulting when a glass capillary is broken on the surface of the specimen. This paper describes the first clear identification of Hertzian cracks which act as point sources of acoustic emission with features corresponding to a vertical force. The temporal characteristics of the force correspond to a Heaviside function with risetime less than 0.1 μs and an amplitude ranging from 1.8×10−3 to 4.2×10−3 N. The unloading of the diamond indenter from the glass also produces characteristic AE signals. These are distinguishable from the loading signals and they are shown to correspond to the development of unloading cracks on the surface of the specimen. Quantitative information about the unloading cracks is obtained from the AE signals by measuring the amplitude of the first pressure or P wave of the unloading signals. It is shown that this feature is directly related to the maximum applied load attained prior to unloading. A load threshold is found below which no unloading signals are detected.
Interdiffusivities in silver-palladium composition-modulated foils
Authors: Henein G. E. , Hilliard J. E.
Published: February 2003

Interdiffusion coefficients were measured from the decay rate of x-ray diffraction satellite intensities at 375 °C in 13 Ag-Pd foils containing composition modulations with wavelengths between 0.94 and 5.08 nm. A sharp decrease in the interdiffusivity was observed at a wavelength of 2.3 nm and a gradual decrease between 4.0 and 5.0 nm. A screening singularity or an increase in the shear modulus (or both) are believed to be responsible for the decrease at 2.3 nm. The drop at 4.0 nm is consistent with a loss of coherency in the foils. A nonlinear regression fit to the wavelength dependence of the diffusion coefficient yielded values of the first four gradient energy coefficients for the system.
Growth of bright (300 K) luminescence InAsxP1−x (λ=1.7–2.1 μ) on InP substrates by molecular beam epitaxy
Authors: Tsang W. T.
Published: February 2003

We have successfully prepared bright room-temperature luminescence InAsxP1−x epilayers in the wavelength region 1.7–2.1 on InP substrates by molecular beam epitaxy. The dependence of the InAs composition in the InAsxP1−x epilayers on substrate temperature during growth was investigated. It was found that for the same P2/As2 (dimers used) flux ratio, the InAs composition increased with increasing substrate temperature in the range 530–620 °C. This is due to the faster decrease of the sticking coefficient of P2 with increasing substrate temperature than that of As2. This composition-temperature dependence can be utilized conveniently for growing composition-graded layers by simply increasing the substrate growth temperature.
Silicon thin films formed on an insulator by recrystallization
Authors: Cline H. E.
Published: February 2003

Encapsulated silicon thin films were both zone heated and uniformly pulse heated over a range of rates and temperatures with quartz–iodine lamp heat sources. Large 100-μ size grains were observed after zone heating in the solid state just below the melting point. In contrast, 10-μ grain sizes were found in comparable pulse heat treatments in the same material. Zone melting results in a columnar subgrain structure. The mechanisms of grain growth, crystal growth from the liquid film and agglomeration are discussed in view of these experiments at relatively low growth rates. A silicon-on-insulator material may be produced at rates less than 0.025 cm/s by directional grain growth.
Laser-induced surface diffusion
Authors: Wu C. H. , Gittleman J. I.
Published: February 2003

A Brownian motion model for laser-induced surface diffusion is proposed to account for the kinetics of surface transport of the evaporated molecules from a thin discontinuous film under a focused laser beam. The model is solved exactly where the evaporation rate of the molecules is assumed to be proportional to the temperature rise above the ambient of the absorber layer. The surface diffusion constant and molecular velocity are obtained by comparing the results of calculations with transmission electron micrographs of recorded pits in Te trilayer opticial discs. These values are in good agreement with Einstein’s relation.
Analysis of conduction band structure of gallium arsenide in the vicinity of two valley and three valley band models using a physical magnetoresistance effect in the temperature range 300–650 K
Authors: Saxena T. K. , Bala Shashi , Mathur P. C. , Hartnagel H. L.
Published: February 2003

Theoretical calculations of physical magnetoresistance (PMR) have been made using a relaxation time technique for the two valley (Γc6−Xc6 −Lc6) and three valley (Γc6−Lc6 −Xc6) conduction band models for n-type GaAs. To resolve between the two possible models for the band structure, physical magnetoresistance measurements have been made on three single crystals in the temperature range 300–650 K having different degrees of doping. The results of the three valley model in the temperature range 500–650 K are found to be in better agreement with the experimental data on PMR. However, it is not possible to distinguish between the two models at temperatures below 500 K.
A theoretical study of the effects of interacting grain boundaries on electron-beam-induced currents
Authors: Luke Keung L. , von Roos Oldwig
Published: February 2003

