bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of low-energy hydrogen ion implantation on dendritic web silicon solar cells
Authors: Rohatgi A. , Meier D. L. , Rai-Choudhury P. , Fonash S. J. , Singh R.
Published: July 2002

The effect of a low-energy (0.4 keV), short-time (2 min), heavy-dose (1018/cm2) hydrogen ion implant on dendritic web silicon solar cells and material was investigated. Such an implant was observed to improve the cell open-circuit voltage and short-circuit current appreciably for a number of cells. In spite of the low implant energy, measurements of internal quantum efficiency indicate that it is the base of the cell, rather than the emitter, which benefits from the hydrogen implant. This is supported by the observation that the measured minority-carrier diffusion length in the base did not change when the emitter was removed. In some cases, a threefold increase of the base diffusion length was observed after implantation. The effects of the hydrogen implantation were not changed by a thermal stress test at 250 °C for 111 h in nitrogen. It is speculated that hydrogen enters the bulk by traveling along dislocations, as proposed recently for edge-defined film-fed growth silicon ribbon.
Rydberg–bremsstrahlung maser
Authors: Palmer A. Jay
Published: July 2002

Stimulated emission of bremsstrahlung radiation by electrons in high Rydberg states is analyzed theoretically. This approach to bremsstrahlung masers is shown to overcome some of the previous difficulties in realizing a practical value for the bremsstrahlung gain in the millimeter-wave regime by allowing volumetric production of monoenergetic electrons within a time period which is short compared to the thermalization time of the electron energy distribution, and by relaxing the criteria on the energy dependence of the collision cross section for achieving a positive bremsstrahlung gain coefficient.
Detection of surface grooves and subsurface inhomogeneities in metals by transmission correlation photoacoustics
Authors: Takaue Ryoichi , Tobimatsu Hiroshi , Matsunaga Morio , Hosokawa Kunisuke
Published: July 2002

Correlation photoacoustics detected from the unilluminated surface of a sample have been studied to detect well-characterized surface grooves and subsurface inhomogeneities in nickel. The correlation image of a line scan across an opaque sample by transmission technique can present the information on the surface or subsurface characteristics of the sample. This method is especially advantageous to detect subsurface grooves or inhomogeneities which exist anywhere in an optically opaque solid because the photoacoustic signals depend on the thermal and geometrical features in the transmission process of thermal waves. The system developed makes it possible to measure the impulse response of unstable samples because of the short time taken to collect data.
Growth and properties of Si films on sapphire with predeposited amorphous Si layers
Authors: Ishida Makoto , Yasuda Yukio , Ohyama Hidenori , Wakamatsu Hidetoshi , Abe Hiroshi , Nakamura Tetsuro
Published: July 2002

Si (001) films of high quality were grown successfully on sapphire substrates with thin predeposited amorphous Si layers, less than 40 Å thick. In order to investigate the growth features and properties of the films, the dependence of the film quality on the growth temperature, growth rate, and predeposited layer thickness were studied by various physical analyses including reflection high-energy electron diffraction (RHEED), replica electron microscopy, secondary ion mass spectroscopy (SIMS), Auger electron spectroscopy (AES) and electron spectroscopy for chemical analysis (ESCA), and electrical measurements of effective mobilities of metal-oxide-semiconductor field effect transistors (MOSFETs). The most remarkable feature of this method is that films with a smooth surface and a high crystalline quality grow even at a slow growth rate, less than 0.1 μm/min and a high growth temperature of about 1000 °C, which are concerned with surface reactions in the initial stage of chemical vapor deposition (CVD). The interface region between the film and the substrate has an abrupt concentration gradient of constituent atoms. The effective mobilities of MOSFETs fabricated on the films do not depend on the growth rate, unlike the case of the usual method, and were 1.5–1.25 times as large as those without predeposited layers. Experimental results indicate that the optimum thickness of the predeposited layer is about 20 Å and that the heat treatment of the layer (∼3 min, 1000 °C) before CVD is important. A model to understand this growth method is proposed.
Surface effects and grain-boundary domination in thin-film Zn3P2 photoconductivity
Authors: Hava S.
Published: July 2002

Photoconductivity spectral response, linearity, and response time measurement indicate that surface effects and intergrain boundaries can play important roles in the characteristics of thin-film Zn3P2. Response time of the order of a few seconds and the dependence of the spectral response on vacuum operation indicate the existence of long-lived states at the surface. Photoconductivity response was found to be a maximum at a wavelength of 400 nm. Vacuum operation and heat treatment were observed to improve responsivity, shift the peak responsivity wavelength towards longer wavelengths, and increase the spectral width of maximum responsivity. The photoconductivity spectral dependence and the response times were found to be light–intensity dependent. It is proposed that effects of the barrier heights at the surface and at the intergrain junctions are light-illumination dependent. The properties of the surface and the grain boundary depend on chemisorption or chemical reactions due to adsorbed gases or impurities.
Photoluminescence study of residual shallow acceptors in liquid-encapsulated Czochralski-grown InP
Authors: Kubota Eishi , Katsui Akinori , Sugii Kiyomasa
Published: July 2002

