bluuebunny/crossref_metadata_2025 huggingface dataset:
Vascular access for haemodialysis
Authors: Murphy G J , White S A , Nicholson M L
Published: July 2002

Background

The recent expansion of renal replacement therapy programmes has been associated with an increase in the number and complexity of patients requiring permanent vascular access. The introduction of strategies designed to maximize secondary access patency is, therefore, increasingly important as a means of prolonging patient survival on dialysis, reducing morbidity and reducing the escalating cost of such programmes.

Methods

A review of the current literature on the planning of vascular access, access surveillance methods and treatment of the most common complications was performed.

Results

Multidisciplinary vascular access planning, increased use of preoperative imaging and the preferential use of autogeneous vein are essential to obtain the best long-term results. While vascular access surveillance, in particular protocols involving direct measurement of access flow, enables the prospective detection and treatment of venous stenosis, the precise indications for treating venous stenosis remain unclear. Surgical revision remains the gold standard for the treatment of failing arteriovenous fistulas, but recent advances in interventional radiological techniques along with the suitability of arteriovenous fistulas for percutaneous intervention may offer an effective alternative. The effect of both these interventions on access patency requires comparison in a randomized trial.

Conclusion

The introduction of strategies to improve access patency rates will change vascular access surgical practice away from the construction of new fistulas towards an increase in outpatient percutaneous intervention and surgical revisional procedures. The role of surgical interventions requires clearer definition.
Hypertonic saline attenuates end-organ damage in an experimental model of acute pancreatitis
Authors: Shields C J , Winter D C , Sookhai S , Ryan L , Kirwan W O , Redmond H P
Published: July 2002

Background

Hypertonic saline (HTS) has been noted previously to reduce neutrophil activation. The aim of this study was to elucidate the effect of hypertonic resuscitation on the development of end-organ damage in an animal model of pancreatitis.

Methods

Pancreatitis was induced in Sprague–Dawley rats by intraperitoneal injection of 20 per cent l-arginine. Animals were randomized into four groups (each n = 8): controls; pancreatitis without intervention; pancreatitis plus intravenous resuscitation with normal saline (0·9 per cent sodium chloride 2 ml/kg) at 24 and 48 h; or HTS (7·5 per cent sodium chloride 2 ml/kg) at these time points. Pulmonary endothelial leakage was assessed by measurement of lung wet: dry ratios, bronchoalveolar lavage protein and myeloperoxidase activity.

Results

Animals that received HTS showed less pancreatic damage than those resuscitated with normal saline (1·0 versus 3·0; P = 0·04). Lung injury scores were also significantly diminished in the HTS group (1·0 versus 3·5; P = 0·03). Pulmonary neutrophil sequestration (myeloperoxidase activity 1·80 units/g) and increased endothelial permeability (bronchoalveolar lavage protein content 1287 μg/ml) were evident in animals resuscitated with normal saline compared with HTS (1·22 units/g and 277 μg/ml respectively; P < 0·02).

Conclusion

HTS resuscitation results in a significant attenuation of end-organ injury following a systemic inflammatory response to severe pancreatitis.
Dose–response relationship between plasma ACTH and serum cortisol in the insulin–hypoglycaemia test in 25 healthy subjects and 109 patients with pituitary disease
Authors: Tuchelt H. , Dekker K. , Bähr V. , Oelkers W.
Published: July 2002

OBJECTIVE: The insulin hypoglycaemia test (IHT) is believed to be the most reliable test for evaluating the entire hypothalamo–pituitary–adrenal (HPA) axis. The lower limit for the normal peak serum cortisol response has been reported to be between 500 and 580 nmol/l. Reference levels for a normal plasma ACTH response have not been reported recently.

DESIGN AND PATIENTS: We performed the IHT in 25 healthy subjects and in 109 patients with proven or suspected pituitary disorders with serial measurements of serum or plasma cortisol and of plasma ACTH, in order to establish reference levels and to study the dose–response relationship between ACTH and cortisol in this test. In most patients, other pituitary hormonal axes were evaluated in addition.

RESULTS:With the cortisol kit from Diagnostic Products Corporation (DPC), serum cortisol was about 13% lower than plasma (EDTA) levels with an excellent correlation between serum and plasma (r = 0.976; P < 0.001). In the normals, the lower limit of the cortisol response (mean cortisol peak level minus 2 SD.) was 570 nmol/l for plasma and 500 nmol/l (calculated) for serum, while the lower limit of the ACTH response was 17.6 pmol/l (80 ng/l). In normals, the cortisol response was independent of the magnitude of the ACTH response. Seventeen out of 30 patients with ACTH responses to levels < 8.8 pmol/l (< 40 ng/l) had subnormal cortisol responses. However, 38 of the patients with pituitary disease had normal cortisol responses in spite of subnormal ACTH responses (group 2), while 47 patients had completely normal IHT results (group 1). Patients in group 2 had more often additional pituitary hormone deficiencies than those of group 1. The dose–response relationship between ACTH and cortisol in the patients resembled a dose–response curve that had been set up previously in normal subjects who received incremental doses of subcutaneous human ACTH (1–39).

