bluuebunny/crossref_metadata_2025 huggingface dataset:
Extrasynaptic NR2B and NR2D subunits of NMDA receptors shape ‘superslow’ afterburst EPSC in rat hippocampus
Authors: Lozovaya Natasha A. , Grebenyuk Sergei E. , Tsintsadze Timur Sh. , Feng Bihua , Monaghan Daniel T. , Krishtal Oleg A.
Published: May 2004

In conditions of facilitated synaptic release, CA3/CA1 synapses generate anomalously slow NMDA receptor‐mediated EPSCs (EPSCNMDA). Such a time course has been attributed to the cooperation of synapses through glutamate spillover. Imitating a natural pattern of activity, we have applied short bursts (2–7 stimuli) of high‐frequency stimulation and observed a spike‐to‐spike slow‐down of the EPSCNMDA kinetics, which accompanied synaptic facilitation. It was found that the early component of the EPSCNMDA and the burst‐induced late component of the EPSCNMDA have distinct pharmacological properties. The competitive NMDA antagonist R‐(−)‐3‐(2‐carboxypiperazine‐4‐yl)‐propyl‐1‐phosphonic acid (D‐CPP), which has higher affinity to NR2A than to NR2B subunits and lowest affinity at NR2D subunits, significantly slowed down the decay rate of the afterburst EPSC while leaving the kinetics of the control current unaffected. In contrast, ifenprodil, a highly selective NR2B antagonist, and [±]‐cis‐1‐[phenanthren‐2yl‐carbonyl]piperazine‐2,3‐dicarboxylic acid (PPDA), a competitive antagonist that is moderately selective for NR2D subunits, more strongly inhibited the late component of the afterburst EPSCNMDA. The receptors formed by NR2B and (especially) NR2D subunits are known to have higher agonist sensitivity and much slower deactivation kinetics than NR2A‐containing receptors. Furthermore, NR2B is preferentially and NR2D is exclusively located on extrasynaptic membranes. As the density of active synapses increases, the confluence of released glutamate makes EPSC decay much longer by activating more extrasynaptic NR2B‐ and NR2D‐subunit‐containing receptors. Long‐term potentiation (LTP) induced by successive rounds of burst stimulation is accompanied by a long‐term increase in the contribution of extrasynaptic receptors in the afterburst EPSCNMDA.
M3 muscarinic acetylcholine receptor plays a critical role in parasympathetic control of salivation in mice
Authors: Nakamura Takeshi , Matsui Minoru , Uchida Keiko , Futatsugi Akira , Kusakawa Shinji , Matsumoto Nagisa , Nakamura Kyoko , Manabe Toshiya , Taketo Makoto M. , Mikoshiba Katsuhiko
Published: May 2004

The M1 and M3 subtypes are the major muscarinic acetylcholine receptors in the salivary gland and M3 is reported to be more abundant. However, despite initial reports of salivation abnormalities in M3‐knockout (M3KO) mice, it is still unclear which subtype is functionally relevant in physiological salivation. In the present study, salivary secretory function was examined using mice lacking specific subtype(s) of muscarinic receptor. The carbachol‐induced [Ca2+]i increase was markedly impaired in submandibular gland cells from M3KO mice and completely absent in those from M1/M3KO mice. This demonstrates that M3 and M1 play major and minor roles, respectively, in the cholinergically induced [Ca2+]i increase. Two‐dimensional Ca2+‐imaging analysis revealed the patchy distribution of M1 in submandibular gland acini, in contrast to the ubiquitous distribution of M3. In vivo administration of a high dose of pilocarpine (10 mg kg−1, s.c.) to M3KO mice caused salivation comparable to that in wild‐type mice, while no salivation was induced in M1/M3KO mice, indicating that salivation in M3KO mice is caused by an M1‐mediated [Ca2+]i increase. In contrast, a lower dose of pilocarpine (1 mg kg−1, s.c.) failed to induce salivation in M3KO mice, but induced abundant salivation in wild‐type mice, indicating that M3‐mediated salivation has a lower threshold than M1‐mediated salivation. In addition, M3KO mice, but not M1KO mice, had difficulty in eating dry food, as shown by frequent drinking during feeding, suggesting that salivation during eating is mediated by M3 and that M1 plays no practical role in it. These results show that the M3 subtype is essential for parasympathetic control of salivation and a reasonable target for the drug treatment and gene therapy of xerostomia, including Sjögren's syndrome.
The mammalian amiloride‐insensitive non‐specific salt taste receptor is a vanilloid receptor‐1 variant
Authors: Lyall Vijay , Heck Gerard L. , Vinnikova Anna K. , Ghosh Shobha , Phan Tam‐Hao T. , Alam Rammy I. , Russell Oneal F. , Malik Shahbaz A. , Bigbee John W. , DeSimone John A.
Published: May 2004

