bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Roles for Human Translation Factor eIF3 in Initiation of Protein Synthesis
Authors: Siridechadilok Bunpote , Fraser Christopher S. , Hall Richard J. , Doudna Jennifer A. , Nogales Eva
Published: December 2005

Protein synthesis in mammalian cells requires initiation factor eIF3, a ∼750-kilodalton complex that controls assembly of 40
S
ribosomal subunits on messenger RNAs (mRNAs) bearing either a 5′-cap or an internal ribosome entry site (IRES). Cryo–electron microscopy reconstructions show that eIF3, a five-lobed particle, interacts with the hepatitis C virus (HCV) IRES RNA and the 5′-cap binding complex eIF4F via the same domain. Detailed modeling of eIF3 and eIF4F onto the 40
S
ribosomal subunit reveals that eIF3 uses eIF4F or the HCV IRES in structurally similar ways to position the mRNA strand near the exit site of 40
S
, promoting initiation complex assembly.
Postseismic Mantle Relaxation in the Central Nevada Seismic Belt
Authors: Gourmelen Noel , Amelung Falk
Published: December 2005

Holocene acceleration of deformation and postseismic relaxation are two hypotheses to explain the present-day deformation in the Central Nevada Seismic Belt (CNSB). Discriminating between these two mechanisms is critical for understanding the dynamics and seismic potential of the Basin and Range province. Interferometric synthetic aperture radar detected a broad area of uplift (2 to 3 millimeters per year) that can be explained by postseismic mantle relaxation after a sequence of large crustal earthquakes from 1915 to 1954. The results lead to a broad agreement between geologic and geodetic strain indicators and support a model of a rigid Basin and Range between the CNSB and the Wasatch fault.
Chromosome Alignment and Segregation Regulated by Ubiquitination of Survivin
Authors: Vong Queenie P. , Cao Kan , Li Hoi Y. , Iglesias Pablo A. , Zheng Yixian
Published: December 2005

Proper chromosome segregation requires the attachment of sister kinetochores to microtubules from opposite spindle poles to form bi-oriented chromosomes on the metaphase spindle. The chromosome passenger complex containing Survivin and the kinase Aurora B regulates this process from the centromeres. We report that a de-ubiquitinating enzyme, hFAM, regulates chromosome alignment and segregation by controlling both the dynamic association of Survivin with centromeres and the proper targeting of Survivin and Aurora B to centromeres. Survivin is ubiquitinated in mitosis through both Lys
48
and Lys
63
ubiquitin linkages. Lys
63
de-ubiquitination mediated by hFAM is required for the dissociation of Survivin from centromeres, whereas Lys
63
ubiquitination mediated by the ubiquitin binding protein Ufd1 is required for the association of Survivin with centromeres. Thus, ubiquitinaton regulates dynamic protein-protein interactions and chromosome segregation independently of protein degradation.
Electrowetting in Carbon Nanotubes
Authors: Chen J. Y. , Kutana A. , Collier C. P. , Giapis K. P.
Published: December 2005

We demonstrate reversible wetting and filling of open single-wall carbon nanotubes with mercury by means of electrocapillary pressure originating from the application of a potential across an individual nanotube in contact with a mercury drop. Wetting improves the conductance in both metallic and semiconducting nanotube probes by decreasing contact resistance and forming a mercury nanowire inside the nanotube. Molecular dynamics simulations corroborate the electrocapillarity-driven filling process and provide estimates for the imbibition speed and electrocapillary pressure.
Radar Soundings of the Ionosphere of Mars
Authors: Gurnett D. A. , Kirchner D. L. , Huff R. L. , Morgan D. D. , Persoon A. M. , Averkamp T. F. , Duru F. , Nielsen E. , Safaeinili A. , Plaut J. J. , Picardi G.
Published: December 2005

We report the first radar soundings of the ionosphere of Mars with the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument on board the orbiting Mars Express spacecraft. Several types of ionospheric echoes are observed, ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes. The oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of Mars. Echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength.
Characterization of the Detachable Rho-Dependent Transcription Terminator of the
fimE
Gene in
Escherichia coli
K-12
Authors: Hinde Paul , Deighan Padraig , Dorman Charles J.
Published: December 2005

The
fim
genetic switch in the chromosome of
Escherichia coli
K-12 is an invertible DNA element that harbors the promoter for transcription of the downstream
fim
structural genes and a transcription terminator that acts on the upstream
fimE
regulatory gene. Switches oriented appropriately for structural gene transcription also allow
fimE
mRNA to read through, whereas those in the opposite orientation terminate the
fimE
message. We show here that termination is Rho dependent and is suppressed in a
rho
mutant or by bicyclomycin treatment when
fimE
mRNA is expressed by the
fimE
gene, either from a multicopy recombinant plasmid or in its native chromosomal location. Two
cis-
acting elements within the central portion of the 314-bp invertible DNA switch were identified as contributors to Rho-dependent termination and dissected. These
fim
sequence elements show similarities to well-characterized Rho utilization (
rut
) sites and consist of a
boxA
motif and a C-rich and G-poor region of approximately 40 bp. Deletion of the
boxA
motif alone had only a subtle negative effect on Rho function. However, when this element was deleted in combination with the C-rich, G-poor region, Rho function was considerably decreased. Altering the C-to-G ratio in favor of G in this portion of the switch also strongly attenuated transcription termination. The implications of the existence of a
fimE
-specific Rho-dependent terminator within the invertible switch are discussed in the context of the
fim
regulatory circuit.
luxS-Dependent Gene Regulation inEscherichia coliK-12 Revealed by Genomic Expression Profiling
Authors: Wang Liang , Li Jun , March John C. , Valdes James J. , Bentley William E.
Published: December 2005