For nominally undoped InP crystals grown in silica, pBN, ceramic AlN, and pG crucibles by the liquid-encapsulated Czochralski (LEC) technique, residual shallow acceptors are investigated by photoluminescence measurements. Mg and Ca, contained in the InP starting materials, are found to be removed due to reactions with the B2O3 encapsulant. Zn and C, of which Zn was dominant throughout the undoped crystals, are found to be residual acceptors incorporated during LEC growth. The B2O3 encapsulant is identified as one Zn contamination source.
High-field tunneling calculations in metal-oxide-silicon capacitors incorporating the perimeter effect
Authors: Hook Terence B. , Ma T.-P.
Published: July 2002

The potential distribution is calculated for a generalized metal-oxide-silicon capacitor using the Schwartz–Christoffel transformation. The results are used to calculate the high-field tunneling current in such a device, with particular attention to the field enhancement effect of the edge of the gate electrode. It is found that the total current through even a large-scale device can be dominated by the perimeter component. The dependence of the field enhancement on several device parameters is examined theoretically. In particular, thick oxides and thin, steep gate electrodes augment the field enhancement.
Electric field-induced negative photoconductivity in GaAs
Authors: Wieder H. H. , Hanson Cynthia M. , Zuleeg Rainer
Published: July 2002

High-field negative photoconductivity observed below the fundamental band gap of GaAs is attributed to the electric field-dependent capture cross section of an electron donor level located at 1.2 eV relative to the valence-band edge and to a dynamic balance between emission, trapping, and recombination of optically induced charge carriers.
Influence of [V]/[III] beam ratio on crystal qualities of GaSb-AlSb superlattice films grown by molecular-beam epitaxy
Authors: Suzuki Yoshifumi , Ohmori Yutaka , Okamoto Hiroshi
Published: July 2002

[V]/[III] ratio dependence of molecular-beam epitaxy (MBE) grown Ga-Al-Sb material system was studied using various kinds of characterizing methods. We found that the MBE-grown Ga-Al-Sb material (GaSb-AlSb superlattice) was very sensitive to the growth condition, especially [V]/[III] beam ratio. Deviation from an optimum value of [V]/[III] during MBE led to deterioration not only in the optical quality (drastic decrease in photoluminescence efficiency) but also in the crystallographical quality (marked increase in the full width at half maximum (FWHM) in the x-ray diffraction peak) of grown epitaxial layers. X-ray microprobe analysis (XMA) showed that the epitaxial layer having a large x-ray FWHM value does not show any deviation from the stoichiometry. X-ray diffraction showed that the layers have no fluctuation of lattice constants, and the layers are imperfect single crystals having a spread orientation of crystal axis. Rutherford backscattering measurement showed that the lattice arrangement was not regular for the sample grown under nonoptimum conditions. Raman scattering showed that even in the epitaxial layer having a large x-ray FWHM value, the superlattice structure is conserved. Transmission electron microscopic observation by different growth conditions showed different fine structures. Some discussions about growth mechanisms are given for different growth conditions.
X-ray structures and magnetic properties of sputtered osmium-doped iron oxide thin films
Authors: Lim G. S. , Huang T. C. , Bullock D. C. , Castillo G.
Published: July 2002

X-ray structures and magnetic properties of sputtered osmium-doped iron oxide thin films prepared under various deposition conditions have been analyzed by x-ray diffraction and vibrating sample magnetometer techniques. Results show that the crystalline phase, macrostain, and grain size play important roles in the coercivity Hc, saturation magnetization 4πMs, and squareness S* of the films. Ferrimagnetic γ-Fe2O3 and/or α-Fe of 400-Å grain size or less were mainly responsible for the good coercivities and magnetizations of the films, i.e., Hc=700–1000 Oe and 4πMs=4000–6000 G. A film which contained appreciable antiferromagnetic α-Fe2O3 phase had much lower Hc(=130 Oe) and 4πMs(=1000 G). Correlation between macrostrain εn, and S* has been observed where the film with large compressive strains had low S*=0.69, and those with little or zero εn gave good squareness S*=0.79–0.81.
Magnesium doping of (Al,Ga)As in metalorganic chemical vapor deposition
Authors: Tamamura K. , Ohhata T. , Kawai H. , Kojima C.
Published: July 2002

Magnesium doping of AlxGa1−xAs in metalorganic chemical vapor deposition and the properties of the grown layer have been investigated. Bis-cyclopentadienylmagnesium, CP2Mg, was used as a precursor of Mg. The hole concentration increased linearly from 3.5×1016 to 1×1019 cm−3 when the ratio of CP2Mg to trimethylgallium was increased. The carrier concentration increased with the increase of Al concentration, decreased with the increase of growth temperature, and was independent of the ratio of arsine to column III elements, V/III. The photoluminescence (PL) intensity increased when the growth temperature was increased and/or the V/III ratio was increased. The intensity of a deep PL band associated with near band-edge emission, usually seen in the low-temperature PL spectra of Zn-doped (Al,Ga)As, was smaller than that in Zn-doped (Al,Ga)As. The activation energy of the Mg acceptor deduced from the temperature dependence of the carrier concentration was smaller than that of the Zn acceptor.
5
7Fe Mössbauer measurements of the spin reorientation in Tm2Fe14B
Authors: Price D. C. , Day R. K. , Dunlop J. B.
Published: July 2002

5 7Fe Mössbauer spectra of Tm2Fe14B, measured above and below the spin reorientation temperature (∼310 K), have been analyzed and are entirely consistent with a rotation of the magnetization from the basal plane to the c axis as the temperature is increased.
Luminescence investigation of copper diffusion into cadmium telluride
Authors: James K. M. , Flood J. D. , Merz J. L. , Jones C. E.
Published: July 2002