The amiloride‐insensitive salt taste receptor is the predominant transducer of salt taste in some mammalian species, including humans. The physiological, pharmacological and biochemical properties of the amiloride‐insensitive salt taste receptor were investigated by RT‐PCR, by the measurement of unilateral apical Na+ fluxes in polarized rat fungiform taste receptor cells and by chorda tympani taste nerve recordings. The chorda tympani responses to NaCl, KCl, NH4Cl and CaCl2 were recorded in Sprague‐Dawley rats, and in wild‐type and vanilloid receptor‐1 (VR‐1) knockout mice. The chorda tympani responses to mineral salts were monitored in the presence of vanilloids (resiniferatoxin and capsaicin), VR‐1 antagonists (capsazepine and SB‐366791), and at elevated temperatures. The results indicate that the amiloride‐insensitive salt taste receptor is a constitutively active non‐selective cation channel derived from the VR‐1 gene. It accounts for all of the amiloride‐insensitive chorda tympani taste nerve response to Na+ salts and part of the response to K+, NH4+ and Ca2+ salts. It is activated by vanilloids and temperature (> 38°C), and is inhibited by VR‐1 antagonists. In the presence of vanilloids, external pH and ATP lower the temperature threshold of the channel. This allows for increased salt taste sensitivity without an increase in temperature. VR‐1 knockout mice demonstrate no functional amiloride‐insensitive salt taste receptor and no salt taste sensitivity to vanilloids and temperature. We conclude that the mammalian non‐specific salt taste receptor is a VR‐1 variant.
Thermoeffector neuronal pathways in fever: a study in rats showing a new role of the locus coeruleus
Authors: Almeida Maria C. , Steiner Alexandre A. , Coimbra Norberto C. , Branco Luiz G. S.
Published: May 2004

It is known that brain noradrenaline (norepinephrine) mediates fever, but the neuronal group involved is unknown. We studied the role of the major noradrenergic nucleus, the locus coeruleus (LC), in lipopolysaccharide (LPS)‐induced fever. Male Wistar rats had their LC completely ablated electrolytically or their catecholaminergic LC neurones selectively lesioned by microinjection of 6‐hydroxydopamine; the controls were sham‐operated. Both lesions resulted in a marked attenuation of LPS (1 or 10 μg kg−1, i.v.) fever at a subneutral (23°C) ambient temperature (Ta). Because electrolytic and chemical lesions produced similar effects, the role of the LC in fever was further investigated using electrolytic lesions only. The levels of prostaglandin (PG) E2, the terminal mediator of fever, were equally raised in the anteroventral third ventricular region of LC‐lesioned and sham‐operated rats during the course of LPS fever, indicating that LC neurones are not involved in febrigenic signalling to the brain. To investigate the potential involvement of the LC in an efferent thermoregulatory neuronal pathway, the thermoregulatory response to PGE2 (25 ng, i.c.v.) was studied at a subneutral (23°C, when fever is brought about by thermogenesis) or neutral (28°C, when fever is brought about by tail skin vasoconstriction) Ta. The PGE2‐induced increases in metabolic rate (an index of thermogenesis) and fever were attenuated in LC‐lesioned rats at 23°C, whereas PGE2‐induced skin vasoconstriction and fever normally developed in LC‐lesioned rats at 28°C. The LC‐lesioned rats had attenuated PGE2 thermogenesis despite the fact that they were fully capable of activating thermogenesis in response to noradrenaline and cold exposure. It is concluded that LC neurones are part of a neuronal network that is specifically activated by PGE2 to increase thermogenesis and produce fever.
Study of an Impulse Turbine for Wave Power Conversion: Effects of Reynolds Number and Hub-to-Tip Ratio on Performance
Authors: Setoguchi T. , Takao M. , Santhakumar S. , Kaneko K.
Published: May 2004

The objective of this paper is to report the effects of Reynolds number and hub-to-tip ratio on the performance of the impulse turbine for wave energy conversion. The turbine was investigated experimentally under steady and sinusoidally oscillating flow conditions by model testing. As a result, it was found that the critical value of Reynolds number and the optimum hub-to-tip ratio are approximately 4.0×104 and 0.7, respectively. Furthermore, their effect on starting characteristics have been clarified.
Practical Airgap Prediction for Offshore Structures
Authors: Sweetman Bert
Published: May 2004

Two new methods are proposed to predict airgap demand. Airgap demand is the maximum expected increase in the water surface elevation caused incident waves interacting with an offshore structure. The first new method enables inclusion of some second-order effects, though it is based on only first-order diffraction results. The method is simple enough to be practical for use as a hand-calculation in the early stages of design. Two existing methods of predicting airgap demand based on first-order diffraction are also briefly presented and results from the three methods are compared with model test results. All three methods yield results superior to those based on conventional post-processing of first-order diffraction results, and comparable to optimal post-processing of second-order diffraction results. A second new method is also presented; it combines extreme value theory with statistical regression to predict extreme airgap events using model test data. Estimates of extreme airgap events based on this method are found to be more reliable than estimates based on extreme observations from a single model test. This second new method is suitable for use in the final stages of design.
Loading History Effects for Deep-Water S-Lay of Pipelines
Authors: Yun Heedo D. , Peek Ralf R. , Paslay Paul R. , Kopp Frans F.
Published: May 2004

For economic reasons S-Lay is often preferred to J-Lay. However in very deep water S-Lay requires a high curvature of the stinger to achieve the required close-to-vertical departure angle (or a large, low curvature stinger). Choosing the high curvature stinger can lead to plastic deformations of the pipe. The high top tension increases the plastic deformations in two ways: firstly it adds an overall tensile component to the strains, thereby increasing the strains at the 12 o’clock position. Secondly, it increases the strain concentrations, which arise due to discontinuous support of the pipe on the stinger. Typically, the pipe is guided over a series of roller beds. The high top tension tends to straighten the spans between the rollerbeds. To accommodate this (so that the pipe can still follow the stinger), higher curvatures occur at the roller beds. Analytical and numerical solutions are provided to quantify this effect. The analytical solution is fully developed for an arbitrary pipe material models, provided that: (i) the moment-curvature relation for the pipe under tension is known, and (ii) no cyclic plastic ratchetting occurs due to repeated bending of the pipe over the roller beds and straightening in the spans between roller beds. Agreement between the analytical and numerical (finite element) results is excellent. Proper loading history must be used in the numerical simulation, otherwise the level of strain concentration can be overpredicted.
Modeling and Identification of a Nonlinear SDOF Moored Structure, Part 2—Comparisons and Sensitivity Study
Authors: Yim S.C.S. , Narayanan S.
Published: May 2004

