Hokkaido University Collection of Scholarly and Academic Papers
(65.351 recursos)
HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.
Mostrando recursos 1 - 20 de 48
1.
High-repetition-rate (6 kHz) and long-pulse-duration (50 ns) ArF excimer laser for sub-65 nm lithography - Kakizaki, Koji; Sasaki, Yoichi; Inoue, Toyoharu; Sakai, Yosuke
Development of high-repetition-rate ArF excimer lasers is vital requirement for achieving high throughput and high energy-dose stability in a scanner system. ArF excimer laser, with increasing light pulse duration, can reduce the peak power without the energy-dose change. Then, the spectral bandwidth ΔλFWHM becomes narrower by increasing the number of light round trips in a cavity, and optical damage is reduced from high-peak power. Laser operation exceeding 4 kHz is needed for next-generation technologies that can enable high numerical aperture and development of high-throughput scanners. In the present work, we examined the possibilities of achieving a repetition rate to 6 kHz...
2.
Preparation of carbon nanoparticles by plasma-assisted pulsed laser deposition method : size and binding energy dependence on ambient gas pressure and plasma condition - Suda, Yoshiyuki; Ono, T; Akazawa, M; Sakai, Y; Tsujino, J; Homma, N
Nanometer-size carbon particles were prepared on a Si substrate using pulsed laser deposition (PLD) assisted by radio frequency (RF) Ar plasma and were compared with ones prepared by PLD in vacuum and Ar gas. In both the plasma and gas ambiences, experiments were carried out in Ar pressure pAr ranging from 0.13 to 13 Pa. The particle size increased as pAr increased. However, the size obtained in the RF Ar plasma was approximately 1.5 times larger than that prepared in the Ar gas. An X-ray photoelectron spectroscopy (XPS) analysis revealed that the carbon film covered by the particles was in...
3.
Fast switching of light propagation in a photorefractive crystal via Pockels effect - Xie, Ping; Mishima, Teruhito
We experimentally demonstrate fast switching of light propagation and phase conjugate generation in a BaTiO3:Ce crystal with a high efficiency. The switching mechanism is based on the phase mismatch in photorefractive beam coupling between an incident beam and a fanning beam. The phase mismatch is induced by an externally applied electric field via Pockels effect. In our experiment we obatin a voltage-generator-determined switching time of the order of 10 μs. The required voltage to reduce the output phase conjugate power by more than 90% is about only 100 volts for our 3.8 mm-thick crystal.
4.
Deposition of fine carbon particles using pulsed ArF laser ablation assisted by inductively coupled plasma - Suda, Yoshiyuki; Nishimura, T; Ono, T; Akazawa, M; Sakai, Y; Homma, N
Carbon thin films containing many fine carbon particles were deposited by a pulsed ArF laser ablation technique assisted by inductively coupled plasma (ICP). The sizes of the particles were found to be - 100 nm. The particles seemed to be coagulated from several finer particles of size - 10 nm. When ICP was applied to a plume, the shape of the coagulated particles became spherical. The deposited surface was assumed to be diamond-like carbon based on the binding energy of carbon (1s) in the particle obtained by XPS spectra.
5.
Behaviour of liquid nitrogen between electrodes in a microgravity environment - Suda, Yoshiyuki; Itoh, M; Sakai, Y; Matsuura, K; Honma, N; Kimura, T
The motion of boiling liquid nitrogen (LN2) between electrodes and its surface profile in a microgravity environment just after release from terrestrial gravity are observed. The dynamic behaviour is analysed considering the following forces: the Maxwell stress, surface tension and viscosity, and is explained consistently by theory including these forces. The velocity of the liquid driven by the Maxwell stress and the capillary force (surface tension) is compared with that driven by the capillary force only. The growth dynamics of bubbles produced on the surface of electrodes is discussed.
6.
Preparation of double layer film of boron and carbon by pulsed laser deposition - Suda, Yoshiyuki; Suganuma, Y; Sakai, Y; Suzuki, K; Tsujino, J; Homma, N
Double layer films of boron and carbon were prepared by pulsed laser deposition (PLD) on silicon substrates. The film surface morphology was examined by atomic force microscopy (AFM). The chemical composition of the elements, carbon, boron, silicon and oxygen, and bonding state of carbon atoms as a function of the depth from the film surface were analyzed by X-ray photoelectron spectroscopy (XPS) with argon ion sputtering technique. Carbon atoms bonded to boron (C---B) were observed as well as carbon atoms bonded to carbon (C---C).
7.
The spatio-temporal development of electron swarms in gases: moment equation analysis and Hermite polynomial expansion - Sugawara, Hirotake; Sakai, Y; Tagashira, H; Kitamori, K
Spatio-temporal development of electron swarms in gases is simulated
using a propagator method based on a series of one-dimensional spatial moment
equations. When the moments up to a suecient order are calculated, the spatial
distribution function of electrons, p(x), can be constructed by an expansion technique
using Hermite polynomials and the weights of the Hermite components are represented
in terms of the electron diausion coeecients. It is found that the higher order Hermite
components tend to zero with time, that is, the normalized form of p(x) tends to a
Gaussian distribution. A time constant of the relaxation is obtained as the ratio of
the second- and third-order diausion...
