bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra-Broadband CW Supercontinuum Generation Centered at 1483.4 nm from Brillouin/Raman Fiber Laser
Authors: Seong Kim Mahendra Prabhu , Ken-ichi Ueda Ken-ichi Ueda
Published: October 2002

About 100 nm CW supercontinuum centered at 1483.4 nm was generated from Brillouin/Raman fiber laser (BRFL). The BRFL consists
of a Raman cavity with 700 m of phosphosilicate fiber (PDF) and pairs of fiber Bragg grating (FBG) mirrors and a Brillouin cavity with the
PDF, 500 m of flexcor-1060 fiber, and output FBG mirrors. With 8.4 W/1064 nm Yb-doped double-clad fiber laser as pump and 50%
feedback FBG mirror at end of BRFL, output power of over 1 W with 100 nm bandwidth centered at 1483.4 nm and weak 0.11 nm spectral
modulation were observed.
Na: A New Flux for Growing Hexagonal Boron Nitride Crystals at Low Temperature
Authors: Khin Yap Masaichi Yano , Mitsuo Okamoto Mitsuo Okamoto , Mamoru Onda Mamoru Onda , Masashi Yoshimura Masashi Yoshimura , Yusuke Mori Yusuke Mori , Takatomo Sasaki Takatomo Sasaki
Published: October 2002

The 2075°C melting temperature of boron has hindered the growth of hexagonal boron nitride (h-BN) crystal. The use of Si flux was reported to decrease the growth temperature to 1850°C. In this work, we discovered Na as a new flux for the growth of h-BN crystals at a temperature as low as 700°C. The growth of h-BN detected by X-ray diffraction (XRD) was consistent with the hexagonal features observed by scanning electron microscopy (SEM). Absorption at ∼1372 cm-1 was indicated by Fourier transform infrared (FTIR) spectroscopy. This absorption was attributed to the in-plane B-N stretching mode of h-BN. Emissions at photon energies as high as ∼5.6 eV are observed from cathodoluminescence (CL) spectra, indicating an optical band gap of at least 5.6 eV.
High-Magnetoresistance Tunnel Junctions Using Co75Fe25 Ferromagnetic Electrodes
Authors: Xiu-Feng Han Xiu-Feng Han , Tadaomi Daibou Tadaomi Daibou , Makoto Kamijo Makoto Kamijo , Kazuya Yaoita Kazuya Yaoita , Hitoshi Kubota Hitoshi Kubota , Yasuo Ando Yasuo Ando , Terunobu Miyazaki Terunobu Miyazaki
Published: October 2002

Tunnel magnetoresistance (TMR) effect and the applied voltage dependence of the TMR ratio
in the tunnel junctions Ta(5 nm)/Ni79Fe21(3 nm)/Cu(20 nm)/Ni79Fe21(3 nm)/
Ir22Mn78(10 nm)/Co75Fe25(4 nm)/Al(0.8 nm)-oxide/Co75Fe25(4 nm)/
Ni79Fe21(20 nm)/Ta(5 nm) were investigated. MR ratio, effective barrier height and
width, and breakdown voltage of the junctions can be remarkably enhanced after annealed at
300°C for an hour using Co75Fe25 as ferromagnetic electrodes and Cu as bottom
conduction electrode. High MR ratio of 49.7% at room temperature and 69.1% at 4.2 K for the TMR
junctions were observed.
Improvement of Crystalline Quality in GaN Films by Air-Bridged Lateral Epitaxial Growth
Authors: Isao Kidoguchi Isao Kidoguchi , Akihiko Ishibashi Akihiko Ishibashi , Gaku Sugahara Gaku Sugahara , Ayumu Tsujimura Ayumu Tsujimura , Yuzaburoh Ban Yuzaburoh Ban
Published: October 2002