A system-identification technique based on the Reverse Multiple-Input/Single-Output (R-MI/SO) procedure is applied to identify the parameters of an experimental mooring system exhibiting nonlinear behavior. In Part 1, two nonlinear small-body hydrodynamic Morison type formulations: (A) with a relative-velocity (RV) model, and (B) with an independent-flow-field (IFF) model, are formulated. Their associated nonlinear system-identification algorithms based on the R-MI/SO system-identification technique: (A.1) nonlinear-structure linearly damped, and (A.2) nonlinear-structure coupled hydrodynamically damped for the RV model, and (B.1) nonlinear-structure nonlinearly damped for the IFF model, are developed for an experimental submerged-sphere nonlinear mooring system under ocean waves. The analytic models and the associated algorithms for parametric identification are described. In this companion paper (Part 2), we use the experimentally measured input wave and output system response data and apply the algorithms derived based on the multiple-input/single-output linear analysis of the reverse dynamic systems to identify the system parameters. The two nonlinear models are examined in detail and the most suitable physical representative model is selected for the mooring system considered. A sensitive analysis is conducted to investigate the coupled hydrodynamic forces modeled by the Morison equation, the nonlinear stiffness from mooring lines and the nonlinear response. The appropriateness of each model is discussed in detail.
Structural Behavior of Dented Tubular Members Under Lateral Loads
Authors: Ruggieri Claudio , Ferrari, Jose´ Alfredo
Published: May 2004

Structural behavior of tubular members with dent damaged caused by local indentation remains a key issue for the safety and failure assessment of critical structures, including marine facilities, oil and gas pipelines. This failure mode most often arises from very large localized plastic deformations caused mainly by excessive or accidental loads such as, for example, during the collision of adjacent risers in deepwater floating production systems (FPS). The complex interaction between the local deformation in the dented region and global bending of the tubular member may severely reduce the plastic collapse load which strongly affects its load-deflection behavior. This study presents an experimental and numerical investigation of the structural behavior of a dented tubular member under lateral load which is applicable to marine risers. Experimental load-deflection curves measured using a 412″O.D. (114 mm) API N80 pipe (580 MPa yield stress) with varying length characterize the plastic response during local indentation and global bending. 3D finite element models are employed to generate numerical solutions describing the large deformation, non-linear behavior for the tested pipes. The experimental results agree well with the numerical results. The analyses provide further insight into the structural response of tubular members and risers with dent damage effects.
Energy band gaps of InN containing oxygen and of the InxAl1−xN interface layer formed during InN film growth
Authors: Alexandrov Dimiter , Scott K. , Butcher A. , Wintrebert-Fouquet Marie
Published: May 2004

The effect of known growth artifacts on the absorption and photoluminescence properties of InN films is determined using linear combination of atomic orbitals electron band structure calculations. InxAl1−xN interfacial layers are examined for various atomic fractions of Al, since these layers are observed to be relatively thick (up to 100 nm) for thin films of InN deposited on AlN or sapphire. It is found that for penetration of Al atoms in InN, forming In-rich InxAl1−xN, a decrease of the energy band gap of InN occurs, despite AlN having a much larger band gap than InN. Γc13↔Γν154 exciton emissions for InxAl1−xN are found to have an energy of 0.765–0.778 eV and may explain recent photoluminescence data for InN. Optical absorption for this alloy is dominated by a 1.58–1.62 eV transition. The second artifact investigated here is high concentration oxygen impurity atoms in wurtzite InN. Segregated oxygen species are not considered, only alloyed species with oxygen substituting on the nitrogen site. For this arrangement a new ternary semiconductor InOyN1−y with y∼0.1 is identified. A model of the tetrahedral cell In–O is made and the energy band gap of InOyN1−y is calculated. It is found that the presence of O atoms in InN can decrease the energy band gap. Optical absorption as low as 1.19 eV can be evident. The exciton emissions Γc12↔Γν151 in InOyN1−y were found to vary in energy over the range 0.84–1.01 eV.
Metalorganic vapor phase diffusion using dimethylzinc. Part I: Analysis of the reproducibility of the resulting diffusion profile as measured by secondary ion mass spectrometry
Authors: Hampel C. A. , Blaauw C. , Calder I. D. , Glew R. , Macquistan D. , Bryskiewicz T. , Guillon S.
Published: May 2004

In this work we investigate metalorganic chemical vapor deposition (MOCVD) diffusion of zinc into undoped InP and InGaAs using dimethylzinc as the diffusant source. The resulting diffusion profiles are measured using secondary ion mass spectrometry. Systematic errors introduced by multiple diffusions are explored and a simple model of reactor transients is introduced to explain the observed departures from the expected square-root behavior. Results of zinc diffusion into high-speed avalanche photodetectors are also presented to demonstrate the ability of MOCVD based diffusion to target diffusion depths with strict tolerances.
Optical add and drop multiplexer using on-chip integration of planar light circuits and optical microelectromechanical system switching
Authors: Liu Xueyuan , Kubby Joel , Chen Jingkuang , Diehl James , Feinberg Kathleen , German Kristine , Gulvin Peter , Herko Larry , Jia Nancy , Lin Pinyen , Ma Jun , Meyers John , Nystrom Peter , Wang Yao Rong
Published: May 2004