The influence of several grain boundaries on the electron beam induced current in polycrystalline silicon is investigated. The simple geometry contemplated here, consisting of two plane parallel grain boundaries possessing different effective, albeit constant, surface recombination velocities, intersecting a planar junction at right angles allows for an exact solution of the corresponding boundary value problem. It is shown that if the distance between the grain boundaries w becomes less than the diffusion length for minority carriers L within the grain, the grain boundary with the smaller effective recombination velocity becomes less and less visible the smaller the ratio w/L.
Effects of interfacial charge on the electron affinity, work function, and electrical characteristics of thinly oxidized semiconductor-insulator-semiconductor and metal-insulator-semiconductor devices
Authors: Ghosh Amal K. , Feng Tom , Haberman Joel I. , Maruska H. Paul
Published: February 2003

A phenomenological theory involving interfacial charge is presented to account for the result that the diode constant n at low forward biases might be temperature dependent in some thinly oxidized (< 20 Å) semiconductor-insulator-semiconductor and metal-insulator-semiconductor devices, resulting in parallel I-V curves. Neither multistep tunneling through the semiconductor space-charge region, nor conventional thermionic emission over the barrier, can explain the low-voltage portion of the I-V characteristics. In this paper it is shown that an interfacial charge redistribution occurs with changes in temperature, resulting in changes in the electron affinity of the base semiconductor and in the work function of the contact material. This results in a linear dependence of n on reciprocal temperature. An explanation is presented to account for the large temperature coefficient that has been observed for both the diffusion potential VD and open-circuit photovoltage Voc in these devices. And an explanation of the I-V characteristics in terms of shunt currents is also given.
Molecular beam epitaxial growth of GaAs using trimethylgallium as a Ga source
Authors: Tokumitsu Eisuke , Kudou Yoshimitsu , Konagai Makoto , Takahashi Kiyoshi
Published: February 2003

Crystal growth of GaAs using trimethylgallium (TMG) as a Ga source in a molecular beam epitaxial system has been studied. Mirror-like monocrystalline epitaxial layers of GaAs were easily obtained on a GaAs substrate at the substrate temperature of 530–630°C. Epitaxial layers were p type and the carrier concentration of these films was about 1018–1019 cm−3. In particular, no deposition was observed on a SiO2 film in this TMG-As4 system. This feature showed the possibility of selective epitaxy of GaAs.
High quality epitaxial films of CdTe on sapphire
Authors: Cole H. S. , Woodbury H. H. , Schetzina J. F.
Published: February 2003

Films of CdTe were grown on (0001) basal plane sapphire by organometallic chemical vapor deposition. X-ray diffraction studies indicated single-crystal (111) orientation CdTe was produced. Typical growth rates were between 2–5 μm/h. Film mobilities as high as 950 cm2 V−1 s−1 at room temperature and 1600 cm2 V−1 s−1 at 77 °K were measured after appropriate annealing.
On the galvanomagnetic effects in semiconductors in the case of electron scattering by optical phonons
Authors: El-Wahidy E. F.
Published: February 2003

The galvanomagnetic effects in n-type semiconductors at low temperatures (KT<hw0) are considered in the electric field interval, in which electrons scatter energy by the spontaneous emission of optical phonons in the active region ε≥hw0, and momentum due to elastic collisions in the passive region ε<hw0. The distribution function of electrons in the active region is used in formulating the flux of electrons from the active region to the passive one as a result of the emission of optical phonons. In terms of the formulated flux the electron distribution in the passive region is determined, which is then used in calculating the galvanomagnetic coefficients. It is shown that the galvanomagnetic coefficients display the dependence on the probability of optical phonon emission, which did not appear in the approximate results of other investigators.
Calculation of the conduction band discontinuity for Ga0.47In0.53As/Al0.48In0.52As heterojunction
Authors: Welch D. F. , Wicks G. W. , Eastman L. F.
Published: February 2003

Photoluminescence studies at 4 K on Ga0.47In0.53As/ Al0.48In0.52As single quantum wells exhibit emission ranging from 1.318 eV for a 15-Å well to 0.82 eV for thick wells. The emission energy of each single quantum well is compared to theoretical curves which are generated from a finite potential square well model. The closest agreement between the experimental curves and the theoretical curves occurs when the conduction band discontinuity is taken to be 70% of the band-gap discontinuity or 0.52 eV.
Device performance degradation due to hot carriers having energies below the Si-SiO2 energy barrier
Authors: Takeda Eiji , Hagiwara Takaaki , Suzuki Norio
Published: February 2003

Device performance degradation due to hot carriers having energies that are below the Si-SiO2 energy barrier are studied. For a test device with Leff =0.3 μm and Tox =5 nm, transconductance degradation and/or threshold voltage, Vth, shifts are detected at a drain voltage as low as 2.5 V, which is lower than the Si-SiO2 energy barrier (3.2 eV) for electrons. It is also found that the time τ that it takes for Vth to shift, e.g., 10 mV, can be expressed as τ∝exp(1/VD), in the VD range of greater than 2.5 V. Thus, hot-carrier-related device degradation may be one of the most significant problems in submicron metal-oxide-semiconductor-field-effect transistors, even after power supply voltage reduction.
Annealing of CdS/CdTe solar cells
Authors: Isett L. C.
Published: February 2003