The bacterial quorum-sensing autoinducer 2 (AI-2) has received intense interest because the gene for its synthase,luxS, is common among a large number of bacterial species. We have identifiedluxS-controlled genes inEscherichia coliunder two different growth conditions using DNA microarrays. Twenty-three genes were affected byluxSdeletion in the presence of glucose, and 63 genes were influenced byluxSdeletion in the absence of glucose. Minimal overlap among these gene sets suggests the role ofluxSis condition dependent. Under the latter condition, themetEgene, thelsrACDBFGoperon, and the flanking genes of thelsroperon (lsrR,lsrK,tam, andyneE) were among the most significantly induced genes byluxS. TheE. coli lsroperon includes an additional gene,tam, encoding anS-adenosyl-l-methionine-dependent methyltransferase. Also,lsrRandlsrKbelong to the same operon,lsrRK, which is positively regulated by the cyclic AMP receptor protein and negatively regulated by LsrR.lsrKis additionally transcribed by a promoter betweenlsrRandlsrK. Deletion ofluxSwas also shown to affect genes involved in methionine biosynthesis, methyl transfer reactions, iron uptake, and utilization of carbon. It was surprising, however, that so few genes were affected byluxSdeletion in thisE. coliK-12 strain under these conditions. Most of the highly induced genes are related to AI-2 production and transport. These data are consistent with the function of LuxS as an important metabolic enzyme but appear not to support the role of AI-2 as a true signal molecule forE. coliW3110 under the investigated conditions.
Simultaneous Deficiency of both MurA and p60 Proteins Generates a Rough Phenotype inListeria monocytogenes
Authors: Machata Silke , Hain Torsten , Rohde Manfred , Chakraborty Trinad
Published: December 2005

We examined eight spontaneously occurring rough mutants ofListeria monocytogenesfor their ability to express two previously reported autolysins, p60 and MurA. All mutants lack MurA expression and show strongly reduced levels of extracellular p60. One rough strain harbors a variant of the p60 protein with a partially truncated catalytic domain. In seven cases there were shifts in the localization of p60 to the membrane fraction. Mutations within thesecA2gene, encoding an auxiliary protein secretion system paralog, were previously shown to be involved in the smooth-rough phenotypic variation seen withListeriastrains. An isogenic ΔsecA2EGDe deletion strain displays a strong pleiotropic reduction of p60 and MurA, in addition to a large number of secreted and surface proteins. However, we observed no apparent SecA2 dysfunction in several of the investigated strains as determined by direct sequencing of thesecA2gene and complementation of the ΔsecA2mutant with the respective allele cloned from the rough mutant. To determine the gene products required for the smooth-rough transition, we created mutants lacking the individualiapandmurAgenes as well as a ΔiapΔmurAdouble mutant. The double mutant displays a rough phenotype and exhibits many of the properties seen with the ΔsecA2mutant. Our results implicate p60 and MurA as important determinants in controlling the cell shape ofL. monocytogenes. We also identified homologous MurA and SecA2 proteins in otherListeriaspecies. The muramidase in two species,L. innocuaandL. welshimeri, shows activity similar to that of the MurA protein inL. monocytogenes.
Only One of the Five CheY Homologs in
Vibrio cholerae
Directly Switches Flagellar Rotation
Authors: Hyakutake Akihiro , Homma Michio , Austin Melissa J. , Boin Markus A. , Häse Claudia C. , Kawagishi Ikuro
Published: December 2005

Vibrio cholerae
has three sets of chemotaxis (Che) proteins, including three histidine kinases (CheA) and four response regulators (CheY) that are encoded by three
che
gene clusters. We deleted the
cheY
genes individually or in combination and found that only the
cheY3
deletion impaired chemotaxis, reinforcing the previous conclusion that
che
cluster II is involved in chemotaxis. However, this does not exclude the involvement of the other clusters in chemotaxis. In other bacteria, phospho-CheY binds directly to the flagellar motor to modulate its rotation, and CheY overexpression, even without CheA, causes extremely biased swimming behavior. We reasoned that a
V. cholerae
CheY homolog, if it directly controls flagellar rotation, should also induce extreme swimming behavior when overproduced. This was the case for CheY3 (
che
cluster II). However, no other CheY homolog, including the putative CheY (CheY0) protein encoded outside the
che
clusters, affected swimming, demonstrating that these CheY homologs cannot act directly on the flagellar motor. CheY4 very slightly enhanced the spreading of an
Escherichia coli cheZ
mutant in semisolid agar, raising the possibility that it can affect chemotaxis by removing a phosphoryl group from CheY3. We also found that
V. cholerae
CheY3 and
E. coli
CheY are only partially exchangeable. Mutagenic analyses suggested that this may come from coevolution of the interacting pair of proteins, CheY and the motor protein FliM. Taken together, it is likely that the principal roles of
che
clusters I and III as well as
cheY0
are to control functions other than chemotaxis.
l-Canavanine Made byMedicago sativaInterferes with Quorum Sensing inSinorhizobium meliloti
Authors: Keshavan Neela D. , Chowdhary Puneet K. , Haines Donovan C. , González Juan E.
Published: December 2005