CONCLUSIONS:The normal increment of plasma ACTH in the IHT is greater than necessary for stimulating serum cortisol to levels > 500 nmol/l. Patients with a subnormal ACTH but normal cortisol response in the IHT have a decreased ACTH secretory reserve. It is unlikely that they are at increased risk of developing an adrenal crisis perioperatively or in other stressful situations unless pituitary function deteriorates. The ACTH‐cortisol relationship in the IHT performed in patients with pituirary disease shows no sharp dividing line between normality and disease, and whether a patient needs permanent glucocorticoid substution is a discretionary decision.
Solubility, sorption and desorption of native and added cadmium in relation to properties of soils in New Zealand
Authors: Gray C. W. , Mclaren R. G. , Roberts A. H. C. , Condron L. M.
Published: July 2002

Solution cadmium (Cd) concentrations and sorption and desorption of native and added Cd were studied in a range of New Zealand soils. The concentration of Cd in solution and the concentrations and patterns of native soil Cd desorbed and added Cd sorbed and desorbed varied greatly between the 29 soils studied. Correlation analysis revealed that pH was the most dominant soil variable affecting solution Cd concentration and sorption and desorption of native and added Cd in these soils. However, organic matter, cation exchange capacity (CEC) and total soil Cd were also found to be important. Multiple regression analysis showed that the log concentration of Cd in solution was strongly related to soil pH, organic matter and total Cd, which in combination explained 76% of the variation between soils. When data from the present study were combined into a single multiple regression with soil data from a previously published study, the equation generated could explain 81% of the variation in log Cd solution concentration. This reinforces the importance of pH, organic matter and total Cd in controlling solution Cd concentrations. Simple linear regression analysis could at best explain 53% of the total variation in Cd sorption or desorption for the soils studied. Multiple regression analysis showed that native Cd desorption was related to pH, organic matter and total Cd, which in combination explained 85% of the variation between soils. For sorption of Cd (from 2 μg Cd g–1 soil added), pH and organic matter in combination explained 75% of the variation between soils. However, for added Cd desorption (%), pH and CEC explained 77%. It is clear that the combined effects of a range of soil properties control the concentration of Cd in solution, and of sorption and desorption of Cd in soils. The fraction of potentially desorbable added Cd in soils could also be predicted from a soil’s Kd value. This could have value for assessing both the mobility of Cd in soil and its likely availability to plants.
Melanoma in Kauai, Hawaii, 1981–1990: the significance of in situ melanoma and the incidence trend
Authors: Chuang Tsu‐Yi , Charles Jonathan , Reizner George T. , Elpern David J. , Farmer Evan R.
Published: July 2002

Background

The incidence of melanoma has often been portrayed as reaching ‘epidemic’ proportions. The reality of such an epidemic is, however, not clearly established due to the methods of data collection and interpretation. The population‐based incidence data and incidence trend of melanoma from the Island of Kauai, Hawaii provide an illustration of this ‘epidemic’.

Methods

We used medical records housed at the dermatology clinic and pathology laboratory in Kauai to: identify residents of Kauai who had their first melanoma during the years 1981–1990; and to measure the 10‐year population‐based incidence of melanoma.

Results

In Caucasians: A total of 53 Caucasian residents (29 men and 24 women), were identified with an initial episode of melanoma (MM) during the 10‐year period. The average annual standardized incidence rate per 100,000 Kauai Caucasian residents was 36. Whereas the incidence of in‐situ MM increased during the 10‐year period, the incidence of invasive MM did not. The average patient age was 55 years. The trunk and the limbs were the most common anatomic sites of MM. In men, one third of MM occur on the back. In women, one third develop on the leg/thigh. Three patients (6%) had metastasis and eventually died of MM. Thirteen patients (25%) had other skin cancers such as basal cell carcinoma and squamous cell carcinoma at some time. In Filipinos, Japanese and Hawaiians: Three Filipinos (all women), two Japanese (one man and one woman) and one Hawaiian (man) had melanoma. The standardized incidence rates, to the U.S.A. Caucasian population, were 3.1, 0.8 and 2.1 per 100,000 residents, respectively.

Conclusions

The melanoma incidence in Kauai is one of the highest rates documented in the U.S.A. However, a decreased incidence of invasive melanoma during the 10‐year period was unexpected. The finding of nonmelanoma skin cancer in these patients supports a common etiology among these skin cancers.
Changes in Nitric Oxide Synthesis and Epileptic Activity in the Contralateral Hippocampus of Rats Following Intrahippocampal Kainate Injection
Authors: Yasuda Hiroaki , Fujii Masami , Fujisawa Hirosuke , Ito Haruhide , Suzuki Michiyasu
Published: July 2002

Summary:  Purpose: To investigate the effects of nitric oxide (NO) on seizure activity observed in brain areas that are remote from a primary epileptic focus.

Methods: Following an injection of kainate (concentration 1 mg/ml, volume 1 μl) in the rat hippocampus, we measured NO synthesis in the contralateral hippocampus and epileptic activity by electroencephalogram (EEG). The NO end products, nitrite and nitrate, were measured by in vivo microdialysis combined with an automated NO end‐product analyzer and then used as indices of NO synthesis. We also assessed the effect of a specific inhibitor of neuronal NO synthase (NOS) on both the epileptic activity and NO synthesis in the contralateral hippocampus. For this assessment, we administered 7‐nitroindazole (7‐NI) (50 mg/kg) intraperitoneally 30 min before the kainate injection.

Results: Epileptic discharges in the contralateral hippocampus were frequently observed 90 min after unilateral hippocampus kainate injection. The duration of these discharges gradually increased until 240 min after the kainate injection. The NO end‐product levels increased immediately after kainate injection and continued to increase gradually throughout the experiments, to a maximum of 213% of the base level. This elevation of NO end products was followed by epileptic discharges. Both the seizure activity and the elevation of contralateral hippocampus NO end‐product levels were markedly attenuated in the animals that received 7‐NI.