The annealing behavior of CdS/CdTe thin-film solar cells in the temperature range 333 to 373 K has been examined. Admittance spectroscopy was used to characterize the cells. The data were fit to first-order annealing kinetics for annealing both without and with AM1 illumination. The activation energy was 0.70 eV in the dark and 0.56 eV in AM1. The kinetics are much reduced in AM1, the rate being decreased by about a factor of 5 at 353 K with AM1.
Field-effect phenomena in hydrogenated amorphous silicon photoreceptors
Authors: Mort J. , Jansen F. , Grammatica S. , Morgan M. , Chen I.
Published: February 2003

The imaging properties of hydrogenated amorphous silicon (a-Si:H) photoreceptors overcoated with insulating passivation layers are discussed. Field-effect phenomena are shown to interfere with the electrophotographic imaging process in this device configuration. Since photoreceptors are majority carrier devices and a-Si:H is an extrinsic material, the field-effect phenomena can be counteracted by proper doping of the a-Si:H-insulator interface.
Transient optoacoustic pulse generation and detection
Authors: Kuo Chien-Yu , Vieira Martha M. F. , Patel C. K. N.
Published: February 2003

The pulse shape of the cylindrical ultrasonic pressure waves generated by transient laser irradiation in a weakly absorbing liquid is calculated for Green’s function formalism. The calculated results are in reasonable agreement with the experimental pulse shapes measured using a thin transducer. The pressure pulse shape is shown to be affected by the relaxation time of the absorbed energy.
Thermally generated transient frequency excursions in doubly-rotated quartz thickness-mode resonators
Authors: Sinha B. K. , Tiersten H. F.
Published: February 2003

The temperature distribution in the electroded quartz plate is obtained from the uncoupled heat conduction equation subject to appropriate initial and boundary conditions. The time-dependent biasing state resulting from the transient temperature distribution is determined from the exact equations of static linear thermoelasticity for electrode films of zero thickness and from a system of approximate thermoelastic extensional plate equations for electrode films of finite thickness. The time-dependent change in resonant frequency resulting from the biasing state is determined from an equation for the perturbation of the eigenfrequency due to a bias. Results are presented for a number of thermally compensated as well as uncompensated cuts of quartz for some physically meaningful temperature inputs. In particular the calculations show that in thermally compensated cuts with electrodes of finite thickness, the frequency initially shifts considerably beyond the equilibrium resonant frequency for the final uniform temperature state.
Noise properties of granular NbN Josephson microbridges
Authors: Claassen J. H.
Published: February 2003

The output noise of a granular NbN microbridge has been measured at frequencies near 25 MHz as a function of bias voltage, temperature, and rf bias at 70 GHz. It is generally greater than predicted by the resistively shunted junction model, but is significantly lower than has previously been observed in clean superconducting microbridges with comparable RIc products. An estimate of the performance of the device as a Josephson mixer at 70 GHz is made on the basis of these measurements. At an operating temperature of 10 K a double sideband mixer noise temperature ∼200 K, with conversion loss of ∼3 dB should be attainable. Using the noise as a probe of the average temperature within the microbridge, it is found that simple self-heating is not a likely explanation for the disappearance of Josephson effects at high dc or microwave bias.
Frequency response of a single-mode optical fiber phase modulator utilizing a piezoelectric plastic jacket
Authors: Jarzynski J.
Published: February 2003

A vinylidene fluoride-tetrafluoroethylene copolymer jacket, 120 μm thick, was melt extruded on single-mode optical fibers, 80 μm diam. The jacket was made piezoactive by poling radially. The performance of the fiber as an optical phase modulator was demonstrated over a wide frequency range, from 300 Hz to 2.5 MHz. A phase shift of 0.03 rad per volt per meter of fiber was measured in the low frequency (axially unconstrained) region, and 0.01 rad/V/m in the high frequency (axially constrained) region. A theoretical model was developed, relating the phase shift in the fiber to the elastic and piezoelectric porperties of the jacket material.
Laser-enhanced reactive ion etching of GaAs with CCl4 and H2 mixed gas
Authors: Tsukada N. , Semura S. , Saito H. , Sugata S. , Asakawa K. , Mita Y.
Published: February 2003

Localized enhancement of the reactive ion etching by laser irradiation has been investigated on GaAs by using CCl4 and H2 mixed gas. A laser-enhanced etching rate more than ten times as large as that for without laser irradiation was obtained. It was conjectured that the enhanced mechanism results mainly from the laser-assisted vaporization of the reaction-product species by localized heating of the sample.
Low loss metallic waveguide for transmission of optical radiation
Authors: Zakowicz Wladyslaw
Published: February 2003

