bluuebunny/crossref_metadata_2025 huggingface dataset:
Aquatic insects play a minor role in dispersing salmon-derived nutrients into riparian forests in southwestern Alaska
Authors: Francis Tessa B , Schindler Daniel E , Moore Jonathan W
Published: November 2006

Recent research has highlighted the importance of nutrients derived from Pacific salmon (Oncorhynchus spp.) carcasses for coastal freshwater and riparian ecosystems. To investigate the role of emerging aquatic insects in dispersing salmon nutrients from spawning streams to riparian habitats, we quantified the emergence and return rates of mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera) on Pick Creek in southwestern Alaska and, using stable isotopes, estimated the associated flux of nutrients derived from sockeye salmon (Oncorhynchus nerka) to streamside forests. Between June and September of 2004, 7.6 mg·m–2 of salmon-derived nitrogen emerged from Pick Creek in the form of aquatic invertebrates, 6.7 mg·m–2 of which was transferred to the terrestrial ecosystem. Dispersal patterns on four area streams showed that the majority of stream-borne nutrients are deposited within 25 m of the stream. Aquatic insects represent a minor vector for salmon nutrients to terrestrial systems, dispersing less than 0.03% of total nitrogen imported to Pick Creek by spawning salmon. Nevertheless, emerging insects make available salmon-derived resources otherwise inaccessible to some terrestrial consumers.
Tributary control of physical heterogeneity and biological diversity at river confluences
Authors: Rice Stephen P , Ferguson Robert I , Hoey Trevor B
Published: November 2006

Investigations utilizing a one-dimensional sediment routing model demonstrate that moderate inputs of water and sediment at tributary junctions greatly increase physical heterogeneity in the recipient channel. Simulated physical heterogeneity is most sensitive to the ratios of tributary to mainstream bed load flux and bed load grain size and is less sensitive to relative discharge. Within the model, aggradation drives the processes that augment habitat variability, and in general, any aggradational confluence will be associated with elevated physical diversity. Model output reveals elevated physical diversity at two scales: between distinctive upstream and downstream zones separated by a confluence step and within each zone as a function of local environmental gradients. Total diversity increases as tributary sediment load and caliber increase relative to the mainstream. The ecological implications of the patterns and magnitude of tributary-induced physical heterogeneity are considered, and testable hypotheses are presented. Results highlight the need to accurately characterise patterns of sediment production, delivery, and routing in order to predict local tributary impacts and thereby understand patterns of habitat diversity and biodiversity at network scales.
A simplified procedure to estimate the shear strength envelope of unsaturated soils
Authors: Vilar Orencio Monje
Published: November 2006

Procedures that allow the prediction of some properties of unsaturated soils or the minimization of the number of tests needed to measure them are advantageous because the control of suction during testing is a formidable task that is time consuming and involves a great degree of expertise. A simplified procedure is proposed in this paper to estimate the shear strength of an unsaturated soil. The procedure is based on an empirical hyperbolic function that has been successfully used to fit experimental data. The function requires two input values, namely the shear strength of a saturated sample and the shear strength of an air-dried sample tested without the need for suction control. Samples tested under a controlled suction larger than the maximum suction expected in the problem can, alternatively, replace the air-dried samples. Both alternatives were tested against results for various soils reported in the literature. The good agreement between the estimates and the experimental data indicates that the proposed procedure is promising and reliable for estimating preliminary unsaturated shear strength parameters.Key words: unsaturated soil, suction, shear strength, prediction, laboratory tests.
Vacuum consolidation and its combination with embankment loading
Authors: Chai J -C , Carter J P , Hayashi S
Published: November 2006

A method is proposed for determining the optimum penetration depth of prefabricated vertical drains (PVDs) in cases where vacuum consolidation is combined with the use of PVDs in a clayey deposit with two-way drainage. The advantages of combining vacuum pressure with embankment loading are discussed in terms of reducing preloading-induced lateral displacement of the subsoil, increasing the effective surcharge loading, and reducing construction time in the case of road construction. A vacuum consolidation project conducted in Saga, Japan, is described, and the results from a fully instrumented test section are presented and analyzed using a two-dimensional finite element approach. The numerical simulations compare well with the field measurements. The validated numerical approach is then used to examine the response of soft subsoil subjected to vacuum consolidation. The results confirm the usefulness of the proposed method for determining the optimum penetration depth of PVDs and the advantages of combining vacuum pressure with embankment loading.Key words: vacuum consolidation, preloading, prefabricated vertical drain, FEM analysis, embankment.
Dynamic characteristics evaluation of Masjed Soleiman Dam using in situ dynamic tests
Authors: Jafari Mohammad Kazem , Davoodi Mohammad
Published: November 2006

The responses to forced vibrations, ambient vibrations, and large explosives were measured for Masjed Soleiman Dam, the highest embankment dam in Iran. Based on the results of these tests, the first 23 modal frequencies of the dam were measured and the related mode shapes for the first 16 modes were identified. A modal analysis of the dam body was also performed. The effects of reservoir water level variation, the rigidity and flexibility of the foundation and abutments and their depths and inertial properties, and the effect of material properties on the dynamic characteristics of the dam body were investigated, and the first eight modes of the dam body were identified. A comparison of the results of the numerical analysis with those from the tests indicates the best fit in lower modes occurs when the complete mass foundation is considered, whereas in higher modes the massless foundation model is a better fit.Key words: embankment dam, forced vibration test, ambient vibration test, explosion, modal properties.
Stochastic stability analysis of a test excavation involving spatially variable subsoil
Authors: Wang Yu-Jie , Chiasson Paul
Published: November 2006

