bluuebunny/crossref_metadata_2025 huggingface dataset:
Mobilization and harvesting of peripheral blood stem cells: randomized evaluations of different doses of filgrastim
Authors: Weaver C. H. , Birch R. , Greco F. A. , Schwartzberg L. , McAneny B. , Moore M. , Oviatt D. , Redmond J. , George C. , Alberico T. , Johnson P. , Buckner C. D.
Published: July 2002

The effects of different doses of filgrastim on yields of CD34+peripheral blood stem cells were evaluated in patients with breast cancer. 55 were randomized to receive filgrastim 10, 20, 30 or 40 μg/kg/d with more CD34+cells/kg/apheresis harvested after the three highest dose levels. 35 additional patients were randomized to receive 10 or 30 μg/kg. The median number of CD34+cells collected after 10 μg/kg (n= 31) was 0.7 × 106/kg/apheresis (range 0.1–4.4) as compared to 1.2 (range 0.1–6.8) after 30 μg/kg (n= 32) (P= 0.04). Among patients randomized to 10v30 μg/kg, more (50%) achieved 5.0 × 106CD34+cells/kg and less aphereses were required to achieve 2.5 × 106CD34+cells/kg after the higher dose (P= 0.04). In multivariate analyses, patients receiving 10 μg/kg (n= 31) had lower yields of CD34+cells (P= 0.026) and had a 3.3‐fold increase in the probability of not achieving 5.0 × 106CD34+cells/kg as compared to patients receiving 20–40 μg/kg (n= 59). Patients who had received radiation had a 2.9‐fold probability of not achieving 2.5 × 106CD34+cells/kg. These data suggest that, in patients with good marrow reserves, doses of filgrastim > 10 μg/kg/d mobilized more CD34+cells and may be useful when high numbers of CD34+cells are desired.
Quaternary beetles: A review and issues for Australian studies
Authors: Porch Nick , Elias Scott
Published: July 2002

Few Australian entomologists, ecologists, biogeographers or Quaternary researchers are familiar with the details of Quaternary beetle research. Since the 1950s the study of fossil beetles has developed to become an important discipline of the Quaternary sciences. Unfortunately, however, the significance of the discipline for ecological and evolutionary research has been slow to penetrate mainstream entomological, ecological, and evolutionary thought. This paper outlines the history, methods and results of Quaternary beetle studies, based primarily upon research from the well‐studied Northern Hemisphere, and then examines issues relevant to Australian research. Analysis of Quaternary beetle assemblages from Australia can contribute to the reconstruction of past environments and climates, in particular quantitative estimation of past temperature regimes, and potentially, effective precipitation. Of more significance to entomology, however, is the potential to reconstruct climatically‐induced changes in distribution, essential for understanding the Quaternary biogeographic history of Australia's insect fauna. Furthermore, it will be possible to examine evidence, or the lack thereof, for speciation during the Quaternary, in the context of Quaternary environmental change.
Conservation Value of Roadside Prairie Restoration to Butterfly Communities
Authors: Ries Leslie , Debinski Diane M. , Wieland Michelle L.
Published: July 2002

Abstract:It has been suggested that restoration of roadsides to native habitat can benefit wildlife by adding habitat and restoring connectivity between fragmented reserves. In Iowa, which has one of the highest road densities in the United States, roadside vegetation has traditionally been managed to maintain a monoculture of exotic grass. Recently, several Iowa counties have begun integrated roadside vegetation management, a program that both restores roadsides to native prairie vegetation and restricts the use of herbicides and mowing. We evaluated the effect of this management regime on butterfly populations along central Iowa roadsides. We surveyed 12 separate prairie roadside areas, comparing the abundance and species richness of disturbance‐tolerant and habitat‐sensitive butterflies in roadside prairies with those of nearby roadsides dominated by either weeds ( primarily non‐native legumes) or non‐native grasses. We found that management of roadsides profoundly affected the butterfly community. Species richness of habitat‐sensitive butterflies showed a two‐fold increase in prairie compared with grassy and weedy roadsides ( p< 0.0001), and abundance increased almost five times more on the prairie than on grassy roadsides ( p< 0.02). Species richness of disturbance‐tolerant butterflies showed no response to roadside management, although abundance was slightly higher in weedy and prairie roadsides than on grassy roadsides ( p< 0.01). Of all habitat variables explored, the species richness of plants in flower showed the strongest effect on mean richness and abundance of both disturbance‐tolerant and habitat‐sensitive butterfly species. Although there were higher concentrations of road‐killed butterflies near weedy and prairie roadsides than on grassy roadsides, relative numbers indicated that mortality risk was more than twice as high on grassy roadsides ( p< 0.0001). Tracking studies showed that butterflies were less likely to exit prairie roadsides, indicating that their mortality rates may be lower and offering preliminary evidence that roadsides have the potential to be used as corridors. Overall, our results indicate that roadside restoration benefits butterfly populations. More detailed demographic data are necessary, however, to explore the possibility that roadsides are acting as sink habitat for some habitat‐restricted species.
The Relationship of Psychosocial Factors to Total Mortality Among Older Japanese‐American Men: The Honolulu Heart Program
Authors: Ceria Clementina D. , Masaki Kamal H. , Rodriguez Beatriz L. , Chen Randi , Yano Katsuhiko , Curb J. David
Published: July 2002

OBJECTIVE:To examine the predictive value of psychosocial factors as risk factors for all‐cause mortality.

DESIGN:A community‐based longitudinal cohort study: The Honolulu Heart Program.

SETTING:Population‐based study conducted in Oahu, Hawaii.

