bluuebunny/crossref_metadata_2025 huggingface dataset:
A prospective randomized trial comparing four biofeedback techniques for patients with faecal incontinence
Authors: Heymen S. , Pikarsky A. J. , Weiss E. G. , Vickers D. , Nogueras J. J. , Wexner S. D.
Published: July 2002

Objective

The aim of this study was to compare four methods of biofeedback therapy for patients with faecal incontinence (FI).

Patients and methods

All patients with FI who were ineligible for surgical management were prospectively randomized using a computer generated randomization method into one of four protocols: 1, out‐patient intra‐anal electromyographic biofeedback training (EMG); 2, EMG plus intrarectal balloon training (BT); 3, EMG plus a home trainer (HT); and 4, EMG, BT and HT. All patients received weekly, 1 h, out‐patient biofeedback training. Success for patients with FI was measured by a reduction in incontinent episodes (days/week). In all instances, patients maintained a daily log in which documentation was recorded regarding each bowel evacuation.

Results

Forty patients were randomized into one of the four groups. Six patients withdrew after one session and were not included in the analysis. Therefore, 34 patients (23 female and 11 male) with a mean incontinence score of 12 (range 7–14) were randomized to one of the four groups (n=8, 8, 8, and 10, respectively). There was a statistically significant reduction in incontinent episodes for all groups. However, there were no significant differences in treatment outcome found in comparisons among the four groups.

Conclusion

Biofeedback therapy significantly improves FI. Moreover, EMG training was as effective alone as was the addition of HT, BT or both for the treatment of FI.
An appraisal of the disc–macula distance to disc diameter ratio in the assessment of optic disc size
Authors: Barr D.B. , Weir C.R. , Purdie A.T.
Published: July 2002

The disc–macula distance to disc diameter ratio (DM:DD ratio) has been advocated as a method of supporting the diagnosis of optic nerve hypoplasia. A DM:DD ratio of 3.00 has been claimed to be a satisfactory threshold value for this purpose. This study has critically evaluated the above claim and found a value of 3.00 to be too low. The threshold DM:DD ratio values for the diagnosis of unequivocal ONH for an adult population, 5 and 2 years of age were found to be respectively 4.20, 3.93 and 3.70, the values for the diagnosis of mild ONH being 3.68, 3.44 and 3.23. Lower computed values reduce the predictive power. The method of computation of the DM:DD ratio was modified to abolish potential error due to disc rotation and foveal displacement. In an adult population, there was no correlation between the DM:DD ratio and amblyopia or disc ovalness. There was a trend of increasing DM:DD ratio towards myopia and decreasing DM:DD ratio towards hypermetropia; the DM:DD ratio may therefore be falsely high in high myopia. DM:DD ratio values below threshold should therefore be interpreted with care until formal optic disc biometry can be performed.
Selection of a Polyurethane Membrane for the Manufacture of Ventricles for a Totally Implantable Artificial Heart: Blood Compatibility and Biocompatibility Studies
Authors: Bélanger Marie‐Claire , Marois Yves , Roy Raynald , Mehri Yahye , Wagner Eric , Zhang Ze , King Martin W. , Yang Mingjing , Hahn Charles , Guidoin Robert
Published: July 2002

Abstract: Membranes made from 4 commercial poly(carbonate urethanes): Carbothane (CB), Chronoflex (CF), Corethane 80A (CT80), and Corethane 55D (CT55), and from 2 poly(ether urethanes): Tecoflex (TF) and Tecothane (TT) were prepared by solution casting and sterilized by either ethylene oxide (EO) or gamma radiation. Their biocompatibility was evaluated in vitro in terms of proliferation, cell viability, and adhesion characteristics of human umbilical veins (HUVEC), monocytes (THP‐1), and skin fibroblasts, and by measuring complement activation through the generation of the C3a complex. Their hemocompatibility was determined by measuring the level of radiolabeled platelet, neutrophil, and fibrin adhesion in an ex vivo arteriovenous circuit study in piglets as well as via an in vitro hemolysis test. The results of this study showed no endothelial cell proliferation on any of the materials. The cell viability study revealed that the CB, CF, and TF membranes sterilized by EO maintained the highest percentage of monocyte viability after 72 h of incubation (>70%) while none of the gamma‐sterilized membranes displayed any cell viability. The fibroblast adhesion and C3a generation assays revealed that none of the materials supported any cell adhesion or activated complement, regardless of the sterilization method. The hemolysis test also confirmed that the 4 poly(carbonate urethanes) were hemolytic while none of the poly(ether urethanes) were. Finally, the ex vivo study revealed that significantly more platelets adhered to the CB and CT55 membranes while the levels of neutrophil and fibrin deposition were observed to be similar for all 6 materials. In conclusion, the study identified the CF and TF membranes as having superior biocompatibility and hemocompatibility compared to the other polyurethanes.
Effect of ischemia and cooling on the response to high frequency stimulation in rat tail nerves
Authors: Andersen Henning , Nielsen Jørgen F. , Sørensen Bodil , Nielsen Viggo K.
Published: July 2002

Abstract  In normal rat tail nerves the effect of temperature and ischemia on the response to long‐term high frequency stimulation (HFS) (143 Hz) was studied. The effect of temperature was studied in two consecutive tests at 14° C and 35° C. Prior to the HFS the peak‐to‐peak amplitude (PP‐amp) of the compound nerve action potential was 139 ± 20 μV (mean ± SD) and 127 ± 37 μV at 35° C and 14° C, respectively (NS). After 15 min of HFS the PP‐amp was reduced to 45.3 ± 20.5% of baseline level at 14° C as compared with 80.8 ± 10.2% at 35° C (p < 0.001). Applying ischemia to the rat tail, an additional fall of the PP‐amp was seen after 15–20 min of HFS at both low (20 Hz) and high (143 Hz) stimulation frequencies. In conclusion, ischemia and cooling result in an impaired ability to transmit high frequency impulses.
JUVENILE, AUTOSOMAL DOMINANT, DISTAL SPINAL MUSCULAR ATROPHY AND NEUROSENSORIAL DEAFNESS NOT LINKED TO CHROMOSOME 12q24
Authors: De Angelis M.V. , Stuppia L. , Passamonti L. , Palka G. , Gambi D. , Uncini A.
Published: July 2002