Sinorhizobium melilotiis a gram-negative soil bacterium, capable of establishing a nitrogen-fixing symbiosis with its legume host, alfalfa (Medicago sativa). Quorum sensing plays a crucial role in this symbiosis, where it influences the nodulation process and the synthesis of the symbiotically important exopolysaccharide II (EPS II).S. melilotihas three quorum-sensing systems (Sin, Tra, and Mel) that useN-acyl homoserine lactones as their quorum-sensing signal molecule. Increasing evidence indicates that certain eukaryotic hosts involved in symbiotic or pathogenic relationships with gram-negative bacteria produce quorum-sensing-interfering (QSI) compounds that can cross-communicate with the bacterial quorum-sensing system. Our studies of alfalfa seed exudates suggested the presence of multiple signal molecules capable of interfering with quorum-sensing-regulated gene expression in different bacterial strains. In this work, we choose one of these QSI molecules (SWI) for further characterization. SWI inhibited violacein production, a phenotype that is regulated by quorum sensing inChromobacterium violaceum. In addition, this signal molecule also inhibits the expression of theS. meliloti expgenes, responsible for the production of EPS II, a quorum-sensing-regulated phenotype. We identified this molecule asl-canavanine, an arginine analog, produced in large quantities by alfalfa and other legumes.
Whole-Genome Transcriptional Analysis of Heavy Metal Stresses in
Caulobacter crescentus
Authors: Hu Ping , Brodie Eoin L. , Suzuki Yohey , McAdams Harley H. , Andersen Gary L.
Published: December 2005

The bacterium
Caulobacter crescentus
and related stalk bacterial species are known for their distinctive ability to live in low-nutrient environments, a characteristic of most heavy metal-contaminated sites.
Caulobacter crescentus
is a model organism for studying cell cycle regulation with well-developed genetics. We have identified the pathways responding to heavy-metal toxicity in
C. crescentus
to provide insights for the possible application of
Caulobacter
to environmental restoration. We exposed
C. crescentus
cells to four heavy metals (chromium, cadmium, selenium, and uranium) and analyzed genome-wide transcriptional activities postexposure using an Affymetrix GeneChip microarray.
C. crescentus
showed surprisingly high tolerance to uranium, a possible mechanism for which may be the formation of extracellular calcium-uranium-phosphate precipitates. The principal response to these metals was protection against oxidative stress (up-regulation of manganese-dependent superoxide dismutase sodA). Glutathione
S
-transferase, thioredoxin, glutaredoxins, and DNA repair enzymes responded most strongly to cadmium and chromate. The cadmium and chromium stress response also focused on reducing the intracellular metal concentration, with multiple efflux pumps employed to remove cadmium, while a sulfate transporter was down-regulated to reduce nonspecific uptake of chromium. Membrane proteins were also up-regulated in response to most of the metals tested. A two-component signal transduction system involved in the uranium response was identified. Several differentially regulated transcripts from regions previously not known to encode proteins were identified, demonstrating the advantage of evaluating the transcriptome by using whole-genome microarrays.
Stereoselective Esterase from
Pseudomonas putida
IFO12996 Reveals α/β Hydrolase Folds for
d
-β-Acetylthioisobutyric Acid Synthesis
Authors: Elmi Fatemeh , Lee Hsin-Tai , Huang Jen-Yeng , Hsieh Yin-Cheng , Wang Yu-Ling , Chen Yu-Jen , Shaw Shyh-Yu , Chen Chun-Jung
Published: December 2005

Esterase (EST) from
Pseudomonas putida
IFO12996 catalyzes the stereoselective hydrolysis of methyl
dl
-β-acetylthioisobutyrate (
dl
-MATI) to produce
d
-β-acetylthioisobutyric acid (DAT), serving as a key intermediate for the synthesis of angiotensin-converting enzyme inhibitors. The EST gene was cloned and expressed in
Escherichia coli
; the recombinant protein is a non-disulfide-linked homotrimer with a monomer molecular weight of 33,000 in both solution and crystalline states, indicating that these ESTs function as trimers. EST hydrolyzed
dl
-MATI to produce DAT with a degree of conversion of 49.5% and an enantiomeric excess value of 97.2% at an optimum pH of about 8 to 10 and an optimum temperature of about 57 to 67°C. The crystal structure of EST has been determined by X-ray diffraction to a resolution of 1.6 Å, confirming that EST is a member of the α/β hydrolase fold superfamily of enzymes and includes a catalytic triad of Ser97, Asp227, and His256. The active site is located approximately in the middle of the molecule at the end of a pocket ∼12 Å deep. EST can hydrolyze the methyl ester group without affecting the acetylthiol ester moiety in
dl
-MATI. The examination of substrate specificity of EST toward other linear esters revealed that the enzyme showed specific activity toward methyl esters and that it recognized the configuration at C-2.
Regulation by
hetC
of Genes Required for Heterocyst Differentiation and Cell Division in
Anabaena
sp. Strain PCC 7120
Authors: Wang Yu , Xu Xudong
Published: December 2005

Unlike those of the wild-type strain, proheterocysts of the
Anabaena
sp. strain PCC 7120
hetC
strain keep dividing.
ftsZ
, the most critical cell division gene, is up-regulated in
hetC
proheterocysts. Heterocyst differentiation genes
hglD
,
hglE
,
patB
,
nifB
, and
xisA
are no longer expressed in the
hetC
mutant.
hetC
also regulates the expression of
patA
, a pattern formation gene.
The Genome of Bacteriophage K1F, a T7-Like Phage That Has Acquired the Ability To Replicate on K1 Strains of
Escherichia coli
Authors: Scholl Dean , Merril Carl
Published: December 2005

Bacteriophage K1F specifically infects
Escherichia coli
strains that produce the K1 polysaccharide capsule. Like several other K1 capsule-specific phages, K1F encodes an endo-neuraminidase (endosialidase) that is part of the tail structure which allows the phage to recognize and degrade the polysaccharide capsule. The complete nucleotide sequence of the K1F genome reveals that it is closely related to bacteriophage T7 in both genome organization and sequence similarity. The most striking difference between the two phages is that K1F encodes the endosialidase in the analogous position to the T7 tail fiber gene. This is in contrast with bacteriophage K1-5, another K1-specific phage, which encodes a very similar endosialidase which is part of a tail gene “module” at the end of the phage genome. It appears that diverse phages have acquired endosialidase genes by horizontal gene transfer and that these genes or gene products have adapted to different genome and virion architectures.
Activation of a Development-Specific Gene,
dofA
, by FruA, an Essential Transcription Factor for Development of
Myxococcus xanthus
Authors: Ueki Toshiyuki , Inouye Sumiko
Published: December 2005

