bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine-scale genetic structure and dispersal in Canada lynx (Lynx canadensis) within Alberta, Canada
Authors: Campbell Véronique , Strobeck Curtis
Published: October 2006

Although mammals are typically characterized by male-biased dispersal, field studies of lynx conflict as to whether dispersal is male-biased or lacks sex-bias. To resolve this issue we dissect fine-scale genetic structure and analyze dispersal in regard to gender using 19 microsatellite loci, teemed with extensive sampling (n = 272 adults) of Canada lynx ( Lynx canadensis Kerr, 1792) throughout Alberta. The level of genetic variation was high (mean He= 71.6%), as reported in previous genetic studies of lynx. No significant barriers to gene flow were detected within Alberta’s lynx population. Despite several reports of long-distance movements in lynx, we observed a slight significant negative correlation between pairwise relatedness values and geographic distance (rM= –0.025, P = 0.048), indicating a decrease in relatedness between individuals as their sampling distance increases. When the same analysis was performed separately on sexes, the slopes of the individual regressions did not differ significantly between males and females (P = 0.708). Our molecular results suggest a lack of sex-biased dispersal in Canada lynx, similar to reports on other lynx species.
Movement patterns of the invasive signal crayfish determined by PIT telemetry
Authors: Bubb Damian H. , Thom Timothy J. , Lucas Martyn C.
Published: October 2006

In one of the first field studies to utilize passive integrated transponder (PIT) telemetry to study space use of invertebrates, movement of the introduced signal crayfish ( Pacifastacus leniusculus (Dana, 1852)) was examined intensively in a high-density population in an upland river in northern England from 18 August to 6 September 2004. Crayfish (carapace length 21.0–67.3 mm) were tracked with externally attached PIT tags, enabling remote detection of tagged crayfish by the use of a portable detector. Of the 406 crayfish tagged, 356 (87.7%) were subsequently relocated at least once. The majority of crayfish remained close to the release location (median distance between release and final locations 36.3 m; 25th percentile 10.4 m, 75th percentile 91.6 m). However, movements of up to 345 m were recorded. There was no relationship between sex or size and distance moved. A small waterfall, upstream of the release location, appeared to form a barrier preventing movements of tagged crayfish upstream past it during the study period. PIT telemetry can provide an effective method for detailed recording of space use compared with standard mark–recapture or radiotelemetry methods.
Food supplementation and abundance estimation in the white-footed mouse
Authors: Shaner Pei-Jen L.
Published: October 2006

Food availability often drives consumer population dynamics. However, food availability may also influence capture probability, which if not accounted for may create bias in estimating consumer abundance and confound the effects of food availability on consumer population dynamics. This study compared two commonly used abundance indices (minimum number alive (MNA) and number of animals captured per night per grid) with an abundance estimator based on robust design model as applied to the white-footed mouse ( Peromyscus leucopus (Rafinesque, 1818)) in food supplementation experiments. MNA consistently generated abundance estimates similar to the robust design model, regardless of food supplementation. The number of animals captured per night per grid, however, consistently generated lower abundance estimates compared with MNA and the robust design model. Nevertheless, the correlations between abundance estimates from MNA, number of animals captured, and robust design model were not influenced by food supplementation. This study demonstrated that food supplementation is not likely to create bias among these different measures of abundance. Therefore, there is a great potential for conducting meta-analysis of food supplementation effect on consumer population dynamics (particularly in small mammals) across studies using different abundance indices and estimators.
Cellular activation patterns of the main olfactory bulb and accessory olfactory bulb following exposure to beddings soiled by same- or opposite-sex conspecifics in Mandarin voles (Microtus mandarinus)
Authors: Tai F.D. , Broders H.G. , Lian Y. , Wang T.Z. , Sun R.Y.
Published: October 2006

Using induction of Fos as an index, we studied cellular activation patterns in the accessory olfactory bulb (AOB) and main olfactory bulb (MOB) of Mandarin voles ( Microtus mandarinus (Milne-Edwards, 1871)) following their exposure to beddings soiled by different sexes. Male and female Mandarin voles that were exposed to beddings soiled by the opposite sex produced significantly more Fos-immunoreactive (Fos-ir) neurons in the anterior portion of the AOB and significantly fewer Fos-ir neurons in the posterior portion of the AOB than voles exposed to beddings soiled by the same sex. Furthermore, male and female Mandarin voles exposed to bedding soiled by different sex produced different numbers of Fos-ir cells in MOB. Mandarin voles exposed to beddings soiled by the opposite sex produced significantly more Fos-ir neurons in MOB than voles exposed to beddings soiled by the same sex. Our results establish that Mandarin voles of each sex showed different cellular activation patterns in AOB and MOB following exposures to sex-specific beddings. We suggest that both AOB and MOB were involved in sexual activities induced by chemosensory signals.
Behaviour, habitat associations, and intrasexual differences of female Stone’s sheep
Authors: Walker Andrew B.D. , Parker Katherine L. , Gillingham Michael P.
Published: October 2006