A stochastic slope stability analysis method is proposed to investigate the short-term stability of unsupported excavation works in a soft clay deposit having spatially variable properties. Spatial variability of undrained shear strength is modelled by a stochastic model that is the sum of a trend component and a fluctuation component. The undrained shear strength trend, which is also spatially variable, is modelled by kriging or a random function. Slope stability analyses are performed on the stochastic soft clay model to investigate the contribution of spatial variability of undrained shear strength to a disagreement among high factors of safety computed from deterministic methods for slopes that have failed. Probabilities of failure as computed from the stochastic analyses give a better assessment of failure potential. Probability of failure values also correlate with time delay before failure. This phenomenon may be related to progressive failure or creep and to pore pressure dissipation with time.Key words: slope stability analysis, failure probability, spatial variability, stochastic modelling, geostatistics, vane tests, sensitive clay.
Détermination expérimentale d'une loi de tassement du ballast des voies ferrées soumises à un chargement latéral
Authors: Bodin-Bourgoin V , Tamagny P , Sab K , Gautier P-É
Published: November 2006

A one-third scale bench test representing a portion of railway track has permited to determine a lateral settlement law of the ballast. The experimentation uses a two-block sleeper with ballast and with elastomeric or wood representing the soil. A jack exerts the same signal as the train. Two similitudes have been tried with the bench test. The first one conserves the volumetric mass of the ballast and the stresses just under the blocks, and the second one conserves the volumetric mass of the ballast and the acceleration. Measured settlements are different in the two cases of similitude. From this it may be deduced that one phenomenon is responsible for the settlement: vibrations. We have identified two laws for the lateral settlement of the ballast: one for a few cycles and another one for a lot of cycles. The sum of these two laws can describe the whole behaviour of the ballast. These laws are in accordance with the measurements made on track.Key words: ballast, settlement, experimentation, reduced scale, railroad track.
NON-EQUIVALENT EMBEDDINGS INTO COMPLEX EUCLIDEAN SPACES
Authors: BORELL STEFAN , KUTZSCHEBAUCH FRANK
Published: November 2006

We study the number of equivalence classes of proper holomorphic embeddings of a Stein space X into ℂn. In this paper we prove that if the automorphism group of X is a Lie group and there exists a proper holomorphic embedding of X into ℂn, 0 < dim X < n, then for any k ≥ 0 there exist uncountably many non-equivalent proper holomorphic embeddings Φ: X × ℂk ↪ ℂn × ℂk. For k = 0 all embeddings will be proved to satisfy the additional property of ℂn\Φ(X) being (n - dim X)-Eisenman hyperbolic. As a corollary we conclude that there are uncountably many non-equivalent proper holomorphic embeddings of ℂk into ℂn whenever 0 < k < n.
EXPLICIT HORIZONTAL OPEN BOOKS ON SOME PLUMBINGS
Authors: ETGÜ TOLGA , OZBAGCI BURAK
Published: November 2006

We describe explicit open books on arbitrary plumbings of oriented circle bundles over closed oriented surfaces. We show that, for a non-positive plumbing, the open book we construct is horizontal and the corresponding compatible contact structure is also horizontal and Stein fillable. In particular, on some Seifert fibered 3-manifolds we describe open books which are horizontal with respect to their plumbing description. As another application we describe horizontal open books isomorphic to Milnor open books for some complex surface singularities. Moreover we give examples of tight contact 3-manifolds supported by planar open books. As a consequence, the Weinstein conjecture holds for these tight contact structures [1].
FINITE COVERS OF GROUPS BY COSETS OR SUBGROUPS
Authors: SUN ZHI-WEI
Published: November 2006

This paper deals with combinatorial aspects of finite covers of groups by cosets or subgroups. Let a1G1,…,akGkbe left cosets in a group G such that [Formula: see text] covers each element of G at least m times but none of its proper subsystems does. We show that if G is cyclic, or G is finite and G1,…,Gkare normal Hall subgroups of G, then the inequality [Formula: see text] holds, where [Formula: see text] if p1,…,prare distinct primes and α1,…,αrare nonnegative integers. When all the aiare the identity element of G and all the Giare subnormal in G, we prove that there is a composition series from [Formula: see text] to G whose factors are of prime orders. The paper also includes some other results and two challenging conjectures.
SPECTRAL ASYMMETRY, ZETA FUNCTIONS, AND THE NONCOMMUTATIVE RESIDUE
Authors: PONGE RAPHAËL
Published: November 2006

In this paper we study the spectral asymmetry of (possibly nonselfadjoint) elliptic ΨDO's in terms of the difference of zeta functions coming from different cuttings. Refining previous formulas of Wodzicki in the case of odd class elliptic ΨDO's, our main results have several consequence concerning the local independence with respect to the cutting, the regularity at integer points of eta functions and a geometric expression for the spectral asymmetry of Dirac operators which, in particular, yields a new spectral interpretation of the Einstein–Hilbert action in gravity.
Two-Dimensional Anisotropic Lattice Deformation Observed in a Commercially Available Strained-Si Wafer
Authors: Fukuda Kazunori , Tomita Naohiro , Hayashi Kazuki , Tsusaka Yoshiyuki , Kagoshima Yasushi , Matsui Junji , Ogura Atsushi
Published: November 2006