Distal spinal muscular atrophy, also classified as a spinal form of Charcot‐Marie‐Tooth‐disease, or distal hereditary motor neuropathy, is genetically heterogeneous and both autosomal dominant and autosomal recessive inheritance have been described. Recently, in an autosomal‐dominant Belgian family with juvenile onset in distal leg muscles, a significant linkage was obtained with markers located at chromosome 12q24 (Timmermann et al. 1996).

We describe a three‐generation Italian kindred with distal spinal muscular atrophy showing autosomal dominant inheritance, onset at 8–10 years with leg weakness and atrophy, later involvement of distal arm muscles, and eventually proximal muscles. The older patients also had neurosensorial deafness. To confirm the previous genetic findings, we used four microsatellite markers located at chromosome 12q23‐24: D12S86, D12S1612, D12S1349, PLA2A. No support for linkage with 12q24 was found in this family, which indicates a genetic heterogeneity in juvenile onset autosomal dominant distal spinal muscular atrophy.
ROSS SYNDROME: CLINICAL AND LABORATORY EVALUATION OF TWO CASES
Authors: De Joanna G. , Perretti A. , Tugnoli V. , Nolano M. , Cruccu G. , Santoro L.
Published: July 2002

We describe two males, aged 41 and 55, come to our observation complaining of heat intolerance, abnormal increase in body temperature with minimal exercising, reduced sweating and, generalized fatigability; one of them had distal paresthesias. Neurologic evaluation showed bilateral Adie's tonic pupil and an absence of deep‐tendon jerks. A diagnosis of Ross' Syndrome was advanced. Autonomic tests, nerve conduction study, H‐reflex, computerized termoregulatory and pain thresholds, laser CO2 cortical evoked potentials, and skin biopsy were performed. One of them performed a histamine test and hand photopletismography resulted positive for sympathetic impairment, and pilocarpine pupil test that showed a parasympathetic denervation hypersensitivity.

The following tests gave the same results in both patients: parasympathetic and most sympathetic tests were normal. Sympathetic skin response was absent and Minor test showed an almost complete absence of sweating. Sweating was possible only in two or three small areas. Positive pilocarpine test suggested a postganglionic involvement of sympathetic nervous system. Sensitive and motor nerve conduction velocities were normal, while H‐reflex was not detectable. Termoregulatory and pain thresholds were abnormal. Laser CO2 cortical evoked potentials showed the absence of C fibre potentials, whereas A‐δ fibres response was abnormal in one of them. Hairy skin biopsy showed a definite reduction of sweat glands and of small vessel innervation; glabrous skin biopsy performed in one of them showed a reduced number of Meissner corpuscles. These findings suggest that in Ross' Syndrome the degenerative process can involve, besides the autonomic fibres, myelinated somatosensory fibres also.
Grating enhancement of quantum well detector response
Authors: Goossen K. W. , Lyon S. A. , Alavi K.
Published: July 2002

We have measured the enhancement in the response of a quantum well infrared detector by the incorporation of a metallic diffraction grating into the structure. We find an enhancement ratio of about 30, and its spectrum indicates that waveguiding of diffracted light occurs within the sample. Strong coupling to evanescent modes of the grating is not observed.
Quaternary quantum wells for electro-optic intensity and phase modulation at 1.3 and 1.55 μm
Authors: Zucker J. E. , Bar-Joseph I. , Miller B. I. , Koren U. , Chemla D. S.
Published: July 2002

We demonstrate for the first time that large quantum-confined Stark effect can be obtained in high quality InGaAsP/InP quantum well p-i-n heterostructures. The compositional flexibility of this material system is particularly suited for quantum well device applications in optical communications systems operating between 1.55 and 1.3 μm. We measure the magnitude of the shift of the ground-state exciton transition with applied electric field and find that it is significantly enhanced over ternary wells. We have also determined the electro-optic intensity and phase modulation response in these structures.
Magnetic and magneto-optic properties of In-alloyed TbFe amorphous films
Authors: Iijima Tetsuo , Ishii Osamu , Hatakeyama Iwao
Published: July 2002

The magnetic and magneto-optic characteristics of indium (In) -alloyed TbFe amorphous films are investigated. Alloying with In drastically decreases the compensation temperature, and increases the Kerr rotation by more than 20%. Both the compensation composition and the compensation temperature are observed to shift to the Tb-rich side when alloying with In. These magnetic property changes are attributed to the influence of In on the Fe and/or Tb moments.
Reactive ion etching of InP with Br2-containing gases to produce smooth, vertical walls: Fabrication of etched-faceted lasers
Authors: Takimoto K. , Ohnaka K. , Shibata J.
Published: July 2002

We describe the reactive ion etching of InP using a mixture of Br2 and either N2 or Ar. We report the first fabrication of straight vertical walls in InP at a very fast etching rate of 2 μm/min. By using a mixture of Br2 and Ar and raising the substrate temperature, smooth walls are obtained. To demonstrate that the etched walls can be used as laser mirrors, we fabricated etched-faceted lasers with threshold currents of 19.0 mA for a laser with one etched and one cleaved facet and 26.6 mA for a laser with two etched facets.
Structure of ionized cluster beam aluminum deposited on (100) silicon
Authors: Madden Michael C.
Published: July 2002