PARTICIPANTS:Three thousand four hundred and ninety‐seven men age 71 to 93 were examined and followed prospectively for all‐cause mortality for an average of 6 years.

MEASUREMENTS:Psychosocial data were obtained using the Lubben Social Networks Scale (LSNS). The LSNS consists of 10 items—family relationships (three items), relationships with friends (three items), and interdependent social supports and living arrangements (four items). We divided the LSNS score into quartiles for comparison, with the first quartile representing the lowest social support and the fourth quartile representing the highest social support.

RESULTS:A significant dose‐response relationship was noted with LSNS score and total mortality: 33.8% in the first quartile died over the follow‐up period, 23.4% in the second, 18% in the third, and 15.7% in the fourth (P< .001). Six‐year age‐adjusted mortality rates were 66.2, 45.7, 37.8, and 33.7 per 1,000 person years in the first, second, third, and fourth, respectively (P< .001). Using age‐adjusted Cox proportional hazards models, with the first quartile of LSNS as the reference group, relative risk for mortality was 0.69 (95% confidence interval (CI) = 0.58–0.82), 0.57 (95% CI = 0.47–0.70), and 0.52 (95% CI = 0.43–0.64) in the second, third, and fourth quartiles, respectively. Cox models were repeated, controlling for age and smoking status, and low LSNS scores remained significantly associated with higher mortality (P= .0001).

CONCLUSIONS:Our findings suggest that social networks were significantly independently associated with 6‐year all‐cause mortality in this cohort of older Japanese‐American men. Social interventions in old age may reduce early mortality.J Am Geriatr Soc 49:725–731, 2001.
The influence of pain intensity on somatosensory perception in patients suffering from subacute/chronic lateral epicondylalgia
Authors: Leffler Ann‐Sofie , Kosek Eva , Hansson Per
Published: July 2002

A confounding factor in the analysis of chronic pain patients is the finding of signs of somatosensory disturbances not only in neuropathic pain patients but also in a subgroup of patients with musculoskeletal pain. The purpose was to investigate if patients suffering from subacute/chronic lateral epicondylalgia demonstrated altered sensibility, and if this was affected by pain intensity. At the start of the experiment, quantitative sensory testing (QST) (thermal, pressure pain, touch) was performed in the local pain area and in the area of pain referral. QST was repeated following pain provocation (weight lifting). A local anaesthetic was then injected into the lateral epicondyle and QST was repeated in the area of pain referral. The contralateral arm was assessed, treated and injected in the same way. At the baseline assessment there was no difference in sensibility between sides, with the exception of a significantly lowered threshold to noxious heat (p< 0.04) in the area of pain referral, present during the whole experiment. In the affected arm only, weight lifting resulted in significantly increased pain intensity in the local (p< 0.01) and referred (p< 0.01) pain areas, respectively. Repeated muscle contractions resulted in altered somatosensory functions in both the affected arm and the unaffected arm, consequently not dependent on ongoing pain in the assessed area. Tactile perception thresholds increased significantly following pain provocation in the area of pain referral (p< 0.04) only and normalized following injection of local anaesthetic (p< 0.02), indicating that the sensitivity to light touch was altered by the nociceptive input from the affected arm. Copyright 2000 European Federation of Chapters of the International Association for the Study of Pain
Injection of hypertonic saline into musculus infraspinatus resulted in referred pain and sensory disturbances in the ipsilateral upper arm
Authors: Leffler Ann‐Sofie , Kosek Eva , Hansson Per
Published: July 2002

A confounding factor in the analysis of chronic pain patients is the finding of somatosensory disturbances not only in neuropathic pain patients, but also in a subgroup of patients with musculoskeletal pain. The purpose of the study was to examine if referred pain, induced by intramuscular injections of hypertonic saline (5% NaCl) into the left musculus infraspinatus, resulted in somatosensory alterations. Thermal sensitivity, pressure pain sensitivity, as well as low threshold mechanoreceptive function, were assessed in the referred pain area and the homologous contralateral site before, during and following the injections. In 10 out of 12 subjects the procedure induced only referred pain localized in the dorsolateral part of the ipsilateral proximal upper arm. In this referred pain area there was a significantly decreased sensitivity to light touch, as tested with von Frey filaments, during the pain period and the post‐injection period compared to the contralateral side (p< 0.004 andp< 0.009, respectively). A trend for thermal hypoaesthesia, which was only demonstrable in the sum of warm and cold thresholds, was found in the referred pain area, but not contralaterally, during the pain period compared to the pre‐injection period. Significantly increased sensitivity to threshold and suprathreshold heat pain was found bilaterally during post‐injection assessments (p< 0.02 andp< 0.006, respectively). There were no statistically significant changes in sensitivity to innocuous thermal stimuli when assessing the two percepts separately, or to pressure pain or brush‐evoked touch. In conclusion, intramuscular injections of hypertonic saline resulted in referred pain and tactile hypoaesthesia in the referred pain area. Copyright 2000 European Federation of Chapters of the International Association for the Study of Pain
Impacts of Infection by Parasitic Angiosperms on Host Photosynthesis
Authors: Watling J. R. , Press M. C.
Published: July 2002