Cu diffusion into CdTe was investigated. Diffusions were carried out at 325 °C for 170 h under vacuum, starting with a surface deposition. The Cu diffusion caused a reduction in the band-edge photoluminescence intensity of the crystals. Hall data indicate that the Cu also inhibited the formation of acceptor states in the lattice during the 325 °C thermal treatment. The luminescence intensity is partially restored by a 2 h, 700 °C anneal under inert gas atmosphere. The spectral features in the exciton region of the spectrum are not significantly changed by the doping, and appear to be dominated by the annealing process itself rather than by the Cu introduced into the crystal. This is in contrast to previously reported data associating Cu doping with increases in the intensity of the 1.5896-eV bound-exciton line. Cathodoluminescence and infrared microscopy indicate that the Cu did not form precipitates or supersaturated areas along defects, as has been previously reported by other workers as the cause of the overall decrease in luminescence intensity with Cu diffusion.
Concentration gradient at an InP/GaAs interface determined by Auger analysis on a chemical bevel
Authors: Cazaux J. , Etienne P. , Razeghi M.
Published: July 2002

Experimental results of Auger profiles obtained on a chemical bevel of an InP/GaAs structure are reported. A theoretical procedure is established to convert the intensity profile into concentration profiles. It is applied to evaluate the concentration distribution of each species–Ga, In, As, P–independently of each others with a precision of ±5%. It is verified that the composition of the interface is GaxIn1−xAsyP1−y (0≤x, y≤1). Owing to differences between the atomic diffusions of III- and V-type elements, the transition region can be subdivided into three regions having the following compositions: (i) GaAsyP1−y with 0.87≤y≤1; (ii) GaxIn1−xAsyP1−y with 0≤y≤0.87 and 0.24≤x<1; (iii) PGaxIn1−x with x<0.24. The width of each region is also indicated.
Heat resistance of hydrogenated amorphous silicon films prepared by compressed magnetic field-magnetron sputtering with He and Ar gases
Authors: Hata T. , Kamide Y. , Nakagawa S. , Hattori K.
Published: July 2002

Usually, an Ar gas adding hydrogen gas is used for the fabrication of hydrogenated amorphous silicon (a-Si:H) films by reactive sputtering. The sputtered films contain Ar atoms of more than 5 at. %. These implanted Ar+ ions degrade the film quality, and H atoms, which terminate dangling bonds, leave the film easily by heating to about 300 °C. A He atom has a lighter atomic mass and smaller atomic radius than an Ar atom. Therefore, the reactive sputtered films using the He gas will be less affected by the implanted He+ ions than they will by the implanted Ar+ ions of those sputtered by Ar gas. Infrared absorption (IR) and electron spin resonance (ESR) measurements of the films sputtered by He gas are made and compared with those sputtered by Ar gas.
Analytical studies of an ablation mass driver system
Authors: Ikuta K. , Kristiansen M. , Rose M. F.
Published: July 2002

The electromagnetic acceleration of projectiles with an ablator using sequential Z pinches in a cylindrical electrode array is studied analytically under an assumption that every stage of the Z pinches, except the first one, is triggered automatically by the Z pinch following after the projectile. The effect of ablation on the acceleration of the projectiles is considered in detail, as well. The force distribution on the base of the projectile changes significantly when the contribution of the ablation to the total acceleration is taken into account. A method of equalizing the stress in the projectile in order to overcome the stress barrier of hypervelocities is also discussed.
Nucleation kinetics and spatial distribution of spherulitic PtSi clusters
Authors: Joubert P.
Published: July 2002

Nucleation kinetics and spatial distribution of spherulitic clusters can be determined from growth rate and cluster size measures. This method presented here was applied to the nucleation of disk-shaped PtSi clusters which grow in solid phase on nitridized Si substrates. It shows that the nucleation occurs in three modes corresponding to three kinetic regimes. A first nucleation phenomenon occurs at the beginning of the annealing on low-density (∼102 cm−2) preferred sites which are not randomly distributed in the plane and probably linked to defects. Then a steady state of nucleation on preferred sites, which are randomly distributed with a density of about 104 cm−2, is observed. A third phenomenon of nucleation is distinguished by a nucleation rate which exponentially increases with time. This ‘‘avalanche state’’ is linked to the presence of microclusters, the density of which can reach 107 cm−2. It depends on temperature and on the ratio of platinum layer thickness to silicon nitride thickness.
Redistribution of excess Si in chemical vapor deposited WSix films upon post-deposition annealing
Authors: Kottke M. , Pintchovski F. , White T. R. , Tobin P. J.
Published: July 2002

WSix films of three different compositions (X>2.0) were deposited by chemical vapor deposition onto polysilicon and Si3N4 coated substrates and subsequently annealed in N2 at 1000 °C. The redistribution of the excess Si was studied using Auger depth profiling and cross-sectional scanning electron microscopy techniques. For polysilicon sublayers the excess Si segregates to the polysilicon interface with a resulting increase in polysilicon thickness and decrease in WSix thickness in proportion to the excess Si content. For Si3N4 sublayers the excess Si precipitates within the WSix layer, but preferentially toward the free surface. Changes in surface and interface topography resulting from the Si redistribution are presented. The kinetics of the Si redistribution observed in the depth profiles are correlated with resistivity measurements.
Transient field-effect and time-of-flight investigation of chalcogenide glasses
Authors: Khan Babar A. , Adler David , Senturia Stephen D.
Published: July 2002