It is shown that a significant reduction of losses for transmission of optical radiation in a hollow metallic waveguide can be achieved by a proper dielectric coating of its walls. We solve and discuss the mode structure of a rectangular waveguide with two coated walls. An estimation of the losses in the metal walls and the dielectric coating is given. For short wavelengths (λ<10 μ) losses occur mainly in the metal wall, while for longer waveguide length they occur mainly in the dielectric. An example shows that for λ=1 μ the losses are reduced from 53 db/m for an uncoated waveguide to 4×10−6 db/m for a coated one.
Operation of a convolute double-emitter relativistic electron beam diode
Authors: Waisman E. M.
Published: February 2003

We give a model for the impedance behavior of a relativistic electron beam diode of ring shape. The diode consists of a double emitter annular cathode: the two emitters are separated by a well to avoid fast plasma closure, opposite to a flat anode plate. It is connected via a triplate vacuum feed to the waterline of a pulsed power machine. We use the concept of magnetic limiting to show that the emitters influence each other magnetically, and give their impedance as a function of emitter voltage, geometry, and the current flowing from one emitter to the other. We also show that under certain circumstances, in which the emitter voltages differ from each other, that magnetic shutoff of one of them by the other can occur in timescales τ∼λ/Z, where λ is the vacuum inductance of the well, V the dominant emitter voltage, and Z its impedannce. We give a pertinent numerical example and comment on posible measures to avoid this dominance.
Radiation damage in InP single crystals and solar cells
Authors: Yamaguchi Masafumi , Uemura Chikao , Yamamoto Akio
Published: February 2003

This paper shows that InP solar cell is more radiation resistant than Si and GaAs solar cells. 60Co γ-ray irradiation damage in InP solar cells was examined. Changes in minority carrier diffusion length and carrier concentration in irradiated InP single crystals were also investigated by electron beam induced current and capacitance-voltage methods for solar cells. A high carrier concentration p-InP substrate has lower concentration damage. Thus, an InP solar cell with a higher carrier concentration substrate has superior radiation resistance. Experimental results for radiation damage in InP solar cells were in satisfactory agreement with theoretical values, calculated from changes in minority carrier diffusion length and carrier concentration due to irradiation. Numerical analysis suggests that an InP solar cell with a higher carrier concentration substrate and a shallower junction should be relatively more radiation resistant. Annealing behavior for radiation damage in InP was also examined.
A cross-sectional transmission electron microscopy study of silicide growth kinetics in the Cr/(100)Si system at 425 °C
Authors: Natan Menachem , Duncan S. W. , Byer N. E.
Published: February 2003

Cross-sectional transmission electron microscopy was used to determine the growth kinetics of silicide films in the Cr/(100)Si system. Growth rate, growth mechanisms, and structural details were obtained from direct observation of the reacted layer after various time intervals. At 425 °C, CrSi2 was the only phase formed; its growth was diffusion-limited, with a rate constant of 6.2×10−13 cm2/s. A thin oxide layer (∼20 Å) at the Cr/Si interface did not prevent silicide growth at 425 °C, but it served as an immobile marker, which confirmed that Si was the main diffusing species.
Liquid phase epitaxial growth of large area Hg1−xCdxTe epitaxial layers
Authors: Edwall D. D. , Gertner E. R. , Tennant W. E.
Published: February 2003

The liquid phase epitaxial technique in a horizontal boat is used to grow large area epitaxial layers of Hg1−xCdxTe on CdTe substrates with x=1 to x=0.15. Areas as large as 25 cm2 have been grown from Te-rich melts that have excellent compositional uniformity (Δx=0.001–0.0028) and run-to-run reproducibility (Δx=0.003–0.004). Results are presented on surface morphology, compositional grading, and electrical properties. Histograms are presented showing run-to-run wavelength reproducibility and uniformity across the epilayers for both 10–15 and 20–25 cm2 areas for selected wavelengths with x≂0.3. Data are presented showing run-to-run uniformity of carrier concentration (4.5±0.66×1016 cm−3) and hole mobility (272±15 cm2/Vs) at 77 K for x≂0.3, including their dependence on wavelength.
Deuterium in germanium: Interaction with point defects
Authors: Pearton S. J. , Kahn J. M. , Hansen W. L. , Haller E. E.
Published: February 2003

Electrical measurements on deuterium plasma-treated germanium samples containing deep level recombination centers show significant neutralization of these defects to depths of ∼80 μm. Chemical measurement of the deuterium profile after similar plasma treatment shows apparent incorporation depths of ∼0.2 μm. We discuss experiments which resolve this discrepancy, and show that hydrogen diffusion into the bulk of the germanium is responsible for the observed neutralization.
Anomalous behavior of the magnetoresistance of NiMn alloys in the spin-glass and ferromagnetic states
Authors: Senoussi S. , Öner Y.
Published: February 2003