Abstract:Parasitic angiosperms are a taxonomically diverse group of plants that invade host tissues and remove resources via a specialized structure known as the haustorium. Through the haustorium, carbon, water and mineral nutrients are withdrawn, often at the expense of host growth and vigour. In addition to the removal of resources from host plants, many parasitic angiosperms are also able to impact host growth via effects on host photosynthesis. In this paper we review what is known about how parasitic angiosperms affect host photosynthesis and the impact this has on host productivity. Holoparasites, that lack chlorophyll, act as extra sinks for host photosynthates and generally either enhance or have a neutral effect on host photosynthetic productivity. In contrast, hemiparasites, that are capable of some autotrophic carbon fixation, usually have a negative impact on host photosynthesis. Irrespective of the outcome of infection, the mechanisms involved in altering host photosynthesis are diverse and may act at either the leaf or whole‐plant level. In some cases, parasites impact directly on host photosynthetic metabolism, while in others the effects are more indirect, for example through changing host architecture.
Performance of electrostatic Aharonov–Bohm interferometers in the diffusive regime
Authors: Bandyopadhyay S. , Porod W.
Published: July 2002

In this letter we discuss the performance of semiconductor electrostatic Aharonov–Bohm interferometers that operate in the diffusive regime. We find that the performance is primarily determined by temperature and carrier concentration, and we have identified the conditions for ‘‘fair,’’ ‘‘good,’’ and ‘‘excellent’’ performance. Our analysis shows that two-dimensional interferometers cannot operate at elevated temperatures but one-dimensional interferometers, on the other hand, could operate at 77 K if the carrier concentration is sufficiently high and the structure is cleverly designed to minimize end reflections.
Small field behavior of critical current in Y1Ba2Cu3O7 sintered samples
Authors: Paternò G. , Alvani C. , Casadio S. , Gambardella U. , Maritato L.
Published: July 2002

Critical currents carried by sintered Y1Ba2Cu3O7 superconducting samples have been measured at different temperatures close to the critical temperature Tc. The effects of an applied magnetic field perpendicular to the current direction have been investigated. A strong reduction of the dc current for field values smaller than the lower critical field Bc1 has been observed. The magnetic field dependence is discussed in terms of weak coupling between grains. The experimental data show an excellent agreement, at low field values, with the theoretical dependence valid for an array of Josephson junctions.
Density rescaling procedure for Monte Carlo simulations of electron transport
Authors: Li Y. M. , Pitchford L. C. , Moratz T. J.
Published: July 2002

A practical difficulty in Monte Carlo simulations of electron transport occurs when the electron number density changes significantly over the time or length scale of the simulation. In this letter, we present a simple scaling procedure to resolve this difficulty that is easy to implement and that is exact for linear collision operators. A simulation of electron transport in nitrogen at high electric field strength is included to illustrate this rescaling procedure.
Growth kinetics of amorphous interlayer formed by interdiffusion of polycrystalline Ti thin-film and single-crystal silicon
Authors: Lur W. , Chen L. J.
Published: July 2002

The growth kinetics of amorphous interlayer (a interlayerbb) in polycrystalline Ti films on single-crystal-silicon has been studied by cross-sectional transmission electron microscopy. The growth was found to follow a linear growth law initially in samples annealed at 350–425 °C. The activation energy of the linear growth was measured to be 1.6±0.3 eV. Maximum thicknesses of the a interlayers were measured to be of the order of 10 nm. The formation of an a interlayer was observed in samples annealed at a temperature as high as 600 °C. The formation and growth kinetics of a interlayers in Ti/Si and Ni/Zr systems are compared. Essential factors for the formation and growth of an a interlayer are discussed. The results represent the first report on the growth kinetics of an a interlayer in metal thin films on single-crystal silicon.
Hydrogen atom detection in the filament-assisted diamond deposition environment
Authors: Celii F. G. , Butler J. E.
Published: July 2002

The resonance-enchanced multiphoton ionization (REMPI) technique was employed for detection of gas phase atomic hydrogen in the filament-asisted diamond growth environment. The H atom REMPI signal varied significantly with the reactant CH4/H2 fraction as well as with the filament temperature. We interpret these observations as evidence for the surface role of atomic hydrogen in the diamond growth mechanism. The spatial resolution of the REMPI technique allowed us to confirm that hydrogen atom transport in the deposition region occurs by diffusion.
Spin-polarized photoemission from AlGaAs/GaAs heterojunction: A convenient highly polarized electron source
Authors: Ciccacci F. , Drouhin H.-J. , Hermann C. , Houdré R. , Lampel G.
Published: July 2002

We analyze the operation of a spin-polarized electron source, consisting of a 100 Å GaAs cap on top of Al0.3Ga0.7As, excited at 300 or 120 K by a He-Ne laser. The cap allows easy activation to negative electron affinity while the alloy permits gap matching to the light source, and thus large electron spin polarization (30% at 300 K, 36% at 120 K). We compare yield curves, energy distribution curves, and polarized energy distribution curves obtained on samples with 100 and 1000 Å caps and on bulk GaAs. The X conduction minimum position in the alloy is also determined.
Time-resolved extreme ultraviolet emission from a highly ionized lithium capillary discharge
Authors: Marconi Mario C. , Rocca Jorge J.
Published: July 2002

A fast discharge current pulse (50 ns FWHM) was used to create a highly ionized plasma in a 500-μm-diam lithium hydride capillary 3.8 cm in length. Time-resolved extreme ultraviolet spectra of the capillary plasma show simultaneous line emission from highly ionized (O VI) and singly ionized (O II) species, indicating the existence of a hot-core plasma (Te>25 eV) surrounded by a significantly cooler plasma near the walls. The intensity of the 72.9 nm emission corresponding to the Li III 3–2 transition was observed to increase during the decay of the current pulse, consistent with excitation by electron-ion recombination. The results are relevant to the possibility of amplification of extreme ultraviolet radiation in a discharge-pumped device.
Amorphous silicon photoconductive diode
Authors: Hack M. , Shur M. , Tsai C. C.
Published: July 2002