We have studied hole transport in amorphous As2Te3 (a-As2Te3) films by time-of-flight (TOF) and transient field-effect (TFE) measurements. Since the mobility gap of this material is small, the TOF experiments could be carried out only at temperatures below 200 K. Transport appears to be dispersive, due to multiple trapping in the valence-band tail. In order to extend the observations to higher temperature and longer times, we have developed a new technique, the TFE. A careful analysis shows that TFE data can be dispersive even if transport is nondispersive, because a long thin-film transistor is equivalent to a transmission line. Nevertheless, the resulting data can be used to characterize the density of states beyond the mobility edge. We find that multiple trapping indeed predominates, and the valence-band tail is exponential with a characteristic temperature of about 290 K. This is somewhat lower than indicated by TOF data, probably because hopping transport predominates at low temperatures. The long-time transients can be associated with either neutral defect interconversion and a continuous distribution of decay times or deep traps near the semiconductor-oxide interface. However, the ultimate disappearance of the response reflects the effects of Fermi-level pinning by valence alternation pairs with a negative effective correlation energy, as expected.
Minority-carrier injection into relaxation semiconductors
Authors: Moreau Y. , Manifacier J.-C. , Henisch H. K.
Published: July 2002

This paper deals with the injection of minority carriers, through a contact or junction, into materials of high resistivity and low carrier lifetime. Semi-insulating III-V compounds and many amorphous materials come under this heading. Since the macroscopic transport equations cannot be analytically solved, it is necessary to resort to numerical computation. Recent work along those lines has shown that the nature of the assumed boundary conditions has a profound effect on the results. The relationships are illustrated by concentration and potential contours of semi-infinite and p-i-n systems, with various ratios of lifetime to dielectric relaxation time.
Measurement of carrier lifetime, effective recombination velocity, and diffusion length near the grain boundary using the time-dependent electron-beam-induced current
Authors: Romanowski A. , Wittry D. B.
Published: July 2002

The apparatus is described that has been used to determine the lifetime, the effective recombination velocity, and the diffusion length near the grain boundary in a polycrystalline silicon solar cell. The lifetime has been estimated from rise of the electron-beam-induced current after switching on the incident electron beam; the diffusion length and the effective recombination velocity have been determined from the steady-state electron-beam-induced current characteristics. The experimental rise-time characteristics are compared with theoretical ones.
Annealing of deformed polymers under dimensional constraint
Authors: Kung Teh-Ming , Li J. C. M.
Published: July 2002

The two-stage process discovered in the recovery of deformed amorphous polymers (PS, PMMA, and PC) is verified in this study. The first stage which takes place below Tg releases part of the stored energy (part 1) and recovers the volume. The second stage which takes place above Tg releases the rest of the stored energy (part 2) and recovers the dimension. The relation between the part 2 stored energy and dimensional changes during deformation is the same as that during recovery. In this study, the dimension is constrained not to change during recovery. As expected, the part 2 stored energy is not released but the part 1 stored energy is released as usual. Furthermore, if in a second scan the constraint is removed and the dimension is allowed to recover, the part 2 stored energy is then released. These results confirm the unique relationship between dimension and the part 2 stored energy and the separability of the two-stage recovery process.
Dependence of striking characteristics of plasma discharge on filament orientation in a toroidal device
Authors: Mattoo S. K. , Venkataramani N.
Published: July 2002

In a torus with a toroidal magnetic field it is found that the discharge cannot be struck between the filament and the vessel wall if the filament (the source of thermionic electrons) is oriented parallel to the magnetic field. This observation and other experimental results lead to a conclusion that electric flux plays a crucial role in the determination of the striking characteristics of the discharge.
Optical properties of UV laser photolytic deposition of hydrogenated amorphous silicon (a-Si:H)
Authors: Zarnani H. , Demiryont H. , Collins G. J.
Published: July 2002

The effects of substrate temperature on the optical properties of the laser assisted chemical vapor deposited (L-CVD) thin films of amorphous-silicon–hydrogen alloy (a-Si:H) are investigated herein. A controlled substrate temperature Ts from 35 to 350 °C was used to vary the hydrogen content in the films. The spectrophotometric transmittance characteristics of the L-CVD a-Si:H films are used to evaluate the optical parameters, including: refractive index n(E); extinction coefficient k(E); and the thickness d of the samples. The L-CVD a-Si films are obtained for Ts >340 °C. The refractive index and energy gap Eg of the L-CVD a-Si films are found to be 3.4 and 1.55 eV, respectively. The optical absorption spectra α vs E of the L-CVD a-Si:H films exhibit Tauc, Urbach, and Urbach tail (shoulder) regions. The ratio of photoconductivity/dark conductivity (σP/σD) of L-CVD a-Si:H films having coplanar electrode geometry with Ag electrodes are experimentally determined. The σP/σD ratio, one rough measure of electronic quality, exhibits a maximum for the L-CVD a-Si:H films deposited at Ts =280 °C with σP/σD =5×105,σD =2.5×10−11 (Ω cm)−1, and the minimum defect density is 3.1×1016 cm−3.
Thermal and photochemical promotion of silicon and silicon dioxide etching by carbonyl difluoride
Authors: Holland R. J. , Bernasek S. L.
Published: July 2002