Conclusions: The results suggest that remote seizure activity caused by the transneuronal spread of kainate‐induced discharges may be related to NO derived from neuronal NOS.
Molecular beam epitaxial growth of Fe/Cr multilayers on (001)GaAs
Authors: Etienne P. , Creuzet G. , Friederich A. , Nguyen-Van-Dau F. , Fert A. , Massies J.
Published: July 2002

Molecular beam epitaxy has been used to grow single-crystal Fe/Cr magnetic multilayer structures on homoepitaxial (001)GaAs layers. The epitaxial relationships between Fe, Cr, and GaAs were determined by in situ reflection high-energy electron diffraction. The sharpness of the different interfaces of the Fe/Cr multilayers is illustrated by Auger electron spectroscopy sputter depth profiling, which shows that no significant intermixing occurs in the investigated growth temperature range −50 to +50 °C.
Enhancing the 10.6 μm absorptivity of copper and aluminum using excimer laser radiation
Authors: Kinsman G. , Duley W. W.
Published: July 2002

Increasing absorption of 10.6 μm laser radiation by Cu and Al surfaces pretreated with excimer laser pulses has been measured. The effective coupling is shown to approach 100% under certain irradiation conditions. This increased absorption arises from a combination of excimer roughening and oxidation.
Off-resonant third-order optical nonlinearities of metal-substituted phthalocyanines
Authors: Shirk James S. , Lindle J. R. , Bartoli F. J. , Hoffman C. A. , Kafafi Zakya H. , Snow Arthur W.
Published: July 2002

The third-order optical susceptibility of the Pt, Pb, and metal-free tetrakis(cumylphenoxy)phthalocyanines was measured by degenerate four-wave mixing at 1.064 μm, far from strong absorption bands. Metal substitution strongly enhances the off-resonant χ(3). The χ(3)xxxx for Pt-phthalocyanine (2×10−10 esu) and Pb phthalocyanine (2×10−11esu) is about 45 times and 5 times that of the metal-free form (4×10−12 esu), respectively.
Single-frequency tunable external-cavity semiconductor laser using an electro-optic birefringent modulator
Authors: Schremer A. , Tang C. L.
Published: July 2002

An external-cavity semiconductor laser employing a birefringent electro-optic modulator for wavelength tuning is described. Wide-band tuning over 70 Å in a single frequency to residual diode modes and narrow-band tuning over 0.42 Å to many longitudinal modes of the external cavity is demonstrated using different modulator configurations. Threshold current and quantum efficiency are nearly as good as that of the solitary laser diode.
Steric hindrance effects in atomic layer epitaxy of InAs
Authors: Jeong Weon G. , Menu E. P. , Dapkus P. D.
Published: July 2002

Atomic layer epitaxy of InAs is demonstrated. Saturation of the growth rate of one monolayer per cycle is achieved at a growth temperature of 340 °C. The growth rate is found to be a strong function of trimethylindium exposure times for the same total amount of reactant exposure per cycle. There is a threshold exposure time to achieve a growth rate of one monolayer per cycle. For shorter exposure time, the growth rate saturates to sub-one monolayer per cycle. The dependence of growth rate on exposure time is explained by steric hindrance effects of the initial adsorbate.
Microstructure of epitactically grown GaAs/ErAs/GaAs
Authors: Zhu Jane G. , Carter C. Barry , Palmstro/m Chris J. , Mounier Suzanne
Published: July 2002

A series of GaAs/ErAs/GaAs epilayer heterostructures has been grown on (100)GaAs substrates by molecular beam epitaxy and characterized by high-resolution transmission electron microscopy and Rutherford backscattering measurements. Good epitaxy of the ErAs on the GaAs is demonstrated. The top GaAs layer is usually epitactically aligned with ErAs/GaAs in most areas; however, growth of (111)GaAs on (100)ErAs has also been observed. Small grains are present in the top GaAs layer which are twinned on {111} with respect to epitactic grains. These give rise to GaAs {122}/ErAs(100) phase boundaries. The {122} oriented GaAs grains do not continue throughout the GaAs growth but are overgrown by the neighboring epitactic grains.
Laser properties of new organic nonlinear optical crystals chalcone derivatives
Authors: Kitaoka Yasuo , Sasaki Takatomo , Nakai Sadao , Yokotani Atsushi , Goto Yoshitaka , Nakayama Masaharu
Published: July 2002

A large single crystal (18×40×15 mm3) of a new nonlinear optical material ‘‘chalcone derivative’’ has been grown by an evaporation method. This crystal was relatively easy to grow to a large size and was chemically stable. The cutoff wavelength was 430 nm. The calculated phase matching angles for the second-harmonic generation (SHG) of Nd:YAG lasers agreed with the experimental data. Effective nonlinear optical coefficients deff of type I and type II for SHG have been measured to be 3.5 pm/V for type I and 5.7 pm/V for type II.
Monolithic hybrid mode-locked 1.3 μm semiconductor lasers
Authors: Morton P. A. , Bowers J. E. , Koszi L. A. , Soler M. , Lopata J. , Wilt D. P.
Published: July 2002

We describe the first results of hybrid mode locking combining both active and passive mode locking of a semiconductor laser. These functions are integrated into a monolithic device with a 1.3 μm GaInAsP gain region, an active waveguide, and a saturable absorber. The devices have low threshold currents, and exhibit hysteresis in their light/current characteristics. The long integrated waveguides allow mode locking at a repetition rate of 15 GHz without the need for an external cavity. Pulse widths as short as 1.4 ps have been demonstrated using the combined effects of active and passive mode locking.
Evidence for tip imaging in scanning tunneling microscopy
Authors: van Loenen E. J. , Dijkkamp D. , Hoeven A. J. , Lenssinck J. M. , Dieleman J.
Published: July 2002