The longitudinal and the transverse magnetoresistances of disordered NiMn alloys with about 21, 26, 28, and 30 at. % Mn have been measured in magnetic fields up to ∼75 kG and in the temperature range 1.2–80 K. For the 21 at. % Mn alloy the magnetoresistance is anisotropic (Δ ρ∥>0, Δ ρ⊥<0) at the lowest fields and temperatures. No detectable anisotropy is seen in the more concentrated sepcimens. In the critical concentration region (∼25 at. % Mn) the competition between ferromagnetic and spin glass effects is very severe and the magnetoresistance is marked by strong and unusual hysteresis effects in the Δ ρ/ρ0 vs H curves. When the sample is prepared with a remanent magnetization both Δ ρ/ρ0 and its field derivative undergo a discontinuity at H∼−1 kG and T=1.2 K.
Organic-on-inorganic semiconductor contact barrier diodes. I. Theory with applications to organic thin films and prototype devices
Authors: Forrest S. R. , Kaplan M. L. , Schmidt P. H.
Published: February 2003

We discuss the properties of organic-on-inorganic (OI) semiconductor contact barrier diodes. A model for charge transport is developed which suggests that thermionic emission over the organic/inorganic contact barrier dominates at low current densities, whereas space-charge effects dominate transport through the organic layer at high current densities. The effects of charge trapping in the organic layer are also considered. This model is applied to OI diodes using thin films of the prototypical aromatic compound; 3,4,9,10-perylenetetracarboxylic dianhydride, (PTCDA) vapor-deposited onto n- and p-Si substrates. Several electrical and optical properties of PTCDA are investigated to provide a basis for analyzing the OI diodes. Both ohmic and space-charge-limited transport are observed in the PTCDA. We discuss mobility, transient response, and photoresponse of the thin-film organic material. Also described are the general properties of organic-on-inorganic contact barrier diodes which employ PTCDA and related compounds on either p- or n-Si substrates. Comparisons between diode performance and the theory are made. The contact barrier diodes exhibit high breakdown voltages (≤230 V) and reverse dark currents limited by generation and recombination of carriers in the Si bulk. From the forward current-voltage characteristics, apparent OI contact barriers of φBp=(0.75±0.02) eV and φBn=(0.61±0.01) eV are formed with p- and n-Si substrates, respectively. The resulting diodes are superior, in many respects, to conventional Schottky diodes due to enhanced contact barriers and reduced edge effects.
Modulation of the n-channel conductivity in liquid phase epitaxially grown p-n-p doped GaAs submicron structures
Authors: Zwicknagl P.
Published: February 2003

p-n-p doped GaAs structures with active n-doped layers with thicknesses of 250 nm>dn>15 nm and doping concentrations of 3×1018 cm−3>n≥1×1017 cm−3, and 6×1017 cm−3>p>7×1015 cm−3, have been grown by liquid phase epitaxy. The modulation of the n-channel conductivity σnn(Unp) by an external potential Unp between the p and n-layers has been measured at 77 and 300 K. The characteristic curves σnn(Unp) are interpreted by the modulation of the two-dimensional carrier concentration n(2) (Unp) with Unp and by the variation of the mobility μn(defn) on the effective channel thickness defn(Unp) . The sensitivity of the p-n-p structure to small variations in design parameters is shown for the threshold voltage Uthnp . In p-n-p specimens with n∼1×1017 cm−3, p<1016 cm−3 and dn≂40 nm, an unexpected enhancement of the conductivity up to one order of magnitude between 300 and 77 K is observed. This is explained essentially by a hole freeze out due to the high acceptor level of the Ge dopant in the p layers and simultaneous release of electrons in the n channel.
Study of the atomic models of three donorlike defects in silicon metal-oxide-semiconductor structures from their gate material and process dependencies
Authors: Sah Chih-Tang , Sun Jack Yuan-Chen , Tzou Joseph Jeng-Tao
Published: February 2003

The atomic models of the generation and annealing of three donorlike defects [the bulk compensating donor, the donorlike interface density-of-state (DOS) peak, and the positive turn-around charge] in silicon metal-oxide-semiconductor capacitors (MOSC) are investigated by studying their dependencies on the gate materials and process conditions. Starting thermal oxides used in this study include 1000 C dry oxides on 〈100〉 p-Si substrates and 750 C high-pressure steam oxides on 〈111〉 p-Si substrates. Gate materials include aluminum, gold, and LPCVD (low-pressure chemical-vapor-deposition) polycrystalline silicon (poly-Si) with several doping methods. The densities of these donors generated during avalanche electron injection in MOSC’s with boron in situ doped LPCVD poly-Si gates are smaller compared with those with aluminum gates. High temperature (>900 C) processes (diffusion or anneal) in dry inert gas after the poly-Si gate deposition inhibit the generation of all three donors. After the inhibition, the donor species can be reintroduced into the MOSC by replacing the poly-Si gate with metal gate using a wet etch process at room temperature, or by a post–aluminum-metallization anneal in water vapor at 400 C. All the experimental results are consistent with a proposed model based on hydrogen. This model consists of four steps: (1) The release of atomic hydrogen from SiO-H and Si-H in the bulk SiO2 and at the SiO2/Si interface, as well as from AlO-H and Al-H at the Al/SiO2 interface by ionizing radiation or energetic electrons or holes; (2) the migration of atomic hydrogen across the oxide, which involves multiple bond-breaking/diffusion/bond-forming processes; (3) the modification of the SiO2/Si interface which gives the buildup and reduction of the donorlike interface DOS peak and the positive turn-around charge; and (4) the formation of the electrically inactive B−H+ pair in the silicon surface space-charge layer.
A search for phase separation in amorphous NiZr2
Authors: Altounian Z. , Strom-Olsen J. O. , Walter J. L.
Published: February 2003