Silicon (111) surfaces that were cleaned and characterized in ultrahigh vacuum were exposed to carbonyl difluoride. After adsorption of COF2, the silicon crystal was heated to 625 °C resulting in a surface etching reaction as evidenced by the desorption of silicon tetrafluoride. Si(111) surfaces covered with a native oxide layer were also exposed to carbonyl difluoride. Dissociation of COF2, using high fluences from the CO2 laser, caused etching of the SiO2 surface. Volatile SiF4(g) was detected by transmission Fourier transform infrared spectroscopy. Two mechanisms, for the thermally enhanced etching of silicon by COF2 and the photochemically promoted etching of silicon dioxide by COF2, are proposed.
Complementary self-aligned laser arrays by metalorganic chemical vapor deposition
Authors: Mawst L. J. , Givens M. E. , Emanuel M. A. , Zmudzinski C. A. , Coleman J. J.
Published: July 2002

A two-step metalorganic chemical vapor deposition growth technique has been used to fabricate multielement arrays of complementary self-aligned lasers using graded barrier quantum well active regions. This technique eliminates any possible difficulty associated with regrowth on a high composition AlGaAs layer by placing the interface outside the stripe region. The complex index guiding and resulting mode discrimination characteristics of self-aligned lasers stabilize the near- and far-field patterns of the array. Comparison studies between shallow mesa arrays and self-aligned arrays are described.
Experimental study of nonlinear current-voltage behavior in undoped polycrystalline silicon
Authors: Kim Dae M. , Qian Feng , Ahmed S. S. , Park H. K. , Sachitano J. L.
Published: July 2002

Electrical conduction data from undoped low-pressure chemically vapor deposited polycrystalline silicon thin films at room temperature and above are presented. The physical mechanisms pertinent to general current-voltage characteristics are experimentally interrogated from three different viewpoints. In the nonlinear current-voltage region, the sheet resistance Rs is shown to vary drastically depending on the device aspect ratio for given applied electrical field Ē. The nonscalability of Rs with respect to Ē, the temperature behavior of Rs, and the photoconductivity data indicate that the nonlinear current-voltage behavior cannot be attributed to field-enhanced conductivity. Other possible mechanisms responsible for observed nonlinearity are discussed.
Equilibrium properties of thin-oxide metal-oxide-semiconductor diodes
Authors: Butler M. A. , Seager C. H.
Published: July 2002

The zero-bias resistance and high frequency capacitance of Al- and Pd-gated thin-oxide metal-oxide-semiconductor diodes have been measured as a function of temperature. The temperature dependence of the semiconductor barrier height is found to be large, primarily due to inversion effects. The relatively low activation energies observed for the zero-bias resistance, as well as actual measurements of spatial variations in device current, strongly suggest the presence of large variations in the semiconductor band bending. These variations may be directly related to thickness nonuniformities which are known to occur in SiO2 films processed at low temperatures.
Dipole scattering from a conducting sphere coated with a lossy dielectric
Authors: Bishop Garner C.
Published: July 2002

A study is made of the scatter of low-frequency electric and magnetic dipole fields from a perfectly conducting sphere coated with a thin and lossy dielectric and immersed in an infinite and lossy medium. Infinite series solutions are obtained for the incident and scattered electric and magnetic fields. The solutions are evaluated numerically for various coating parameters and orthogonally oriented transmitter-receiver systems traveling along linear paths beneath the coated sphere. Results are compared with those obtained for the scatter of dipole fields from an uncoated sphere and used to determine the extent to which the scatter of low-frequency electric and magnetic dipole fields may be used to detect such objects and to obtain information about the nature of the coating.
rf and dc discharge characteristics for opposed-targets sputtering
Authors: Matsuoka Morito , Hoshi Yoichi , Naoe Masahiko
Published: July 2002

An rf opposed-targets sputtering (OTS) system, which can also be used as a dc OTS one, has been constructed and its discharge and plasma characteristics have been investigated. The rf OTS system has discharge and plasma characteristics similar to those of rf magnetron sputtering. Ionization of sputtering gases using high-energy γ electrons is the main mechanism for producing high-density plasma in both rf and dc OTS, though the ionization of gases by the rf excitation of electrons in the rf electric field becomes prominent at low plasma density in rf OTS. The absolute value of the self-bias potential (‖Vsb‖) of targets in rf OTS during sputtering is much higher than that of the applied target voltage (‖Va‖) in dc OTS. This is mainly caused by the fact that the trapping efficiency of γ electrons is much higher in dc OTS than in rf OTS, since the γ electrons are lost at the target surface in rf OTS but not in dc OTS. It was found that the bombardment of ions to the substrate surface is markedly heavier in rf OTS than in dc OTS, though it can be made lighter by sputtering at higher gas pressure and plasma densities.
Scattering and depolarization of linearly polarized waves by finitely conducting particles of irregular shape
Authors: Bahar Ezekiel , Fitzwater Mary Ann
Published: July 2002

In this work a layer consisting of a large variety of randomly distributed finitely conducting particles with irregular shapes is assumed to be excited at infrared and optical frequencies by a linearly polarized wave. The resulting incoherent specific intensities, as well as the copolarized and cross polarized intensities, are evaluated. Both single scatter and multiple scatter results are presented for particles with smooth and rough surfaces, and the effects of particle surface roughness on the degree of polarization are considered in detail.
Stoichiometric disturbances in compound semiconductors due to ion implantation
Authors: Avila R. E. , Fung C. D.
Published: July 2002