It is demonstrated that scanning tunneling microscopy (STM) images often contain three-dimensional ghost images of the tunneling tip. These ghost images directly reflect the shape of the tip, as is proven by comparing them with tip indentations made in Si. Tip images appear as a set of identical protrusions, and have been observed regularly on Si surfaces annealed at 1200 K in ultrahigh vacuum. Imaging of rough surfaces may be fully dominated by this effect which can lead to incorrect image interpretations in STM and AFM.
Blue light-emitting organic electroluminescent devices
Authors: Adachi Chihaya , Tsutsui Tetsuo , Saito Shogo
Published: July 2002

Organic electroluminescent (EL) devices with multilayered thin-film structures which emitted bright blue light were constructed. Two empirical guides for the selection of blue-emitting materials were established. The keys to obtain the EL cells with high EL efficiency were excellent film-forming capability of an emitter layer and the appropriate combinations of emitter and carrier transport materials for avoiding the formation of exciplexes. In one of our organic electroluminescent devices, blue emission with a luminance of 700 cd/m2 was achieved at a current density of 100 mA/cm2 and a dc drive voltage of 10 V.
Photostimulated evaporation of SiO2 films by synchrotron radiation
Authors: Akazawa H. , Utsumi Y. , Takahashi J. , Urisu T.
Published: July 2002

Irradiation by synchrotron radiation on SiO2 films induces continuous removal of this material at elevated temperatures. The photostimulated evaporation rate for a thermally grown SiO2 film increases steeply with temperature giving an activation energy of 0.7 eV. The experimental results indicate that photon-induced bond breaking assists decomposition and thermal desorption of the film. Applications to microfabrication of a line-and-space pattern and low-temperature cleaning of Si(100) surface are demonstrated.
Magnetic field dependence of the critical current anisotropy in normal metal-YBa2Cu3O7−δ thin-film bilayers
Authors: Ono R. H. , Goodrich L. F. , Beall J. A. , Johansson M. E. , Reintsema C. D.
Published: July 2002

We have measured the transport critical current density (Jc) in epitaxial quality films of YBa2Cu3O7−δ some of which were covered by thin (10 nm) Ag films. The films, both with and without Ag, had Jc values greater than 106 A/cm2 in liquid nitrogen. The effect of the Ag was to greatly reduce the dependence of Jc on external magnetic fields in the case where the field was oriented in the plane of the film, that is, perpendicular to the c axis. It is unlikely that the effect is simply due to altered surface pinning, although qualitative agreement with critical state models is observed.
Asymmetric line broadening in intracavity loss modulated quantum well distributed feedback lasers
Authors: O’Gorman J. , Levi A. F. J. , Tanbun-Ek T. , Logan R. A.
Published: July 2002

We report for the first time high-speed (Gbit s−1), single mode, digital (on-off) modulation of intracavity loss modulated 1.55 μm InGaAs/InP multiple quantum well distributed feedback lasers. The lasing spectrum, observed to be asymmetrically broadened under high-speed modulation, is shown to result from large carrier density variations which accompany this switching scheme. We also show, for the first time, digitally current-modulated lasers have broader linewidths than devices which use intracavity loss modulation.
Semiconductor hot-electron alternating current cold cathode
Authors: Dalacu N. , Kitai A. H.
Published: July 2002

A ZnS semiconductor thin film grown on a dielectric layer is demonstrated as a cold cathode. Hot electrons are generated in ZnS and are emitted through a thin gold layer. Electron current density is controlled by means of alternating current (ac) coupling between the rear electrode and the ZnS layer. This yields a pulsating sheet source of electrons with controlled and spatially uniform current density. A current density of ∼1 μA/cm2 with efficiency of ∼10−3 is obtained. The ability to modulate and address this device makes it attractive for flat panel displays and other applications.
Monolithic, photoconductive impulse generator using a GaAs wafer
Authors: Kim A. , Zeto R. , Youmans R. , Conrad J. , Kondek C. , Weiner M. , Brisker H. , Agee J. , Jasper L. , Lalevic B.
Published: July 2002

A new technique for generating multikilovolt, nanosecond pulses was demonstrated. The technique relies on the use of a semi-insulating GaAs substrate, which performs the dual functions of energy storage and switching. The energy storage was realized by fabricating disk-shaped electrodes on a 7.5-cm-diameter GaAs wafer, thereby forming a radial transmission line. A mode-locked Nd:YAG laser was used to activate the switch, which is vertically fabricated in the central region of the substrate. This device generated and delivered about a 2 MW pulse with a rise time of less than 500 ps to a 50 Ω load.
Hydrogen loss from laser-annealed amorphous hydrogenated carbon films studied by secondary-ion mass spectrometry
Authors: Armeyev V. Yu. , Loubnin E. N. , Ralchenko V. G. , Strelnitsky V. E.
Published: July 2002

Secondary-ion mass spectrometry was used to measure the amount of hydrogen retained in dense (ρ =2.4 g/cm3) amorphous hydrogenated carbon films subjected to Ar+ laser annealing in intensity range I=(1–6)×105 W/cm2. Hydrogen effusion, accelerating with laser power, is accompanied by a decrease of the film density and strengthening of the carbon skeleton that is interpreted as a transformation of the film from amorphous to a graphite-like state.
Thermally stable low resistance ohmic contacts to n-type gallium arsenide: Magnetron cathodic sputter-deposited NiInW contacts
Authors: Hugon M. C. , Agius B. , Varniere F. , Dubon-Chevallier C. , Bresse J. F. , Froment M.
Published: July 2002