A study on the structure of amorphous NiZr2 prepared by quenching from different temperatures shows no evidence for phase separation, in contrast to recent claims. Instead, we suggest that different quench temperatures produce different coordinations on the atomic scale (i.e., different degrees of chemical short-range order), which are invisible to electron microscopy but which give rise to different growth and nucleation characteristics in crystallization and different superconducting properties.
Thin-film transistors on molecular-beam-deposited polycrystalline silicon
Authors: Matsui Makoto , Shiraki Yasuhiro , Maruyama Eiichi , Ohwada Jun-ichi
Published: February 2003

Thin-film transistors (TFT’s) have been fabricated on molecular-beam-deposited (MBD) polycrystalline silicon (poly-Si) on transparent glass substrates using low temperature (below 600 °C) processes. The field-effect mobility of the TFT is 40 cm2/V s at a gate voltage of 10 V, and the response time is less than 10 ns. Output characteristics of the TFT’s depend on the poly-Si film thickness. The threshold gate voltage and the field-effect mobility become lower and higher, respectively, with increasing film thickness. These results can be explained in terms of the thickness-dependent crystallinity of the surface region in the MBD poly-Si film. A 10×10 TFT matrix has been fabricated, and by combining the TFT matrix with a twisted-nematic liquid-crystal layer, a transmissive-type active matrix liquid-crystal display panel has been fabricated. This poly-Si TFT matrix has proved to be compatible with a liquid-crystal cell from the viewpoints of both device fabrication and transistor characteristics.
Failure mode analysis of planar zinc-diffused In0.53Ga0.47As p-i-n photodiodes
Authors: Chin A. K. , Chen F. S. , Ermanis F.
Published: February 2003

In order to understand the irreversible failure mechanisms of planar InGaAs p-i-n photodiodes, 32 devices from 19 different wafers that shorted during aging were first examined in the scanning electron microscope. Included were devices that failed during long term aging (>103 h) as well as those that failed during short term aging (<102 h) at higher reverse bias. With a few exceptions, the diodes failed as a result of a single localized leakage source located at the perimeter of the p-n junction. Three types of leakage sources were found: (a) a microplasma, (b) a microplasma associated with a region of high recombination rate, and (c) a microplasma associated with a thermally damaged region. Analysis of ∼40 devices before and after aging shows that leakage paths found after aging result from microplasmas initially present in the device. Defect analysis shows that neither threading dislocations nor misfit dislocations are generally responsible for these microplasmas. Analysis of the processing shows that the p-contact/semiconductor interface is stable during device operation. Thus, the leakage source, attributed to contact migration in other studies, is not present in our devices. However, pinholes in the SiNx diffusion mask close (<5 μm) to the perimeter of the p-n junction were found to be the major source of microplasmas. The high-electric field at the shallow (≲0.5 μm) p-n junctions formed by unintentional diffusion through the dielectric pinholes is believed to cause the microplasmas. Electron-hole pairs, recombining at the microplasma site, are believed to create defects. These defects were observed as a localized region of enhanced recombination in electron-beam induced current (EBIC) images of the p-n junction without applied bias. The enhanced leakage current as a result of the defects leads to thermal runaway.
Spin glassiness and ferromagnetism in disordered Ni-Mn (invited)
Authors: Abdul-Razzaq W. , Kouvel J. S.
Published: February 2003

With decreasing Mn concentration near 25 at. %, disordered Ni-Mn alloys are seen to evolve from a characteristic spin-glass behavior, with the magnetic polarizability rapidly increasing, to a magnetic behavior that signifies the onset of ferromagnetic order and the appearance of a spin-glass-like phase at lower temperatures. Moreover, the latter phase is ‘‘mixed’’ in that its equilibrium state (in the fields applied during cooling) manifests a spontaneous ferromagnetic moment, while its magnetization reversals with field exhibit the unidirectional anisotropy of a spin glass. The unusual magnetic properties of the mixed phase in the zero-field-cooled state can be ascribed to a domain structure in which the domains have unidirectional anisotropies of random orientation.
Threshold field for the de Almeida–Thouless transition line in Eu0.4Sr0.6S spin glass
Authors: Paulsen C. , Hamida J. A. , Williamson S. J. , Maletta H.
Published: February 2003