In this letter we describe the operation of a new high-speed, high-gain amorphous silicon sensor. The device gain originates from the photoconductive properties of amorphous silicon but good light to dark sensitivity is obtained by suppressing the sensor dark current by means of a lightly p-type barrier layer. Optical gains in excess of 100 have been achieved with response times of approximately 200 μs.
Sticking coefficient of the SiH2 free radical on a hydrogenated silicon-carbon surface
Authors: Robertson Robert M. , Rossi Michel J.
Published: July 2002

The sticking coefficient of SiH2 on a hydrogenated silicon-carbon surface is measured in a low-pressure pulsed-photolysis experiment. Thermal and vibrationally excited SiH2 are created by infrared multiphoton decomposition of n-butylsilane. The first-order wall loss rates of the radicals are determined from the time dependence of the resonance-enhanced multiphoton ionization signal. The sticking coefficients of SiH2 (∼0.1) and vibrationally hot SiH2 (>0.5) are determined from the measured first-order loss rate constants and the calculated wall collision rate constant.
Conversion of InP/In0.53Ga0.47As superlattices to Zn3P2/In1−xGaxAs and Zn3P2/Zn3As2 superlattices by Zn diffusion
Authors: Hwang D. M. , Schwarz S. A. , Mei P. , Bhat R. , Venkatesan T. , Nazar L. , Schwartz C. L.
Published: July 2002

A standard 600 °C closed-tube Zn diffusion into an unstrained InP/In0.53Ga0.47As superlattice was found to produce new superlattices containing Zn3P2 layers, and in some cases Zn3As2 layers. Crystalline properties and diffusion profiles were examined by transmission electron microscopy and secondary-ion mass spectrometry. Initial doping of Zn enhances the diffusion of In and Ga and results in a superlattice of uniform In and Ga distribution. Upon further infusion of Zn, Zn3P2 forms selectively in the phosphorus layers and propagates from the surface while maintaining an atomically abrupt Zn3P2/In1−xGaxP interface. Zn3As2 conversion is also observed to occur under sufficiently stringent conditions. Diffusion of P and As was not observed.
Superconducting InGaAs junction field-effect transistors with Nb electrodes
Authors: Kleinsasser A. W. , Jackson T. N. , McInturff D. , Rammo F. , Pettit G. D. , Woodall J. M.
Published: July 2002

We describe the design, fabrication, and characterization of superconducting In0.47Ga0.53As junction field-effect transistors (JFETs) with Nb source and drain electrodes. In0.47Ga0.53As has the advantage of combining large coherence length and high Schottky barrier transmission, making it a very attractive material on which to base superconducting FETs. At large voltages these devices behave as normal FETs in either enhancement or depletion modes, while at small voltages they act as Josephson junctions or super-Schottky diodes. Both normal and super- currents are controlled by the gate.
Anisotropic and inhomogeneous strain relaxation in pseudomorphic In0.23Ga0.77As/GaAs quantum wells
Authors: Grundmann M. , Lienert U. , Bimberg D. , Fischer-Colbrie A. , Miller J. N.
Published: July 2002

The structural properties of pseudomorphic In0.23Ga0.77As/GaAs single quantum wells are investigated with x-ray double-crystal diffractometry. Anisotropic tilting of lattice planes along dislocations and anisotropic reflectivity of fully relaxed domains coexisting with strained domains are reported for the first time. Due to the anisotropic strain relaxation the crystal symmetry changes from tetragonal in the fully strained case to monoclinic in a partially relaxed quantum well.
Microwave surface resistance in Tl-based superconducting thin films
Authors: Chang L. D. , Moskowitz M. J. , Hammond R. B. , Eddy M. M. , Olson W. L. , Casavant D. D. , Smith E. J. , Robinson M. , Drabeck L. , Grüner G.
Published: July 2002

We report measurements of microwave surface resistance in Tl-based superconductor thin films made by laser ablation followed by a post-deposition thermal process. The films were measured by using cavity methods. The data at 9.5 and 148 GHz indicate that the residual resistance scales as f2. At 77 K, the 9.5 GHz surface resistance is ten times smaller than oxygen-free high-conductance copper at the same temperature and frequency. The 9.5 GHz measurement also indicates that the film-substrate interface does not cause more microwave loss than the film surface.
Influence of GaAs surface stoichiometry on the interface state density of as-grown epitaxial ZnSe/epitaxial GaAs heterostructures
Authors: Qiu J. , Qian Q.-D. , Gunshor R. L. , Kobayashi M. , Menke D. R. , Li D. , Otsuka N.
Published: July 2002

Epitaxial ZnSe/epitaxial GaAs interfaces have been formed by molecular beam expitaxy and evaluated by several techniques including capacitance-voltage measurements. In the study reported here, the GaAs surface stoichiometry was systematically varied prior to the nucleation of ZnSe. A dramatic reduction of interface state density occurred when the GaAs epilayer was made As deficient. The resulting interface state densities of as-grown structures are comparable to values obtained with (Al,Ga)As/GaAs interfaces.
Evidence for the existence of a negatively charged hydrogen species in plasma-treated n-type Si
Authors: Tavendale A. J. , Pearton S. J. , Williams A. A.
Published: July 2002

We demonstrate the drift of a donor-passivating hydrogen species under the action of the electric field in the depletion region of a reverse-biased Au/n-Si Schottky diode hydrogenated by exposure to a low-frequency discharge. The redistribution is explained by the unidirectional drift of a negatively charged passivating species and is confirmed by secondary-ion mass spectrometry profiling in deuterated diodes. The results are consistent with the presence of an acceptor level for hydrogen in n-type Si, and are analogous to the situation in p-type Si where drift experiments reveal the existence of positively charged hydrogen donor species.
High sensitivity low dark current 10 μm GaAs quantum well infrared photodetectors
Authors: Levine B. F. , Bethea C. G. , Hasnain G. , Shen V. O. , Pelve E. , Abbott R. R. , Hsieh S. J.
Published: July 2002