Stone’s sheep ( Ovis dalli stonei Allen, 1897) in northern British Columbia segregate sexually during most of the year, and intrasexually between maternal and nonmaternal females during spring and early summer. Our objective was to quantify intrasexual habitat use of female Stone’s sheep relative to maternal status using measures of behaviour and habitat use. We reviewed three hypotheses of intersexual segregation (predation-risk, forage-selection, and activity-budget hypotheses) to determine if they also explained intrasexual segregation of female Stone’s sheep. Female Stone’s sheep spent the majority of their active time foraging. Nursery groups spent shorter durations of time active, more time active in solid rock escape features, and less time active in shrub habitat than nonmaternal groups. The best predictive model describing intrasexual differences incorporated distance to nearest escape feature and size of nearest escape feature. Regardless of maternal status, female Stone’s sheep used low-elevation plant communities early in the growing season that were characterized by more shrub species and increased cover. As the growing season progressed, they tracked a phenological stage, moving up in elevation and associating with communities that contained increasing amounts of moss and lichen cover. The patterns in behaviour, habitat use, and vegetation associations between intrasexual groups of Stone’s sheep were best characterized by the predation-risk hypothesis.
Distributed Ferromagnetic Inductively Coupled Plasma as an Alternative Plasma Processing Tool
Authors: Godyak Valery , Chung Chin-Wook
Published: October 2006

A new type of plasma source for the uniform processing of large surfaces, that is distributed ferromagnetic inductively coupled plasma (DFICP) is explored in this study as an alternative to existing schemes. The basic principles of operation, the main features of DFICPs and their distinctions from the existing rf plasma sources are considered here. The electrical and plasma characteristics of different DFICPs operated at 400 kHz measured in wide ranges of rf power and gas pressure are investigated here and compared with those measured in a conventional ICP operated at 13.56 MHz.
Flow Energy Control of Nitrogen Ions Generated by Electron Cyclotron Resonance
Authors: Takahashi Kazunori , Kaneko Toshiro , Hatakeyama Rikizo
Published: October 2006

The flow energy of nitrogen ions produced by an electron cyclotron resonance (ECR) discharge is controlled by electrostatic acceleration in a plasma synthesis method. The source consists of an ion production region using ECR and a plasma synthesis region. Two grids for potential control and electron reflection of the ion production region, and an electron emitter with mesh shape are installed. In the synthesis region, electrons emitted from the emitter and ions accelerated by electrostatic potential difference between these regions are synthesized, which yields the generation of ion flow in the synthesis region. The electron temperature in the plasma synthesis region can be reduced to about 0.5 eV because of a reflection of high-energy electrons in the ion production region and a supply of thermionic electrons. In addition, it is observed that the density ratio of nitrogen atomic to molecular ions in the synthesis region markedly increases compared with that in the ion production region.
Planar Plasma of 30 cm Diameter Maintained by Hybrid Surface Microwave through Annular Slot Antenna
Authors: Liang Rongqing , Ou Qiongrong , Liang Bo , Xu Xu , Wang Fei
Published: October 2006

Planar plasma of 30 cm diameter excited by microwave with an annular slot antenna is described. The annular slot antenna consists of two layers of dielectric plates with a filling of an aluminum foil. Its structure resembles a sandwich but the diameter of the aluminum foil is slightly less than that of a plate so as to form an annular slot at the margin of plates. The experimental results showed that the uniformity of plasma density in the radial direction has been improved. No plasma density jump was found when Ar gas pressure increased from 20 to 100 Pa or microwave power increased from 200 to 800 W. The working mechanism of the antenna used in our experiment has been analyzed with the experimental results.
Experimental and Simulation Studies of Gas Phase Reaction in Planar Microwave Plasma
Authors: Yasaka Yasuyoshi , Sakae Atsushi , Sugimoto Naoki , Takeno Hiromasa
Published: October 2006

It is necessary to supply nitrogen radical fluxes in high uniformity to form high-quality nitrogen-incorporated films. An experiment on gas phase chemical reaction using a microwave discharge device with a multi-slotted planar antenna is performed. We use a three-dimensional simulation code, which calculates wave propagation in plasma obtained by the finite difference time domain method, power deposition, and plasma transport using a fluid model. The code can reproduce experimental results to a large extent. The code is capable of calculating several types of gas-phase reaction of neutral species. The results of both the experiment and the simulation show that the uniformity of the density distribution of nitrogen radicals strongly depends on the uniformity of the plasma.
Alkali-Halogen Plasma Generation Using Alkali Salt
Authors: Oohara Wataru , Nakahata Masahiro , Hatakeyama Rikizo
Published: October 2006

An alkali-halogen plasma can be used as an ion source in plasma applications. The plasma is generated by a dc magnetron discharge using thermal cathodes under a uniform magnetic field. Alkali-salt vapor is dissociated and ionized by E×B-drift electron impact, and alkali positive ions and halogen negative ions are produced. A magnetic-filter region is located at an exit of the discharge region and electrons are removed from the plasma. Pronounced thermionic emission and a strong B field are optimized, resulting in the generation of alkali-halogen plasma with an ion density of 3×108 cm-3 at B=0.2 T.
Sheath Structure for Positively-Charged Fine-Particle Levitation between Magnetized Double Plasmas
Authors: Gohda Takuma , Iizuka Satoru
Published: October 2006

We have investigated positively-charged fine particles in a cross-field sheath between magnetized double plasmas with different potentials separated vertically by the horizontal magnetic field. In the sheath the charges on the particles become positive, because ion current flowing from a lower high-potential plasma surpasses electron current coming across the magnetic field from an upper low-potential plasma. In this report, we have found a phenomenon that the particles can be sustained in the cross-sheath even when the levitation electrode is completely removed from the cross-sheath region. We also discuss the sheath structure between magnetized double plasmas.
Control Performance of Interactions between Reactive Plasma Jet and Substrate
Authors: Nishiyama Hideya , Sato Takehiko , Niikura Shota , Chiba Genta , Takana Hidemasa
Published: October 2006