FruA is an essential transcription factor for
Myxococcus xanthus
development. The expression of
tps
and
dofA
genes is
fruA
dependent. In this study, we show by gel shift and footprint assays with the C-terminal DNA-binding domain of FruA and by a
lacZ
fusion assay that FruA may directly activate
dofA
expression during development.
HOMOGENIZATION OF A NONLOCAL ELASTOHYDRODYNAMIC LUBRICATION PROBLEM: A NEW FREE BOUNDARY MODEL
Authors: BAYADA G. , MARTIN S. , VÁZQUEZ C.
Published: December 2005

This paper deals with the homogenization of a lubrication problem, using two-scale convergence techniques. We study in particular the Reynolds–Hertz model, which takes into account elastohydrodynamic deformations of the upper surface, when highly oscillating roughness effects occur. The difficulty arises when considering cavitation free boundary phenomena, leading to highly nonlinear and nonlocal problems.
FORMULATING BUSINESS STRATEGIES FROM A STAKEHOLDER'S PERSPECTIVE: KOREAN HEALTHCARE IT BUSINESS CASES
Authors: LIM GEUNCHAN , LEE HEESEOK , KIM TAEHUN
Published: December 2005

The management of competing stakeholders has emerged as an important topic for formulating business strategies. This is especially the case in the complicated business environment like the healthcare IT (Information Technology) industries. This paper proposes a methodology to formulate business strategies based on stakeholders' demands. Our methodology begins with the understanding of stakeholders' demands. This understanding is particularly useful for businesses with conflicting stakeholders. Our methodology consists of four phases: current business analysis, strategy development, strategy evaluation, and strategy implementation. Power, legitimacy, urgency, interdependence, cooperation, and conflict are used as stakeholders related variables. Strategic alternatives are derived on the basis of stakeholders' demands. Resolution, replacement, integration, reaggregation, and balance guidelines are employed for this derivation. Strategic alternatives are then evaluated according to a business social performance index. In order to demonstrate the practical usefulness of our methodology, three business cases for the Korean healthcare IT industry are illustrated. The case results imply that our methodology is useful for strategy formulation, especially in the case of competing business stakeholders.
SPATIAL DECISION SUPPORT SYSTEM FOR ZINC CONTENT IN SOIL
Authors: SHARMA DINESH K. , SHARMA RAKESH K. , GHOSH DEBASIS
Published: December 2005

Spatial decision support systems can enhance the efficiency and effectiveness of decision-making about the zinc status of soil. In this paper, we present an interactive spatial decision support system (ISDSS), identifying the zinc deficiency zone(s), thus enabling the decision-maker to take appropriate measures for correcting zinc deficiencies in soil. The system can display a contour map of the required Block, District, or State of West Bengal along with information about the quantity of zinc to be added to the soil, if the available zinc is not sufficient for a particular crop. The ISDSS consists of a non-spatial database management system and corresponding spatial database, a model base management system, and a user interface. The ISDSS is developed using the scripting language EASI (Engineering Analysis and Scientific Interface) under the GIS software tool, SPANS (Spatial Analysis System). The system runs under the Microsoft Windows operating system.
YINYANG BIPOLAR LATTICES AND L-SETS FOR BIPOLAR KNOWLEDGE FUSION, VISUALIZATION, AND DECISION
Authors: ZHANG WEN-RAN
Published: December 2005

YinYang bipolar sets, bipolar lattice, bipolar L-crisp sets, and Bipolar L-fuzzy sets are presented for bipolar information/knowledge fusion, visualization, and decision. First, a bipolar lattice B is defined as a 4-tuple (B, ⊕, &, ⊗) in which every pair of elements has a bipolar lub (blub ⊕), a bipolar glb (bglb &), and a cross-pole glb (cglb ⊗). A bipolar L-set (crisp or fuzzy) B = (B-, B+) in X to a bipolar lattice BL is defined as a bipolar equilibrium function or mapping B : X ⇒ BL. A strict bipolar lattice B is defined as a 7-tuple (B, ≡, ⊕, ⊗, &, -, ¬, ⇒) that delegates a class of isomorphic bounded and complemented bipolar lattices. A refined and generalized 9-set axiomatization is presented on a class of strict bipolar lattices. The notions of bipolar L-relations and equilibrium relations are introduced as bipolar L-sets. Remarkably, YinYang bipolar L-sets lead to a bipolar universal modus ponens (BUMP) which presents a unified non-linear bipolar generalization of classical modus ponens and builds a bridge from a linear, static, and closed world to a non-linear, dynamic, and open world of equilibria, quasi-equilibria, and non-equilibria for bipolar information/knowledge fusion, visualization, and decision. A number of potential applications are outlined.
Weak Temperature Dependence of Non-Coulomb Scattering Component of HfAlOx-Limited Inversion Layer Mobility in n+-Polysilicon/HfAlOx/SiO2 N-Channel Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Yasuda Naoki , Hisamatsu Hirokazu , Ota Hiroyuki , Mizubayashi Wataru , Toriumi Akira
Published: December 2005