By increasing the quantum well barrier width, we have dramatically reduced the tunneling dark current by an order of magnitude and thereby significantly increased the blackbody detectivity D*BB. For a GaAs quantum well infrared detector having a cutoff wavelength of λc=10.7 μm, we have achieved D*BB =1.0×1010 cm (Hz)1/2/W at T=68 K, a temperature which is readily achievable with a cryogenic cooler.
Role of native oxide layers in the patterning of InP by Ga ion beam writing and ion beam assisted Cl2 etching
Authors: Wang Y. L. , Harriott L. R. , Hamm R. A. , Temkin H.
Published: July 2002

We have studied the mechanism of increased etch rate induced in InP substrates by focused Ga ion implantation and Cl2 etching. We cannot account for the depth of surface steps formed in this process with a purely kinetic mechanism. The preferential etching of implanted areas is attributed instead to local modification or removal of native oxides from the surface of InP. The thin oxide layer effectively protects the substrate and inhibits Cl2 etching. Consistent with the thermodynamic prediction, a cleaned InP(100) surface is etched by Cl2 (5×10−4 Torr) with a rate of approximately 1000 Å/min at 200 °C. Surface steps as deep as 3 μm have been reproducibly prepared using an oxide mask believed to be approximately 20 Å thick. In the etching process, any substrate damage caused by the Ga beam writing is completely removed. The oxide mask, which can be patterned on a very fine scale by energetic particle bombardment, provides a new avenue for in situ processing of InP.
Monte Carlo analysis of ionization threshold in Si
Authors: Sano Nobuyuki , Tomizawa Masaaki , Yoshii Akira
Published: July 2002

Monte Carlo simulations of electronic high-field transport in Si are performed. Contrary to previous treatments of impact ionization, we do not employ the ordinary Keldysh formula [Sov. Phys. JETP 21, 1135 (1965)] with a soft threshold, but rather a new expression, which is an explicit function of the wave vector of the initiating electron, is used. The calculation results of drift velocity, ionization coefficient, and quantum yield show excellent agreement with the experimental data. Our results strongly substantiate the idea that the ionization threshold is basically hard even in Si in the sense that the electrons rapidly ionize when they approach the threshold energies and that the softness of the ionization threshold is introduced through the wave vector dependence of the threshold energies.
Particulates reduction in laser-ablated YBa2Cu3O7−δ thin films by laser-induced plume heating
Authors: Koren G. , Baseman R. J. , Gupta A. , Lutwyche M. I. , Laibowitz R. B.
Published: July 2002

Experimental demonstration of reduction in the number and size of particulates formed in the laser ablation deposition of YBa2Cu3O7−δ thin films is obtained by the use of a second laser which further heats and fragments the blowoff material in the plume formed by the first laser. This results in a smoother film with higher critical current density as compared to that obtained without the second laser irradiation of the plume.
High-pressure vapor transport of ZnGeP2
Authors: Xing G. C. , Bachmann K. J. , Posthill J. B.
Published: July 2002

Nominally undoped n-type single crystals of ZnGeP2 have been fabricated for the first time by high-pressure vapor transport. These crystals have higher phosphorus concentration than melt-grown bulk single crystals and exhibit lower sub-band-gap absorption in the transparency range between 0.64 and 12 μm. A heretofore unreported absorption peak at 13 μm and a transparency window extending from l5 μm to at least 23 μm have been identified in the infrared for these crystals, as well as in crystals grown from melt.
Dependence of the saturated light-induced defect density on macroscopic properties of hydrogenated amorphous silicon
Authors: Park H. R. , Liu J. Z. , Roca i Cabarrocas P. , Maruyama A. , Isomura M. , Wagner S. , Abelson J. R. , Finger F.
Published: July 2002

We report a study of the saturated light-induced defect density Ns,sat in 37 hydrogenated (and in part fluorinated) amorphous silicon [a-Si:H(F)] films grown in six different reactors under widely different conditions. Ns,sat was attained by exposing the films to light from a krypton ion laser (λ=647.1 nm). Ns,sat is determined by the constant photocurrent method and lies between 5×1016 and 2×1017 cm−3. Ns,sat drops with decreasing optical gap Eopt and hydrogen content cH, but is not correlated with the initial defect density Ns,ann or with the Urbach tail energy Eu. We discuss our results within the framework of existing models for light-induced defects.
InxGa1−xAs/GaAs multiple quantum well optical modulators for the 1.02–1.07 μm wavelength range
Authors: Woodward T. K. , Sizer Theodore , Sivco D. L. , Cho A. Y.
Published: July 2002

We report the operation of strained-layer InxGa1−x As/GaAs 50- and 100-period multiple quantum well optical modulators at wavelengths ranging from 1.02 to 1.07 μm. Structures were grown on GaAs substrates, as well as on strain relief InxGa1−xAs buffer layers. Devices show favorable electrical characteristics and absorption contrasts up to 57% at the exciton peak. Optical modulation of a Nd:YAG laser is demonstrated, via operation of self-electro-optic effect devices at 1.064 μm.
Laser-induced surface acoustic waves and photothermal surface gratings generated by crossing two pulsed laser beams
Authors: Harata Akira , Nishimura Hiroyuki , Sawada Tsuguo
Published: July 2002