When a nonequilibrium Ar/N2 plasma jet is impinging onto a substrate, the effects of operating pressure, applied magnetic field on the radiation intensity from nitrogen radicals, heat flux into the substrate, behaviors of the plasma jet impinging onto the substrate are experimentally clarified. The constant-value control of radiation intensity, substrate heat flux, jet axis deviation, and jet width fluctuation is achieved for high-quality material processes by a proportional plus integral (PI) control method with the suppression of the unstable fluctuation of plasma jet.
Blue Diode Laser Absorption Spectroscopy of Pulsed Magnetron Discharge
Authors: Olejnicek Jiri , Do Hoang Tung , Hubicka Zdenek , Hippler Rainer , Jastrabik Lubomir
Published: October 2006

Laser absorption spectroscopy of aluminium atoms in pulsed magnetron discharge with pure argon, argon/oxygen, and argon/methane gas mixtures is reported. Time-averaged densities and temperatures of sputtered aluminium atoms were extracted from the absorption signal. The measured Al density depended almost linearly on the pulse current and showed a small dependence on pressure. Al atom temperature increased with discharge current and vice versa with pressure. A drastic decrease of the Al atom density was observed in the Ar/O2 mixture. The Al density dropped to a value close to zero once a critical oxygen gas flow rate was reached. This critical oxygen gas flow was significantly higher in pulsed mode than in DC mode.
Development of Supersonic Metastable Helium Pulsed Beam Source for Plasma Diagnostics
Authors: Namba Shinichi , Andruczyk Daniel , Takiyama Ken , Ueno Daijiro , Furukawa Shinya , James Brian W.
Published: October 2006

A supersonic metastable helium (21S) pulsed beam source, which consists of an electromagnetic valve, a collimation skimmer, and discharge electrodes for production of a plasma, has been constructed, which is essential for the direct measurement of electric fields in plasmas by means of polarization laser-induced fluorescence spectroscopy. A supersonic helium atomic beam with a short pulselength (∼300 µs), narrow divergence (∼1.1°), and high density of ∼1.4×1014cm-3has been achieved. In order to generate metastable atoms in this beam source, a Penning-type discharge was employed, which is suitable for producing stable plasma with high temperature, even at low gas densities, due to the particular configuration of electrodes together with a magnetic field. Spectroscopic observations indicated that the temporal behaviors of neutral atom and ion emissions were almost the same as that of the helium atom profile, and on increasing the discharge voltage applied between electrodes, the spectral intensity increased approximately linearly. Moreover, the fact that the ion emission can also be observed showed that it was probable that a high-temperature plasma was generated by the Penning discharge.
Study on Temporal and Spatial Distributions of Ba Atoms in Fluorescent Lamp Discharge Using Laser-Induced Florescence
Authors: AlyHendy Ahmed Samir , Yamashita Go , Yamagata Yukihiko , Uchino Kiichiro , Ueda Takashi , Manabe Yoshio
Published: October 2006

A laser-induced fluorescence (LIF) technique was applied to the measurements of the temporal and spatial distributions of Ba atoms in the vicinity of the electrode of a fluorescent lamp operated at 60 Hz. Ground-state (61S0) Ba atoms were excited to a 51P1level (350.1 nm) by a frequency-doubled dye laser beam, and the subsequent fluorescence (51P1–51D2, 582.6 nm) was detected. Over a whole periodic time (16.67 ms), the density of the Ba atoms was found to have two peaks, and the number of Ba atoms emitted in the anode half-cycle was about twofold larger than that emitted in the cathode half-cycle. This difference between the Ba atoms emitted during the anode half-cycle and those emitted during the cathode half-cycle was studied for lamps with different gas pressures. Ba atoms were found to be emitted mainly from the hot spot of the filament electrode. It is suggested that the main factor for Ba atom emission from the electrode is not sputtering by ion bombardment but thermal evaporation.
Measurements of Electron Energy Distribution Functions in Pulse-Modulated Ar and Ar/O2Inductively Coupled Plasmas using Laser Thomson Scattering
Authors: El-Sabbagh Mansour A. M. , Nakamura Akinobu , Yanagai Toshiro , Yamagata Yukihiko , Uchino Kiichiro
Published: October 2006

The time-resolved electron energy distribution functions (EEDFs) in Ar and Ar/O2pulse-modulated inductively coupled plasmas have been measured in the afterglow for the first time using laser Thomson scattering. The measurements were performed for RF powers of 100 and 500 W at a frequency of 13.56 MHz, a duty cycle of 50%, and a pulse repetition frequency of 12.5 kHz. The Ar pressures were 20 and 100 mTorr at a flow rate of 132 sccm, and the Ar/O2(10% O2) pressure was 20 mTorr at a flow rate of 132 sccm. The measured EEDFs were all Maxwellian for the Ar and Ar/O2(10% O2) plasmas. The Maxwellian distributions in the afterglow may be attributed to electron–electron collisions.
Holographic Interferometry of Barrier-Torch Discharge in Argon and Helium
Authors: Olejnicek Jiri , Hubicka Zdenek , Kriz Pavel , Adamek Petr , Churpita Oleksandr , Virostko Petr , Jastrabik Lubomir , Blazek Josef
Published: October 2006

Holographic interferometry of atmospheric RF barrier-torch discharge burning in argon and helium is reported. Holographic interferometer of Mach–Zehnder type with He–Ne laser was used for temperature measurement of neutral particles of working gas. Interference pattern was registered by a high-speed charge-coupled devices (CCD) camera. Resulting temperature ranged from 330 to 450 K. A slight difference between temperatures measured close to the glass nozzle outlet and close to the substrate was observed.
Pulsed Regime of a Hollow-Cathode Discharge Used in a Sputter Source
Authors: Apetrei Radu , Alexandroaei Dumitru , Luca Dumitru , Balan Petru , Ionita Codrina , Schrittwieser Roman , Popa Gheorghe
Published: October 2006