Ionized cluster beam aluminum deposited on (100) silicon has a unique grain structure consisting of only two crystallographic orientations. Both are (110), but are rotated 90° with respect to each other about the (110) axis so that their (220) planes are perpendicular. This structure arises from a close match between the (200) planes in the aluminum and the (220) planes in the silicon along one direction, and the existence of a interfacial superlattice consisting of three (220) planes from the silicon and four (220) planes from the aluminum, along the orthogonal direction. This grain structure contains no triple points and curved grain boundaries.
X-ray diffraction from corrugated crystalline surfaces and interfaces
Authors: Macrander A. T. , Slusky S. E. G.
Published: July 2002

Satellite peaks analogous to superlattice peaks have been observed for both corrugated InP substrates and for such substrates overgrown with epitaxial InGaAsP. These satellites are entirely due to the corrugations. High-resolution x-ray diffraction using extremely asymmetric reflections in the glancing exit configuration was used. A kinematical expression for the intensities of the satellite peaks is derived for strain-free structures.
Hydrogenation of GaAs-on-InP
Authors: Chakrabarti U. K. , Pearton S. J. , Hobson W. S. , Lopata J. , Swaminathan V.
Published: July 2002

Incorporation of atomic hydrogen into heteroepitaxial Si-doped GaAs layers grown directly on InP substrates by organometallic vapor phase epitaxy produces substantial increases in the reverse bias breakdown voltage of TiPtAu Schottky diodes fabricated on the GaAs-on-InP. Plasma hydrogenated diodes annealed at 400 °C to restore the electrical activity of the passivated shallow donors have reverse breakdown voltages (VB) of ∼6.5 V compared to 4.5 V for untreated samples. The increases in VB are stable to 500 °C annealing for 5 min. Atomic profiling of deuterated samples showed substantial outdiffusion of deuterium from the GaAs at 600 °C, with increasing accumulation at the heterointerface. The deuterium in this disordered region after 600 °C annealing is in a relatively immobile, electrically inactive state.
Misfit dislocation dynamics in Si1−xGex/(100) Si: Uncapped alloy layers, buried strained layers, and multiple quantum wells
Authors: Houghton D. C.
Published: July 2002

Misfit dislocation glide velocities have been measured in Si/Si1−xGex/Si heterostructures. Si capped single Si1−xGex alloy layers and multiple quantum well geometries were investigated and no difference was found between dislocation kinetics in these structures and the equivalent alloy layer of the same average composition. Velocities in the range 25 nm s−1 to 2 nm s−1 were determined from the length of a/2〈110〉 60° type misfit dislocation segments after annealing in the temperature range 450–950 °C, for times between 5 and 2000 s. Two dislocation mechanisms were observed; a single misfit array at the first Si1−xGex/Si interface was found in multiple quantum wells and alloy layers while paired misfit segments were observed at both strained interfaces in Si capped Si1−xGex alloy layers. An expression for the effective stress, τeff, for single and paired misfit dislocation propagation is presented which accommodates variation in the unstrained Si cap thickness. The mean activation energy for misfit disclocation glide Qv for Si1−xGex/Si heterostructures with 0.035<x<0.25 was found to be 2.25±0.05 eV and Qv was independent of τeff. For all geometries and for τeff in the range 100–750 MPa the misfit dislocation glide velocity can be defined by V(mm s−1)= (4±2)×1014(τeff/μ)2 exp−(2.25/kT).
Theoretical study of structures and growth of strained Si/Ge superlattices
Authors: Zi Jian , Zhang Kaiming , Xie Xide
Published: July 2002

The geometry structures of strained (Si)n/(Ge)n (1≤n≤6) superlattices grown pseudomorphically on (001) oriented Si1−xGex (0≤x≤1) substrates are studied. The calculations indicate that with proper choice of the Ge composition factor x symmetrically strained superlattices can be approximately obtained, which might render the growth of a superlattice with larger thickness possible.
Fabrication of amorphous-crystalline superlattices in GeSi-Si and GaAs-AlAs
Authors: Eaglesham D. J. , Poate J. M. , Jacobson D. C. , Cerullo M. , Pfeiffer L. N. , West K.
Published: July 2002

A study is presented of MeV ion beam amorphization of epitaxial superlattices of GeSi-Si and GaAs-AlAs. In both superlattice systems, we observe preferential damage of one layer type (using transmission electron microscopy and Rutherford backscattering). Selective amorphization of the faster-damaging layers is demonstrated at higher doses, allowing us to form amorphous-crystalline (a-c) superlattices of c-Si/a-GeSi and c-AlAs/a-GaAs. By studying the buildup of damage in the two systems, we deduce differences between the ion beam damage processes in group III-V and IV semiconductors. The most marked distinction is that the AlAs layers inhibit amorphization of the GaAs contiguous with the interface, while Si layers do not appear to affect the amorphization of the adjacent GeSi. This leads us to the tentative conclusion that GaAs amorphization is strongly affected by the local concentration of point defects which may diffuse hundreds of angstroms at ≊80 K and recombine in the AlAs layer.
500 GHz electrically steerable photoconducting antenna array
Authors: Froberg N. , Mack M. , Hu B. B. , Zhang X.-C. , Auston D. H.
Published: July 2002

When illuminated by a train of properly spaced ultrashort optical pulses, an array of short photoconducting dipole antennas emits a submillimeter wave beam which can be electrically steered by varying the periodicity of the voltage bias applied to the individual antenna elements.
Improved electronic properties of GaAs surfaces stabilized with phosphorus
Authors: Viktorovitch P. , Gendry M. , Krawczyk S. K. , Krafft F. , Abraham P. , Bekkaoui A. , Monteil Y.
Published: July 2002