On-chip integration of optical switches and planar light circuits (PLCs) can greatly reduce the size, manufacturing cost, and operating cost of multicomponent optical systems. A silicon-on-insulator platform for integrating microelectromechanical system (MEMS) latching optical waveguide switches with PLCs is presented including a working example of chip scale integration of reconfigurable-optical add/drop multiplexer and λ-Routers, along with details of the integrated latching MEMS optical switches.
Copper coplanar waveguides in Si substrates for 10 GHz applications
Authors: Amaya R. E. , Levenets V. , Tarr N. G. , Plett C.
Published: May 2004

This article presents an experimental study of copper coplanar waveguides fabricated on silicon substrates. The waveguides are separated from the substrate by thick layers of polyimide, and can be formed on commercial integrated circuit cores using a simple postprocessing sequence. Waveguide performance is compared to simulations and that of aluminum control devices underlayed with silicon dioxide. The lower resistance of the copper and improved substrate isolation obtained with the low-k polyimide dielectric provide a significant performance boost compared to the controls. Distributed model parameter are provided for frequencies up to 14 GHz to support circuit applications for theses devices.
Arrays of holes fabricated by electron-beam lithography combined with image reversal process using nickel pulse reversal plating
Authors: Awad Yousef , Lavallée Eric , Lau Kien Mun , Beauvais Jacques , Drouin Dominique , Cloutier Melanie , Turcotte David , Yang Pan , Kelkar Prasad
Published: May 2004

A critical issue in fabricating arrays of holes is to achieve high-aspect-ratio structures. Formation of ordered arrays of nanoholes in silicon nitride was investigated by the use of ultrathin hard etch mask formed by nickel pulse reversal plating to invert the tonality of a dry e-beam resist patterned by e-beam lithography. Ni plating was carried out using a commercial plating solution based on nickel sulfamate salt without organic additives. Reactive ion etching using SF6/CH4 was found to be very effective for pattern transfer to silicon nitride. Holes array of 100 nm diam, 270 nm period, and 400 nm depth was fabricated on a 5×5 mm2 area.
Oligo-p-phenylevinylene organic thin-film transistors with chemically modified dielectric surfaces
Authors: Gorjanc T. C. , Lévesque I. , D’iorio M.
Published: May 2004

In this article, we report on organic thin film transistors based on a modified oligo-p-phenylevinylene oligomer, 1,4-bis[4-(4-octylphenyl)styryl]-benzene (oligo-S) on chemically modified gate dielectrics. Previously, we have reported on oligo-S devices fabricated on unmodified SiO2 surfaces [T. C. Gorjanc, I. Lévesque, C. Py, and M. D’Iorio, Appl. Phys. Lett. (submitted)]. By using either hexamethyldisilazane (HMDS) or octadecyltrichlorosilane (OTS), both the hole mobility and on/off current ratios, Ion/off, have been increased. Maximum mobilities and on/off ratios of 0.14 cm2/V s with Ion/off>106 and 0.26 cm2/V s with Ion/off>107 were achieved with HMDS and OTS modified devices, respectively.
Characterization of GaAs1−xNx epitaxial layers by ion beam analysis
Authors: Wei P. , Chicoine M. , Gujrathi S. , Schiettekatte F. , Beaudry J.-N. , Masut R. A. , Desjardins P.
Published: May 2004

GaAs 1−x N x epitaxial layers grown on (001) GaAs substrates by metal organic vapor phase epitaxy, with x ranging from 0.01 to 0.036, were characterized by ion beam analysis. The layers thickness and quality were measured by Rutherford backscattering spectrometry (RBS) in channeling mode. The channeling results confirm that GaAs1−xNx epitaxial layers are of high crystalline quality, in agreement with high resolution x-ray diffraction and transmission electron microscopy analyses. For the sample with x=0.036, the results reveal a 0.7 at. % of misplaced (or highly locally strained) Ga or As atoms. More than 80% of nitrogen atoms in this layer occupy substitutional sites, as determined by the N14(α,p)17O nuclear reaction analysis (NRA). Furthermore, RBS analyses using a 5 MeV O3+ probe beam reveal measurable departures from III–V stoichiometry near the surface, which remains unexplained. Finally, the total content of nitrogen in the layers measured both by NRA and elastic recoil detection by time-of-flight are compared with the results obtained by secondary ion mass spectrometry.
Temperature distribution and heating in multiple emitter SiGe HBTs
Authors: McAlister S. P. , McKinnon W. R. , Kovacic S. J. , Lafontaine H.
Published: May 2004

High power bipolar transistors require the use of multiple emitters which, at high current densities, show significant self-heating and temperature increases. In this study we use a multiemitter SiGe HBT, with multiple emitter contacts, to examine the temperature distribution in the emitters in such a device. By biasing one emitter at a time and using the other base-emitter junctions as thermometers we have measured the temperature increase in different emitters and effectively the thermal coupling between the emitters. We compare the data with simulations for a simple thermal model.
Use of the focused ion beam to locate failure sites within electrically erasable read only memory microcircuits
Authors: Haythornthwaite Ray , Nxumalo Jochonia , Phaneuf Michael W.
Published: May 2004