The average and local lattice structures of a strained-Si layer and a SiGe layer epitaxially grown on a [001]-oriented Si wafer are evaluated by means of high-resolution X-ray diffractometry using a usual X-ray beam and a highly parallel synchrotron X-ray microbeam. Lattices in the constant composition of the SiGe (CC) layer are greatly disarranged mainly due to an anisotropic lattice tilt feature with respect to the [110] and [110] directions in the surface plane. Although the crystallinity of the strained-Si layer was found to follow directly that of lattice tilt variations in the CC layer, the lattice parameter of the strained-Si layer still has the expected value.
Analysis of Deviation of Threshold Voltage from Hole Accumulation Model at High Excitation
Authors: Taguchi Hirohisa , Murakami Hiroaki , Oura Mashashi , Iida Tsutomu , Takanashi Yoshifumi
Published: November 2006

The energy state, concentration, and potential energy for both electrons and holes in the channel of InAlAs/InGaAs high electron mobility transistors (HEMTs) were studied using the theory based on the local density functional method. The numerical result shows that the potential profile changes from the triangle to the square well as the sheet concentration of holes accumulated in the source region ( p
s) increases above the sheet concentration of the two-dimensional electron gas (2DEG) because the same amount of electrons as holes was injected from the source to maintain the charge neutrality in the channel. As a result, the quasi-Fermi energy increased and the potential energy of electrons in the channel approached that of the square-well potential, the former led to an increase in the threshold voltage (V
TH). The overlap integral between the wavefunctions of an electron and a hole was estimated as a function of the channel thickness (L

z
) and was shown to decrease with increasing L

z
. A detailed theory concerning the relation between the V
TH shift and p
s was developed and compared with the experimental results. In this theory, the recombination of holes with 2DEG was taken into account, on the assumption that the dominant process was due to the non-radiative Auger recombination mechanism.
Screening-Driven Denuded Zones in Coalescence Growth
Authors: Shorlin Kelly , Zinke-Allmang Martin
Published: November 2006

We measure the width of denuded or empty zones surrounding clusters growing via coalescence during the annealing of Ga on GaAs(100), annealed above the decomposition temperature for 300 s. It is seen that the width of the zones increases with cluster size. We present arguments to show that these zones are not diffusion-driven but rather produced by a screening mechanism.
Characteristics of Germanium-on-Insulators Fabricated by Wafer Bonding and Hydrogen-Induced Layer Splitting
Authors: Chao Yu-Lin , Scholz Roland , Reiche Manfred , Gösele Ulrich , Woo Jason C. S.
Published: November 2006

There is considerable interest in germanium-on-insulator (GeOI) because of its advantages in terms of device performance and compatibility with silicon processing. In this paper, fabricating GeOI by hydrogen-induced layer splitting and wafer bonding is discussed. Hydrogen in germanium exists in molecular form and is prone to outdiffusion, resulting in a storage-time dependence of blistering. In contrast to the case of silicon, little effect of substrate doping on blistering is observed in germanium. Hydrogen implantation in germanium creates both {100}- and {111}-type microcracks. These two types of platelets are located in the same region for (111)-oriented wafers, but in different zones for (100) samples. This variation in distribution explains the smoother splitting of (111) surfaces than that of (100) surfaces. Hydrogen implantation also introduces a significant concentration of charged vacancies, which affect dopant diffusion in the transferred germanium film. Boron, with a negligible Fermi-level dependence, shows an identical diffusion profile to that of bulk germanium. In contrast, phosphorus diffusion is enhanced in the fabricated GeOI layers. These results also shed light on the understanding of dopant diffusion mechanisms in germanium.
Hall Mobility and Scattering Mechanism of Holes in Boron-Doped Homoepitaxial Chemical Vapor Deposition Diamond Thin Films
Authors: Tsukioka Kunio , Okushi Hideyo
Published: November 2006

The temperature dependence of the Hall mobility µH has been measured from 140 to 870 K for nine boron-doped homoepitaxial chemical vapor deposition (CVD) diamond thin films. The experimental µH data are compared with their theoretical µH values that are calculated by an iterative technique, assuming scattering by ionized impurities, acoustic deformation potential and nonpolar optical phonons. The donor concentration N
D, the acoustic deformation potential constant E
1 and the coupling constant of nonpolar optical phonons D
npo are used as fitting parameters. The experimental data of the hole concentration p are also analyzed by a fitting procedure. The acceptor concentration N
A, the donor concentration N
D, and the acceptor ionization energy E
A are used as fitting parameters. The fitting analyses of µH yielded an average D
npo=(1.2±0.2)×1012 eV/m. Considerable differences were observed between N
D values estimated from the fitting analyses of µH and those from the p-analyses. The average E
1 for the samples with little difference between the two types of N
D is 14.5 eV, which is in agreement with that of a natural diamond of high quality. The average E
A for the samples with a low or medium doping level is 0.365 eV, which is in good agreement with those in the literature. Some indications of the contribution of hopping conduction in the low-temperature range were observed.
Growth of Ge Thick Layers on Si(001) Substrates Using Reduced Pressure Chemical Vapor Deposition
Authors: Park Ji-Soo , Curtin Michael , Bai Jie , Carroll Mark , Lochtefeld Anthony
Published: November 2006