W/Ni0.9-In0.1 refractory ohmic contacts presenting low specific resistivity have been formed on n-type GaAs by magnetron cathodic sputtering and subsequently annealed by rapid thermal processing at 850 °C for 10 s. The increase of Ni-In film thickness (with a W layer of 80 nm) stimulated the Schottky-to-ohmic behavior conversion with a minimum specific resistivity value of 10−5 Ω cm2. By increasing the W layer thickness to 160 nm, the specific resistivity was dropped to a minimum value of 10−6 Ω cm2. Such a low value was attributed to the presence of InGaAs phase. The W/Ni0.9-In0.1 contact showed excellent thermal stability at 400 °C and during 100 h.
Spark channel plasma electrode
Authors: Labun A. H. , Seguin H. J. J. , Capjack C. E.
Published: July 2002

A plasma electrode potentially suitable for dc discharge pumped lasers has been developed based on the repetitive creation of a spark channel. The high-density plasma within the arc serves as a source of charge carriers for the dc discharge, thereby largely eliminating the cathode fall. Reduction in the cathode fall potential improves with increasing spark repetition frequency until about 9 kHz, after which a constant, near-zero value is achieved.
Observation of plasmon-enhanced optical extinction in silver-coated silver bromide nanoparticles
Authors: Nedeljkovic Jovan , Patel Ramesh C.
Published: July 2002

Silver bromide nanoparticles exposed briefly to intense UV light in the presence of ethylenediaminetetraacetic acid (EDTA) have optical extinction spectra similar to those computed for distributions of silver-coated silver bromide nanoparticles. With longer exposure times the plasmon resonance maximum is shifted to shorter wavelengths, a result consistent with theory so long as the coat thickness increases with exposure to light. The resonance maximum of the distribution of coated particles can be controllably shifted from 400 up to 700 nm.
Preparation of superconducting thin films of Bi(Pb)-Sr-Ca-Cu-O by the thermal decomposition method
Authors: Sumiyoshi F. , Uehigashi K. , Yamaguchi H. , Hakuraku Y. , Shimura H. , Miyahara S.
Published: July 2002

The thin Bi(Pb)-Sr-Ca-Cu-O film composed of the high Tc phase has been successfully made by the thermal decomposition method using an organic acid salt, which is spread on the MgO(100) substrate by the spin-coat method. A preannealing process before a final annealing is added to the usual film preparation in order to prevent the metallic compounds in the salt from diverging to the atmosphere. The film obtained here has a flatter and smoother surface, and a higher zero-resistivity temperature Tc0 (=107.0 K) than those of the films without the preannealing process. However, the homogeneity of the film seems to be slightly insufficient as the onset critical temperature of the real part of a complex susceptibility is about 3 K larger than Tc0.
Picosecond dynamics in gain-switched uncoupled and coupled quantum well lasers
Authors: Sogawa T. , Arakawa Y.
Published: July 2002

We experimentally demonstrate the importance of two-dimensional carrier confinement for picosecond dynamics in gain-switched quantum well lasers, measuring time-resolved spectra of gain-switched quantum well (QW) lasers with coupled QWs and uncoupled QWs. The result indicates that an extremely short pulse (<2 ps) is generated in the uncoupled QW lasers. On the other hand, the pulse duration is about 10 ps in the coupled QW lasers in which the two-dimensional confinement effect is significantly reduced owing to the miniband formation. These results demonstrate the importance of the two-dimensional confinement of carriers for the short pulse generation in the semiconductor lasers. The measured dynamic spectral shift of the gain-switched QW lasers also confirm the significant role of the two-dimensional carrier confinement.
B doping using B2H6 in gas source Si molecular beam epitaxy
Authors: Hirayama Hiroyuki , Hiroi Masayuki , Koyama Kazuhisa
Published: July 2002

A new gas mixing system was devised for the control of a gaseous dopant during gas source Si molecular beam epitaxy. The performance of this gas mixing system was demonstrated using B2H6 gas dopant for B doping. B doping level control over five decades was successfully achieved. The B-doping concentration was found to be proportional to the B2H6/Si2H6 flow rate ratio. This relationship holds in both the supply-controlled and the reaction-controlled growth regions. This result indicates that B2H6 is incorporated into epitaxial layers by a similar dissociative adsorption mechanism on Si2H6.
Energy states of finite-barrier quantum wires in the presence of an external electric field
Authors: Juang C. , Chang C. Y.
Published: July 2002

Energy level shift in finite-barrier quantum wires systems is found to be enhanced in comparison to finite-barrier single quantum well systems. The ground-state solutions of the two-dimensional Schrödinger equation are obtained using the inverse power method combined with the successive over relaxation method. In addition, the two-dimensional changes in the wave function due to an external electric field in cylindrical quantum wires are presented.
Wave packets in a semiconductor superlattice
Authors: Biermann Mark L. , Stroud C. R.
Published: July 2002

A theoretical study of hole wave packets in a GaAs, Al0.3Ga0.7As superlattice is presented. Formation of the wave packet by short laser pulse excitation and the time-dependent nature of the wave packet are discussed, with particular attention given to the quasi-periodic nature of the time dependence. Phenomena analogous to those displayed in atomic and molecular wave packet systems are predicted. The wave packet formalism provides a powerful tool for studying coherent hole dynamics, including quantum beat phenomena, and could be useful in determining heavy and light hole relaxation rates.
Time-resolved reflectivity studies of the GaAs(100)/oxide and GaAs(100)/ZnSe interface
Authors: Cheville R. A. , Haynes W. B. , Halas N. J.
Published: July 2002