Gigahertz surface acoustic waves have been optically generated and detected on aluminum metallic films and silicon wafers using the laser-induced grating technique. The acoustic velocities were in good agreement with those of Rayleigh waves. Photothermal surface gratings could also be detected as a nonpropagating component of the thermoelastic waves. The relaxation time of the grating was related to the thermal diffusivity of the material. A simplified theory for the generation of surface transient gratings containing acoustic waves is presented in addition to the experimental results.
GaAs-oxide removal using an electron cyclotron resonance hydrogen plasma
Authors: Lu Z. , Schmidt M. T. , Chen D. , Osgood R. M. , Holber W. M. , Podlesnik D. V. , Forster J.
Published: July 2002

The surface chemistry of GaAs-oxide removal with an electron cyclotron resonance (ECR) hydrogen plasma has been investigated with x-ray photoelectron spectroscopy. It is found that As oxide is efficiently removed at room temperature, and heating expedites the removal of Ga oxide. Band bending changes during ECR hydrogen-plasma oxide reduction are also discussed.
Homogeneous cylindrical plasma source for short-wavelength laser experiments
Authors: Hartmann W. , Bauer H. , Christiansen J. , Frank K. , Kuhn H. , Stetter M. , Tkotz R. , Wagner T.
Published: July 2002

A plasma source suitable for repetitive operation, going beyond single shot experiments for research into soft x-ray lasers, is reported. Successful operation of an ultrafast, small-diameter, highly uniform z pinch has been achieved at currents of 35–50 kA, for a variety of gases and a large range of mass densities. Due to an efficient preionization of the working gas, a high-temperature and a high cooling rate of the plasma column are obtained. The plasma is less than 1 mm in radius, over 30 mm long, and over 1018 cm−3 ion density. A soft x-ray recombination laser experiment for the λ≊182 Å Balmer-alpha-like transition in C vi is proposed.
Strain relief study concerning the InxGa1−xAs/GaAs (0.07<x<0.5) material system
Authors: Krishnamoorthy V. , Ribas P. , Park R. M.
Published: July 2002

The evolution of dislocations in the InxGa1−xAs/GaAs material system has been studied as a function of the ternary alloy comparison in the range 0.07<x<0.5. Cross-sectional transmission electron microscope observations indicate that for x<0.18, threading dislocations are absent in the epilayer and dislocations propagate from the heterointerface into the GaAs material, while, for 0.18<x<0.28, dislocations appear to propagate into both the epilayer and the GaAs. Furthermore, for x ≳0.28, all the dislocations are observed in the epilayer while the GaAs appears to be dislocation-free. We propose a model involving the balance of forces acting on misfit dislocations generated at the heterointerface which includes a surface image force term to explain our observations of dislocation evolution as a function of the ternary alloy composition.
GaPSb: A new ternary material for Schottky diode fabrication on InP
Authors: Loualiche S. , Le Corre A. , Salaun S. , Caulet J. , Lambert B. , Gauneau M. , Lecrosnier D. , Deveaud B.
Published: July 2002

Despite its excellent transport properties, the low value of the Schottky barrier height on n- type InP (0.43 eV) prevents its use in electronic applications. A new InP lattice- matched material (GaPSb with 65% Sb) has been grown for the first time by gas source molecular beam epitaxy and studied. The material gap is 0.9 eV and the gold Schottky diode reaches 0.6 eV on this compound. This is the highest barrier ever reported on InP lattice-matched materials which do not contain aluminum. Continuous and picosecond luminescence results show that the GaPSb/InP is a type II heterostructure with ΔEc=50 meV at 4 K.
Kinetics of silicide formation in chromium-amorphous silicon multilayered films
Authors: Schlesinger T. E. , Cammarata R. C. , Prokes S. M.
Published: July 2002

Silicide formation in multilayered thin films of chromium and amorphous silicon was investigated by differential scanning calorimetry (DSC). The DSC traces gave a large main peak that was associated with the growth of the silicide. The growth kinetics followed a linear rate law, with an activation energy of 2.6 eV and a pre-exponential factor of 7.5×107 m/s for the rate constant. An explosive silicide reaction, observed in other metal-silicon multilayered films, could not be induced in this system.
Valence-band offset in strained GaAs-InxGa1−xAs superlattices
Authors: Jogai B.
Published: July 2002

The valence (or conduction)-band offset for GaAs-InGaAs superlattices is determined by comparing the calculated energies with conduction intersubband energies obtained from electronic Raman scattering (ERS). A valence-band offset of 40% is estimated for samples with an In content of about 20%, whereas the offset is found to be 60% for samples with an In content of about 5%.
New contactless method for carrier diffusion measurements in silicon with a high precision
Authors: Grivickas Vytautas , Linnros Jan
Published: July 2002

A novel, contactless transient grating method is demonstrated for excess carrier diffusion coefficient determination at an arbitrarily chosen injection density. The method is based on free-carrier absorption decay measurements along a grid of carriers excited in the bulk of the sample by a YAG laser pulse. The focused infrared probe beam, with an excess-carrier detection limit as low as 1012 cm−3, monitors the lateral interdiffusion of carriers by scanning across the carrier grating. Measurements on a 1015 cm−3, p-doped Si sample at injection levels in the range 1013–1017 cm−3 show a considerable reduction of the carrier diffusion coefficient at injection levels Δn ≥ 1016 cm−3.
Monitoring material grain size by laser-generated ultrasound
Authors: Aharoni A. , Tur M. , Jassby K. M.
Published: July 2002