We propose a new extraction method for mobility limited by high-k dielectrics, and discuss the scattering mechanism for halfnium aluminate (HfAlO
x
) in the strong inversion region. In our method, mobility degradation properties are evaluated as a function of interfacial SiO2 thickness. The temperature dependence of the mobility in the strong inversion region is analyzed with the expression 1/µ=1/µRexp
(-2k
F
T
int)+1/µSiO2/Si, where µ is the measured mobility, µR is the prefactor mobility limited by a high-k dielectric, k
F is the Fermi wavenumber of the channel carriers, T
int is the thickness of the interfacial SiO2 layer, and µSiO2/Si is the mobility for n+poly-Si/SiO2 n-channel metal–oxide–semiconductor field-effect transistors (MOSFETs). This analysis method is applied to n+poly-Si/HfAlO
x
[Hf/(Hf+Al)=60 at. %]/SiO2/p-Si n-channel MOSFETs. It is found that the mobility limited by the HfAlO
x
film, µR, decreases with a temperature increase in the range of 77–297 K. This temperature dependence indicates the predominance of non-Coulomb scattering for the mobility limited by HfAlO
x
in the strong inversion region. The mobility due to the non-Coulomb scattering shows a weak temperature dependence that is explainable by surface optical phonons (i.e., those appearing at the Si-surface channel region due to the longitudinal-optical (LO) modes of HfAlO
x
) with the corresponding transverse-optical (TO) phonon energy in the range of 10–20 meV.
Molecular Dynamics Study of Fast Diffusion of Cu in Silicon
Authors: Shirai Koun , Michikita Toshiyuki , Katayama-Yoshida Hiroshi
Published: December 2005

A distinguishing property of copper impurities in silicon is their very fast diffusivity, which is undesirable in silicon device processes. This paper is the first attempt to simulate the fast diffusion of Cu by first-principles calculations. It is shown that, even near room temperature, the amplitude of Cu vibrations is very large; this is a consequence of the fact that the local mode of Cu has very low frequencies. At T>1000 K, the simulations demonstrate clear migration between adjacent cells. The diffusion path is from an interstitial T site to the next T site through an H site. The Arrhenius plot of the calculated diffusion constants agrees with the experimental data on the intrinsic diffusion of Cu, which are currently most reliable data available.
Investigation of the Divided Deposition Method of TiN Thin Films for Metal–Insulator–Metal Capacitor Applications
Authors: Okudaira Tomonori , Hayashi Takeshi , Sakashita Shinsuke , Tsuchimoto Junichi , Kobayashi Kiyoteru , Yoneda Masahiro
Published: December 2005

TiCl4-based chemical vapor deposition (CVD) of TiN films was studied for the application of the top electrode of TiN/Ta2O5/TiN metal–insulator–metal (MIM) capacitors in embedded dynamic random-access memories (eDRAMs). In order to achieve a low level of capacitor leakage current, TiN-CVD at low deposition temperatures of 450°C or less was effective. At such low deposition temperatures, the resistivity of the TiN films increased rapidly as the film thickness decreased. On the other hand, the density of the anomalous growth substances on the TiN film surfaces was higher for the thicker TiN films. We clarified that these two problems were simultaneously unsolvable by means of the usual TiCl4-based TiN-CVD method. In order to avoid the appearance of these phenomena, we applied the divided TiN deposition method to the top electrode formation of the MIM capacitors. This method consists of several repetitions of the deposition step and a subsequent NH3 annealing step. The low film resistivity (∼1800 µΩ cm) and the low capacitor leakage current were achieved without the anomalous growth by using the divided deposition method at 350°C. It is expected to be a promising method for the top electrode formation of MIM capacitor structures of the eDRAMs.
RF Diamond Transistors: Current Status and Future Prospects
Authors: Umezawa Hitoshi , Hirama Kazuyuki , Arai Tatsuya , Hata Hideo , Takayanagi Hidenori , Koshiba Toru , Yohara Keiichiro , Mejima Soichi , Satoh Mitsuya , Song Kwang-Soup , Kawarada Hiroshi
Published: December 2005

RF diamond transistors have been developed on a hydrogen-terminated surface conductive layer. f
T and f
max of 23 and 25 GHz, respectively, have been achieved in a diamond MISFET with a 0.2 µm gate length. Utilizing de-embedding and small-signal equivalent circuit analysis, parasitic components are extracted. The intrinsic f
T and f
max of the 0.2-µm-gate diamond MISFET are estimated to be 26 and 36 GHz, respectively. In this report, some of the challenging steps in device fabrication processes such as the development of a low-resistivity ohmic layer, a high-quality gate insulator and acceptor density control technology, toward high-power and high-frequency diamond transistors with high reliability, are introduced.
Characteristics of Copper Indium Diselenide Thin Films Formed on Flexible Substrates by Electrodeposition
Authors: Huang Chien-Jung , Su Yan-Kuin , Chen Kan-Lin , Lai M. Y.
Published: December 2005

A CuInSe2 (CIS) thin film was electrodeposited (ED) on a Au-coated plastic substrate using an aqueous acidic solution containing 1 mM CuCl2, 5 mM InCl3, 1 mM SeO2 and 1 M triethanolamine (TEA) adjusted to pH 1.65. With this new technology, the quality of ED-CIS thin film can be suitably improved with 0.1 M Na citrate to control the growth solution. The composition of the CIS thin film was “Cu:In:Se=25.6%:25.0%:49.4%” prepared at -1.5 V (SCE) after annealing at 150°C for 1 h in a N2 atmosphere. Neither the CIS thin film nor the plastic substrate was found to have cracked after the heat treatment. The ED-CIS thin-film quality demonstrates its potential in the fabrication of a flexible CIS-based solar cell.
Surface Treatment of Si Using Hydrogen-Plasma to Improve Optoelectronic Property of ZnO on (111)Si
Authors: Yamauchi Satoshi , Kawasaki Hirokatsu , Hariu Takashi
Published: December 2005