The pulsed operation of a cavity hollow-cathode post-discharge sputtering source was proposed to facilitate the sputtering of low-conductivity materials. Self-oscillating and externally driven pulsed regimes were investigated. The plasma density, temperature and relative density of atomic species along the discharge axis were determined by optical emission spectroscopy and Langmuir probe diagnostics. The temporal evolution of these parameters and dynamic current–voltage characteristics of the discharge were recorded in both regimes as functions of gas pressure and discharge current. The results bring more insight into the utilization of the above-mentioned device as a small sputtering source.
A Model Analysis of Feature Profile Evolution and Microscopic Uniformity during Polysilicon Gate Etching in Cl2/O2 Plasmas
Authors: Osano Yugo , Mori Masahito , Itabashi Naoshi , Takahashi Kazuo , Eriguchi Koji , Ono Kouichi
Published: October 2006

A phenomenological model has been developed to simulate the feature profile evolution of polycrystalline silicon (poly-Si) gate etching in Cl2/O2 plasmas. The model takes into account the deposition of etch products, surface oxidation, and the forward reflection of energetic ions on feature sidewalls. To describe the formation of multilayer SiCl
x
or SiCl
x
O
y
on feature surfaces during etching, the substrates consist of a number of small cells or lattices of atomic size in the computational domain; this model provides a nanometer-scale representation of the feature geometry and the chemical constituents therein. The inelastic or nonspecular reflection of incoming ions from feature surfaces and the penetration of ions into substrates are incorporated into the model by calculating the trajectory of ions through successive binary collisions with substrate atoms. Etching experiments were performed to evaluate and improve the accuracy of the model. To analyze the effects of the control variables of a plasma reactor on profile evolution, the simulated profiles for different gas flow ratios and incident ion energies were compared with the etched profiles obtained in the experiments. The numerical results reproduced the behaviors of profile anomalies such as sidewall tapering and microtrenches at the corner of the feature bottom, upon varying the incident fluxes of O neutrals and etch by-products, and the incident energy of ions. Moreover, the simulated profiles exhibited passivation layers deposited on feature sidewalls, which is a similar geometry to those obtained in the experiments.
Simulation of the Electrical Properties of SiH4/H2 RF Discharges
Authors: Lyka B. , Amanatides E. , Mataras D.
Published: October 2006

The results of a two-dimensional fluid simulator were validated against the experimentally measured electrical properties (power dissipation and discharge current) of SiH4/H2 RF discharges used for the deposition of microcrystalline or amorphous silicon thin films. The use of the typical values for the electron–SiH4 and H2 collision cross sections found in the literature, results in a significant underestimation of the calculated power dissipated in the discharge and an overestimation of the current flow. A study of the main parameters affecting the model results showed that this deviation is mainly due to the H2 ionization rate. An improved calculation of the power dissipated in the discharge was then possible, leading to a significant improvement in the prediction of the deposition rate. This result underlines the importance of H2 chemistry in SiH4/H2 discharges and also indicates that the correct estimation of the discharge electrical properties is a necessary first step in the development of a code for simulating the deposition of silicon films from SiH4/H2 discharges.
Electron Impact Ionization of SiClx and TiClx (x = 1–4): Contributions from Indirect Ionization Channels
Authors: Becker K. , Mahoney J. , Gutkin M. , Tarnovsky V. , Basner R.
Published: October 2006

We measured absolute partial cross sections for the formation of various singly charged positive ions produced by electron impact on SiCl
x
(x = 1–4) using two different experimental techniques, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam apparatus. The energy range covered was from the threshold to 900 eV in the TOF-MS and to 200 eV in the fast neutral beam apparatus. In the case of SiCl4, the absolute cross sections obtained by the two different experimental techniques were found to agree very well. The ionization of the SiCl
x
(x = 1–3) free radicals can only be studied using the fast-beam technique. Some of the partial cross section curves were found to exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30 eV, which is in some cases followed by a shallow minimum at about 40 eV and a broad second maximum at around 100 eV. This pronounced low-energy maximum is indicative of the presence of an indirect ionization channel and is similar to what has been observed earlier for TiCl4 and the TiCl
x
(x = 1–3) radicals. Similarities in the contribution of the indirect ionization channel to the formation of the various SiCl
x

+ and TiCl
x

+ (x = 1–4) ions will be highlighted in this paper.
Electron Scattering on Triatomic Molecules: The Need for Data
Authors: Karwasz Grzegorz P. , Wróblewski Tomasz , Brusa Roberto S. , Illenberger Eugen
Published: October 2006

We review data sources for electron–molecule scattering cross sections, paying particular attention to triatomic molecules, such as CO2, N2O, and OCS. Experimental cross sections obtained by beam techniques are compared with those obtained by swarm-data modeling. The need for measurements of inelastic processes, particularly electronic excitation and dissociation, is stressed.
Experimental Study of C3F6Electron Impact Spectroscopy
Authors: Kato Hidetoshi , Makochekanwa Casten , Hoshino Masamitsu , Kimura Mineo , Cho Hyuck , Tanaka Hiroshi
Published: October 2006