Growth of Ge thick layers with and without a low temperature Ge buffer has been investigated using reduced pressure chemical vapor deposition with emphasis on the evolution of surface morphology and its roughness. Growth at 400 °C exhibited a 200 s incubation period for which about 1 equivalent monolayer of Ge was deposited with a surface roughness of around 0.1 nm followed by an abrupt increase due to an island growth. Higher growth temperature resulted in shorter or no observed incubation period and led to rougher surface due to larger size of islands. Ge layers grown at 600 °C on at low temperature Ge buffer first grown at 400 °C exhibited around 1 nm surface roughness independent of the layer thickness, which is much lower than those at 400–600 °C without the low temperature buffer. The Ge thick layer with the low temperature Ge buffer had thinner defective interface of Ge/Si than that without the buffer.
Control of Compositional Profile and Crystallinity of CuIn1-xAlxS2 Thin Films
Authors: Bhandari Ramesh Kumar , Hashimoto Yoshio , Ito Kentaro
Published: November 2006

A CuIn1-x
Al
x
S2 thin film was prepared on a borosilicate glass substrate by sulfurizing a vacuum-evaporated metallic stack of Cu, In and Al precursor layers. Using a Cu-rich precursor, the alloy film with both good crystallinity and homogeneity was obtained. The lattice constants a and c of the film varied almost linearly with Al composition. The optical band gap of the film increased nonlinearly from 1.5 to 3.5 eV with Al composition. A high sulfurization temperature of up to 570 °C was also found effective in enhancing homogeneity. The use of a Cu-poor precursor gave rise to the film in which Al composition increased stepwise when scanned from the top surface to the bottom.
Reactive Ion Etching of Zinc Oxide Using Methane and Hydrogen
Authors: Guo Qixin , Uesugi Nozomu , Tanaka Tooru , Nishio Mitsuhiro , Ogawa Hiroshi
Published: November 2006

The reactive ion etching characteristics of ZnO have been investigated as functions of CH4/H2 gas composition, total gas pressure, and radio frequency (rf) plasma power. It was found that the etching rate of ZnO strongly depends on gas composition and gas pressure, suggesting that the etching of ZnO largely involves a process in which a volatile metalorganic zinc compound is formed. The etching rate of ZnO increased linearly with rf plasma power owing to its high bond-breaking efficiency, dc bias, and the degree of sputter desorption of etch products.
Finite Element Analysis of Dependence of Programming Characteristics of Phase-Change Memory on Material Properties of Chalcogenides
Authors: Yin You , Sone Hayato , Hosaka Sumio
Published: November 2006

The programming characteristics of a phase-change memory (PCM) cell with a chalcogenide layer contacted by a resistive heater are investigated by finite element modelling. As analyzed in this study, the characteristics are markedly affected by the resistivity of the phase-change chalcogenide material. A higher reset current of 1.6 mA is required for the as-fabricated virgin PCM than that of 1.3 mA for the cycled PCM because of the resistivity difference of the chalcogenides in the two cases. More importantly, a chalcogenide layer with a much higher resistivity than the resistive heater is necessarily adopted for a higher energy efficiency to markedly reduce reset current to 0.6 mA or even lower while slightly increasing reset voltage.
In Situ Observation of Initial Nucleation and Growth of Chemical Vapor Deposition of Copper by Surface Reflectivity Measurement
Authors: Momose Takeshi , Shimogaki Yukihiro
Published: November 2006

Initial nucleation and growth of Cu thin films on a Ta substrate via chemical vapor deposition (Cu-CVD) for ultra large scale integration (ULSI) interconnects is monitored in situ by irradiating the substrate surface with 635-nm-wavelength laser light and then measuring the change in reflected-light intensity. The effect of injection of water vapor during deposition on initial nucleation and growth is investigated by using X-ray photoelectron spectroscopy (XPS) to measure the surface chemical state of the Ta substrate. Results show that water-vapor injection during Cu-CVD enhances both the nucleation and growth of Cu by introducing adsorbed OH groups onto the substrate surface and yields a smooth, continuous surface morphology. The optimal time at which to inject water vapor before and/or during deposition is also determined using our in situ monitoring technique.
Preparation and Characterization of Amorphous Fluorinated Carbon Film Using Low-Global-Warming-Potential Gas, C4F6, by Plasma-Enhanced Chemical Vapor Deposition
Authors: Watanabe Hiroki , Shimogaki Yukihiro
Published: November 2006

Low-dielectric-constant amorphous fluorinated carbon (a-C:F) films were prepared using plasma-enhanced chemical vapor deposition (PECVD) from C4F6 (hexafluoro-1,3-butadiene) gas, which is expected to be a substitutional gas owing to its low global warming potential (GWP). Kinetic analysis revealed that the density of C4F6 in plasma has a proportional relation to film growth rate, which suggests that C4F6 is a main deposition precursor. From our previous study, this density affects the C–CF bond ratio in the film. In this study, we studied the effect of C–CF bond ratio on the thermal stability of the films by examining residual film thickness after vacuum annealing. A higher C–CF bond ratio resulted in a higher thermal stability, but the film became leaky after 300 °C annealing.
Silicon Nitride Two-Level-Temperature Passivation on InP/InGaAsP Light-Emitting Diodes
Authors: Kim Jaeho , Cha Jung-Ho , Kwon Young-Se
Published: November 2006