Measurements of the imaginary component of the ac magnetic susceptibility of a spherical sample of Eu0.4Sr0.6S at frequencies between 7 Hz and 5 kHz reveal that the temperature for the onset of hysteresis decreases as approximately Ha2/3 in an applied dc magnetic field Ha but only when the field exceeds a frequency-dependent threshold H0( f). This threshold also marks the onset for nonlinearity in the real component of the susceptibility and thus delineates two regions of distinctly different dynamical response.
Lower critical dimensionality of the spin-glass phase transition
Authors: Benyoussef A. , Boccara N.
Published: February 2003

We used a variety of real space renormalization group techniques to investigate nearest-neighbor bond dilute frustrated Ising models for various space dimensionalities d and found that for d=3 a stable spin-glass phase can exist only at T=0. To find the lower critical dimensionality of the paramagnetic-spin-glass phase transition, i.e., the space dimensionality d* below which such a transition ceases to take place, we used Migdal’s approximation which is known to give the correct answer in the case of a paraferromagnetic phase transition and which is simple enough to allow systems with noninteger space dimensionalities to be studied. We found d*=2.48.
Elastic light scattering from the reentrant spin glass EuxSr1−xS
Authors: Geschwind S. , Devlin G. E. , Dillon J. F. , Batlogg B. , Maletta H.
Published: February 2003

Elastic light scattering from the reentrant spin glass EuxSr1−xS has been used to display the transition from paramagnet to ferromagnet and finally to spin glass as the temperature is lowered. The results suggest the persistence in the spin glass region of a correlation length which is a sizable fraction of the wavelength of visible light.
Relaxations in spin glasses: Similarities and differences from ordinary glasses
Authors: Ngai K. L. , Rajagopal A. K. , Huang C. Y.
Published: February 2003

Relaxation phenomena have become a major concern in the physics of spin glasses. There are certain resemblances of these relaxation properties to those of ordinary glasses. In this work, we compare the relaxation properties of spin glasses near the freezing temperature with those of glasses near the glass transition temperature. There are similarities between the two types of glasses. Moreover, the relaxation properties of many glasses and spin glasses are in conformity with two coupled ‘‘universality’’ relations predicted by a recent model of relaxations in condensed matter.
Studies on the magnetic properties of amorphous Ni-Mn-P-B-Al alloys
Authors: Kote G. , Hedman L. , Dahlberg D. , Rao K. V.
Published: February 2003

Magnetic properties of amorphous (Ni1−xMnx) 75P16B6Al3 alloys have been probed using transverse magnetoresistance (in fields up to 9 T), and susceptibility measurements (in low fields using a SQUID magnetometer, and at high fields of up to 1 T using a Faraday balance), in the temperature range 4–300 K. Low field susceptibility data show a spin-glass type of behavior for alloys with x>0.1. At low concentrations of Mn the spin freezing temperature Tf is found to increase linearly with x. A maximum value of Tf=61 K is observed for the alloy with x=0.6. Analyses of the high field susceptibility data indicates that in this amorphous matrix Ni does not carry a moment. The transverse magnetoresistance is found to be negative at all temperatures and applied fields, and for T>2Tf the magnetoresistance is found to have a quadratic field dependence.
PAC study of spin glass freezing in A
uFe alloys
Authors: Rots M. , Van Cauteren J. , Hermans L.
Published: February 2003

We introduce perturbed angular correlation (PAC) on radioactive isotopes as a new and feasible technique to sense the hyperfine field distribution in randomly disordered alloys. This technique is similar to μSR in the sense that it is a nuclear spin precession measurement, but more widely applicable in view of the limited instrumentation. We present our first results obtained using 111Cd as a typical PAC probe in Au–Fe alloys of different magnetic impurity concentration. Our data clearly show the onset of the spin glass freezing and allows one to derive the mean field value as a function of temperature as well as magnetic impurity concentration.
Microwave properties of (Fe0.82B0.18)0.09La0.05R0.05 amorphous metal alloys
Authors: Vittoria C. , Koon N. C. , Lubitz P. , Geohegan J. A.
Published: February 2003

Static magnetic field measurements have been reported on amorphous metal alloys of (Fe0.82B0.18)0.90La0.05R0.05, where R=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er. Microwave properties of these alloys are now reported. The microwave measurements consisted of fixed (9 GHz) and swept (0.01–18 GHz) frequency magnetic resonance experiments. The ferromagnetic resonance (FMR) linewidth, ΔH and g factor were measured. ΔH has a minimum for R=Gd and is equal to 100 Oe. ΔH appears to scale with 〈L⋅S〉 where L and S are the spin and orbital angular momentum operators of the R ion. The measured g factor obeys the Wangsness relation, as R is varied.
Aging phenomena in TbFe thin films
Authors: Bernstein P. , Gueugnon C.
Published: February 2003