8.
Spin-polarized scanning tunneling microscopy and spectroscopy study of c(2x2) reconstructed Cr(001) thin film surfaces - Oka, Hirofumi; Sueoka, Kazuhisa
Spin dependent electronic properties of c(2x2) Cr(001) thin film surfaces grown on MgO(001) substrates are investigated by means of spin-polarized scanning tunneling microscopy and spectroscopy. An averaged dI/dV spectrum obtained on the c(2x2) Cr(001) thin film surfaces exhibits a surface state around +0.1 eV above the Fermi level. The intensity of the surface state peak in the spectra measured on (001) terraces is alternately varied whenever a monatomic step is crossed. Therefore, the shifted surface state as well as an original one on (1x1) Cr(001) surfaces has spin-polarized feature. (C) 2006 American Institute of Physics.
9.
Experimental realization of a ballistic spin interferometer based on the Rashba effect using a nanolithographically defined square loop array - Koga, Takaaki; Sekine, Yoshiaki; Nitta, Junsaku
We succeeded in observing gate-controlled electron spin interference in nanolithographically defined square loop arrays that were fabricated in
In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum wells (QWs). In this experiment, we demonstrated electron spin precession in ballistic channels within the QW that is caused by the Rashba effect. It turned out that the spin precession angle θ was gate controllable by more than 0.75π for a length of 1.5 µm. Thus, the demonstration of the large controllability of θ by the applied gate voltage was carried out in a more direct way using spin interference of an electron wave function than the conventional beating analysis...
10.
An analysis of transverse evolution of electron swarms in gases using moment equations and a propagator method - Sugawara, Hirotake; Sakai, Yosuke
A simulation technique for analysis of transverse evolution of electron
swarms in gases was developed based onmoment equations derived from the Boltzmann
equation. A numerical calculation of the moment equations for an electron swarm was
performed using a propagator method and it was demonstrated that the propagator
method can be used to calculate the higher-order transverse diffusion coefficients stably.
Applying a Hermite expansion technique, the electron distribution in real space and
other electron swarm parameters were derived as functions of the transverse position.
The calculation result was verified by comparisons with those by a Monte Carlo
simulation and other methods. Features of the transverse electron swarm evolution
were presented.
11.
Tunnel magnetoresistance in epitaxial magnetic tunnel junctions using full-Heusler alloy Co2MnGe thin film and MgO tunnel barrier - Marukame, Takao; Ishikawa, Takayuki; Matsuda, Ken-ichi; Uemura, Tetsuya; Yamamoto, Masafumi
We fabricated fully epitaxial magnetic tunnel junctions (MTJs) using a Co-based full-Heusler alloy Co2MnGe (CMG) thin film as a lower electrode, an MgO tunnel barrier, and a Co50Fe50 upper electrode and investigated their tunnel magnetoresistance (TMR) characteristics. The microfabricated MTJs showed strongly temperature-dependent TMR characteristics with typical TMR ratios of 70% at 7 K and 14% at room temperature (RT). Furthermore, the TMR characteristics exhibited the following notable features in the bias voltage (V) dependence: (1) a cusplike V dependence within a range of similar to +/- 200 mV around V=0 at 7 K, which was smeared out at RT,...
12.
Structural and magnetic properties of epitaxially grown full-Heusler alloy Co2MnGe thin films deposited using magnetron sputtering - Ishikawa, Takayuki; Marukame, Takao; Matsuda, Ken-ichi; Uemura, Tetsuya; Arita, Masashi; Yamamoto, Masafumi
Full-Heusler alloy Co2MnGe thin films were epitaxially grown on MgO (001) substrates using magnetron sputtering. The films were deposited at room temperature and subsequently annealed in situ at temperatures ranging from 400 to 600 degrees C. X-ray pole figure measurements for the annealed films showed (111) peaks with fourfold symmetry, which gives direct evidence that these films are epitaxial and crystallized in the L2(1) structure. Furthermore, cross-sectional transmission electron microscope images of a fabricated film indicated that it is single crystalline. The annealed films had sufficiently flat surface morphologies with roughnesses of about 0.26 nm rms at film thicknesses of...
13.
Properties of electron swarms in gases in the upstream region of an electron source - Sugawara, H.; Sakai, Y.; Tagashira, H.
Exponential spatial growth of electron swarms in gases under steady-state
Townsend conditions may be observed not only in the downstream region of an electron
source but also in the upstream region due to backward diffusion. Relations among
swarm parameters in the upstream region were deduced and found to have peculiar
characteristics. For example, the sign of the average electron velocity vd for steadystate
Townsend conditions depends on whether the gas is electro-positive or electronegative.
This property is confirmed quantitatively by calculating the electron energy
distribution using a propagator method modified for analysis in the upstream region.
As an example of the effect of backward diffusion, the decay in...
14.