The use of silicon nitride with a two-level temperature technique is proposed for the passivation of InP-based devices. InGaAsP/InP light-emitting diodes (LEDs) were fabricated by this passivation technique. The reverse current was decreased by about two orders of magnitude, and light–current linearity at a low current was improved.
Optical Cavity Properties of Metal Mirror Microcavities with InAsSb Quantum Dots
Authors: Ueta Akio , Gozu Sin-ichiro , Akahane Kouichi , Yamamoto Naokatsu , Tsuchiya Masahiro , Ohtani Naoki
Published: November 2006

The optical properties of metal mirror microcavities with InAsSb quantum dots (QDs) were studied. Metal mirror microcavities, consisting of InAsSb QDs and GaAs, were fabricated using lift-off methods and mounted on a (001) Si substrate. The micro-photoluminescence (µ-PL) spectra of these structures showed a modulation of emission properties at a resonance wavelength determined by µ-reflection measurement. The temperature dependence of cavity resonance wavelength was also investigated. The slope of the cavity resonance at approximately room temperature (RT) was found to be about 0.075 nm/K.
Second Order Nonlinear Optical Properties of the Single Crystal of N-Benzyl 2-methyl-4-nitroaniline: Anomalous Enhancement of the d333 Component and Its Possible Origin
Authors: Fujiwara Masazumi , Yanagi Kazuhiro , Maruyama Minoru , Sugisaki Mitsuru , Kuroyanagi Kazuyoshi , Takahashi Hironori , Aoshima Shin-ichiro , Tsuchiya Yutaka , Gall Andrew , Hashimoto Hideki
Published: November 2006

A single crystal of N-benzyl 2-methyl-4-nitroaniline (BNA) whose dimensions were 8×10 mm (diameter × length) was grown using a vertical Bridgman method with sufficient optical transparency for spectroscopic use. Polarized reflection spectra of the crystal were measured in order to determine its linear optical parameters (refractive indices and extinction coefficients). The relative magnitudes of the d-tensor components of the crystal were determined to be d
333=(17±9)×d
322, d
322>d
311, d
311∼0 from polarization dependencies of the second harmonic generation. These results are in disagreement with previously reported theoretical studies, in which the effects of intermolecular interactions were completely neglected. Here, we have included these intermolecular interactions in the calculations assuming the presence of supra-molecular clusters. We conclude that the anomalous enhancement of d
333 is due to the interactions along the direction of the hydrogen bonds in the crystal and the resonance effect.
Copper Doped Methylene Blue Sensitized Poly(vinyl alcohol)–Acrylamide Films for Stable Diffraction Efficiency
Authors: John Beena Mary , Joseph Rani , Sreekumar K. , Kartha C. Sudha
Published: November 2006

Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride concentration was optimized as 3.18×10-3 mol/l for a dye concentration of 6.2×10-4 mol/l. The gratings recorded on the optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.
Fabrication and Characterization of Thick Zinc Methacrylate/Phenanthrenequinone Codoped Poly(methyl methacrylate) Photopolymers for Volume Holographic Recording
Authors: Hsiao Yi-Nan , Whang Wha-Tzong , Lin Shiuan Huei , Hsu Ken Y.
Published: November 2006

We fabricate and characterize a novel holographic recording photopolymer named ZnMA/PQ co-doped PMMA, a poly(methyl methacrylate) (PMMA) doped with two materials: zinc methacrylate (ZnMA) and 9,10-phenanthrenequinone (PQ) molecules. A technique for fabricating thick samples of 2 mm thick is described. The optical and holographic characteristics of the samples are experimentally investigated. The results show that by adding ZnMA, the material M/# and sensitivity for holographic recording have been improved.
Material Properties and Plasma Display Panel Discharging Characteristics Depending on MgO Evaporation Rate
Authors: Kwon Sang Jik , Kim Yong Jae , Lee Seong Eui
Published: November 2006

MgO thin film is most widely used as a protecting layer in ac Plasma Display Panel. The film is deposited using electron beam evaporation. The effects of the evaporation rate of MgO film deposited using an electron beam on the MgO properties and the discharge characteristics of the plasma display panel (PDP) were investigated. The evaporation rate was changed from 3 to 15 Å/s at a substrate temperature of 300 °C. MgO properties such as crystal orientation, surface roughness, contact angle, and film structure were inspected using X-ray diffraction (XRD), analysis atomic force microscopy (AFM), drop shape analysis, and secondary electron microscopy (SEM). The MgO properties were shown to be strongly dependent on the evaporation rate. We also studied the relation between MgO properties and PDP discharging characteristics. The minimum firing voltage and maximum luminous efficiency were obtained at an evaporation rate of 5 Å/s. In the MgO film deposited at 5 Å/s, the (200) orientation was most intensive and surface roughness was minimum.
Improvement of Signal-to-Noise Ratio of Terahertz Electromagnetic Waves by Bias Field Modulation of Photoconductive Antenna
Authors: Yano Ryuzi , Hattori Toshiaki , Shinojima Hiroyuki
Published: November 2006