A method is developed to calculate the depth distribution of the local stoichiometric disturbance (SD) resulting from ion implantation in binary-compound substrates. The calculation includes first-order recoils considering projected range straggle of projectiles and recoils and lateral straggle of recoils. The method uses tabulated final-range statistics to infer the projectile range distributions at intermediate energies. This approach greatly simplifies the calculation with little compromise on accuracy as compared to existing procedures. As an illustration, the SD profile is calculated for implantation of boron, silicon, and aluminum in silicon carbide. The results for the latter case suggest that the SD may be responsible for otherwise unexplained distortions in the annealed aluminum profile. A comparison with calculations by other investigators using the Boltzmann transport equation shows good agreement.
Walpole bounds on the effective elastic moduli of isotropic multicomponent composites
Authors: Salerno Catherine M. , Watt J. Peter
Published: July 2002

Explicit results are presented for Walpole bounds on the effective elastic properties of overall isotropic multiphase composites of randomly oriented crystals of materials with either cubic or hexagonal symmetry. The Walpole bounds are considerably narrower than the widely used Voigt and Reuss bounds, but slightly further apart than the Hashin–Shtrikman bounds. The difference between the Walpole and Hashin–Shtrikman bounds arises because of the way the comparison material that optimizes the bounds is chosen. The usual Hashin–Shtrikman (and Voigt-Reuss) approach to estimating the overall elastic moduli of multiphase composites from the single-crystal elastic stiffnesses of the component phases calculates polycrystalline averages for each phase separately, then uses the arithmetic means of the polycrystalline bounds as ‘‘the’’ elastic properties of the (isotropic) components of the multiphase aggregate. This technique is not appropriate for all isotropic multiphase composites, depending on how the composite is formed. The Walpole averaging technique performs the averaging for all the components simultaneously. We demonstrate that the widely used Voigt–Reuss–Hill average can differ from the arithmetic mean of the Walpole or Hashin–Shtrikman bounds up to 10 or 20% in composites with large differences in the elastic properties of the components.
Boron, phosphorus, and arsenic diffusion in TiSi2
Authors: Gas P. , Deline V. , d‘Heurle F. M. , Michel A. , Scilla G.
Published: July 2002

The diffusivities of B, P, and As implanted in TiSi2 are analyzed between 500 and 900 °C by secondary ion mass spectroscopy. It is shown that P and As have high (and almost equal) diffusivities compared with B which appears immobile. This difference is presumed to be related to the very high stability of TiB2 (as compared with TiSi2) and the probable precipitation of B in the form of a titanium boride. The lattice diffusion coefficients for As and P are deduced from the diffusion profiles; they range from 10−17 to 10−14 cm2/s between 550 and 800 ° C. The activation energies are found to be, respectively, 1.8 and 2.0 eV; values close to the activation energy for the self-diffusion of Si in TiSi2, 1.8 eV. The diffusion profiles also show a high grain boundary diffusivity and an accumulation of dopant at the TiSi2–Si interface.
Copper centers in CdSe
Authors: Türe I. E. , Claybourn M. , Brinkman A. W. , Woods J.
Published: July 2002

Deep levels in single crystals of CdSe intentionally doped with copper have been investigated by photoconductivity and space-charge region capacitance techniques. The only center which can be conclusively associated with the copper impurity was found to have an activation energy of ∼1 eV with respect to the valence band. Estimates of 10−13 and 10−18 cm2 were made for the hole and electron capture cross sections for this center. The capture cross-section ratio of ∼105 indicates that this center is behaving as a photoconductivity sensitizing center. However, another center with an activation energy of ∼0.65 eV with respect to the valence band, and which is commonly observed in undoped material, would appear to be the dominant sensitizing center for all but the highest levels of copper doping. Two further centers, with activation energies of ∼0.5 and ∼0.9 eV, relative to the conduction band, were also found. In addition, there is evidence for the existence of at least two distinct centers with the same activation energy of ∼0.2 eV with respect to the valence band, one of which appears to be copper related.
Carrier spilling in spreading resistance analysis of Si layers grown by molecular-beam epitaxy
Authors: Jorke H. , Herzog H.-J.
Published: July 2002

In spreading resistance analysis, which is a method usually employed in doping profiling, carrier spilling effects become evident in doping structures in the 0.1-μm range. Profiles from spreading resistance analysis with such thin layers are to be interpreted rather in terms of ‘‘on bevel’’ carrier distribution than as actual doping profiles. Due to specific boundary conditions introduced by beveling, carrier spilling decisively depends on whether high-low or low-high transitions are considered. Using sample mounting both in standard and in upside down configuration high resolution of high-low as well as low-high transition is achieved.
Experimental evidence of thermoelectric amplification of acoustic waves in nickel
Authors: Rodrigues N. A. S. , Ghizoni C. C. , Miranda L. C. M.
Published: July 2002

We present experimental results on the detection of an exponentially growing acoustic signal in nickel as a function of the temperature gradient applied to the sample. These results are interpreted as resulting from the onset of the thermoelectric amplification of acoustic waves in the sample.
Dynamical x-ray rocking curve simulations of nonuniform InGaAs and InGaAsP using Abeles’ matrix method
Authors: Macrander A. T. , Minami E. R. , Berreman D. W.
Published: July 2002