Air-bridged lateral epitaxial growth (ABLEG), a new technique of lateral growth of GaN films, has been developed using low-pressure metalorganic vapor phase epitaxy. A previously grown 1-µm-thick GaN film is grooved along the <1\bar100 >GaN direction, and the bottoms of the trenches and the sidewalls are covered with a silicon nitride mask. A free-standing GaN material is regrown from the exposed (0001) surface of the ridged GaN seed structure. Cross-sectional transmission electron microscopy analysis reveals that the dislocations originating from the underlying seed GaN extend straight in the <0001 > direction and dislocations do not propagate into the wing region. The wing region also exhibits a smooth surface and the root mean square roughness is found to be 0.088 nm by atomic force microscopy measurement of the (0001) face of the wing region.
Experiment on Deflection of High-Speed Plastic Pellets Using Curved Guide Tubes
Authors: Nihei Hitoshi , Ogawa Yuichi , Nakajima Toru , Ohno Masashi , Hosono Yoneichi , Morikawa Junji , Shirai Yoshiaki , Morita Shigeru
Published: October 2002

High-speed plastic pellets for plasma diagnostics have been
transported using guide tubes curved at 90°. The ratio of
the output velocity to the input one has depended on the roughness
of the inner surface of the curved tube, but not on the curvature of
the tube. The pellets are transported through the curved guide tube
without being broken and without a significant reduction in
speed. The output velocities required for plasma diagnostics have
been obtained. The experimental results show that the pellets do not
pass through the curved tube by means of sliding, but via repeated
reflections.
Precise Laser Ultrasonic Technique with Application to Silicon Velocity Measurements
Authors: Matsuda Youichi , Nakano Hidetoshi , Nagai Satoshi
Published: October 2002

A technique based on high-frequency laser ultrasound has been developed for
sound velocity measurements. Precise velocity measurements were realized by
employing a 140 MHz ultrasonic rf burst generated by a mode-locked laser in
combination with a pulse-echo-overlap method. As an illustrative application of this
technique, longitudinal and shear velocities in silicon single crystals at 25°C were
measured with precision better than 50 ppm and 110 ppm, respectively. Diffraction
effects were calculated and verified experimentally. Furthermore, longitudinal velocities
in the <110 > direction were successfully measured up to
800°C.
Analysis of Waveguides and Waveguide Bends in Photonic Crystal Slabs with Triangular Lattice
Authors: Alongkarn Chutinan Alongkarn Chutinan , Susumu Noda Susumu Noda
Published: October 2002

Numerical studies on waveguides and waveguide bends in two-dimensional photonic crystal triangular lattice slabs are presented. The waveguides are created by filling a row of air holes in the Γ-J direction. Instead of using the leaky waveguide modes, we focus our designs in the frequency range where the waveguide mode is nonleaky. It is shown that a high transmission of more than 90% through the sharp bend can be obtained in some frequency ranges.
Current Injection Free-Exciton Recombination Emission from Synthesized Diamond
Authors: Horiuchi Kenji , Nakamura Kazuo , Yamashita Satoshi
Published: October 2002

Emission in the UV region is obtained at room temperature from a current
injection light-emitting device composed of high-quality synthesized diamond
crystal. The operating wavelength is observed to be as short as 235 nm. The main
mechanism for the UV emission is found to be TO-phonon-assisted free-exciton
recombination, both in the surface conduction device as well as in the p-type one. Since
the exciton plays the role of an intermediate state in the photon emission process even
at room temperature, the emission efficiency is expected to be higher than that of
other indirect semiconductors.
UV Photoemission Study of AlGaN Grown by Metalorganic Vapor Phase Epitaxy
Authors: Takahiro Kozawa Takahiro Kozawa , Tomohiko Mori Tomohiko Mori , Takeshi Ohwaki Takeshi Ohwaki , Yasunori Taga Yasunori Taga , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

The electronic surface properties of AlxGa1-x
N have been studied with ultraviolet photoemission spectroscopy (UPS). Samples were grown by metalorganic vapor phase epitaxy and prepared with multiple cycles of nitrogen ion sputtering and annealing to obtain clean surfaces. The energy position of the valence band maxima of the GaN surface was at 3.0 eV below the Fermi level and the upward band bending was 0.35 eV. The widths of the UPS energy distribution curves of AlxGa1-x
N yielded the ionization energy, and the electron affinity was determined to be 3.6–2.9 eV for x = 0–0.6. It was found that the electron affinity of AlxGa1-x
N was positive and reduced with increasing the AlN molar fraction.
Direct Preparation of Crystalline SrBi2(Ta1-xNbx)2O9 Thin Films by Thermal Metalorganic Chemical Vapor Deposition at Low Temperature
Authors: Mitsuya Masatoshi , Nukaga Norimasa , Funakubo Hiroshi
Published: October 2002