Inversion of the direction of the DC bias field applied to a photoconductive (PC) antenna produces a terahertz wave with its sign changed. We succeeded in increasing the signal amplitudes of the terahertz electromagnetic waves emitted from a pc antenna by a factor of 2 by modulating the polarization of the bias field applied to the PC antenna in the lock-in detection scheme. By this method, we were able to increase the signal-to-noise ratio of the terahertz electromagnetic waves by a factor of 2.
Direct Wafer Bonding of GaInAsP/InP Membrane Structure on Silicon-on-Insulator Substrate
Authors: Maruyama Takeo , Okumura Tadashi , Arai Shigehisa
Published: November 2006

Wafer bonding technology was investigated to integrate active photonic devices on a silicon-on-insulator (SOI) substrate for highly compact photonic integrated circuits. A single-quantum-well (SQW) GaInAsP/InP membrane structure bonded onto an SOI substrate was successfully obtained by a direct bonding with thermal annealing at 300–450 °C in H2 atmosphere. The photoluminescence intensity of the SQW membrane structure did not degrade after this direct bonding and its spectral shape did not change. This wafer bonding technique can be applied to the realization of direct optical coupling using SOI passive waveguides from a membrane's active region.
Solid-State Dye-Sensitized Solar Cells Using Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] as a Hole-Transporting Material
Authors: Li Jian , Osasa Takahiro , Hirayama Yasuko , Sano Takeshi , Wakisaka Kenichiro , Matsumura Michio
Published: November 2006

Solid-state dye-sensitized solar cells (DSSCs), consisting of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEHPPV) as a hole-transporting material, an indium tin oxide (ITO) electrode, and a titanium dioxide (TiO2) electrode, were studied with respect to the factors affecting their properties. The morphology of TiO2 electrodes, which was controlled by changing preparation conditions, affected the performance of solid-state DSSCs, and cells with a TiO2 electrode having a smooth surface showed better properties. The carrier transportation between the TiO2 layer and the MEHPPV layer was one of the most important factors that determined the overall efficiency of the solar cells. This carrier transportation process was improved by the addition of an interlayer consisting of potassium iodide (KI) and iodine (I2). In addition to improving the carrier transportation, this KI/I2 blend interlayer also improved the pore filling of the solid-state DSSC. By controlling these parameters, a solid-state DSSC was obtained, with a short-circuit current density of about 1.51 mA/cm2, an open circuit voltage of about 0.65 V, a fill factor of about 0.5, and an energy conversion efficiency of about 0.51%.
Properties of Single Domain Pb(Zn1/3Nb2/3)O3–(6–7)%PbTiO3 Single Crystal
Authors: Jin J. , Rajan K. K. , Lim L. C.
Published: November 2006

A complete set of elastic, piezoelectric and dielectric properties of a [111]-poled single-domain Pb(Zn1/3Nb2/3)O3–(6–7)%PbTiO3, or PZN–(6–7)%PT, single crystal have been determined by means of a combination of resonance and quasi-static measurement techniques. The present work shows that the d
15 value determined by the resonance measurement technique using a length-shear sample and that measured by quasi-static measurement technique are comparable, suggesting that the length-shear resonance behavior is valid for a crystal of 3 m symmetry provided that the length-to-thickness ratio is sufficiently large, for example, >10. The single-domain PZN–(6–7)%PT crystal exhibits very high d
15 and d
22 values, namely, 6000 and -1280 pC/N, respectively.
Method of Estimating Dielectric Properties of Dielectric Layers in Low-Temperature-Cofired Ceramic Devices
Authors: Jao Jui-Chu , Lin Pang
Published: November 2006

A method of estimating the dielectric constant (ε) of dielectric layers in low-temperature-cofired ceramic (LTCC) devices was developed. A band-pass filter (BPF) circuit was designed such that its second harmonic frequency (SHF) strongly depended on the ε of the relevant capacitor built in the BPF. The ε–SHF correlation was established by model simulation. The design of the BPF was realized with various dielectric layers, and the measured SHF was used to determine the ε values of the capacitors from the ε–SHF relationship. These ε values were found to be consistent with those of the sintered pellets, prepared with the same dielectrics and process as BPFs. The ε values of the dielectric layers in other LTCC devices were estimated by this method, in which the BPFs made of the same dielectric layers were fired as dummy samples along with the devices.
First-principles Study of Microscopic Origin of Piezoelectric Effect in α-Quartz
Authors: Zhang Tao , Zheng Yanqing , Chen Jianjun , Song Lixin , Shi Erwei
Published: November 2006

Using a first-principles approach based on the density-functional theory, the piezoelectric properties of α-quartz are calculated. The computation is based on local-density approximation (LDA) and the density-functional perturbation theory (DFPT), directly yielding appropriate piezoelectric stress coefficients. The calculated results are in agreement with the experimental results. The internal piezoelectric coefficients e
11,int and e
14,int is decomposed into each ion and SiO4 tetrehedron in the primitive cell, respectively. In ionic decomposition, the ions most responsible for piezoelectric effects are Si1
4+, O2
2-, and O3
2-. In tetrahedral decomposition, the tetrahedra centered by Si2
4+ and Si3
4+ exhibit a higher piezoelectric coefficient than the tetrahedron centered by Si1
4+. The reason for these phenomena has been interpreted to be the difference between the geometric orientations of these two kinds of tetrahedra in α-quartz with respect to strain tensors.
Optically Induced Conversion of Ge Centers in Quartz
Authors: Hattori Wataru , Katsura Makoto , Yamanaka Chihiro
Published: November 2006