Occasional electronically erasable programmable read only memory retention failures occurred after thousands of read write cycles. The physical sites of the failed cells were known, but not their location within the individual memory bits. Memory storage transistors have normal gate oxides and thinner tunneling oxide regions for programming. Focused ion beam (FIB) images are brighter when samples are grounded due to a passive voltage contrast mechanism. Thus, using precision etching and polishing to expose memory cells, transistors with leaky (grounded) gate-to-channel characteristics stand out. FIB examination successfully identified the failed transistors and additionally highlighted previously undetected leaky but still functional cells. FIB etching was next used to physically isolate the normal gate and tunneling oxide regions of failed transistors. This proved that the leakage only occurred within the tunnel oxide regions. Further analysis using precision focused ion beam/transmission electron microscopy cross sectioning and atomic force microscopy, identified local thickness reductions in the tunnel oxide which occurred during manufacture. Gate dielectric breakdown failures increase very rapidly with reduced thickness. Calculations showed that unacceptable gate oxide leakage would develop in a time comparable with the observed memory loss failures.
Excimer laser annealing of p-type perovskite thin films
Authors: Du X. , Dubowski J. J. , Post M. , Wang D. , Tunney J.
Published: May 2004

The ability of excimer laser irradiation to anneal and to crystallize amorphous films of the p-type perovskite SrFeyCo1−yO2.5+x (y=0.5) has been investigated. The films were prepared by the pulsed laser deposition technique on Si and sapphire substrates held at room temperature or 240 °C. Both film deposition and film annealing were carried out using a KrF excimer laser (λ=248 nm). Films of SrFe0.5Co0.5O2.5+x deposited at room temperature on sapphire substrates have been crystallized with 160 laser pulses at 50 mJ/cm2, while irradiation of a film deposited at room temperature on a Si substrate has resulted in its crystallization following 40 pulses at 100 mJ/cm2. Films deposited at 240 °C have been crystallized with 480 and 320 pulses at 50 and 60 mJ/cm2, respectively. The application of the excimer laser annealing technique permits the modification of film crystallinity after deposition, and because this can be achieved with a high degree of control of irradiation energy, this facilitates the integration of crystalline films of high melting temperature perovskites with substrates which have a low melting point.
Forced convection magnetoelectroplating for enhanced semiconductor metallization
Authors: Said R. A.
Published: May 2004

An efficient method that controls the rate and characteristics of copper electroplating for semiconductor metallization is demonstrated. Unlike typical electroplating processes, the proposed method operates with a forced flow of the electrolyte in the presence of an externally applied magnetic field, hence inducing a Lorentzian force that enhances the transport of depositing ions toward deposition regions. The magnitude of the induced force has been estimated to be at least one order of magnitude larger than other forces encountered in electroplating processes. A constructed experimental setup is described and used to demonstrate and investigate effects of induced Lorentzian forces on the rate and formation characteristics of deposited copper metallization. The obtained experimental results clearly demonstrate the technical and economical impact of the method in terms of providing a compact (low porosity) deposit with thin sidewalls and reducing the required deposition time by controlling the intensity of the applied magnetic field and the electrolyte flow velocity. The method holds promise for related metallization issues.
Fabrication of (NH4)2S passivated GaAs metal-insulator-semiconductor devices using low-frequency plasma-enhanced chemical vapor deposition
Authors: Jaouad A. , Aimez V. , Aktik Ç. , Bellatreche K. , Souifi A.
Published: May 2004

Metal-insulator-semiconductor (MIS) capacitors were fabricated on n-GaAs(100) substrate using (NH4)2S surface passivation and low-frequency plasma-enhanced chemical vapor deposited silicon nitride as gate insulators. The electrical properties of the fabricated MIS capacitors were analyzed using high-frequency capacitance–voltage and conductance–voltage measurements. The high concentration of hydrogen present during low-frequency plasma deposition of silicon nitride enhances the passivation of GaAs surface, leading to the unpinning of the Fermi level and to a good modulation of the surface potential by gate voltage. The electrical properties of the insulator-semiconductor interface are improved after annealing at 450 °C for 60 s, as a significant reduction of the interface fixed charges and of the interface states density is put into evidence. The minimum interface states density was found to be about 3×1011 cm−2 eV−1, as estimated by the Terman method.
Raman and transmission electron microscopy study of disordered silicon grown by molecular beam epitaxy
Authors: Tay L. , Lockwood D. J. , Baribeau J.-M. , Wu X. , Sproule G. I.
Published: May 2004

Silicon films were deposited by molecular beam epitaxy onto crystalline silicon (c-Si) and native oxide on c-Si (001) substrates at temperatures ranging from 98 to 572 °C. Raman spectroscopy of these films showed that both the short-range disorder and intermediate-range disorder decreases as the deposition temperature increases. The onset of a phase transition in the amorphous Si films can be effectively identified by the appearance of the polycrystalline and crystalline Si Raman bands, which allowed quantification of the crystalline volume fractions present. Both the transmission electron microscopy and Raman results confirmed that films grown on the amorphous substrates at temperatures less than 414 °C are entirely amorphous, but exhibit c-Si features at higher temperatures. Films grown on c-Si substrates exhibit a characteristic limiting thickness for epitaxy and the transformation of the resulting upper amorphous layer into crystalline form takes place at a much lower temperature (∼290 °C) than for the amorphous substrates.
Reset noise in active pixel image sensors
Authors: Lai Jackson , Nathan Arokia
Published: May 2004

In most image sensor pixel architectures, signal detection involves the reset of charge in a capacitive node. This operation gives rise to reset noise, and in particular, partition noise. In modern day transistors, with the shrinkage of device critical dimensions and increase of clock frequency, reset noise impacts many aspects of active pixel sensor operation. An additional spurious noise component has been observed from the reset noise model that is closely related to the switching operation, and is known as partition noise. Partition noise has been found to relate closely to the fall times of the applied reset pulse. However, existing noise models assume a constant charge density at the onset of transistor pinch-off, thus resulting in an underestimation of partition noise. This work investigates the influence of reset noise and other related noise generation on active pixel sensor performance.
Optical and electrical properties of sputtered vanadium oxide films
Authors: Gan F. Y. , Laou P.
Published: May 2004