Polycrystalline SrBi2(Ta1-x
Nb
x
)2O9 (SBTN) thin films with large ferroelectricity were directly prepared on Pt/Ti/SiO2/Si substrates even at 585°C by thermal metalorganic chemical vapor deposition (MOCVD). Thin films mainly consisting of the SBTN phase were obtained even at 585°C. The (103)-oriented film changed to a (001)-oriented one when the deposition temperature increased. The 200-nm-thick film deposited at 585°C had large ferroelectricity, i.e., two times the remanent polarization (2Pr) and two times the coercive field (2Ec) of 12.2 µC/cm2 and 160 kV/cm, respectively. When the deposition temperature was increased to 670°C, the 2Pr and 2Ec values increased to 23.8 µC/cm2 and 190 kV/cm, respectively.
Fabrication of Zn:LiNbO3 Waveguides by Diffusing ZnO in Low-Pressure Atmosphere
Authors: Suhara Toshiaki , Fujieda Tasuku , Fujimura Masatoshi , Nishihara Hiroshi
Published: October 2002

Fabrication of Zn:LiNbO3 planer and channel waveguides by diffusing ZnO in low-pressure air is presented. The process is simple and does not require special apparatus. Pressure control is crucial to ensure modest indiffusion with suppressed outdiffusion. The waveguides support both ordinary and extraordinary polarization modes, and are expected to be photorefractive-damage resistant. The diffusion temperature considerably lower than that for Ti-indiffusion is advantageous for applications to quasi-phase matched nonlinear optic devices. Single-mode guides of ∼1 dB/cm propagation loss for 1.5 µm wavelength band were obtained.
Ellipsometric Study of the Optical Properties of InGaAsN Layers
Authors: Li Pei-Wen , Guang Huei-Chen , Li Nein-Yi
Published: October 2002

We report the optical properties of the quaternary compound semiconductor, In
x
Ga1-x
As1-y
N
y
, with various indium and nitrogen contents. The refractive indices of In
x
Ga1-x
As1-y
N
y
epilayers were systematically studied by variable angle spectroscopic ellipsometry (VASE) in the wavelength range of 400 to 700 nm. Analysis of the spectroscopic ellipsometry data indicated that the refractive index of In
x
Ga1-x
As1-y
N
y
increases in proportion to the indium and nitrogen contents. It is also found that the rate of increase of the refractive index in In
x
Ga1-x
As1-y
N
y
with increasing nitrogen content is much larger than that with increasing indium content. The transition energy E
1 as a function of N composition for In0.3Ga0.7As1-y
N
y
epilayers was also examined based on the second-derivative spectra of the dielectric function.
Organic Light-Emitting Devices Patterned by Screen-Printing
Authors: Mori Kentaro , Ning TaiLu , Ichikawa Musubu , Koyama Toshiki , Taniguchi Yoshio
Published: October 2002

We have demonstrated a patterned organic light-emitting device fabricated by screen-printing on the basis of the doped hole-transport layer (DHTL) which is our novel concept. The DHTL, which consisted of a polymeric compound of N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (P-TPD) as a hole-transport material and tris (4-bromophenyl) aminium hexachloroantimonate (TBAHA) as an electron-accepting dopant, was patterned by screen-printing. The luminous area of the device was restricted to the DHTL-printed area. The device was operated at approximately 5 V, and a luminance of 4800 cd/m2 was obtained at a current density of 150 mA/cm2. The appropriate concentration of P-TPD was 80 g/l in dichlorobenzene, at which a smooth and pinhole-less layer was obtained with a thickness of 0.5 µm. The suitable concentration of TBAHA in P-TPD was approximately 8 wt%.
Phosphorus Diffusion from Doped Polysilicon through Ultra-Thin SiO2 Films into Si Substrates
Authors: Tsubo Yumiko , Komatsu Yukio , Saito Kazumasa , Matsumoto Satoru , Sato Yoshiyuki , Yamamoto Ikunao , Yamashita Yoshifumi
Published: October 2002