An electron spin resonance (ESR) study of natural single crystalline quartz was performed to clarify the effect of ultraviolet rays (UV) exposure on electron traps at germanium impurities. ESR spectra of artificially γ-irradiated single crystalline samples from two different natural sites mainly showed a common Ge center, [Ge(C)e-/Li+], which is an electron trapped center at a Si-substituting Ge ion with a charge compensator of Li+. UV light exposure using a low-pressure mercury lamp converted [Ge(C)e-/Li+] into a different paramagnetic center. The observed ESR parameters of this center did not coincide with those of other known centers. This signal gradually decayed at room temperature and simultaneously produced a third center, Ge E2', which is a germanium dangling bond neighboring an oxygen vacancy with the form ≡Si–H •Ge≡. The experimental results indicated a two-step conversion of Ge centers, which was caused by UV exposure and aging. The total spin concentration was kept constant throughout the experiments.
Dielectric and Piezoelectric Properties of [Bi0.5(Na1-xLix)0.5]TiO3 Lead-Free Ceramics
Authors: Lu Wenzhong , Fan Guifen , Wang Xiaohong , Liang Fei
Published: November 2006

The structural, dielectric and piezoelectric properties of [Bi0.5(Na1-x
Li
x
)0.5]TiO3 ceramics were studied in the compositional range of x=0–0.30. The samples were fabricated by a conventional sintering technique. X-ray diffraction results showed that the ceramics possessed a pure perovskite structure with a rhombohedral symmetry in the range of x=0–0.2. The scanning electron microscope (SEM) micrographs indicated that the sintering temperature of the ceramics decreased with an increase in the amount x of Li+. The optimum piezoelectric constant d
33 and planar electromechanical coupling factor k
p were 110 pC/N and 0.18 at x=0.15, respectively.
Horizontal Switching of Double-Cellgap Liquid Crystal Cell for Superachromatic Transflective Display
Authors: Lee Gak Seok , Kim Jae Chang , Yoon Tae-Hoon
Published: November 2006

We propose optical configurations of a double-cellgap liquid crystal cell for transflective displays that show achromatic properties. The reflective part is designed in a wide-band quarter-wave structure to achieve a dispersion-free dark state. For the transmissive part, a compensation method is introduced to achieve a superachromatic dark state. To achieve a bright state, horizontal switching as well as vertical switching can be used.
Partially Erasable Photoalignment Layer Formed in Dye-Doped Liquid Crystal Films
Authors: Fuh Andy Ying-Guey , Cheng Ko-Ting
Published: November 2006

In this study, we propose biphotonic (i.e., two-color pumping beams) erasure for partially erasing a photoalignment layer on an indium–tin-oxide (ITO)-coated glass slide resulting from adsorbed azo dye molecules doped in a liquid crystal film. The results indicate that neither of the two-color pumping beams erases the adsorbed dye layer. However, ∼75% erasure is obtained when both two-color beams are applied simultaneously for a suitable pumping period, at suitable values of intensity ratio and relative polarization. Finally, the biphotonic erasure of a twisted nematic (TN) grating fabricated using a dye-doped liquid crystal film is demonstrated.
Energy Dissipation Mechanisms in Lead Zirconate Titanate Thin Film Transduced Micro Cantilevers
Authors: Lu Jian , Ikehara Tsuyoshi , Zhang Yi , Maeda Ryutaro , Mihara Takashi
Published: November 2006

A high quality factor (Q-factor) is most desirable for resonant mass sensors because their sensitivity greatly depends on the detectable frequency shift after mass adsorption. The authors fabricated lead zirconate titanate (PZT) thin film transduced micro cantilevers and studied the energy dissipation mechanisms to better understand the essential aspects affecting the Q-factor. It was found that energy dissipation induced by the multi-layered device structure and the PZT thin film was noteworthy even under atmospheric pressure conditions. The effects of the PZT film on the energy dissipation became dominant under reduced pressure. Accordingly, the Q-factors of cantilevers without PZT film became larger than those with PZT film when pressure was reduced into the molecular flow region. The single-layered SiO2 cantilever exhibited the largest intrinsic Q-factor. The electro-mechanical conversion in the PZT film and the thermoelastic damping caused by the property difference between each layer contributed significantly to the energy dissipation.
Investigation on Electrical Properties of Low-Dielectric-Constant Fluorinated Amorphous Carbon Film
Authors: Oh Teresa
Published: November 2006

The bonding structure of fluorinated amorphous carbon film was changed with the electron density of the carbon which depends on the effect of C–H bond elongation and condensation. The leakage current in the fluorinated amorphous carbon film with an electron rich group was caused by the electron tunneling effect, depending on the Schottky effect, but in the film with an electron-deficient group, the leakage current decreased markedly because of the large barrier height attributed to the increase in electron affinity. The barrier height of the film with the electron-deficient group was calculated using the Poole–Frenkel model, and the barrier height increased with the increase in annealing temperature of the substrate.
Height Measurement Using High-Precision Atomic Force Microscope Scanner Combined with Laser Interferometers
Authors: Murayama Ken , Gonda Satoshi , Kinoshita K. , Koyanagi Hajime , Terasawa Tsuneo , Hosaka Sumio
Published: November 2006