Conductance measurements of nanoscale regions with in situ transmission electron microscopy - Arita, Masashi; Hirose, Ryusuke; Hamada, Kouichi; Takahashi, Yasuo
Conductance measurements of nanostructures with simultaneous transmission electron microscopy (TEM) were performed on thin insulating SrF2 films (3 nm thick) and Fe-SrF2 granular films (10 nm thick) deposited on tip-shaped An electrodes. By using a movable counter electrode, nanoscale regions were selected for investigation. Systematic measurements taken during the deformation of the SrF2, film by the counter-electrode provided a tunnelling barrier height of about 2.5 eV The conductance of Fe-SrF2 in nanoscale (similar to 500 nm(2)) showed the Coulomb staircase like characteristics at room temperature. The staircase period approximately corresponded to the value estimated from the geometry observed by TEM....
15.
Electron acceleration in gas by impulse electric field and its application to selective promotion of an electron–molecule reaction - Sugawara, Hirotake; Sakai, Yosuke
We have simulated electron acceleration under short intense impulse electric fields of 0.1–1 kV cm-1 strength and ~1 ns duration in N2 at 65.5 Pa. The electron acceleration is completed in a practically collisionless condition when the impulse duration is comparable with or shorter than the electron mean free time. On the basis of this feature, we have proposed a way to produce a group of monoenergetic electrons. The electron energy after acceleration is controllable by the impulse strength and duration, and we have demonstrated selective promotion of the excitation producing N2(A 3Σu+) metastable excited molecules. The selectivity has been...
16.
Two-peaked velocity distribution function of electrons in carbon tetrafluoride in crossed electric and magnetic fields - Sugawara, Hirotake; Oda, Akinori; Sakai, Yosuke
Monte Carlo simulation shows that the electron velocity distribution function (EVDF) in CF4 in crossed electric and magnetic fields (ExB fields) has two peaks at low E/B values. The EVDF peaks are formed around a pair of points in velocity space at which electrons are stationary against the acceleration under the E´B fields and scattering by collisions with CF4 molecules. The stationary points appear when the E/B value is lower than the electron speed at which the total electron collision frequency in CF4 takes its minimum.
17.
Barrier effect of collisional processes on electron swarms in nitrogen - Sugawara, Hirotake; Satoh, Kohki; Sakai, Yosuke
The electron velocity distribution function (EVDF) of electron swarms in N2 has a constricted part at an electron energy of around 2-3 eV. This feature has been explained by considering the barrier effect of vibrational excitation collisions that prevents the gain of energy by slow electrons. In order to investigate the barrier effect in detail further, we simulated the electron behaviour around the energy range of the barrier. We found that momentum transfer collisions also contribute to the barrier effect in collaboration with vibrational excitation. In addition, an evaluation of the electron flow in velocity space is thought to indicate...
18.
Effect of near-threshold ionization on electron attachment in gaseous dielectrics - Sugawara, Hirotake; Ishigaki, Takuya; Hirochi, Yuuki; Sakai, Yosuke
It has been predicted that near-threshold ionization (NTI) in a gaseous dielectric inhibits the development of electron avalanche when the gaseous dielectric has a sufficient capability for
low-energy electron attachment. The NTI leaves little energy for the primary and secondary electrons involved in the ionization; thus, both electrons can be captured by dielectric gas molecules without further ionization. A computational estimation indicates that this process can occur in SF6.
19.
Predicting the amount of carbon in carbon nanotubes grown by CH4 rf plasmas - Okita, Atsushi; Suda, Yoshiyuki; Ozeki, Atsushi; Sugawara, Hirotake; Sakai, Yosuke
Carbon nanotubes (CNTs) were grown on Si substrates by rf CH4 plasma-enhanced chemical vapor deposition in a pressure range of 1–10 Torr, and then characterized by scanning electron microscopy. At 1 Torr, the CNTs continued growing up to 60 min, while their height at 4 Torr had leveled off at 20 min. CNTs hardly grew at 10 Torr and amorphous carbon was deposited instead. CH4 plasma was simulated using a one-dimensional fluid model to evaluate the production and transport of radicals, ions, and nonradical neutrals. The amount of simulated carbon supplied to the electrode surface via the flux of radicals...
20.
Fabrication and Characterization of InGaAs/InAlAs Insulated Gate Pseudomorphic HENTs Having a Silicon Interface Control Layer - XIE, Yong-Gui; KASAI, Seiya; TAKAHASHI, Hiroshi; JIANG, Chao; HASEGAWA, Hideki
A novel InGaAs/InAlAs insulated gate (IG) pseudomorphic high electron mobility transistor (PHEMT) having a silicon interface control layer (Si ICL) is successfully fabricated and characterized. Systematic efforts to characterize and optimize the insulated gate structure and the PHEMT fabrication process were made by using in-situ X-ray photoelectron spectroscopy (XPS) and capacitance-voltage (C-V) techniques. This led to successful fabrication of a novel IG-PHEMT showing excellent stable DC characteristics with a good pinch off and a high transconductance (177 mS/mm), very small gate leakage currents, very high gate breakdown voltages (about 40 V) and respectable RF characteristics fT = 9 GHz and...
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