Hydrogen-terminated (111)Si was treated by Zn-contained hydrogen plasma at low temperatures ranging from 200–500°C prior to ZnO growth at 400°C by plasma-assisted epitaxy using oxygen gas plasma excited by rf-power at 13.56 MHz. Spot pattern corresponding to c-ZnO surface was observed by reflection high-energy electron diffraction from the layer grown on the Si treated by Zn-contained hydrogen gas plasma at 500°C, in contrast to the ring-pattern from the layers on the Si non-treated or treated at lower temperatures. Optoelectronic property was significantly improved by the surface treatment at 500°C, because the photoluminescence spectra of the ZnO layers grown on the Si treated at 500°C showed strong and sharp bandedge emissions due to bound exciton accompanied with free-exciton emission without significant deep-level emissions at 10 K, while the weak bandedge emissions and green emission due to deep level can be observed from the layers on the substrates non-treated or treated below 400°C in the plasma.
Highly Reliable Flash Cell for Low Power Application
Authors: Park Young Sam , Choi Yong Seok , Kang Sung Taeg , Han Jeong Uk , Yoon Seung Beom , Chung Chil Hee , Yoon Sung Min , Ryu Sang Ouk , Yu Byoung Gon
Published: December 2005

The electrical properties of a split-gate-type flash cell are investigated and optimized by junction engineering to obtain a high reliability. Phosphorus implantation is conducted to form a cell source junction, and the following three different anneal conditions change voltage coupling ratio between the source and the floating gate. As the ratio increases, it is observed that program characteristic is improved and endurance property is degraded, which matches well with simulation result. Therefore, cells in the pure N2 group are considered to be optimized cells. Optimized cells guarantee 105 cycle endurance, and show excellent program disturbance and bake retention properties.
Realization of Low CoSi2/p+-Silicon Contact Resistance with Low Junction Leakage Current and Junction Capacitance Using Laser Thermal Process
Authors: Yamamoto Tomonari , Kubo Tomohiro , Wang Yun , Talwar Somit , Kase Masataka
Published: December 2005

In this paper we report source–drain engineering for the realization of low contact resistance between CoSi2 and p+ Si with low junction leakage current and low junction capacitance using laser thermal processing (LTP) and the optimization of ion implantation conditions. We first demonstrate the impact of pre-amorphization on the reduction of the contact resistivity of a CoSi2/p+ deep source–drain (deep-SD) interface using laser thermal processing (LTP). A highly activated dopant profile at the CoSi2/deep-SD interface is required to reduce the contact resistivity there. Dopant profile can be finely controlled by implanting heavy ions to preamorphize a region to the desired depth and then using an appropriate laser power to selectively melt the amorphous Si, which has a melting temperature lower than that of single-crystal Si. We can thus form a highly activated boxlike dopant profile suitable for a deep-SD by using LTP and relatively deep preamorphization. Then, we discuss how to suppress the leakage current and the capacitance of the junctions. The larger junction capacitance and junction leakage current due to the abrupt deep-SD profile can be greatly reduced by combining LTP with lower-dose, higher-energy implantation and RTA prior to preamorphization (predoping and pre-RTA) to form a graded deep-SD profile beyond the abrupt deep-SD profile and overwhelm the channel doping profile, resulting in a wide depletion layer.
Hydrogen Ion Drift into Underlying Oxides by RF Bias during High-Density Plasma Chemical Vapor Deposition
Authors: Yamaguchi Tadashi , Sawada Mahito , Asai Koyu , Kobayashi Kiyoteru , Yoneda Masahiro
Published: December 2005

High-density plasma chemical vapor deposition (HDP-CVD) is a deposition method of current interest for the gap-filling process of the intermetal dielectric (IMD) in semiconductor circuits. We first demonstrated that hydrogen ions drift into underlying thermal oxides during HDP-CVD with a SiH4–O2–Ar system, and that they degrade the reliability of gate oxides. The characteristics of the oxides were investigated using secondary ion mass spectroscopy (SIMS), thermal desorption spectroscopy (TDS), and capacitance–voltage (C–V) measurements of metal–oxide–semiconductor (MOS) capacitors. The hydrogen ions that are dissociated from SiH4 in plasma penetrate into the HDP-CVD oxides, and some of the hydrogen ions in the HDP-CVD oxides drift into the underlying thermal oxides by rf bias. The drifting hydrogen creates two chemical bonding states and generates hole trap sites in the underlying thermal oxides.
Fundamental Properties of Organic Low-k Dielectrics Usable in the Cu Damascene Process
Authors: Nomura Yutaka , Ota Fumihiko , Kurino Hiroyuki , Koyanagi Mitsumasa
Published: December 2005

The material parameters for organic low-k dielectrics usable in the damascene process were studied using two different types of polymers with similar low dielectric constants, namely, the PQ-600 thermoplastic polymer and the SiLK thermosetting polymer. The resistibility of these polymers in the damascene process was investigated through hard-mask (SiO2) deposition, etching and chemical mechanical polishing (CMP) processes using scanning probe microscopy (SPM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and a modified edge liftoff test (m-ELT). For the PQ-600 film, damage was observed in the deposition process and dissolution of the film occurred during chemical cleaning in the etching process. On the other hand, the SiLK film was combinable with the Cu damascene process and usable as an interlayer dielectric (ILD) in one-level Cu wiring. A high glass transition temperature (T
g) and chemical resistance resulting from the thermosetting structure are considered to be the essential properties required for the desired organic low-k dielectrics. In eddition, the electrical properies of the SiLK film were investigated using a one-level test element group (TEG) formed through a single Cu damascene process. The dielectric constant of the SiLK film extracted from the Cu damascene TEG compared with that of bulk SiO2 was reduced by 24%. The leakage current measured at 1 MV/cm between the adjoining Cu lines at the TEG pattern with a hard mask was 9.7×10-10 A/cm2, and dielectric breakdown occurred at 5.5 MV/cm.
Effects of Single-Crystalline GaN Target on GaN Thin Films in Pulsed Laser Deposition Process
Authors: Nagata Takahiro , Yoo Young-Zo , Ahmet Parhat , Chikyow Toyohiro
Published: December 2005