A noncontact, nondestructive, laser-based method for remote monitoring of material grain size is described. A surface acoustic wave surge, generated in the material under test by a short, high-power laser pulse, is detected optically. The leading-edge rise time of the acoustic signal is found to relate to the material grain size through frequency-dependent scattering. In assuming a Rayleigh scattering model, a good correlation with metallurgical measurements is obtained in steel specimens.
Optically addressed asymmetric Fabry–Perot modulator
Authors: Larsson A. , Maserjian J.
Published: July 2002

A low power, high contrast optically addressed modulator, operating with normal incidence, has been fabricated. Optically controlled reflection modulation is achieved through optically induced absorption modulation in a periodically δ-doped InGaAs/GaAs multiple quantum well structure inserted in an integrated asymmetric Fabry–Perot resonator. A contrast ratio≳60:1 was measured using a spectrally matched low power InGaAs/GaAs quantum well laser to generate the write (control) signal. The insertion loss for the normally off modulator is 4.6 dB at the highest write signal power (30 mW) used. The device lends itself to the fabrication of arrays for optically addressed spatial light modulation.
Soft x-ray spectra produced by subpicosecond laser-double-pulses
Authors: Teubner U. , Kühnle G. , Schäfer F. P.
Published: July 2002

Soft x-ray spectra generated on flat Al targets by a 500 fs KrF* laser pulse (intensity 5.3×1015 W/cm2), preceded by a prepulse of the same pulse duration, have been measured as a function of the pulse separation and the prepulse intensity. It was found that not only the total x-ray emission was much stronger when the prepulse was present but, in particular, lines in the shorter wavelength region had a higher intensity than without prepulse, and were strongly dependent on the time separation between the prepulse and the main pulse.
Electrically detected magnetic resonance of a transition metal related recombination center in Si p–n diodes
Authors: Rong F. C. , Gerardi G. J. , Buchwald W. R. , Poindexter E. H. , Umlor M. T. , Keeble D. J. , Warren W. L.
Published: July 2002

A hyperfine structure has been observed by electrically detected magnetic resonance from a Si p–n diode. From the hyperfine splitting, and the natural abundance of the interacting I=1/2 nuclear species, the recombination center is found to be consistent with a platinum complex.
Magnetic properties of multiple-structure multilayered Co/Pd films
Authors: Maeno Y. , Yamane H. , Sato K. , Kobayashi M.
Published: July 2002

Co/Pt and Co/Pd multilayered films exhibit large perpendicular magnetic anisotropy and have attracted attention as new materials for magneto-optical recording media and for applications in other areas. The coercivity and the squareness ratio of these films are small at thick films of 1000 Å or more. We studied Co/Pd multiple-structure multilayered films, consisting of periodic piles of Co/Pd multilayered film layers and Pd thin-film layers in order to improve the magnetic characteristics. By adopting such multiple structures, a squareness ratio of unity, coercivity of 2.5 kOe, and residual magnetization of 1.5 kG were obtained at a thick film of 2000 Å.
Sub-mA threshold operation of λ=1.5 μm strained InGaAs multiple quantum well lasers grown on (311)B InP substrates
Authors: Thijs P. J. A. , Binsma J. J. M. , Tiemeijer L. F. , Slootweg R. W. M. , van Roijen R. , van Dongen T.
Published: July 2002

1.5 μm wavelength InxGa1−xAs-InGaAsP (x=0.7, resulting in 1.2% compressive strain and x=0.53, resulting in zero strain) multiple quantum well (MQW) structures were grown on (311)B, (511)A, (511)B, and (001)InP substrates by low-pressure organometallic vapor phase epitaxy (LP-OMVPE). Intense and narrow linewidth room-temperature photoluminescence spectra indicate the device quality of the MQW structures. Strained MQW lasers grown on InP substrates misoriented towards (111)B show about 25% lower threshold current densities than the unstrained MQW lasers. The high quality of the strained MQW structures grown on (311)B InP substrates is demonstrated by the realization of 0.9 mA threshold current buried heterostructure lasers employing semi-insulating current blocking layers, and entirely grown by LP-OMVPE.
Multiple quantum well light modulators for the 1.06 μm range on InP substrates: InxGa1−xAsyP1−y/InP, InAsyP1−y/InP, and coherently strained InAsyP1−y/InxGa1−xP
Authors: Woodward T. K. , Chiu T-H. , Sizer II Theodore
Published: July 2002

We compare InP-based materials systems for multiple quantum well modulator application in the 1.06 μm wavelength range. Quantum well/barrier systems studied are the lattice-matched system InxGa1−xAsyP1−y/InP, the strained system InAsyP1−y/InP, and the strain-balanced system InAsyP1−y/InxGa1−xP. 50 period samples were grown on InP substrates by chemical beam epitaxy. We find the ternary systems to be better than the quaternary in terms of exciton peak sharpness. The InAsyP1−y/InxGa1−xP system was best overall, with our results suggesting that it is coherently strained to the InP substrate.
Growth of GaN(0001)1×1 on Al2O3(0001) by gas-source molecular beam epitaxy
Authors: Powell R. C. , Lee N.-E. , Greene J. E.
Published: July 2002

Gas-source molecular beam epitaxy (GSMBE), utilizing Ga and NH3, has been used to grow single-crystal GaN(0001)1×1 on Al2O3(0001) substrates at temperatures Ts between 700 and 850 °C. In situ reflection high-energy electron diffraction studies show a transition from three-dimensional to two-dimensional growth at Ts≳770 °C. For ≂1-μm-thick GaN layers, the best room-temperature carrier mobilities, 100–110 cm2 V−1 s−1, with carrier concentrations of 1–4×1018 cm−3, were obtained at Ts≥780 °C. These are the highest reported mobilities for MBE GaN. Band-to-band photoluminescence was observed in these films at room temperature. Cross-sectional transmission electron microscopy showed that the primary defects in the films were threading dislocations, with Burgers vectors a0/3〈21̄1̄0〉, and stacking faults.
Electron effective mass and band-gap dependence on alloy composition of AlyGaxIn1−y−xAs, lattice matched to InP
Authors: Kopf R. F. , Wei H. P. , Perley A. P. , Livescu G.
Published: July 2002