A series of subpicosecond time-resolved reflectivity measurements on n-type GaAs(100) interfaces at photoexcitation densities of 1018 cm−3 is reported. It is observed that the temporal dependence of the reflectivity signal within the first several picoseconds following photoexcitation is highly dependent upon interface preparation. The surface of the GaAs was prepared in several ways: by the growth of a thermal oxide overlayer, a photochemically passivated oxide overlayer, and an epitaxial ZnSe overlayer.
Cu passivation: A method of inhibiting copper-polyamic acid interactions
Authors: Shih D-Y. , Kim J. , Walker G. F. , Chang C-A. , Paraszczak J. , Nunes S. , Yang C.
Published: July 2002

The use of passivation metals to protect Cu from interacting with polyamic acid precursor has been investigated by means of cross-sectional transmission electron microscopy, Rutherford backscattering spectroscopy, and resistivity measurements. Palladium or platinum, each 100 nm in thickness, was electron-beam evaporated onto Cu surface. Although not a good diffusion barrier against Cu outdiffusion, these metals can still effectively inhibit the Cu-polyamic acid interactions and, consequently, prevent the formation of Cu oxide precipitates in the polymer film. The trade-off is that, since Pd and Pt both diffuse into Cu and form solid solution alloys, the resistivity of Cu is raised significantly due to the enhanced electron-impurity scattering. In contrast, Cr serves both as a passivation metal and a good diffusion barrier without raising Cu resistivity. This is probably due to the lack of mutual solubility between Cr and Cu.
Interface reaction model for process voiding in aluminum conductor lines
Authors: Tseng W. T. , Stark J. P.
Published: July 2002

A model is proposed to give a new account for process induced voiding in aluminum conductor lines in integrated circuits. The chemical reaction along the glass/aluminum interface is considered and yields a volume change. Simple calculations of changes in molecular volumes, using Wigner–Seitz radii and ionic radii for the silicon oxide reduction by aluminum all indicate vacancy creation in aluminum as the reduction proceeds. Aggregation of the vacancies will produce the voids noted from room-temperature anneals or storage.
Silicon epitaxial growth on GaAs using a rapid thermal chemical vapor deposition process
Authors: Nissim Y. I. , Sapriel J. , Gao Y. , d’Anterroches C. , Regolini J. L. , Bensahel D.
Published: July 2002

Epitaxial silicon layers are grown on GaAs substrates in a light-assisted cold wall horizontal reactor. High quality silicon is obtained at the surface when the growth is conducted in a two-step sequence. The first step is a silane exposure at 700 °C where epitaxial silicon starts to grow and where tensile stress relaxes to form a highly defective layer. The second step is an epitaxial growth of silicon at 800 °C. The crystalline perfection and stress in both the layer and the substrate are characterized by Raman scattering. Cross-section transmission electron microscopy analysis shows mainly the formation of stacking faults at the interface. Their number reduces as the Si film thickness increases. The rapid thermal chemical vapor deposition does not require arsenic overpressure to protect the GaAs substrate from thermal degradation during epitaxial growth.
Enhanced flux pinning by combined atomic substitution and phase decomposition in cuprate superconductors
Authors: Tallon J. L. , Pooke D. M. , Buckley R. G. , Presland M. R. , Flower N. E. , Gibson S. , Gilberd P. W.
Published: July 2002

The use of combined atomic substitution and phase decomposition is shown to achieve substantial enhancement of flux pinning in Y–Ba-Cu–O ceramics. The substituent is chosen to provide a high density of nucleation sites for decomposition and at the same time enhancing Tc in the resulting composite superconductor. Bulk YBa2Cu4O8 (124) with 2.5% La substituted for Ba is decomposed by a short anneal beyond the stability boundary for YBa2Cu3O7 (123) at low oxygen pressure. The product, principally La-substituted 123 with stacking faults and precipitates of CuO in the grain boundaries, exhibits a 17-fold enhancement in intragrain Jc at 77 K and 0.75 Tesla over unprocessed 123, rising to 50-fold at 85 K. Magnetization Jc exceeds 104 A/cm2 at 0.75 Tesla for temperatures up to 87 K, the highest so far observed for a superconductor.
Identification of the misfit dislocations at an FeAl/AlAs/GaAs interface using moiré fringe contrast in a transmission electron microscope
Authors: Angelo J. E. , Kuznia J. N. , Wowchak A. M. , Cohen P. I. , Gerberich W. W.
Published: July 2002

Moiré fringe contrast in plan-view transmission electron microscopy (TEM) is adapted to measure the Burgers vector of misfit dislocations at the interface between FeAl and AlAs. This technique had originally been used to determine the Burgers vector of dislocations in bulk materials. The aluminide was grown by molecular beam epitaxy on AlAs which was pseudomorphic on GaAs(001). The observed misfit dislocations are determined to have [100] and [010] Burgers vectors, as measured in the FeAl, with [010] and [100] line directions, respectively. These are pure edge dislocations which cannot glide on the {110} or {112} slip systems of FeAl. This requires that the misfit dislocations either form at the edges of islands, during three dimensional (3D) growth or by climb from the free surface during two-dimensional (2D) growth. The TEM results along with in situ reflection high-energy electron diffraction (RHEED) results show that the growth is indeed 2D which suggests the misfit dislocations must form by dislocation half-loops climbing from the free FeAl surface.
Low-voltage interferometric modulator in zinc-diffused strontium barium niobate (SBN:60)
Authors: Eknoyan O. , Swenson V. P. , Quinn J. D. , Neurgaonkar R. R.
Published: July 2002