The effects of a GaN single-crystal target (SC-GaN) of laser-ablated GaN thin films on sapphire were investigated. GaN thin films were grown on a single-crystalline c-plane sapphire substrate using the SC-GaN. Unlike the usual growth behavior in laser ablation of a sintered ceramics GaN target (CR-GaN), the rocking curves of the obtained GaN films were superimposed patterns composed of sharp and broad components. The interface between the GaN film and sapphire substrate was atomically flat and sharp. To investigate the effects of the target on the plume of a pulsed laser deposition process in detail, the plume was analyzed by Langmuir probe methods and optical emission spectroscopy (OES). The Langmuir probe results showed that the electron temperature for the plume of an SC-GaN was nearly one third of that of a CR-GaN, although the ion density in the plume of the SC-GaN was found to be greater than the ion density in that of the CR-GaN. OES data showed a significant fraction of the oxygen species in the plume of the CR-GaN. These are thought to be the primary cause of damage and/or impurity to growing films in the plume of the CR-GaN.
Antistatic Technique for Suppressing Charging in Focused Ion Beam Systems Using Microprobing and Ion-Beam-Assisted Deposition
Authors: Komoda Hirotaka , Nakatani Ikuko , Watanabe Heiji , Yasutake Kiyoshi
Published: December 2005

We have developed a novel antistatic technique for suppressing focused ion beam (FIB)-induced charging in a combined system of an FIB and a scanning electron microscope. Microprobing and FIB-assisted carbon deposition are utilized to make a current path through which FIB-induced positive charges flow to ground. The effects of our method on charge neutralization capability were investigated by measuring parameter shifts of n-channel metal–oxide–semiconductor transistors. The results showed that our method prevents parameter shifts of transistors even for high-current (nanoampere-order) FIB irradiation. We also evaluated the upper-limit resistance of the current path formed by FIB-assisted carbon deposition to prevent charging induced by a given FIB current.
Simulation of InGaN Quantum Well Laser Performance Using Quaternary InAlGaN Alloy as Electronic Blocking Layer
Authors: Chang Yi-An , Luo Chuan-Yu , Kuo Hao-Chung , Kuo Yen-Kuang , Lin Chia-Feng , Wang Shing-Chung
Published: December 2005

Laser performance of an InGaN edge-emitting laser using a quaternary InAlGaN electronic blocking layer is investigated. Varying the aluminum (Al) composition in InAlGaN with a fixed indium (In) value (Al:In=5:1) indicates that a lower threshold current and higher characteristic temperature (T
0) value can be obtained when the Al composition is higher than 20%. When Al=25%, the threshold current is reduced at the expense of a decreased T
0 value from 149 to 130 K when the In composition increases from 1 to 7% in a temperature range of 300–370 K. The decreased T
0 value is mainly attributed to the increase in electronic leakage current.
Red Doped Organic Light-Emitting Diodes with Teflon Buffer Layer
Authors: Wang Liduo , Wang Haifeng , Zhang Deqiang , Gao Yudi , Qiao Juan , Qiu Yong
Published: December 2005

In this study, Teflon was employed as the anode buffer layer of red doped organic light-emitting diodes (OLEDs) with a 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) dopant dye and a bis(salicylidene-o-aminophenolato)-bis(8-quinolinoato)-bisgallium(III) [Ga2(Saph)2q2] host. The OLEDs with the Teflon buffer layer achieved a higher efficiency than OLEDs with a copper phthalocyanine (CuPc) buffer layer. It was also found that the color purity of devices was improved due to the introduction of the Teflon buffer layer.
Morphological Characteristics of a-Plane GaN Grown on r-Plane Sapphire by Metalorganic Vapor-Phase Epitaxy
Authors: Kusakabe Kazuhide , Ohkawa Kazuhiro
Published: December 2005

We report the morphological evolution of a-plane GaN thin films grown on r-plane sapphire substrates by atmospheric metalorganic vapor-phase epitaxy. The surface flatness is improved under optimized growth conditions which are different from those of c-plane epitaxy. The peak-to-valley height of surface roughness is reduced from 4 to 0.8 µm when GaN is grown at 1120°C on a 40-nm-thick low-temperature GaN (LT-GaN) buffer layer, as well as at 1150°C on a 20-nm-thick LT-GaN. These samples show their highest electron mobility of 220 cm2/(V s) at an electron concentration of 1.1×1018 cm-3 at room temperature.
Theoretical Investigation of Electric and Magnetic Properties of Benzene–Vanadium Sandwich Complex Chain
Authors: Rahman Md. Mahmudur , Kasai Hideaki , Dy Eben Sy
Published: December 2005