This paper reports on the first measurements of the electron impact electronic excitation cross sections for hexafluoropropene (C3F6) measured at the two experimental conditions of 20 eV and 10°, and 100 eV and 5°, while sweeping the energy loss over the range 2–14 eV. Similarity between these two spectra shows the insignificance of optically forbidden transitions in these molecules. Three broad features have been observed at about 7, 7.5, and 8.2 eV and attributed to the C=Cπ→C–Fσ*; C=Cπ→C=Cσ*(both dissociative); and 8.2 eV, due to C=Cπ→C=Cπ*excitations. The EELS for impact energy 100 eV and angle 5° rise rapidly above 11 eV and shows a broad resonance structure centered around 12.7 eV. Similarities in the repulsive energy loss features have been observed in the comparative study of the C3F6EELS for 100 eV, 5° with the similar one for C2F4and attributed to the common electronic transitions into C=C antibonding orbitals, albeit with peak position differences below 10 eV.
Theoretical Investigation of the Influence of the Wall Temperature on the Probability for Surface Atomic Recombination of a Single Species
Authors: Guerra Vasco
Published: October 2006

The probability for surface atomic recombination of a single gas is theoretically investigated, for a system that takes into account atomic adsorption in physisorption and chemisorption sites, surface desorption, surface diffusion, and both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) recombination mechanisms. Analytic asymptotic solutions are obtained for the value of the recombination probability and are validated by their comparison with numeric calculations for the system of equations describing the same sequence of elementary processes. The dependence of the recombination probability on the value of the wall temperature is analysed in detail.
Fragment Ions of Dimethylsilane Produced by Hot Tungsten Wires
Authors: Yoshimura Satoru , Toh Akinori , Sugimoto Satoshi , Kiuchi Masato , Hamaguchi Satoshi
Published: October 2006

Fragment ions produced from dimethylsilane with a hot tungsten wire (i.e., catalyzer) in catalytic chemical vapor deposition (Cat-CVD, which is also known as hot wire CVD) processes are identified with a use of a low-energy mass analyzed ion beam system. The mass analysis shows that dominant fragment ions from dimethylsilane are H1
+, H2
+, CH3
+, Si+, SiH3
+, SiCH4
+, SiC2H+, and SiC2H7
+. The energy distributions of these ions are also measured. It is found that the spreads of the energy distributions are narrow and no energetic ions are produced, suggesting that the produced ions are unlikely to cause any significant damage to the deposited films in actual dimethylsilane Cat-CVD processes. The ion production rates are found to be strongly dependent on the catalyzer temperature.
Observation and Modeling of Molecular and Atomic Ions in Hydrogen Plasma
Authors: Yazawa Hiroyuki , Tonegawa Akira , Ono Masataka , Shibuya Takehisa , Kawamura Kazutaka
Published: October 2006

Measurements of the densities of the molecular and atomic ions (n
H
+, n
H2
+, n
H3
+) were carried out in hydrogen plasma with a hydrogen gas puff at discharge current of 50 A. The molecular and atomic ion currents were detected using an “omegatron” mass analyzer. The electron density and temperature were measured using a Langmuir probe and a double probe. From the measured parameters, a zero-dimensional model using the relevant rate balance equations was found to predict the observed dominant ion density.
Characteristics of Hydrogen Negative Ions in Sheet Plasma
Authors: Tonegawa Akira , Kumita Kentaro , Ono Masataka , Shibuya Takehisa , Kawamura Kazutaka
Published: October 2006

The system of a magnetized sheet plasma crossed with a vertical gas flow has been proposed to produce a high H- density. Under a secondary hydrogen gas supply entering into the plasma, the peak position of the H- ion density n
H-
is localized in the periphery of the sheet plasma. The value of n
H-
increases with increasing the discharge current I
d. The variation of the hydrogen negative ion density is proportional to the vacuum ultraviolet (VUV) emission intensities of the Lyman band and the Werner band in hydrogen molecular bands. The measured H- density was compared with the theoretical calculation based on the rate equation of the transport of vibrationally excited hydrogen molecules H2
*(X1Σg
+, v''>5).
Particle Modeling of Transport of α-Ray Generated Ion Clusters in Air
Authors: Tong Lizhu , Nanbu Kenichi , Hirata Yosuke , Izumi Mikio , Miyamoto Yasuaki , Yamaguchi Hiromi
Published: October 2006

A particle model is developed using the test-particle Monte Carlo method to study the transport properties of α-ray generated ion clusters in a flow of air. An efficient ion–molecule collision model is proposed to simulate the collisions between ion and air molecule. The simulations are performed for a steady state of ion transport in a circular pipe. In the steady state, generation of ions is balanced with such losses of ions as absorption on the measuring sensor or pipe wall and disappearance by positive–negative ion recombination. The calculated ion current to the measuring sensor agrees well with the previous measured data.
Reactive Evaporation of Metal Wire and Microdeposition of Metal Oxide Using Atmospheric Pressure Reactive Microplasma Jet
Authors: Shimizu Yoshiki , Bose Arumugam Chandra , Mariotti Davide , Sasaki Takeshi , Kirihara Kazuhiro , Suzuki Tsunehisa , Terashima Kazuo , Koshizaki Naoto
Published: October 2006

We developed a safe technique without using a toxic gas source to deposit tungsten oxide on a localized specific area using an atmospheric pressure microplasma jet. In this technique, a consumable tungsten wire, inserted into a quartz nozzle for microplasma generation, was etched with an O2/Ar microplasma, and the resultant tungsten oxide was deposited on the substrate placed downstream. The process mechanism was determined by the detailed observation of the deposit and consumed wire surface after processing, and optical emission spectroscopy. This technique is expected to be utilized for the localized deposition of a variety of metal oxides by varying the kind of consumable metal wire.
Production of Pulse Glow Discharge in Atmospheric Pressure Nitrogen Using Needle-Array Electrode
Authors: Takaki Koichi , Kirihara Hidekazu , Noda Chiharu , Mukaigawa Seiji , Fujiwara Tamiya
Published: October 2006