Optical waveguides have been produced in Z-cut Sr0.6Ba0.4Nb2O6 (SBN:6O) by zinc diffusion from vapor phase at 1000 °C for 30 min. Values of 7.3 μm for the diffusion depth and a surface concentration of 4.2×1020 cm −3 for Zn were obtained from an electron microprobe analysis. Electro-optic modulation at 0.83 μm wavelength has been demonstrated on a Mach–Zehnder interferometer produced by this diffusion technique. An extinction ratio of 78% and a voltage-length (VL) product of 0.48 V cm for a TM polarized input light were obtained. Prism coupler measurements on planar waveguides diffused at 800 °C for 6 h have shown an effective index increase of 0.025 for the fundamental mode in both TE and TM polarization.
Photoinduced optical absorption in BaTiO3:Fe
Authors: Temple Doyle A. , Warde Cardinal
Published: July 2002

Measurements of the steady state photoinduced absorption Δα have been performed on single crystalline samples of pure and iron-doped BaTiO3. The results show that Δα has a sublinear intensity dependence, similar to that observed in photorefractive grating decay measurements.
Lateral tunneling through voltage-controlled barriers
Authors: Manion S. J. , Bell L. D. , Kaiser W. J. , Maker P. D. , Muller R. E.
Published: July 2002

We report on a detailed experimental investigation of lateral tunneling between electrodes of a two-dimensional electron gas separated by the voltage-controlled barrier of a nanometer Schottky gate. The experimental data are modeled using the WKB method to calculate the tunneling probability of electrons through a barrier whose shape is determined from a solution of the two-dimensional Poisson equation. This model is in excellent agreement with the experimental data over a two order of magnitude range of current.
Generation of pulse trains in the normal dispersion regime of a dielectric medium with a relaxing nonlinearity
Authors: Soto-Crespo Jose M. , Wright Ewan M.
Published: July 2002

We show that modulation-type instability can occur in the normal dispersion regime of a dielectric medium for the case of a relaxing self-focusing nonlinearity. This instability leads to the generation of pulse trains with almost no pedestal when periodic boundary conditions are applied.
Observations of hollow cathode light emission from a transient hollow cathode discharge
Authors: Wyndham E. , Chuaqui H. , Favre M. , Choi P.
Published: July 2002

Experimental observations are presented on the light emission from the hollow cathode region of a pulsed hollow cathode discharge. A 2 mJ, 30 ns, 1.06 μm laser pulse incident on the back of the cathode is used to trigger the discharge. The temporal evolution of the light emission from this region is recorded in 50 nm spectral bands. Comparisons are made with the laser applied before and after the application of voltage across the discharge chamber. Clear experimental evidence is found of the importance of a transient volume hollow cathode process prior to gas breakdown in the main discharge region.
Deposition and characterization of fullerene films
Authors: Hebard A. F. , Haddon R. C. , Fleming R. M. , Kortan A. R.
Published: July 2002

Thermal sublimation of pure C60 and C70 has been used for depositing well-characterized fullerene films on a variety of substrates. Film purity is determined by infrared absorption spectra and the extent of crystallinity of the face-centered cubic structure by x rays. Thickness-dependent optical and electrical measurements reveal uniform films over the thickness range 200–1000 Å. We obtain optical absorption coefficients having values between those of Si and Ge and a relative permittivity having a value close to that of amorphous SiO2.
Etching of aluminum film by hydrogen atoms
Authors: Hara M. , Domen K. , Onishi T. , Nozoye H.
Published: July 2002

The reaction between hydrogen atoms and an ultrathin aluminum film (2 monolayer) on a Mo(111) substrate was studied by thermal desorption (TD) and Auger electron spectroscopy (AES). Through TD experiments for the hydrogen precovered aluminum films, desorption of aluminum hydride was observed at 370 K. It was confirmed that 1/3 monolayer of aluminum was desorbed as aluminum hydrides after a TD experiment for the aluminum film on which hydrogen was preadsorbed to a full monolayer coverage. The aluminum film was continuously etched at 410 K by a steady flow of hydrogen atoms. These results indicate the potential capability of hydrogen atoms as a selective etchant for aluminum.
Quantum corrections to ultrafast thermalization in binary/ternary double heterostructures
Authors: Joshi R. P.
Published: July 2002

A Monte Carlo study of transient electronic thermalization in double heterostructures following femtosecond laser excitation is presented. Quantum corrections arising from the short time scales of interest have been explicitly incorporated into the simulations. These include the effects of collisional broadening to account for the finite lifetime of the interactions, and of finite collision durations that retard the thermalization process and impart a nonlocal time dependence to the scattering rates. Details of the phonon modes supported by the binary/ternary quantum-well structures have also been carefully included. Results at low-carrier densities demonstrate that adequate inclusion of the finite collision durations is necessary for an accurate transient analysis.
Simple integral screenprinting process for selective emitter polycrystalline silicon solar cells
Authors: Szlufcik J. , Elgamel H. E. , Ghannam M. , Nijs J. , Mertens R.
Published: July 2002

This letter describes a new simple fabrication process, developed recently for ‘‘blue response’’ improvement in low-cost polycrystalline silicon solar cells. A selective emitter is created by heavily doping the emitter, followed by a wet etching-back of the cell area between the fingers. An improvement up to 17 mV in Voc, 1.5 mA/cm2 in Jsc, and 1% (absolute value) in η is obtained. Effective phosphorus gettering, self-alignment, and application in a low-cost full screenprinting technology are the main advantages of the proposed process.
Rapid solidification of a plasma-sprayed ceramic coating melted by a CO2 laser
Authors: Shieh June-Hua , Wu Shinn-Tyan
Published: July 2002