We have developed a high-precision atomic force microscope (AFM) for measuring fine pattern structures for semiconductor process evaluation. Three-axis ultrahigh-resolution displacement sensors using modularized laser interferometers were built into an AFM scanner combined with piezoactuators, elastic parallel-plate structures and an on-axis optical microscope. A newly designed symmetrical layout of the optical path of homodyne interferometers and a digital signal processor (DSP) enabled highly stable measurements of the mechanical displacements of the tip of an AFM scanner. As a result of their ultrafine positioning capabilities, a resolution of the displacement sensors of 0.05 nm was achieved. The periodic error of laser waves was compensated by employing DSP-based processing. Thus, a wide linearity range from 0.1 to 1000 nm was demonstrated and a one-sigma repeatability of 0.25 nm was obtained by measuring reference samples of 50 and 1000 nm step heights. Finally, micro-roughness with a 0.1 nm height, a GaAs atomic step with a 0.3 nm height, patterns with high aspect ratios, and resist patterns were clearly observed using an interferometer displacement signal.
Quantitative Analysis of Polarization Phenomena in CdTe Radiation Detectors
Authors: Toyama Hiroyuki , Higa Akira , Yamazato Masaaki , Maehama Takehiro , Ohno Ryoichi , Toguchi Minoru
Published: November 2006

Polarization phenomena in a Schottky-type CdTe radiation detector were studied. We evaluated the distribution of electric field in a biased CdTe detector by measuring the progressive change of Schottky barrier lowering with time. The parameters of deep acceptors such as detrapping time, concentration, and the depth of the energy level were quantitatively evaluated. In the case of applying the conventional model of charge accumulation, the obtained result shows that the CdTe bulk is never undepleted. We modified the charge accumulation model by taking account of the occupation state of the deep acceptor level. When a modified model is applied, the time that the depletion width in the bulk begins to diminish closely fits the time that the photopeak position begins to shift in radiation measurements. In this paper, we present a distribution of electric field during biasing and a simple method for the evaluation of the parameters of deep acceptors in CdTe bulk.
Fabrication of Boron-Mixed Carbon Stripper and Target Backing Foils for High-Power Accelerators
Authors: Sugai Isao , Takeda Yasuhiro , Oyaizu Michihiro , Kawakami Hirokane , Hattori Toshiyuki , Kawasaki Katsunori
Published: November 2006

We have succeeded, for the first time, in making long-lifetime boron-mixed carbon stripper foils for high-power accelerators. Foils of 10–1000 µg/cm2 thickness were made by controlled DC arc discharge. The lifetime of the foils was tested using 3.2 MeV Ne+ DC beams of 2.5 µA, by which a significant amount of energy was deposited in the foils. The maximum lifetime was found to be extremely long, 110 and 450 times longer than those of diamond and commercially available carbon foils, respectively. The foils turned out to be free from any shrinkage, and showed an extremely low thickness reduction rate, even at a high temperature of 1800 K.
Harmonic Analysis of Leakage Current in Salt-Fog Aging Test for Polymeric Material
Authors: Zhu Yong , Haji Kenichi , Otsubo Masahisa , Honda Chikahisa
Published: November 2006

In this paper, we describe the waveform of the leakage current that flows along the surface of a silicone rubber (SR) specimen exposed to a salt fog. In this study, a plate-shaped SR specimen energized with an ac voltage was set in a fog chamber, and its surface state was observed using a high-speed video camera. Simultaneously, the waveform of the leakage current with elapsed time was measured. In accordance with frequency analysis, it was confirmed that the ratio of the third-harmonic component in the leakage current waveform increased with elapsed time. Information on the frequency characteristics of the leakage current was extracted and correlated with the insulation surface condition. The harmonic component of the leakage current can be considered as a diagnostic index for the electrical characteristics and insulation state of polymer insulators under wet conditions.
Radio Frequency Plasma in Water
Authors: Maehara Tsunehiro , Toyota Hiromichi , Kuramoto Makoto , Iwamae Atsushi , Tadokoro Atsushi , Mukasa Shinobu , Yamashita Hiroshi , Kawashima Ayato , Nomura Shinfuku
Published: November 2006

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000–4500 K. Spectroscopic measurements show that hydrogen and oxygen are excited in the plasma. The plasma is also obtained in tap water or NaCl solution with a high conductivity. In the solution, sodium spectral lines are observed. Colored water containing methylene blue is exposed to the plasma. The absorbence spectra of the colored water before and after exposure to the plasma suggest the decomposition of organic matter due to chemical reactions involving active species, such as OH-radicals.
Characteristics of Large Area Inductively Coupled Plasma Using a Multiple Linear Antennas with U-Type Parallel Connection for Flat Panel Display Processing
Authors: Kim Kyong Nam , Min Kyung Seok , Yeom Geun Young
Published: November 2006

In this study, the characteristics of large area internal linear inductively coupled plasma (ICP) sources of 1,020×920 mm2 (substrate area is 880×660 mm2) were investigated using a multiple linear antennas with U-type parallel connection. Using the multiple linear antennas with U-type parallel connection, a high plasma density of 2×1011 cm-3 and a high power transfer efficiency of about 88% could be obtained at 5 kW of RF power and with 20 mTorr Ar. A low plasma potential of less than 26 V and a low electron temperature of 2.6–3.2 eV could be also obtained. The measured plasma uniformity on the substrate size of fourth generation (880×660 mm2) was about 4%, therefore, it is believed that the multiple linear antennas with U-type parallel connection can be successfully applicable to the large area flat panel display processing.