Computer simulations of the intrinsic (400) reflecting power of In1−xGaxAs layers having graded compositions are presented. We find that multiple x-ray peaks can result from a linearly graded region which implies that an interpretation which ascribes individual peaks to sublayers having a constant lattice parameter may not always be correct. We find that, in general, the simulations are asymmetric and that they have a full width at half maximum less than ∼100 arcsec. We have simulated an actual rocking curve of a single In1−xGaxAs1−yPy layer grown on a (100) InP substrate by vapor-phase epitaxy which exhibited multiple peaks, and we find that a good fit is possible if the layer had a graded lattice parameter. Comparing dynamical to kinematical simulations for a 3-μm-thick linearly graded layer, we find that most of the features resulting from the grading can be explained using kinematical theory. However, only the dynamical simulations can properly account for the reflecting power in the vicinity of the substrate peak and for the lack of fine structure which is observed in the absence of a discontinuity in Bragg spacing at the layer/substrate interface.
Experiments on soliton motion in annular Josephson junctions
Authors: Davidson A. , Dueholm B. , Pedersen N. F.
Published: July 2002

We report here the results of an extensive experimental investigation of soliton dynamics in Josephson junctions of different annular geometries. The annular geometry is unique in that it allows for the study of undisturbed soliton motion as well as soliton–antisoliton collisons, since there are no boundary effects. We have successfully trapped a single soliton in an annular junction and found good agreement with perturbation theory at low soliton velocity, and evidence of departure from perturbation theory at higher velocity. We also discuss the observation of fine structure on the I-V curve for a single trapped soliton, and evidence linking the stability of the soliton to surface damping.
GaAs/AlGaAs distributed feedback structure with multiquantum well for surface-emitting laser
Authors: Nomura Y. , Shinozaki K. , Asakawa K. , Ishii M.
Published: July 2002

We demonstrate laser emission by photopumping at room temperature from a distributed feedback structure for a surface-emitting laser constructed by alternating growths of a GaAs/AlGaAs multiquantum well and an Al0.7Ga0.3As layer using molecular-beam epitaxy. A threshold photoexcitation intensity lower than 3.1×105 W/cm2, a 34-nm longitudinal mode spacing, and a 2.3-nm peak width of the laser emission were observed for the 6-μm-thick multilayer.
Effects of fluorine implantation on the kinetics of dry oxidation of silicon
Authors: Kuper F. G. , De Hosson J. Th. M. , Verwey J. F.
Published: July 2002

Kinetics of dry oxidation of silicon after implantation of fluorine in the oxide layer are investigated. It appeared that implanted fluorine can result in negative values of the linear oxidation rate constant. Fluorine profiles obtained by the nuclear reaction analysis (NRA) method using a resonant 19F(α, p)22Ne nuclear reaction will be presented. At 1200 °C the fluorine moves to the interface of Si and SiO2, both in dry oxidizing and inert atmospheres. Based on these findings, a model is presented that explains quantitatively the observed anomalous behavior of the linear oxidation rate constant.
A new nuclear magnetic resonance imaging technique for unambiguous unidirectional measurement of flow velocity
Authors: Cho Z. H. , Oh C. H. , Kim Y. S. , Mun C. W. , Nalcioglu O. , Lee S. J. , Chung M. K.
Published: July 2002

A new nuclear magnetic resonance (NMR) flow-velocity-imaging method applied to the study of the fluid dynamics is introduced. In the proposed technique, a selection gradient is used for the phase encoding, and since the selection gradient is relatively small compared with the conventional gradient for phase encoding it allows the measurement of high-velocity flow. To obtain the phase-velocity relationship, the Bloch equation is solved numerically and establishes the quantitative phase-velocity relationship of the flow under the slice selection gradient and echo radio frequency pulse. The flow effect compensation in the directions other than the slice selection direction is achieved by applying additional flow coding gradients similar to the conventional flow phase coding. The experimental NMR flow images obtained with the new technique are compared with the velocity measurements made with a laser Doppler velocimeter, and are found to be in close agreement.
Conditions for uniform growth of GaAs1−xPx superlattices
Authors: Blakeslee A. E. , Kibbler A. , Wanlass M. W. , Biefeld R. M.
Published: July 2002

Nonplanar morphology and compositional inhomogeneity are observed in GaAs1−xPx superlattices when the phosphorus content is substantially different in adjacent sublayers. The main characteristic feature of the distortion is a series of ribbonlike regions running through the superlattice which etch at a faster rate and contain more phosphorus than the surrounding material and are also the source of clusters of dislocations. Morphological stability and a general decrease in dislocation density can be effected by decreasing the interlayer strain, i.e., compositional difference, between the superlattice sublayers.
Effect of pressure on the Raman modes in LiNbO3 and LiTaO3
Authors: Jayaraman A. , Ballman A. A.
Published: July 2002

The pressure dependence of the optical phonons in LiNbO3 to 21 GPa and in LiTaO3 to 10 GPa has been investigated by Raman spectroscopy, using the diamond anvil cell. All the observed modes increase in frequency with pressure, and no mode softening occurs. This is in contrast to the behavior observed in BaTiO3 and PbTiO3, which are well-known displacive-type ferroelectric. It is suggested that this difference in pressure behavior may stem from a different type of phase transition in LiNbO3 and LiTaO3, namely the order-disorder type.
Theory of response of radiation sensing field-effect transistors in zero-bias operation
Authors: Hughes R. C.
Published: July 2002