Thin films of vanadium oxide with thickness of 0.1 to 0.2 μm were deposited on Si3N4/Si substrate by reactive rf magnetron sputtering. The oxide films were sputtered using a vanadium metal target in various ratios of Ar and O2 gases. The O2 content in the mixed atmosphere has a significant influence on the metal-insulator transition characteristics of the oxide films. The oxide film deposited in an Ar/O2 ratio of 98/2 exhibited high optical transmission of 70% to 80% in wavelength from 2 to 10 μm in insulating state while very low transmission of less than 5% in metallic state. Films prepared with higher O2 concentration showed no metal-insulator transition. In low O2 concentration, films showed characteristics of having both a broader transition region spanning over 30 °C and a lowered transition temperature which are similar to those of doped vanadium oxide films.
Numerical simulations of variable range hopping conductivity in deoxyguanosine deoxyribose nucleic acid nucleoside films
Authors: Singh Mahi R. , Tsang Chi-Ming
Published: May 2004

Numerical simulations are performed for conductivity due to the variable range hopping conduction in deoxyribose nucleic acid nucleotides (deoxyguanosine). Self-assembled deoxyguanosine (SAD) crystals are composed of H-bonded planar ribbons, which tend to stack and form solid-state fibers. These ribbons are connected to each other by a π–π bond and form crystalline and amorphous films. We consider that the carriers are localized in H bond and π–π bond sites and the hopping conduction is the result of many series of hops in these sites. The electric field and temperature dependent conductivity expressions are used to explain the conductivity experiments of SAD films. Good agreement between theory and experiment is found.
1.5 μm to 0.87 μm optical upconversion using wafer fusion technology
Authors: Luo H. , Ban D. , Liu H. C. , SpringThorpe A. J. , Wasilewski Z. R. , Buchanan M. , Glew R.
Published: May 2004

Wafer fusion is an important processing tool for heterogenous integration of different materials regardless of their lattice constants. It removes the limitation of conventional epitaxial growth techniques and introduces a design parameter for achieving high performance semiconductor devices. In this article, we propose and demonstrate a 1.5 μm to 0.87 μm optical upconversion device based on wafer fusion technology. The device consists of an In0.53Ga0.47As (InGaAs) p-i-n photodetector and an AlGaAs/GaAs light-emitting diode (LED) integrated with wafer fusion. Incoming 1.5 μm light is absorbed by the InGaAs photodetector and generates a photocurrent. The resultant photocurrent drives the GaAs LED, which emits radiation at 0.87 μm. An internal quantum efficiency of 20% and an external quantum efficiency of 0.27% was obtained at room temperature. The results show the potential of the upconversion device in near-infrared imaging applications.
Thickness measurements by quartz microbalance during thin-film growth by organic-molecular-beam deposition
Authors: Campione M. , Cartotti M. , Pinotti E. , Sassella A. , Borghesi A.
Published: May 2004

The problem of in situ monitoring the film thickness by quartz microbalance during vacuum deposition of organic-molecular semiconductors is addressed herein by setting a procedure for sensor calibration based on ex situ analysis of the deposited molecular film by atomic-force microscopy measurements. The procedure is applied to the growth of molecular-organic thin films on silica. Some physical parameters of the materials are deduced.
Hydrogenated-amorphous carbon nitride films formed from the dissociative excitation reaction of CH3CN with the microwave-discharge flow of Ar: Correlation of the [N]/([N]+[C]) ratio with the relative number densities of the CH(A2Δ) and CN(B2Σ+) states
Authors: Ito Haruhiko , Miki Hiroshi , Namiki Kei-ichi C. , Ito Noriko , Saitoh Hidetoshi , Suzuki Tsuneo , Yatsui Kiyoshi
Published: May 2004

High-resolution optical emission spectra of the CN(B2Σ+–X2Σ+) and CH(A2Δ–X2Π) transitions were observed in the dissociative excitation reaction of CH3CN with the microwave-discharge flow of Ar. The H2O molecules contained in the starting materials and/or adsorbed on the wall of the apparatus were removed by using P2O5 as a desiccant. The pressure of Ar, PAr, was in the range of 0.1–0.8 Torr. From the simulation analysis of the observed spectra, the ratio of the concentrations of the CH(A2Δ) and CN(B2Σ+) states, NCH(A)/NCN(B), was determined as 0.09–0.41. It was indicated that the CN(B2Σ+) state was formed via the ion–electron recombination as well as the energy transfer from the metastable state of Ar. Based on the correlation between the NCH(A)/NCN(B) and [N]/([N]+[C]) ratios reported in the system without desiccation [Jpn. J. Appl. Phys. 40, 332 (2001)], the [N]/([N]+[C]) ratio in the desiccated system was predicted to be ≈0.18. The hydrogenated-amorphous carbon nitride films prepared under the conditions of PAr=0.1, 0.4, 0.6, and 0.8 Torr were characterized by the Rutherford backscattering (RBS) analysis and the Fourier transform infrared (FTIR) spectroscopy. The observed [N]/([N]+[C]) ratios of the films were in the range of 0.17–0.21, being in good agreement with the above prediction. The structure of the films was independent of PAr. The observed correlation between the NCH(A)/NCN(B) and [N]/([N]+[C]) ratios can be rationalized by the consideration that the relative concentrations of the CH(A2Δ) and CN(B2Σ+) states and those of the precursor free radicals of the films are supposed to originate commonly to the relative concentrations of the active species of the discharge flow of Ar.
Effect of deposition temperature on thermal stability in high-density plasma chemical vapor deposition fluorine-doped silicon dioxide
Authors: Cheng Y. L. , Wang Y. L. , Chen H. W. , Lan J. L. , Liu C. P. , Wu S. A. , Wu Y. L. , Lo K. Y. , Feng M. S.
Published: May 2004