An atmospheric pressure glow discharge was generated using a needle-array electrode in nitrogen. A pulsed high voltage with short rise time under 10 ns was employed to generate streamer discharges simultaneously at all needle tips. The large number of streamer discharges prevented glow-to-arc transition caused by inhomogeneous thermalization. Semiconductor opening switch (SOS) diodes were employed as an opening switch to shorten the rise time. The glow current was drastically decreased by eliminating the SOS diode, in which case the charging voltage was directly applied to the electrode. Spatial- and time-averaged electron densities in a positive column were estimated from calculations based on nitrogen swarm data. The density was estimated to be 1.8×1011 cm-3, which was much larger than 9.7×109 cm-3 in the case without the SOS diode.
Characteristics of Atmospheric-Pressure DC Glow Discharge in Pin–Plate Electrodes by Gas Flow Stabilization Method
Authors: Hattori Kunihiko , Yamada Haruyosi , Kumagai Tomoyuki , Ando Akira , Inutake Masaaki
Published: October 2006

We experimentally determined the characteristics of atmospheric-pressure glow discharge (APGD) produced by pin–plate electrodes with a gas flow between the electrodes. APGD is sustained by applying a DC voltage between the electrodes with main and auxiliary air flows. The auxiliary air flow is added to the main flow in a localized region using a small nozzle. It is found for the first time that glow discharge current significantly increases when the auxiliary nozzle is set near the anode plate. By adding only 6% of the main flow as the auxiliary air flow, the maximum current of APGD increases threefold that in the case without the auxiliary flow.
Decomposition of Volatile Organic Compounds at Low Concentrations Using Combination of Densification by Zeolite Adsorption and Dielectric Barrier Discharge
Authors: Yamagata Yukihiko , Niho Kouichiro , Inoue Kouji , Okano Hiroshi , Muraoka Katsunori
Published: October 2006

The decomposition of toluene at very low concentrations (10–20 ppm) using a combination of densification by zeolite adsorption and dielectric barrier discharge (DBD) was investigated. The characteristics of toluene decomposition using DBD under open and closed-loop flow conditions were determined. Under the closed-loop gas flow condition, a high decomposition ratio (70–93%) and a high energy efficiency [8–19 g/(kW h)] were achieved for the adsorbed toluene (63% of the initial amount) by DBD treatment even at a high flow rate of 150 L/min. Also, by the periodic operation of adsorption/DBD treatment, it was demonstrated that DBD treatment regenerated the honeycomb sheet containing zeolites for subsequent adsorption. The usefulness of this method for the decomposition of hazardous materials at low concentrations was shown.
Spatiotemporal Surface Charge Measurement in Two Types of Dielectric Barrier Discharges Using Pockels Effect
Authors: Abolmasov Sergey N. , Abo Rei , Shirafuji Tatsuru , Tachibana Kunihide
Published: October 2006

The longitudinal electro-optic modulator technique based on Pockels effect has been applied for measuring the surface charge density in two types of dielectric barrier discharges: volume and coplanar. Discharges were generated in noble gases such as helium, neon and argon at pressures of a few hundreds of Torr. It is shown that the thickness of electro-optical crystal used determines not only the spatial resolution of the method, but also affects the value of surface charge density.
Observation of OH Radical Reactions with Atomic Hydrogen in He/H2O Plasmas by Laser-Induced Fluorescence Spectroscopy
Authors: Takiyama Ken , Namba Shinichi , Yamasaki Tsutomu , Shoji Akira , Kwon Jun-Hyoun , Park Rae-Eun , Nojima Hideo
Published: October 2006

A novel atmospheric pressure plasma device that generates atomic hydrogen has been developed. The reaction of OH radicals with atomic hydrogen supplied from the device was investigated in a He/H2O mixture at a pressure of 530 Torr by laser-induced fluorescence (LIF) spectroscopy. OH radicals were generated using a dielectric barrier discharge (DBD) plasma and excited to A2Σ+(v'=1) from X2Π(v''=0) by a frequency-doubled dye laser (282 nm). When the device was operated, OH-LIF intensity was reduced near the DBD plasma. The spatial density profile of the OH radicals was also obtained when the device was turned on and off. The reaction mechanism was briefly discussed.
Temporal Variations in Distributions of NO and NO2 Densities in Streamer Corona Discharges
Authors: Kurakane Hiroshi , Aramaki Mitsutoshi , Sasaki Koichi
Published: October 2006

The distributions of NO and NO2 densities were measured in high-pressure streamer corona discharges by laser-induced fluorescence imaging spectroscopy at various delay times after applying pulsed high voltages between needle and planar electrodes. It was found that the decrease in NO2 density in an N2/O2/NO2 discharge was more efficient than that in an N2/NO2 discharge. The dominant removal reaction of NO2 from the N2/O2/NO2 discharge was NO2+O→NO+O2. The importance of this reaction has been confirmed by the simultaneous observation of the distributions of the NO and NO2 densities. The total amount of NO2 removed from the N2/O2/NO2 discharge roughly coincided with the total amount of NO observed at the same delay time.
Ultraprecision Machining Utilizing Numerically Controlled Scanning of Localized Atmospheric Pressure Plasma
Authors: Yamamura Kazuya , Sano Yasuhisa , Shibahara Masafumi , Yamauchi Kazuto , Mimura Hidekazu , Endo Katsuyoshi , Mori Yuzo
Published: October 2006