We investigate the electric and magnetic properties of a benzene–vanadium complex chain [V(C6H6)]∞. By performing first principles calculation based on the spin-polarized density functional theory, we find that this system shows a half metallic ferromagnetic behavior, i.e., majority-spin (spin-up) electrons have a semiconducting band gap, while minority-spin (spin-down) electrons are metallic. We suggest that this ferromagnetic order is due to a double-exchange mechanism.
c-Axis Oriented Face-Centered-Tetragonal-FePt Nanoparticle Monolayer Formed on a Polycrystalline TiN Seed Layer
Authors: Noda Suguru , Tsuji Yoshiko , Sugiyama Akira , Kikitsu Akira , Okada Fumio , Komiyama Hiroshi
Published: December 2005

c-Axis oriented face-centered-tetragonal (fct)-FePt magnetic nanoparticles are a promising candidate for high density perpendicular magnetic recording media. In this study, TiN was investigated as a seed layer to achieve c-axis orientation of fct-FePt nanoparticles. First, a (200)-oriented, polycrystalline TiN layer with grain size around 10 nm was prepared by reactive sputter-deposition at 873 K on SiO2, and then FePt was sputter-deposited at 973 K on it. Both in-plane and out-of-plane X-ray diffraction revealed that FePt had fct structure with c-axis orientation. Plan-view field emission scanning electron microscopy showed that FePt formed well-isolated nanoparticles. The particle diameter increased with increasing nominal thickness of FePt, and it was similar to the size of the TiN grains when nominal thickness was 1.4 nm. Cross-sectional transmission electron microscope images indicated that single FePt nanoparticles grew on single TiN grains, namely, one nanoparticle per grain, with an epitaxial relationship. Superconducting quantum inference device measurement at 300 K revealed that the FePt nanoparticles had coercivity of 6.2 and 0.8 kOe for the out-of-plane and in-plane directions, respectively. The FePt nanoparticle monolayer sputter-deposited on polycrystalline TiN seed layer is a promising candidate for perpendicular magnetic recording media.
Electron Redistribution and Coherent Radiation of Laser-Sliced Beam Bunches in Storage Ring
Authors: Miyahara Yoshikazu , Ando Ainosuke
Published: December 2005

Coherent radiation in the millimeter and sub millimeter wavelength regions can be generated using short electron beam bunches and laser-sliced beam bunches in a storage ring. Longitudinal dipped profiles produced by the laser slicing are rapidly smeared by the synchrotron motion and by the electron diffusion due to a random photon emission. In the present work, the characteristics of the diffusion are studied in detail but simply for practical applications. Diffusion effects are expressed as a point transfer probability function, with which the smearing of dipped profiles can be calculated straightforwardly. The emittance of diffusion gradually increases and finally reaches the natural emittance of the beam. Smeared profiles by the diffusion can be observed as a pulsed coherent radiation at the time of half multiples of synchrotron oscillation period, when there is almost no smearing by the synchrotron motion. Expected coherent radiation spectra due to the dipped profiles are given for the New SUBARU storage ring.
Ce3+-Doped LiCaAlF6 Crystals as a Solid-State Ultraviolet Saturable Absorber and Role of Excited State Absorption
Authors: Hai Le Hoang , Hung Nguyen Dai , Quema Alex V. , Diwa Gilbert A. , Murakami Hidetoshi , Ono Shingo , Sarukura Nobuhiko
Published: December 2005

Nonlinear absorption properties of Ce3+-doped LiCaAlF6 (Ce:LiCAF) crystals at wavelength of 266 nm are studied using open-aperture Z-scan method and a Q-switch Nd:YAG laser. Saturable absorption of solid-state materials in ultraviolet region is demonstrated for the first time.
Time-Resolving Image Analysis of Drilling of Thin Silicon Substrates with Femtosecond Laser Ablation
Authors: Yokotani Atsushi , Mukumoto Toru , Kanamitsu Yasushi , Fukumoto Hideto , Kurosawa Kou
Published: December 2005

We have analyzed a drilling process with a femtosecond laser on a silicon surface in order to investigate the degree of the thermal effect during the dicing of a very thin silicon substrate (thickness: 50 µm). A femtosecond laser pulse (E=30–500 µJ/pulse, τ=200 fs, λ=780 nm, f=10 Hz) was focused on a thin silicon substrate using a lens with a focal length of 100 mm. An image-intensified charge-coupled device (CCD) camera with a high-speed gate of 200 ps was utilized to take images of a drilled hole during the drilling process. As a result, it was found that the smaller the pulse energy, the faster the formation of the hole. Therefore, we tried to estimate the degree of the thermal effect semi quantitatively by analyzing the rise time of the formation of the hole. By measuring the rise time in 8 kinds of metallic material, it was found that the rise time strongly correlates with the thermal conductivity in these materials. This knowledge is thought to be very important and useful for developing a dicing technique for thin silicon wafers using a femtosecond laser.
Reconstruction of Photon Number Distribution without Relying on Photon Number-Resolving Detector
Authors: Yoshizawa Akio , Tsuchida Hidemi
Published: December 2005

The photon number distribution is reconstructed from the measured statistics of vacuum states in single-photon detection. Numerical results are presented for the coherent, thermal, number and squeezed-vacuum states. The quantum efficiency of single-photon detection should be high for the successful evaluation of the number state. The quantum efficiency provides the marginal influence for the evaluation of the coherent, thermal and squeezed-vacuum states. However, the accuracy of the reconstructed photon number distribution of the squeezed-vacuum state is low even though the quantum efficiency is unity. For a more accurate reconstruction, we must obtain a priori information on the photon number distribution of the squeezed-vacuum state.
Extinction Ratio Improvement and Negative Bit-Error-Rate Penalty in Mach–Zehnder Interferometric Wavelength Converter for Optical 2R Regeneration
Authors: Kim Dong Churl , Jeon Min Yong , Leem Young Ahn , Shim Eun Deok , Yee Dae-Su , Park Kyung Hyun
Published: December 2005

We have fabricated a semiconductor optical amplifier-based Mach–Zehnder interferometric wavelength converter with preamplifiers. For 2R regeneration, we have measured the extinction ratio (ER) and the bit-error-rate (BER) penalty of the wavelength-converted signal by optimizing the applied currents to the preamplifiers in varying the ER of a non-return-to-zero input signal at 10 Gbit/s. The ER was more improved and the BER showed a larger negative power penalty for an input with a smaller ER. For a typical input signal with a 5 dB ER, the ER improvement was 5.5 dB and the power penalty was -2.6 dB.