Thermal stability of fluorine-doped silicon dioxide films deposited by high-density plasma chemical vapor deposition as a function of deposition temperature were investigated in this study. Both thermal desorption spectrum and annealing test results show that SiOF films deposited above 400 °C have better thermal stability. Furnace annealing data indicate that non –Si–F– bonding fluorine does exist in low-deposition-temperature SiOF films. Furthermore, secondary-ion mass spectrometer results also reveal that the fluorine in SiOF films with a lower-deposition temperature is easily diffused out and turned into the underlayer, which results in less thermally stable SiOF films. Moreover, short-loop simulation results have been subsequently tested and it was concluded that the deposition temperature of the SiOF film is extremely important for thermal stability.
Two-dimensional a-Si:H based n-i-p sensor array
Authors: Chang J. H. , Vygranenko Yu. , Nathan A.
Published: May 2004

This article presents the design and fabrication process of a two-dimensional hydrogenated amorphous silicon (a-Si:H) n-i-p photodiode array, developed for low light level sensor applications. Utilization of the single a-Si:H switching diode for signal readout enables simpler device design and fabrication. Since the sensing and switching diodes are formed simultaneously by dry etching the a-Si:H layers deposited over the whole area, the number of masks required in lithography was reduced to six. A significant reduction of the leakage current has been achieved by tailoring defects at the i-p interface and optimizing the plasma processing conditions. Details of device fabrication along with results of the sensor array performance are presented.
Properties of C4F8 inductively coupled plasmas. I. Studies of Ar/c-C4F8 magnetically confined plasmas for etching of SiO2
Authors: Li Xi , Ling Li , Hua Xuefeng , Oehrlein Gottlieb S. , Wang Yicheng , Vasenkov Alex V. , Kushner Mark J.
Published: May 2004

Gas mixtures containing c-C4F8/Ar are commonly used for the plasma etching of dielectric materials such as SiO2. To quantify the dependence of fundamental plasma parameters of systems using these mixtures, inductively coupled plasmas in the pressure range of 6–20 mTorr, with and without magnetic confinement, were investigated. Measurements were also made in pure Ar and O2 to provide a comparison baseline. We found that use of magnetic confinement strongly influences the total ion flux, ion composition, and ion energy distributions in these discharges. Magnetic confinement increases the ion saturation current density, as measured with a Langmuir probe, most effectively at the lowest pressure examined here (6 mTorr). The increase in current density generally decreases as the pressure increases. Mass spectroscopic measurements of the ion flux showed that the CF+ ion flux dominates in C4F8 discharges, both with and without magnetic confinement. When Ar is added to C4F8 discharges with magnetic confinement, the CF2+ and CF3+ ion fluxes increase, and CF3+ becomes the dominant fluorocarbon ion. The ion energy distributions with and without magnetic field indicate that the plasma potential is generally lower for the magnetically confined discharges, although these trends are not monotonic when diluting C4F8 with Ar. Etching rates of SiO2, Si, and photoresist are higher with magnetic confinement, while etching yields are lower. The chemical compositions of passively deposited fluorocarbon films on Si, as measured by x-ray photoemission spectroscopy, differ little with and without magnetic confinement for varying C4F8/Ar gas compositions.
Properties of c-C4F8 inductively coupled plasmas. II. Plasma chemistry and reaction mechanism for modeling of Ar/c-C4F8/O2 discharges
Authors: Vasenkov Alex V. , Li Xi , Oehrlein Gottlieb S. , Kushner Mark J.
Published: May 2004

Gas mixtures containing Ar, c-C4F8, O2, and CO are often used for the plasma etching of silicon dioxide. Gas phase reaction mechanisms are required for first principles modeling of these systems to both provide insights to the plasma chemistry and to help optimize the process. In this article, results from computational and experimental investigations of the plasma chemistry of inductively coupled plasmas (ICPs) sustained in Ar, O2, Ar/c-C4F8 and O2/c-C4F8 gas mixtures with and without magnetic confinement are discussed. These results were used to develop a reaction mechanism for low-pressure and low-temperature plasmas sustained in mixtures initially consisting of any combination of Ar/c-C4F8/O2/CO. Predictions for ion saturation current and ion mass fractions were compared to experiments for validation. The consequences of charge exchange of fluorocarbon species with Ar+ and CO+ on the ratio of light to heavy fluorocarbon ion densities in Ar/c-C4F8/O2/CO plasmas are discussed. We found that the electron density and ion saturation current significantly increase with the addition of Ar to c-C4F8 but weakly depend on the addition of O2. The ratio of light to heavy fluorocarbon ion densities increases with power, especially for ICPs with magnetic confinement.
Effects of germanium content on sol-gel GeO2/γ-glycidoxypropyltrimethoxysilane hybrid planar waveguides prepared at low temperature
Authors: Que Wenxiu , Hu X.
Published: May 2004