By the application of atmospheric pressure plasma, we have developed a new ultraprecision machining method named plasma chemical vaporization machining (CVM). In this method, several types of rotary or pipe electrodes are prepared for optimizing the required machining. In particular, by rotating the electrode in a high-pressure environment, both the supply of reactive species to the machining point and the exhaust of reaction products are effectively performed. In the case of fabricating a grazing-incidence total-reflection X-ray mirror, figuring accuracies of 3 nm (p–v) or less were achieved and a nearly diffraction-limited focusing performance was realized. As a result of the correction of the thickness distribution of the AT cut quartz crystal wafer, thickness uniformity was improved to a 10 nm level, and resonance property was also markedly improved without degradation by high-energy ion bombardment.
Removal of Methyl-tert-butyl Ether from Water by a Pulsed Arc Electrohydraulic Discharge System
Authors: Angeloni Danielle M. , Dickson Sarah E. , Emelko Monica B. , Chang Jen-Shih
Published: October 2006

The removal of methyl-tert-butyl ether (MTBE) from water by a pulsed arc electrohydraulic discharge (PAED) system was investigated experimentally at the laboratory scale. The effects of arc electrode gap, detention time and initial solution pH on the efficacy of MTBE treatment by PAED were investigated. A 0.3 kJ/pulse spark-gap-type power supply was employed in combination with a 3.0 L flow-through reactor. Experimental results showed that: 1) oxidation reactions are induced by this PAED system; 2) removal efficiency increases with increasing cumulative input energy (kW·h/m3 or kJ/L); 3) removal efficiency decreases with increasing arc electrode gap; and 4) initial solution pH does not have a significant effect on the efficacy of MTBE removal by PAED when the water matrix is buffered prior to treatment.
Radio-Frequency-Driven Atmospheric-Pressure Plasmas in Contact with Liquid Water
Authors: Kitano Katsuhisa , Aoki Hironori , Hamaguchi Satoshi
Published: October 2006

Atmospheric-pressure plasmas were produced on the surface of liquid water by radio-frequency (RF) power supply. A quartz chamber with an off-center inner electrode was used to generate discharges with a wide range of filling gas pressures. When the chamber was filled with fuel gas and liquid water and a sufficient RF power was supplied to the system, plasmas were observed to be produced around the inner electrode as well as on the water surface. Optical emission spectroscopy (OES) identified the generation of oxidative hydroxyl (OH) radicals and decoloration of methylene blue in the solution demonstrated oxidative capacity of water plasmas generated in this system.
Preparation of FePt Magnetic Nanoparticle Film by Plasma Chemical Vapor Deposition for Ultrahigh Density Data Storage Media
Authors: Matsui Isao
Published: October 2006

We prepared an FePt nanoparticle film for magnetic storage media using 13.56 MHz glow-discharge plasma. Vapors of metal organics, namely biscyclopentadienyl iron (ferrocene) for Fe and (methylcyclopentadienyl)trimethyl platinum for Pt, were introduced into a capacitively coupled flow–through plasma chamber, which consisted of a shower head RF electrode and a grounded orifice plate electrode. Synthesized nanoparticles were directly collected onto a transmission electron microscope (TEM) grid or MgO substrate placed just below the grounded orifice electrode. TEM images showed two kinds of particles, one of which was nanometer sized and isolated and the other appeared as a coagulate of small particles. The diameter of the coagulated particle was larger than 10 nm. Nanometer size particles were separated and deposited on MgO substrate by adjusting the gas flow rate through the grounded orifice plate. The magnetization of the FePt nanoparticle film was evaluated by magneto-optical Kerr effect (MOKE) spectroscopy. As-synthesized nanoparticles did not exhibit a loop-shape magnetization curve. Annealing in atmospheric hydrogen was conducted to transform crystal from fcc structure to fct L10 ordered structure. The higher annealing temperature resulted in the more ordered L10 phase formation and the larger coercivity. A sample annealed at 750 °C exhibited a room temperature coercivity of 10 kOe. Also, it was confirmed that nanoparticle film density is critical to the magnetization.
Highly Aligned Growth of Carbon Nanotubes by RF-Plasma-Assisted DC Plasma Chemical Vapor Deposition at High Pressure
Authors: Hayashi Yasuaki , Fukumura Takuya , Isshiki Toshiyuki , Utsunomiya Risa
Published: October 2006

Very highly aligned carbon nanotubes (CNTs) were synthesized by radio-frequency-plasma-assisted direct current (DC) plasma chemical vapor deposition, which was developed for the large-area growth of highly aligned CNTs under a stable condition in a DC plasma. Three parallel electrodes, namely, an RF electrode, a grounded electrode, and a DC cathode, were arranged in a vacuum chamber. It was found that the application of a high DC voltage at a high pressure forms a high sheath electric field, resulting in the highly aligned growth of CNTs without severe damage.
Etching of Multi-Walled Carbon Nanotubes Using Energetic Plasma Ions
Authors: Cho Jung-Hyun , Kim Gon-Ho
Published: October 2006