We report on a new passivation procedure of the GaAs surface based on a thermal treatment under a PH3 overpressure. This treatment results, by As/P exchange, in the formation of a thin superficial GaP layer which prevents the formation of an arsenic oxide, as observed by x-ray photoelectron spectroscopy analysis. Subsequent increase of the photoluminescence signal indicates improved electronic properties of GaAs surfaces as a result of this passivation procedure.
Intersubband absorption and infrared photodetection at 3.5 and 4.2 μm in GaAs quantum wells
Authors: Schneider Harald , Fuchs Frank , Dischler Bernhard , Ralston John D. , Koidl Peter
Published: July 2002

We propose and demonstrate a novel concept for intersubband detectors at operating wavelengths of 3–5 μm using GaAs quantum wells. An extremely large intersubband spacing is obtained by using ultrathin AlAs barriers on either side of the GaAs quantum wells followed by a thicker Al0.3Ga0.7As layer. Simultaneously, the confining AlAs layers act as tunnel barriers which allow an electrical detection of the intersubband excitation.
Epitaxial growth of β-SiC on silicon-on-sapphire substrates by chemical vapor deposition
Authors: Pazik J. C. , Kelner G. , Bottka N.
Published: July 2002

Cubic (β) silicon carbide films have been grown epitaxially on silicon-on-sapphire (SOS) substrates by chemical vapor deposition. The β-SiC films were grown between 1340–1370 °C on SOS substrates which have a layer of silicon deposited in situ or were grown directly on the as-is SOS substrate. In both cases, the silicon surface was carbonized prior to growth of the β-SiC epilayer. With a growth rate of ∼3.5 μm/h, 7 μm β-SiC films have been obtained. The films have been characterized by infrared reflectance spectroscopy, optical and scanning electron microscopy. Specular films are obtained which have growth columns and pits. Electrical transport properties of the films were measured by the Van der Pauw–Hall method. The films are p type with carrier concentrations between 1×1018 and 2×1018 cm−3 and Hall mobilities of approximately 30 cm2/V s.
Electrostatic trapping of contamination particles in a process plasma environment
Authors: Carlile Robert N. , Geha Sam , O’Hanlon John F. , Stewart John C.
Published: July 2002

A number of authors have observed, by using light scattering from a laser beam, contamination particles suspended in an rf process plasma. The region of space occupied by the particles appears finite, e.g., a ring; there is experimental evidence that the particles are negatively charged. We show, by using a tuned Langmuir probe, that the trap is electrostatic in nature. The volume of a trap is as much as 5 V larger in electrostatic potential than the surrounding plasma. This means that the volume of the trap is positively charged with the electric field being directed outward from the trap. Thus, negatively charged particles will flow into it. The electrostatic potential rises so rapidly at a trap boundary that a double layer may exist there. Finally, the plasma-sheath interface is found to follow the topographic contour of the rf electrode surface.
P2S5 passivation of GaAs surfaces for scanning tunneling microscopy in air
Authors: Dagata J. A. , Tseng W. , Bennett J. , Schneir J. , Harary H. H.
Published: July 2002

We report a novel method of GaAs substrate preparation which imparts significantly improved topographical and chemical uniformity to the surface. The procedure, employing an aqueous P2S5/(NH4)2S solution, leaves the surface in a highly ordered state and resistant to air oxidation for periods of a day or more without the presence of foreign chemical layer such as sulfur. Surface quality was determined by scanning tunneling microscopy (STM), time-of-flight secondary ion mass spectrometry, reflection high-energy electron diffraction, and x-ray photoelectron spectroscopy. The remarkable stability and smoothness of treated III-V surfaces is illustrated by STM imaging of an Al0.51Ga0.49As/GaAs superlattice in air. The superlattice consisted of periodic alternating AlGaAs/GaAs layers of various thicknesses from 10 to 1000 nm.
High-performance latchable optical switch and logic gates based on the integration of surface-emitting lasers and photothyristors
Authors: Zhou Ping , Cheng Julian , Schaus C. F. , Sun S. Z. , Hains C. , Zheng K. , Torres A. , Myers D. R. , Vawter G. A.
Published: July 2002

Latching optical switches and cascadable optical logic gates and and or are demonstrated by the monolithic integration of a vertical-cavity surface-emitting laser with heterojunction photothyristors. Excellent optical switching characteristics, including low switching power (tens of nW), high optical gain (≳104), and a large on/off ratio, have been achieved.
Evaluation of the surface structure of diamond films prepared in a combustion flame by surface-enhanced Raman scattering
Authors: Okada Katsuyuki , Komatsu Shojiro , Ishigaki Takamasa , Matsumoto Seiichiro , Moriyoshi Yusuke
Published: July 2002

Surface-enhanced Raman scattering (SERS) was performed on the surface characterization of polycrystalline diamond films prepared in a C2H2-O2 combustion flame. The conventional Raman spectra of a diamond film showed only the peak at 1333 cm−1 corresponding to diamond. However, if Ag island films were coated onto the diamond surface (Ag overlayer method), the resultant spectra changed drastically. The peaks around 1580 and 1355 cm−1 were remarkably enhanced; the former is assigned to the sp2 graphite structure and the latter is assigned to the disordered microcrystalline graphite structure, respectively. This would indicate that the diamond surface has a sp2-like structure, which is different from the sp3 structure in bulk. This surface configuration is discussed from the viewpoint of the surface reconstruction.
Optical emission properties of semi-insulating GaAs grown at low temperatures by molecular beam epitaxy
Authors: Viturro R. Enrique , Melloch Michael R. , Woodall Jerry M.
Published: July 2002