The effects of germanium content on the structural and optical properties of GeO2/γ-glycidoxypropyltri-methoxysilane hybrid materials processed by the sol-gel technique are studied for optical waveguide applications. Glass planar waveguide thin films with thickness of more than 2.0 μm are prepared by a single-coating process and low-temperature heat treatment from this high germanium content hybrid material. Multimode light guiding is demonstrated in the hybrid planar waveguide films. The properties of the planar waveguide films such as refractive index, thickness, and transparency as well as structural characterization using the prism coupling technique, atomic force microscopy, thermal gravimetric analysis, UV-visible spectroscopy, and Fourier transform infrared spectroscopy, are systematically studied. These results indicate that the refractive index increases and film thickness decreases with an increase in GeO2 content, and thus dense, low absorption, and high transparency in the visible range waveguide films can be obtained at a low temperature. Waveguide propagation characteristics, at 632.8 and 1550 nm, are studied. The propagation loss of the hybrid waveguide film with a GeO2 content of 0.3 M is measured to be 1.2 dB/cm at the wavelength of 1550 nm.
In situ photoemission study of a Pr2O3 thin film on GaAs(111)
Authors: Wu J. X. , Wang Z. M. , Li S. , Ma M. S.
Published: May 2004

A Pr2O3 thin film, with a thickness of about 30 Å, was grown on GaAs(111) at room temperature by depositing Pr in an oxygen ambiance. In situ ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy were employed to investigate the Pr2O3/GaAs system as a function of annealing temperature. The valence-band offset of the Pr2O3/GaAs interface is 1.2±0.1 eV. After Pr2O3 deposition, some Ga atoms are bonded to Pr at the interface. Annealing leads to the decreases in the intensity of the Pr–Ga bond and facilitates the reaction between oxygen and semiconductor surface. Interfacial oxygen, observed after annealing at 430 K, is initially bonded to As and gradually transfers to Ga forming Ga2O3 for further annealing.
Study of AlGaInP multiquantum-well/double heterostructure light-emitting diodes with In-added GaP window layer regrown by antimony-based liquid phase epitaxy
Authors: Chang L. B. , Kuei P. Y. , Hsieh L. Z. , Chang L. Y. , Lin R. M.
Published: May 2004

The characteristics of surface-emitting AlGaInP multiquantum-well (MQW) and double heterostructure (DH) light-emitting diodes (LEDs) with a GaP window layer regrown by a GaP source melt with the addition of indium in the liquid phase epitaxy (LPE) system are studied. Using antimony in the source melt instead of gallium eliminates the phenomenon of melt back at the top layer of the LED during the LPE regrowth process. Meanwhile, adding In and Zn to the source melt significantly increases the GaP growth rate and effectively reduces residual melt during the regrowth process. Thus, the AlGaInP LED with a Zn-doped GaP window layer regrown by In being added, Sb-based LPE exhibits a lower turn-on voltage and higher light output power than that without the regrown GaP window layer. However, the emission peak wavelength of the MQW LED shifts a little after the LPE regrowth process. The DH LED does not shift. Thus, the DH structure is more suitable than the MQW structure for the LPE regrowth process of GaP.
Template stripping using cold welding
Authors: Blackstock Jason J. , Li Zhiyong , Jung Gun-young
Published: May 2004

A method for fabricating ultra-flat template-stripped (TS) metal surfaces on standard silicon/silicon-oxide wafers by means of gold cold-welding is presented, and cold-welded template-stripped (CWTS) platinum surfaces are demonstrated as an example. Due to the lack of any adhesives, the final TS metal “sandwiches” are fully compatible with all organic solvents, as well as ultra-high vacuum (UHV). The produced CWTS platinum surfaces are demonstrated to have the same surface properties—most importantly single-angstrom rms roughness—as previously studied TS platinum. The effectiveness of the cold-welding technique is shown to decrease as a function of time exposed to ambient laboratory conditions after removal from vacuum and prior to pressurized cold-welding. Contact angle measurements demonstrate this decrease to be due to a gradual increase in surface contamination of the evaporated gold layers prior to their being joined by cold-welding. The potential versatility and scalability of the CWTS fabrication process is briefly discussed.
Etching of high aspect ratio structures in Si using SF6/O2 plasma
Authors: Gomez Sergi , Jun Belen Rodolfo , Kiehlbauch Mark , Aydil Eray S.
Published: May 2004

We have investigated etching of deep (∼10 μm) submicron diameter holes with high aspect ratios (>10) using plasmas maintained in mixtures of SF6 and O2 gases. The etching experiments were conducted in a low-pressure (5–80 mTorr), high-density, inductively coupled plasma etching reactor with a planar coil. We have studied the effects of pressure, rf-bias voltage, and SF6-to-O2 gas ratio on the etch rate, selectivity, and feature profile using Si wafers patterned with 0.35–0.5 μm diameter holes in a SiO2 mask. Visualization of the profiles with scanning electron microscopy is used in conjunction with plasma diagnostics such as optical emission and mass spectroscopies to understand the key factors that control the anisotropy, selectivity, and etch rate. The F-to-ion flux ratio and F-to-O flux ratio are found to be the important plasma parameters that determine the etch rate and anisotropy. Increasing the SF6-to-O2 ratio in the feed gas increases the F-to-O ratio in the plasma. At high SF6-to-O2 ratio, the mask undercut is severe because sidewall passivation by O atoms cannot keep up with the chemical etching by F atoms. As the F-to-O ratio is decreased, effective sidewall passivation by O atoms results in nearly vertical sidewalls. A further reduction in the F-to-O ratio results in sidewalls that slope inwards toward the bottom of the feature.