The aging phenomenon of amorphous TbFe thin films when protected with a SiO2 layer is studied by plotting the hysteresis cycles of the films at various time intervals. The changes observed in the coercive field are related to the changes in the Tb content of the layer. It is suggested that Tb atoms, in spite of their size, can move easily in the layer and tend to migrate out of the amorphous TbFe film. This hypothesis is confirmed by the differences observed in TbFe films deposited on pure Tb underlayers of different thicknesses and by Auger profiles carried out on aged samples.
Small angle magnetic scattering from amorphous DyCu
Authors: Pickart S. J. , Alperin H. A. , Gambino R. J. , McGuire T. R.
Published: February 2003

The unusual magnetic transition previously reported for the random anisotropy amorphous alloy DyCu was investigated by small−angle neutron scattering methods. The measurements were made on two 150-μm sputtered films at the NBSR SANS spectrometer with incident 6.0-Å wavelength, at temperatures between 5 and 77 K, and for wavevectors 0.016≤q≤0.165 Å−1. The small−angle magnetic intensity at fixed q shows a pronounced break at T≂17 K, corresponding to the weak-field susceptibility cusp as measured on the same sample. The lineshapes at all temperatures were observed to be Lorentzian, with a correlation length slowly increasing as T decreases to a maximum of ∼13 Å at 17 K and remaining constant thereafter. These results are compared with susceptibility and specific heat measurements for insight into the proposed mechanism for the transition.
Small planar domains in amorphous thin films: Nucleation and equilibrium conditions (abstract)
Authors: Labrune M. , Hamzaoui S. , Puchalska I. B. , Battarel C. , Hubert A.
Published: February 2003

The purpose of this work is to investigate a new type of small flat domain in the shape of lozenges. Such domains may be used for high-density nonvolatile shift register memories [C. Battarel, R. Morille, and A. Caplain, IEEE Trans. Magn. July (1983)]. Experimental and theoretical results for nucleation and stability of small lozenge domains less than 10 μm in length in Co–Ni–P and CoTi [G. Suran, K. Ounadjela, and J. Sztern (this Proceedings)] amorphous thin films 1500 Å thick are presented. The films have a low coercivity (Hc ∼1 Oe) and a significant in-plane uniaxial anisotropy (HK ∼35 Oe). The domains were observed in an optical microscope by longitudinal Kerr effect using an experimental method described by Prutton. Domain nucleation is obtained by applying a local field higher than HK. It must be emphasized that to stabilize the domain two constant fields having opposite direction are required: H1 applied inside the domain and parallel to its magnetization; H2 parallel to the main magnetization of the film (H1>H2). Experimental results obtained for such configuration of magnetic fields will be presented and compared with numerical computations. The theoretical model will be discussed and the role played by the magnetostatic energy emphasized. The model takes into account the spreading of the magnetic charges which appear at the boundary of the domain. Finally, application to experimental devices as mentioned in the first reference above will be shown.
Saturation and engineering magnetostriction of an iron-base amorphous alloy for power applications
Authors: Datta A. , Nathasingh D. , Martis R. J. , Flanders P. J. , Graham C. D.
Published: February 2003

The saturation magnetostriction λs of a ferromagnetic material is measured by determining the strain that occurs when the saturation magnetization vector is rotated through 90°. However, the magnetostrictive strain responsible for transformer noise is the net strain measured parallel to the applied field when the material is magnetized from the demagnetized state. Because of its engineering significance, we propose to call this net strain measured parallel to the applied field the engineering magnetostriction λe. The value of λe depends on the domain structure both in the demagnetized and magnetized states whereas λs is an intrinsic property of the material. In the present study, λe for an iron-base amorphous alloy, Metglas 2605S2, is measured as a function of the direction of the field induced anisotropy using a piezoelectric transducer. Although Metglas 2605S2 has a high value of λs (∼27×10−6), the value of λe in the longitudinal field annealed condition is found to be nearly zero. The magnitude of λe measured on a prototype transformer core is also discussed.
Effects of chromium and carbon additions on the high-frequency magnetic properties of an Fe-B-Si alloy
Authors: Nathasingh D. M.
Published: February 2003

The high-frequency magnetic properties of an Fe-B-Si amorphous alloy have been improved and made reproducible by the addition of chromium and carbon. Controlled crystallization of α-Fe has been demonstrated to be primarily responsible for optimum high-frequency properties in Fe-base amorphous alloys. However, oxidation of metalloids on the ribbon surfaces introduces variabilities in crystallization of α-Fe in the metalloid-depleted areas. Consequently, variability in core losses occurs. The prevention of metalloid oxidation at the ribbon surface is expected to enhance reproducibility. Addition of chromium was found to develop a protective layer of chromium oxide on the ribbon surface minimizing surface oxidation of metalloids. The chromium oxide layer increases the interlaminar resistance and is expected to reduce eddy current losses. Addition of chromium also reduces saturation magnetostriction (λs). The effect of small additions of carbon on the Fe-B-Si-Cr system was also evaluated. Carbon additions were found to enhance and control the formation of α-Fe crystallites. The resulting high-frequency core losses were found to be routinely reproducible and appreciably lower than the Permalloys. Detailed high-frequency properties of the Fe-B-Si-Cr-C system are discussed.