The interactions between energetic ions and nanotubes are important in the fabrication of plasma-aided carbon nanotubes, especially in the process of sputter-etching and particle encapsulation into the nanotubes. In this study, it was investigated that the bamboo structured multi-walled carbon nanotubes (MWNTs) was sputter-etched by plasma ion irradiation with various energies which were less than those used in the ion beam experiments. In the plasma, the surface opening of the MWNTs began at the irradiated ion energy of 20 eV and the open tips of the MWNTs were obtained by increasing the irradiated ion energy as 70 eV. When the ion energy exceeded 100 eV, the etching was enhanced by the rupturing and breaking processes and almost half of the MWNTs were etched out by the 150 eV ions. The irradiated ion energy was controlled effectively by the sheath potential formed in front of the MWNTs which was immersed in the nitrogen plasma.
Analysis of Oxidation State of Multilayered Catalyst Thin Films for Carbon Nanotube Growth Using Plasma-Enhanced Chemical Vapor Deposition
Authors: Okita Atsushi , Ozeki Atsushi , Suda Yoshiyuki , Nakamura Junji , Oda Akinori , Bhattacharyya Krishnendu , Sugawara Hirotake , Sakai Yosuke
Published: October 2006

We synthesized vertically aligned carbon nanotubes (CNTs) using multilayered catalyst thin films (Fe/Al2O3 and Al2O3/Fe/Al2O3) by RF (13.56 MHz) CH4/H2/Ar plasma-enhanced chemical vapor deposition. Pretreatment of the catalyst is crucial for CNT growth. In this paper, we analyzed the effect of catalyst reduction on CNT growth. Catalyst thin films on substrates were reduced by H2 plasma pretreatment at 550 °C to form nanometer-sized catalyst particles. The multilayered thin films were analyzed; the chemical composition and oxidation state by X-ray photoelectron spectroscopy (XPS) and the surface morphology by scanning electron microscopy (SEM). The Fe 2p peak of the XPS spectra showed that Fe
x
O
y
in the as-deposited catalyst was effectively reduced to Fe by a pretreatment of duration 4 min. Using this catalyst, we obtained CNTs with an average diameter of 10.7 nm and an average length of 5.3 µm. However, pretreatment longer than 4 min resulted in shorter CNTs and the Fe peak was shifted from Fe to Fe3O4. These transitions (Fe2O3→Fe3O4→Fe→Fe3O4) can be explained by the enthalpy of the oxides. This result indicates the presence of an optimum ratio between Fe and Fe
x
O
y
to maximize the CNT lengths.
Modification of Double-Walled Carbon Nanotubes by Cs Plasma Ion Irradiation
Authors: Li Yongfeng , Izumida Takeshi , Okada Takeru , Kato Toshiaki , Hatakeyama Rikizo , Qiu Jieshan
Published: October 2006

The synthesis of Cs-encapsulated double-walled carbon nanotubes (DWNTs) is realized for the first time by plasma irradiation. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) spectrometry confirm that Cs clusters can be doped inside DWNTs. The structural deformation of Cs-encapsulated DWNTs synthesized under different applied negative DC bias voltages from -25 to -150 V during plasma irradiation is examined by Raman spectroscopy, and the obtained results indicate that DWNTs have structural merits compared with single-walled carbon nanotubes (SWNTs). In addition, the electronic transport properties of pristine and Cs-encapsulated DWNTs are investigated by their fabrication as the channels of field-effect transistor (FET) devices. We find that, in contrast to pristine ambipolar DWNTs, unipolar n-type semiconducting DWNTs can be created by Cs plasma irradiation.
Effects of Ion Energy Control on Production of Nitrogen–C60 Compounds by Ion Implantation
Authors: Abe Shigeyuki , Sato Genta , Kaneko Toshiro , Hirata Takamichi , Hatakeyama Rikizo , Yokoo Kuniyoshi , Ono Shoichi , Omote Kenji , Kasama Yasuhiko
Published: October 2006

Nitrogen–C60 compounds such as azafullerene (C59N) and nitrogen-atom-encapsulated fullerene (N@C60) are produced by implanting nitrogen ions into C60 thin films on a substrate immersed in an electron cyclotron resonance plasma under a mirror magnetic field. Each compound is found to be synthesized, depending on the ion energy provided by the potential difference between the substrate and the plasma. The optimum energy for C59N synthesis is approximately 40–50 eV, and the amount of C59N decreases in an ion energy range larger than 50 eV. In contrast, an ion energy larger than 20 eV is required for N@C60 synthesis.
Continuous Production of Carbon Nanostructures Using Plasma Jet
Authors: Yamatani Yoichi , Fukumasa Osamu
Published: October 2006

We have developed a continuous synthesis technique to produce carbon nanostructures using a well-controlled plasma jet. In this method, numerous fiber-like structures can be produced readily using CH4 gas and H2 gas without a catalyst. Without a catalyst, carbon nanostructures that have small diameters in the range of about 10–100 nm are mostly produced. The effect of metal catalysts on carbon nanostructure synthesis is also studied. The yields of carbon nanostructures are dramatically increased using Ni substrate and/or Ni powders in the gas-phase synthesis of CH4 and H2.
Hydroxyapatite Coating Using DC Plasma Jet
Authors: Kurita Masanori , Fukumasa Osamu
Published: October 2006

Hydroxyapatite (HAP)-coated implants on metallic substrates have been used as biomaterials. The problem is that the HAP coating on metallic substrates is easily exfoliated at the boundary between HAP and metallic, e.g., titanium (Ti) substrates. Therefore, a Ti–HAP functionally graded coating (FGC) is considered to improve the adhesion of Ti–HAP coatings. In this paper, Ti–HAP FGC is tested using a well-controlled DC plasma jet and discussed. It is confirmed that Ti–HAP FGC films with good adhesion within three layers are prepared.