AlyGaxIn1−y−xAs structures were prepared by molecular beam epitaxy to determine both the electron effective mass and band-gap dependence of the InP lattice-matched alloy. Cyclotron resonance and photoluminescence measurements were used, respectively. The effective mass obtained after nonparabolicity correction is m*=0.0403+0.0817y. The band-gap relationships obtained at 300 and 5.5 K are Eg (eV)=0.752+1.453y, and Eg (eV)=0.792+1.530y, respectively.
Photoluminescence and formation mechanism of chemically etched silicon
Authors: Shih S. , Jung K. H. , Hsieh T. Y. , Sarathy J. , Campbell J. C. , Kwong D. L.
Published: July 2002

Room-temperature photoluminescence (PL) from Si chemically etched (CE) in HF-HNO3-based solution has been observed. Scanning electron microscopy reveals that the etched Si has a surface morphology similar to that of luminescent porous Si fabricated by conventional anodization. PL spectra show an order of magnitude smaller luminescent intensity and a shorter wavelength intensity peak for CE Si. A CE Si thickness limitation was observed. The formation of CE Si can be readily explained by a local anodization model.
Nanosecond laser-driven reflection high energy electron diffraction system providing digital imaging in real time
Authors: Kitriotis D. , Ozasa K. , Meguro T. , Shimoda S. , Nishi K. , Aoyagi Y.
Published: July 2002

High current densities of 1940 A/cm2 have been produced by a Cu/Be alloy photocathode, activated by 355 nm Q-switched laser pulses. The transient photocurrent, 7 ns full width, is utilized for the development of a pulsed reflection high energy electron diffraction (RHEED) system. Digital imaging and storage of single shot, two-dimensional diffraction patterns are achieved in real time with good spatial and intensity resolution.
Highly efficient quasi-phase-matched second-harmonic generation using a first-order periodically domain-inverted LiTaO3 waveguide
Authors: Mizuuchi Kiminori , Yamamoto Kazuhisa
Published: July 2002

We report blue-light generation using a first-order quasi-phase matched second-harmonic generation (QPMSHG) in LiTaO3 waveguide. A first-order periodically domain-inverted structure can be fabricated using a quick heat-treatment technique. We have examined the dependence of the depth of the fabricated domain-inverted region on its width, which critically affects the conversion efficiency of SHG, and designed an optimum domain-inverted structure for the QPMSHG device. As a result, 15 mW of blue light was generated for a conversion efficiency of 10.3%.
Domain inversion in LiTaO3 by electron beam
Authors: Hsu Wei-Yung , Gupta Mool C.
Published: July 2002

Domain inversion in Z-cut LiTaO3 by injecting electrons into negative C face was observed but no domain inversion was observed on injecting electrons on positive C face. At low electron-beam currents, small multidomains are observed. At a scan rate of 2 μm/s and beam current of 100 pA, a domain width of about 6 μm was obtained. We present results of domain width and domain size variation with electron-beam scan rate.
Microscopic thickness variation of macroscopically uniform quantum wells
Authors: Warwick Colin A. , Kopf Rose F.
Published: July 2002

Recently, GaAs/AlxGa1−xAs quantum wells were grown, which display remarkable uniformity, over macroscopic distances, in the splitting of their photoluminescence lines. The negligible variation of the peak splitting was interpreted as being consistent with a number of possible interface configurations, the simplest of which was abrupt, atomically smooth interfaces with discrete thickness changes of integer multiples of monolayers. However, here, further analysis of the splittings show them to be slightly below one monolayer, supporting a modification of the ‘‘atomically smooth island’’ picture to one of microroughness, defined as that having a length scale below the exciton diameter (≊15 nm), superimposed on islands larger than the exciton diameter. In addition, by extending these measurements to the ‘‘mesoscopic’’ regime by a high resolution cathodoluminescence technique, we directly show that these microrough islands can have sizes smaller than the spatial resolution of our scanning cathodoluminescence microscope, ≊60 nm.
Imaging performance of multilayer x-ray mirrors
Authors: Spiller Eberhard , Wilczynski Janusz , Stearns Daniel , Golub Leon , Nystrom George
Published: July 2002

We analyze soft x-ray images of the solar corona, obtained on the day of the solar eclipse in July 1991, and find that the deviations of our telescope mirror from the perfect surface are less than 1 Å for spatial periods between 1 μm and 1 mm. Our thin film deposition technique allows us to reduce errors over larger periods to the 1 Å level. Thus, we are able to produce large (diameter over 20 cm) x-ray mirrors with diffraction limited resolution below 0.01 arcsec.
Very low noise photodetector based on the single electron transistor
Authors: Cleland A. N. , Esteve D. , Urbina C. , Devoret M. H.
Published: July 2002

We demonstrate the use of the single electron transistor (SET) as an amplifier for a photodetector operated at 20 mK. The unparalleled low input noise of the SET permits the observation of very small numbers of charge carriers generated in a bulk p-type Si substrate. We present data showing the response of the detector when it is illuminated by extremely low levels of red light (λ=650 nm). From the ‘‘dark current’’ noise of 0.06 e/s, we estimate a dc noise-equivalent power NEP=2×10−21 W/√Hz for infrared light with λ=30 μm, and from this calculate a detectivity D*=8×1017 cm⋅√Hz/W.