We have used cathodoluminescence (CL) and photoluminescence spectroscopy to observe deep-level states in GaAs grown at low-substrate temperatures by molecular beam epitaxy (LT GaAs) and the evolution of these states upon annealing. The as-grown material shows intense deep-level emissions which can be associated with an excess concentration of arsenic, mostly present as As-antisite and As-interstitial defects. These emissions subside with annealing for a few minutes at temperatures above 450 °C. CL measurements clearly show a dramatically reduced concentration of traps in the post-growth 600 °C annealed material. Additional measurements carried out on As/GaAs systems indicate a high surface-recombination velocity for these interfaces. These results account for a diminished role of electronic point defects in controlling the insulative behavior of LT GaAs and strongly supports a ‘‘buried’’ Schottky barrier model, which involves ultrafast recombination of carriers at surfaces of embedded arsenic clusters formed during the annealing processing of LT GaAs.
Native donors and acceptors in molecular-beam epitaxial GaAs grown at 200 °C
Authors: Look D. C. , Walters D. C. , Mier M. , Stutz C. E. , Brierley S. K.
Published: July 2002

Absorption measurements at 1.1 and 1.2 μm were used along with the known electron and hole photoionization cross sections for EL2 to determine deep donor (EL2-like) and acceptor concentrations ND=9.9×1019 and NA=7.9×1018 cm−3, respectively, in a 2-μm-thick molecular-beam epitaxial GaAs layer grown at 200 °C on a 2-in.-diam semi-insulating wafer. Both lateral and depth uniformities of ND over the wafer were excellent as was also the case for the conductivity. Band conduction was negligible compared to hopping conduction at 296 K as evidenced by the lack of a measurable Hall coefficient.
Atomic scale saw by dislocation slipping: A new method to generate one-dimensional structure
Authors: Peyrade J. P. , Voillot F. , Goiran M. , Atmani H. , Rocher A. , Bedel E.
Published: July 2002

A new method to generate one-dimensional (1D) semiconductor structures or controllable steps on a surface is proposed. This method, which is not material specific, is based on intrinsic dislocation slip properties and heterogeneity of straining. Dislocations can be used as an atomic scale saw to cut two-dimensional structures (2D) in order to obtain 1D wires. Atomic force microscope observations of GaAs surfaces and transmission electronic microscopy cross sections of GaAs/GaAlAs single quantum wells are presented to demonstrate the feasibility of the method. Although being based on dislocation slipping this method is shown to preserve the optical and crystalline properties of the starting 2D structure as confirmed by photoluminescence spectra.
Improved aqueous etchant for high T
c superconductor materials
Authors: Ashby Carol I. H. , Martens Jon , Plut Thomas A. , Ginley David S. , Phillips Julia M.
Published: July 2002

We have developed an aqueous etchant suitable for producing feature sizes of 1 μm or less in YBa2Cu3O7 and TlBaCaCuO while not degrading high-frequency surface resistance. The 10%–300% increase in surface resistance previously seen in aqueous solutions is largely due to the presence of dissolved CO2; decarbonation of the water by bubbling N2 before and during etching can produce a better than 50% reduction in the surface-resistance degradation. Surface-resistance degradation can be further reduced by selecting the appropriate solution pH for ethylenediaminetetraacetic acid (EDTA)-based etchants. We have minimized increases in surface resistance to less than 5% following etching in decarbonated disodium EDTA solutions for both YBa2Cu3O7 and TlBaCaCuO superconductors. Similar improvements can be expected from decarbonation and pH control of other aqueous processing solutions.
Growth mode and strain relaxation during the initial stage of InxGa1−xAs growth on GaAs(001)
Authors: Lentzen M. , Gerthsen D. , Förster A. , Urban K.
Published: July 2002

The growth mode and relaxation of the misfit strain of thin InxGa1−xAs layers grown by molecular-beam epitaxy on GaAs(001) were studied by plan-view transmission electron microscopy. The indium concentration was varied between x=0.13 and x=1.0. The transition from two-dimensional to island growth was found at x=0.4. The island growth mode is characterized by islands of different sizes in various states of strain relaxation which is determined by the density of misfit dislocations at the interface.
Single-crystal thin film InP: Fabrication and absorption measurements
Authors: Augustine G. , Jokerst N. M. , Rohatgi A.
Published: July 2002

A new process for separating high quality single-crystal InP thin films from the growth substrate is reported. These thin films were used for transmission measurements to determine InP absorption coefficients above the band edge. Photoluminescence measurements performed on these films before and after the fabrication process verified that the high quality of the separated thin film was not affected by the fabrication process. Two n-type InP thin films, one with a doping concentration of 1.4×1017 cm−3 (1 μm thick) and the other with a doping concentration of 3.2×1018 cm−3 (2.5 μm thick), were grown and subsequently separated from the substrate. Using these separated films, the first direct transmission measurements of above band edge absorption coefficients in doped InP films are reported in this letter.
Photoinduced grating and intensity dependence of defect generation in Ge-doped silica optical fiber
Authors: Tsai T. E. , Askins C. G. , Friebele E. J.
Published: July 2002

Ge E′ centers photoinduced in Ge-doped silica by 5 eV photons of various intensities and fluences were found by electron spin resonance to be induced and bleached by one- and two-photon absorption processes, respectively. The observation that Ge E′-type centers are the only paramagnetic centers induced by very low intensity 5 eV photons in Ge-doped silica supports the proposal that Ge E′-type centers are responsible for the photoinduced gratings observed in both Bragg grating and second-harmonic generation fibers.
Rapid thermal annealing and the anomalous threshold voltage shift of metal-oxide-semiconductor structure in n+ polycrystalline silicon gate complementary metal-oxide-semiconductor technology
Authors: Fang Y. K. , Hsieh J. C. , Chen C. W. , Koung C. H. , Tsai N. S. , Lee J. Y. , Tseng F. C.
Published: July 2002