The diffusion of phosphorus into ultra-thin oxides from phosphorus-doped polysilicon sources was studied. The two-boundary diffusion model can be applied to the diffusion of phosphorus in ultra-thin oxides, and the diffusivity and segregation coefficient were obtained based on the model. The dependence of the diffusivity on oxide thickness and drive-in ambients was investigated. The enhanced diffusion, which has been observed for boron diffusion in ultra-thin oxides, was not observed for phosphorus diffusion. For the diffusion in dry O2 and wet O2 ambients, the enhanced diffusion due to high phosphorus concentration in the polysilicon was observed.
Diode-Laser-Array End-Pumped Actively Q-Switched Nd:GdVO4 Laser at 1.06 µm Formed with a Flat-Flat Resonator
Authors: Liu Junhai , Yu Xiaoqiang , Xu Xinguang , Meng Xianlin , Zhang Huaijin , Zhu Li , Wang Jiyang , Shao Zongshu , Jiang Minhua
Published: October 2002

A diode-laser-array end-pumped acousto-optically Q-switched Nd:GdVO4 laser formed by a simple flat-flat cavity was developed. A maximum average output power at 1.06 µm of 6.15 W at a pulse repetition frequency (PRF) of 60 kHz was obtained with an optical conversion efficiency of 36.2% and a slope efficiency of 42%. The highest single pulse energy and the highest peak power were achieved at a PRF of 10 kHz, and were measured to be 267 µJ and 19.1 kW, respectively. The shortest laser pulse was found to occur at a PRF of 20 kHz, with a full width at half-maximum (FWHM) width measured to be 10.5 ns. It has also been shown that the cavity length; the Q-switching repetition frequency; and the pump power level, all the factors had significant influences on the generated laser pulse width.
Dynamical Behavior of Higher Harmonic Generation from a Picosecond-Laser-Produced Solid Surface Plasma
Authors: Atsushi Ishizawa Atsushi Ishizawa , Teruto Kanai Teruto Kanai , Tsuneyuki Ozaki Tsuneyuki Ozaki , Hiroto Kuroda Hiroto Kuroda
Published: October 2002

We have studied experimentally the efficiency of the harmonics from solid surface plasma by varying the electron density scale length produced during the interaction of a 2.2 ps, 100 mJ, 1054 nm, p-polarized laser pulse with deposited Al targets. Although third harmonic radiation can also be observed when a single beam is used, an approximately 5 ps time difference between the prepulse and the main pulse results in an increase in the harmonic signal by a factor of 2–3, which then decreases after 10 ps. The results for the 4th- and 5th-order harmonic generation are also similar. We have also calculated the electron density scale length by using the one-dimensional (1D) hydrodynamic code HYADES. The calculation results are in good agreement with our experimental results. It is found that it is possible to generate high efficiency harmonics by controlling the density gradient using a double laser pulse.
Pulsed Ion-Beam Evaporation for Thin-Film Deposition
Authors: Jiang Weihua , Ide Koji , Kitayama Shinji , Suzuki Tsuneo , Yatsui Kiyoshi
Published: October 2002

The process of pulsed ion-beam evaporation was studied by investigating its three important stages: target ablation, plasma expansion, and thin-film deposition. The diagnostic results have shown that the target mass loss caused by ion-beam ablation mainly depends on the melting and boiling temperatures of the target materials. In addition, high-speed photographs have shown that the expansion of the ablation plasma is highly directional. The result of thin-film composition analysis has indicated that the ablation plasma moved along the substrate surface during thin-film deposition.
Room Temperature Annealing Behavior of Copper-Related Deep Levels in P-Type Floating Zone Silicon Wafers
Authors: Kurita Kazunari , Shingyouji Takayuki
Published: October 2002