Successful modeling of the solidification process during laser melting has been achieved by numerical solution of a one-dimensional heat transfer equation. Good agreement with experiments performed on ZrO2-8 wt % Y2O3 coating is demonstrated. Radiation heat loss from the surface to the environment is found to be important to the microstructure of the solidified coating. The calculation provides a plausible explanation of the experimental observation that a remelted layer usually consists of an equiaxed layer on top of a columnar zone.
Nonlinear resolution improvement and second-harmonic generation of a pressurized superfluid 4He acoustic microscope
Authors: Karaki Koichi , Saito Takehiko , Matsumoto Koichi , Okuda Yuichi
Published: July 2002

We observed the input power dependence of the second-harmonic generation of a 370-MHz focused acoustic beam in pressurized superfluid 4He at about 300 mK. We also measured the resolving power of a reflection mode acoustic microscope using pressurized superfluid 4He as a coupling liquid under 11 atm (anomalous dispersion region) and 21 atm (normal dispersion region). At the nonlinear power region of each pressure, the resolution was improved beyond the diffraction limit. Results of these two experiments confirmed that the higher harmonics are generated and they are converted to the fundamental as the wave propagates through the focal point. The higher harmonics play an important role in recently observed exotic nonlinear phenomenon in pressurized superfluid 4He.
Enhanced nonlinear recording using a thermoplastic plate
Authors: Paek Eung Gi , Jung E. C. , Silberberg Y. , Ravi T. S.
Published: July 2002

Enhanced diffraction efficiency of arbitrary higher order by using a thermoplastic plate is described. Such an enhanced diffraction efficiency is obtained by adjusting the angle between the two recording beams so that the diffraction angle of the desired order is tuned to the angle at which a thermoplastic plate gives the maximum frequency response and optimizing the exposure time. Using this method, any order can be selectively enhanced with the diffraction efficiency comparable to that of maximum attainable first order. Also, competition between different orders are sensitively affected as the tuning angle varies.
The influence of oxygen on intrinsic stress and growth of iron and nickel films
Authors: Winau D. , Koch R. , Rieder K. H.
Published: July 2002

Growth and microstructure of UHV-deposited thin films of Fe and Ni−two metals used in magnetic storage technology−have been investigated with intrinsic stress measurement. Fe exhibits tensile film forces typical of columnar grain growth. At oxygen partial pressure higher than 5×10−9 hPa the films incorporate oxygen leading to an increasing compressive stress contribution; at 2×10−7 hPa a magnetic oxide film is deposited. Ni exhibits film forces characteristic of pronounced island growth which gradually transform to the ones indicating columnar grain growth at oxygen pressures above 1×10−9 hPa; at 1×10−6 hPa a transparent oxide film is deposited.
High dielectric permittivity in sol-gel derived SiO2-As2O3 glasses
Authors: Datta A. , Giri Anit K. , Chakravorty D.
Published: July 2002

Glasses in the system x As2O3(1−x) SiO2 with 0.05<x<0.16 have been prepared by sol-gel route. They exhibit anomalously large dielectric permittivity in the temperature range 275 to 325 K. The permittivity values are found to be in the range 400–100 000 depending on the glass composition and the frequency of measurement. This effect is believed to arise due to a fairly large value of ratio [As5+]/[As3+] in these glasses and its drastic change as a function of temperature.
Plasma immersion ion implantation of SiF4 and BF3 for sub-100 nm P+/N junction fabrication
Authors: Qian X. Y. , Cheung N. W. , Lieberman M. A. , Felch S. B. , Brennan R. , Current M. I.
Published: July 2002

Sub-100 nm P+/N junctions were fabricated using plasma immersion ion implantation (PIII). With this technique, the silicon wafer was immersed in SiF4/BF3 plasma and biased with a negative voltage. The positively charged ions in the plasma sheath were accelerated by the electric field and implanted into the wafer. The dose rate of PIII can be much higher than that of conventional ion implanter. Whereas the dopant activation behavior is similar. For extremely shallow P+/N junction formation, sample preamorphization and short cycle rapid thermal annealing (RTA) are required. With SiF4 PIII preamorphization followed by BF3 PIII doping and RTA at 1060 °C for 1 s, 80 nm P+/N junctions were successfully obtained. Test diodes fabricated with this technique show good characteristics.
In-process ellipsometric monitoring of diamond film growth by microwave plasma enhanced chemical vapor deposition
Authors: Hayashi Yasuaki , Drawl William , Collins R. W. , Messier Russell
Published: July 2002

In-process monitoring of diamond film growth was performed with near-infrared ellipsometry (1550 nm). The trajectories in the ellipsometric parameters (ψ,Δ) differ according to the method of substrate pretreatment and the CO/H2 gas ratio used in the microwave plasma-enhanced chemical vapor deposition process. The nucleation density determined from ellipsometry shows qualitative agreement with that from scanning electron microscopy performed after deposition. The rate at which nuclei develop is also monitored, and the observed induction time is shorter for conditions leading to a higher nucleation density.
Origin of dual epitaxy in the growth of CdTe on (2̄1̄1̄) GaAs
Authors: Nakamura Y. , Otsuka N. , Lange M. D. , Sporken R. , Faurie J. P.
Published: July 2002

The atomic structure of the (1̄3̄3̄)CdTe/(2̄1̄1̄)GaAs interface is analyzed by high resolution transmission electron microscopy in order to elucidate the origin of the dual epitaxy in the growth of CdTe on (2̄1̄1̄)GaAs by molecular beam epitaxy. The analysis shows that the lattice mismatch at the interface is accommodated by a novel mechanism, which occurs with the combination of the 14.6% lattice mismatch between CdTe and GaAs and one wurtzite type bond sequence on the (2̄1̄1̄) substrate surface.