An anomalous different threshold voltage shift between P-channel metal-oxide-semiconductor field effect transistor (P-MOSFET) and N-channel MOSFET under high temperature rapid thermal annealing (RTA) borophosphosilicate glass reflow has been studied using 1 μm n+ polygate complementary MOS technology. The boron transient enhanced outdiffusion and phosphorus pileup at channel surface, as well as the interface states generated due to the degradation of thin gate oxide under high RTA process, are proposed as the main sources of this anomalous shift. A detailed model is proposed to interpret the mechanism and some methods to solve the anomalous shift are suggested.
On the theory of steady-state electromigration in thin films
Authors: Bauer C. L. , Mullins W. W.
Published: July 2002

Steady-state electromigration along grain boundaries in a monatomic polycrystalline thin film has been analyzed in a two-dimensional model by balancing the (applied) electric and (induced) stress driving forces to achieve a zero flux divergence. The continuity of chemical potential requires a unique stress normal to each of the three boundaries terminating at a given triple point. These stresses and the steady-state fluxes are determined by a set of linear equations subject to boundary conditions at the intersection of grain boundaries with the film edge (edge points). When the normal stress is assumed zero at all edge points, the stress typically attains maxima and minima at triple points, whereas, when the flux is assumed zero at all edge points, the stress typically builds up monotonically in the field direction.
Donor neutralization in GaAs after plasma silicon nitride deposition
Authors: Seaward K. L.
Published: July 2002

Loss of conductance has been observed in Si-doped GaAs after plasma silicon nitride deposition in a 2.45 GHz electron cyclotron resonance reactor and in a 30 kHz parallel-plate reactor, but not in a 13.56 MHz parallel-plate reactor. Based on the temperature at which conductance is restored in test structures subjected to a variety of plasmas, observation of atomic hydrogen in the plasmas by optical emission, and secondary ion mass spectrometry measurement of hydrogen in the test structures, the loss of conductance appears to be from formation of the hydrogen-silicon complex. The extent of neutralization correlates with an abundance of atomic hydrogen in the plasmas and the nitride deposition rate. When the deposition rate is high, the GaAs surface is protected quickly and donor neutralization is minimized.
Quantum efficiencies greater than unity: A computer study of a photogating effect in amorphous silicon p-i-n devices
Authors: Hou J. Y. , Fonash S. J.
Published: July 2002

We report a new effect, which we call photogating, that can be present in amorphous Si-based p-i-n structures under certain illumination conditions. This phenomenon feeds photogenerated carriers created by a bias light beam of one wavelength into the current response to a second probe light beam of a different wavelength. We demonstrate that this phenomena can lead to measured quantum efficiencies greater than unity. Our computer simulations show that this new effect owes its origins to trapped charge and to the condition that there is a low field region in the front of the structure in the presence of certain bias light.
Annealing effect on the carrier concentration in heavily Si-doped n+-InGaAs
Authors: Watanabe Noriyuki , Nittono Takumi , Watanabe Kazuo
Published: July 2002

Carrier concentration in very heavily silicon-doped (about 2.7×1019 cm−3) n+-In0.52Ga0.48As epilayer grown on GaAs substrate by metalorganic chemical vapor deposition is decreased by post-growth annealing in the temperature range of 500–800 °C but keeps a value higher than 1.4×1019 cm−3. This value is fairly higher than the reported value for heavily Si-doped GaAs after annealing. It is suggested that the decrease of carrier concentration is not caused by the formation of Si-Si pairs or SiAs acceptors but caused by silicon atom movement from Ga- or In-substitutional sites to interstitial sites at temperatures up to 600 °C and silicon atom outdiffusion at higher temperatures around 800 °C. In less doped (about 5.2×1018 and 1.6×1019 cm−3) samples, a smaller carrier or no decrease is detected after annealing.
Precursors for Si atomic layer epitaxy: Real time adsorption studies on Si(100)
Authors: Koleske D. D. , Gates S. M. , Beach D. B.
Published: July 2002

Adsorption of SiClH3 and SiCl2H2 on Si(100) is studied as a function of surface temperature, comparing these precursors for Si atomic layer epitaxy (ALE). At 450–550 °C, a substantial surface H coverage (θH) exists during SiClH3 adsorption, and θH exhibits transient behavior. During SiCl2H2 adsorption, θH is much smaller. At 500 °C with SiCl2H2, ≂1 monolayer of Cl is formed after ≂4×1019 cm−2 exposure. Dichlorosilane is a suitable precursor for Si ALE, but desorption of HCl is significant at T≳500 °C so that SiCl2H2 adsorption is not strictly self-limiting.
Novel biphotonic holographic storage in a side-chain liquid crystalline polyester
Authors: Ramanujam P. S. , Hvilsted S. , Andruzzi F.
Published: July 2002

We report novel biphotonic holographic storage of text and gratings on unoriented films of a side-chain liquid crystalline polyester capable of high density storage and complete erasure. The holograms have a typical size of 1 mm. The recording utilizes unusual photochemistry involving azo dye molecules. We believe that this technique would have a great potential in the recording of thousands of holograms in a two-dimensional plane, as for instance in text retrieval systems and in the fabrication of high density interconnects in optical neural networks.
Properties of center and edge δ-doped GaAs-AlGaAs quantum wells grown by metalorganic chemical vapor deposition
Authors: Kim Yong , Kim Moo-Sung , Min Suk-Ki
Published: July 2002