Radiation sensing field-effect transistors operated at zero bias show a low-dose response that is roughly linear in the thickness of the gate oxide. The same devices show a thickness squared dependence if a bias is applied during the irradiation. This effect can be explained by examining the effect of diffusion and electron trapping on the buildup of net positive charge in the gate oxide.
A dislocation model relating apparent charge density to lattice mismatch in epitaxial InGaAs/InP
Authors: Hutson A. R.
Published: July 2002

Using a new model relating dislocation charge to Fermi level, we have simulated the differential capacitance resulting from the inclined dislocations accompanying the misfit dislocations in epitaxial InGaAs/InP samples. The result is a quadratic dependence of charge upon mismatch which is in quantitative agreement with experiments of Macrander et al. for a misfit dislocation segment length equal to about nine times the dislocation spacing.
Influencing factors and calculation of residual currents for modified metal-oxide-semiconductor devices covered with various silicone elastomers
Authors: Yokoyama Takashi , Kinjo Noriyuki , Wakashima Yoshiaki
Published: July 2002

An equation for the residual current induced by electric potential during charging of the gate electrode in modified transistors was derived by using electrical conductivity, Atalla’s model, and Ihantola’s equation for metal-oxide-semiconductor devices. The equation was examined by comparing calculated values with measured values of the residual current in a transistor covered with a silicone elastomer vulcanized by various reactions. Factors causing variations in hardness affect the electrical conductivity of the silicone elastomers. These are analyzed based on the vulcanization reaction system and the catalyst species.
Collection efficiency and crosstalk in closely spaced photodiode arrays
Authors: Holloway H.
Published: July 2002

Lateral diffusion of carriers in closely spaced photodiode arrays leads to image degradation. The effect is analyzed for backside illuminated arrays in the limiting cases of very small and very large optical absorption lengths. It is concluded that closely spaced two-dimensional arrays for thermal imaging applications will require the use of semiconductors whose thicknesses are less than the diameters of the photodiodes.
Effect of diamagnetic substitution on growth-induced anisotropy in (YBi)3Fe5O12
Authors: Fratello V. J. , Slusky S. E. G. , Brandle C. D. , Norelli M. P.
Published: July 2002

Films of (Y3−x−yBixPby) (Fe5−zGaz)O12 (z=0–1.1) and (Y3−x−yBixPby) (Fe5−wInw)O12 (w=0–0.6) garnets were prepared by liquid-phase epitaxy. The effects of tetrahedral Ga and octahedral In substitution on the Bi-based growth-induced uniaxial anisotropy in (YBi)3Fe5O12 films were measured. Both Ga and In resulted in a linear decrease in the anisotropy with increasing substitution. The effect of octahedral In was twice that of tetrahedral Ga.
Measurements of thermal conductivity of materials using a transient technique. II. Description of the apparatus
Authors: Piorkowska E. , Galeski A.
Published: July 2002

In this paper, an apparatus for measurements of the thermal conductivity of materials as a continuous function of the temperature is described. It works on the principle of continuous recording of the temperature difference between the surfaces of the sample caused by the flux of heat while the ambient temperature is linearily changed. The theoretical background described in the preceding paper by E. Piorkowska and A. Galeski [J. Appl. Phys. 60, ▪▪▪▪ (1986)] showed that the utilization of the results of two continuous measurements with different heat fluxes makes it possible to eliminate all components of the thermal response of the sample except the one depending on the heat flux and the thermal conductivity only. Testing measurements were conducted on samples of several nonmetalic materials. The results obtained indicate high precision of the method and the apparatus and reveal new possibilities of studying the thermal conductivity of materials during phase transitions.
Characterization of the effects of different capping layer structures on the laser recrystallization of silicon by using electrical test structures and Raman spectroscopy
Authors: Lu Hsindao E. , Boyd Joseph T. , Jackson Howard E. , Janning John L.
Published: July 2002

Polycrystalline silicon on insulator is laser-recrystallized using three different capping layer structures on separate wafers. The capping layer structures used include a 6-nm nitride layer, a combination of 64-nm nitride and 20-nm oxide layers, and 50-nm nitride antireflection periodic stripes oriented parallel to the direction of laser scanning. Electrical characteristics are measured by metal-oxide-semiconductor (MOS) silicon-on-insulator (SOI) test structures fabricated in the laser-recrystallized silicon films. Measurement of carrier mobilities, MOS interface properties, leakage currents, and ring oscillator delay times are compared for wafers having different capping layer structures. Stress in each case is characterized using a Raman spectrometer with microprobe.
Chemical annealing of the aluminum-oxygen hole center in vitreous silica
Authors: Shelby James E.
Published: July 2002

A kinetic model presented earlier for the reaction of hydrogen with optical defects in glasses is used to explain the results of an expanded study of the elimination of the aluminum-oxygen hole center in vitreous silica by reaction with hydrogen and deuterium gases. The model is shown to predict the observed effects of time, temperature, gas pressure, and the identity of the hydrogen isotope on the kinetics of the chemical annealing process.
Reply to ‘‘Comment on ‘Shortening of electron conduction pulses by electron attachers O2, N2O, and CF4’ ’’ [J. Appl. Phys. 5
6, 3169 (1984)]
Authors: Lee L. C.
Published: July 2002

This is a reply to Hunter’s comment on our papers.