We have investigated the properties of center and edge δ-doped GaAs-AlGaAs quantum wells grown by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) by means of capacitance voltage (C-V) profiling and temperature-dependent photoluminescence (PL) measurements. For the center δ-doped quantum well, a narrow C-V profile and the Fermi-edge singularity in PL have been confirmed. In contrast, for edge δ-doped quantum wells, a double-peaked C-V profile and a sharp luminescence enhancement near the Fermi level which is not due to the Fermi-edge singularity, have been observed. The results are explained by a simple model based on the asymmetrical potential well induced by the band bending due to the δ-doping at one side of the heterointerfaces.
Blue emission of porous silicon
Authors: Lee M. K. , Peng K. R.
Published: July 2002

Thermally treated porous silicon shows blue photoluminescence (400–520 nm) excited by a He-Cd laser (320 nm) at room temperature. Stable and uniform Schottky blue light emitting diodes have been fabricated from thermally treated porous silicon in this work. The emission of blue light may be explained by the wide optical energy band gap attributed to the quantum wire effect.
Measurement of nonradiative Auger and radiative recombination rates in strained-layer quantum-well systems
Authors: Wang M. C. , Kash K. , Zah C. E. , Bhat R. , Chuang S. L.
Published: July 2002

To understand the feasibility of using strain to reduce the nonradiative Auger recombination rate of 1.5 μm semiconductor lasers, we have directly measured the radiative and nonradiative Auger recombination rates in strained-layer InGaAs/AlGaInAs quantum-well systems, using time-resolved photoluminescence measurements. We find that the Auger recombination rate can be reduced in either biaxial compressively or tensilely strained quantum-well structures. A longer radiative carrier lifetime is observed for the tensile-strained materials. The effect of strain and quantum confinement on the carrier lifetime is discussed.
Heteroepitaxially grown diamond on a c-BN {111} surface
Authors: Wang Long , Pirouz Pirouz , Argoitia Alberto , Ma Jing Sheng , Angus John C.
Published: July 2002

A continuous diamond film with a thickness of about 10 μm was grown on {111} faces of a single-crystal cubic boron nitride (c-BN) by hot-filament chemical vapor deposition (CVD). Cross-sectional selected area diffraction pattern (SADP) and high resolution electron microscopy (HREM) of the diamond/c-BN interface show that the diamond has a parallel orientation relationship with respect to the substrate.
Diamond deposition on polycrystalline films of cubic boron nitride
Authors: Friedmann T. A. , Bernardez L. J. , McCarty K. F. , Klaus E. J. , Ottesen D. K. , Johnsen H. A. , Clift W. M.
Published: July 2002

We have grown diamond films on films of cubic boron nitride (cBN). The cBN films were grown on Si(100) substrates using ion-assisted pulsed laser deposition. Fourier transform infrared (FTIR) spectroscopy indicated that the BN films contained ∼75% sp3-bonded cBN. The as-grown cBN films were inserted with no surface pretreatment (e.g., abrading or scratching) into a conventional hot filament diamond reactor. In situ Raman spectroscopy was used to confirm diamond synthesis during growth. The nucleation density of the diamond films was estimated at 1×109/cm2, equivalent to or higher than the best values for scratched silicon substrates. In addition, we found that the cBN films were etched in the diamond reactor; a film thickness ≳1500 Å was required to prevent total film loss before diamond nucleation occurred. The presence of cBN under the diamond was established using FTIR spectroscopy and Auger electron spectroscopy.
Electronic passivation of n- and p-type GaAs using chemical vapor deposited GaS
Authors: Tabib-Azar Massood , Kang Soon , MacInnes Andrew N. , Power Michael B. , Barron Andrew R. , Jenkins Phillip P. , Hepp Aloysius F.
Published: July 2002

We report on the electronic passivation of n- and p-type GaAs using chemical vapor deposited cubic GaS. Au/GaS/GaAs fabricated metal-insulator-semiconductor (MIS) structures exhibit classical high-frequency capacitor versus voltage (C-V) behavior with well-defined accumulation and inversion regions. Using high- and low-frequency C-V, the interface trap densities of ∼1011 eV−1 cm−2 on both n- and p-type GaAs are determined. The electronic condition of GaS/GaAs interface did not show any deterioration after a six week time period.
Photoinduced luminescence enhancement from anodically oxidized porous Si
Authors: Shih S. , Jung K. H. , Yan J. , Kwong D. L. , Kovar M. , White J. M. , George T. , Kim S.
Published: July 2002

We have investigated the phenomenon of photoluminescence (PL) increase in anodically oxidized porous Si with increasing laser illumination time by transmission Fourier transform infrared spectroscopy (FTIR), PL spectroscopy, and electron paramagnetic resonance. The adsorption of oxygen without hydrogen loss was observed during laser illumination by FTIR. The PL intensity increased linearly, while the dangling bond (DB) density decreased with increasing illumination time. By assuming that the decrease of DB density has a linear response to the illumination time, we identify that the change in DB density is mainly responsible for the observed PL increase after laser illumination.
Dynamic electronic compensation of fixed gratings in photorefractive media
Authors: Orlov Sergei , Psaltis Demetri , Neurgaonkar Ratnakar R.
Published: July 2002

We present a model describing the formation of a photorefractive grating in the presence of photorefractively inactive space-charge modulation. The treatment is based on standard linearized Kukhtarevs equations. The model developed is applied to the interpretation of experimental results on electrical fixing in Sr0.75Ba0.25Nb2O6.
True oxide electron beam induced current for low-voltage imaging of local defects in very thin silicon dioxide films
Authors: Lau W. S. , Chan D. S. H. , Phang J. C. H. , Chow K. W. , Pey K. S. , Lim Y. P. , Cronquist B.
Published: July 2002

A new low-voltage contrast mechanism due to electron hole pairs generated in the oxide by an electron beam was observed at an electric field lower than 3.5 MV/cm in addition to the tunneling current microscopy (TCM) contrast mechanism at electric fields higher than 3.5 MV/cm. The new contrast mechanism is opposite in sign to the TCM contrast mechanism. Good contrast can be obtained at an electric field as low as 2.4 MV/cm, which is two to three times smaller than that needed for TCM contrast. Potential applications include large area imaging and quantitative imaging of oxide defects.
Birefringent bistability in (Pb,La)(Zr,Ti)O3 thin films with a ferroelectric-semiconductor interface
Authors: Wang Feiling , Haertling Gene H.
Published: July 2002

We report a birefringent bistability exhibited in ferroelectric thin films with a ferroelectric-semiconductor interface. Such birefringent bistability is observed in (Pb,La)(Zr,Ti)O3 (PLZT) thin films which are sandwiched between a platinum and a semiconducting indium-tin oxide (ITO) electrode. The magnitude of the birefringence between the two remanent states is approximately 0.9×10−3. The Pt/PLZT/ITO structure features a nonvolatile electro-optic memory operation, i.e., the switching between the two remanent birefringent states with bipolar electric pulses.
Very low friction for diamond sliding on diamond in water
Authors: Tzeng Y.
Published: July 2002

This letter reports the lowest coefficient of friction measured for diamond sliding on diamond. When a natural diamond stylus with a spherical tip about 50 μm in diameter slides on a polished polycrystalline chemically vapor deposited diamond film in water at a speed of 0.05 mm/s under a load of 50 g, the coefficient of friction falls to ∼0.001. This clearly shows the effectiveness of water for lubricating diamond sliding on diamond.
Pulsed laser deposition of epitaxial Si/TiN/Si(100) heterostructures
Authors: Chowdhury R. , Chen X. , Narayan J.
Published: July 2002

We have successfully deposited multilayer Si/TiN/Si(100) epitaxial heterostructures using pulsed laser deposition technique. This silicon-on-conductor device configuration has potential applications in three-dimensional integrated circuits and radiation hardened devices. The Si and TiN films were deposited by pulsed laser (KrF: λ=248 nm, τ =25 ns) physical vapor deposition technique at a substrate temperature of 600 °C in a chamber maintained at a vacuum of ∼10−7 Torr. The epitaxial nature of the films was characterized using x-ray diffraction, Rutherford backscattering, and high resolution transmission electron microscopy techniques. The two interfaces (100)TiN/Si(100)substrate and (100)Si/(100)TiN layers were quite sharp without any indication of interfacial reaction between them. The epitaxial relationship was found to be 〈100〉Si∥〈100〉TiN∥〈100〉Si. In the plane, four unit cells of TiN matched with three unit cells of silicon with less than 4.0% misfit. This domain matching epitaxy provides a mechanism of epitaxial growth in systems with large lattice mismatch. Modeling of the domain matching epitaxial growth in the high lattice mismatch (100)Si/(100)TiN/(100)Si system and possible device implications are discussed.
Doping and damage dose dependence of implant induced transient enhanced diffusion below the amorphization threshold
Authors: Griffin P. B. , Lever R. F. , Packan P. A. , Plummer J. D.
Published: July 2002

Special test structures were used to isolate the dependence of transient enhanced diffusion on damage dose and on doping concentration. The structures consisted of 200 nm boron-doped layers with an undoped silicon capping layer 300 nm thick. The boron concentrations varied from 5×1016 to 5×1018/cm3. Damage was introduced by 75 keV, Si implants with doses ranging from 1×1012 to 5×1013/cm2. Annealing at 750 °C for 120 min produced a large enhancement in the boron diffusivity. The enhancement increased with increasing Si dose, but in a sublinear manner. The enhancement decreased with increasing boron doping concentration, even for doping concentrations below the intrinsic electron concentration. A phenomenological defect-doping reaction model is described which predicts both of these essential features of damage enhanced diffusion. We conclude that it will be necessary to treat the full coupling between defects and dopant atoms in order to model damage enhanced diffusion effects.
N-channel metal-oxide-semiconductor transistors fabricated in a silicon film bonded onto sapphire
Authors: Wang J. H. , Jin M. S. , Ozguz V. H. , Lee S. H.
Published: July 2002

N-channel metal-oxide-semiconductor transistors were fabricated in silicon films that were bonded onto sapphire substrates. The bonded silicon films can withstand high processing temperatures (850 °C). The electrical performance of the resulting devices is comparable to that of devices fabricated in bulk silicon wafers. This technology can be applied to silicon-on-insulator device development and for integrated optoelectronic device research.
Hydrogenation of GaN, AlN, and InN
Authors: Zavada J. M. , Wilson R. G. , Abernathy C. R. , Pearton S. J.
Published: July 2002

Hydrogen incorporation depths of ≥1 μm are measured for 2H plasma exposure of GaN and AlN at 250–400 °C for 30 min. The concentration of 2H incorporated is in the range 5–10×1017 cm−3 for GaN and 5–30×1018 cm−3 for AlN under these conditions. No redistribution of the hydrogen is observed for annealing temperatures up to 800 °C, but at 900 °C there is substantial loss of hydrogen from the samples. Similar results are obtained for 2H implantation into GaN, AlN, and InN, with no significant redistribution observed up to 500–600 °C in either AlN or InN, and motion only at 900 °C in GaN. The thermal stability of hydrogen in III-V nitrides explains previous results for Mg-doped GaN grown using NH3, where post-growth annealing at high temperatures was required to achieve appreciable doping efficiencies.