Deep level transient spectroscopy analysis of copper-doped p-type floating-zone silicon (FZ-Si) wafer was performed. Five deep energy level states observed in copper-doped silicon (E
v+0.1 eV, E
v+0.15 eV, E
v+0.22 eV, E
v+0.26 eV and E
v+0.43 eV) with concentrations of 1×1011 to 1×1012 cm-3 were detected. We observed that the amplitude of only one peak (deep level at E
v+0.26 eV) dramatically decreased with time during storage at room temperature, but stabilized at a concentration of about 1×1012 cm-3 after 2 days. The other deep level concentrations did not change after two months storage at room temperature. Therefore, it was concluded that room-temperature annealing resulted in a decrease in the deep level at E
v+0.26 eV due to the formation of copper-precipitate related defects and out-diffusion to the silicon surface.
Temperature Dependence of Excitonic Γc–Γv Transition Energies of GaxIn1-xP Crystals
Authors: Ishitani Yoshihiro , Yaguchi Hiroyuki , Shiraki Yasuhiro
Published: October 2002

The excitonic Γc–Γv transition energies of disordered Ga
x
In1-x
P (x=0.0, 0.52, 0.70, and 1.0) crystals have been measured by photoreflectance (PR) measurements at temperatures from 20 to 300 K. The photoluminescence (PL) peak energy at 20 K is found to be lower than the energy obtained from PR or photoluminescence excitation (PLE) spectra by about 6 meV. The temperature dependence of the transition energy is expressed by a function consisting of several terms, each of which represents the effect of the volume-thermal expansion or the electron-phonon interaction. It is found that the temperature-dependent decrease of the transition energy from the pure electronic transition energy is mainly caused by the electron-phonon interaction. The energy shift due to the electron-phonon interaction increases as the GaP mole fraction increases.
Planar-type Ferromagnetic Tunnel Junctions Fabricated by Atomic Force Microscope for Nonvolatile Memory
Authors: Takemura Yasushi , Shirakashi Jun-ichi
Published: October 2002

A nonvolatile magnetic memory based on a planar-type ferromagnetic single electron transistor is proposed. A sense signal dominated by a co-tunneling current under Coulomb blockade enables a low-power operation of the memory. The small tunnel junctions required for a room temperature operation of the device can be consisted of planar-type tunnel junctions fabricated by a nano-oxidation technique using atomic force microscope.
A Modified Transparent Conducting Oxide for Flat Panel Displays Only
Authors: Chae Gee Sung
Published: October 2002

To keep up with the current development trends of thin film transistor liquid-crystal display (TFT-LCD), two major requirements must be satisfied in the transparent conducting oxide (TCO)-meterial itself. First, there must be no etch residue after TCO patterning and good etch selectivity against low electrical resistivity metals. Second, there must be good chemical endurance of the TCO material to secure a good electrical signal that is transported from the controller to the TFT-LCD by way of contact between the TCO and the tape carrier package (TCP). To obtain a new TCO material to achieve the kind of trade-off behavior that a TCO film has, the method in which ZnO is alloyed into indium tin oxide (ITO) was studied. It was determined that the 2.0–4.0 wt% ZnO-alloyed ITO film (named ITZO) is desirable in order to obtain a well-defined patterning ability and the stable TCP-contact property simultaneously. It is concluded that ITZO film can replace ITO and IZO for the pixel electrodes of a TFT-LCD designed with specifications for high resolution and large display size.
Threshold Gain due to Distributed-Feedback in Two-Dimensional Triangular- and Square-Lattice Photonic Crystal Lasers
Authors: Susa Nobuhiko
Published: October 2002

Numerical simulation of 2D square (SQ)- and triangular (TR)-lattice infinite-width photonic crystal distributed-feedback (DFB) lasers showed that the threshold gain (g
th) for the 3rd photonic band was the smallest in the Γ–X direction (SQ-lattice), and was next smallest in the Γ–M direction (TR-lattice), but one order of magnitude larger. The g
th values for the 3rd photonic bands were qualitatively proportional to the slopes approximated for the 3rd bands, but the g
th values for the 1st bands were independent of the lattice structure and direction. All the g
th values for the 1st and 3rd bands decreased to about 1/50 of the original values when the thickness was increased from 8 to 32 cylinders because of the approaching of the threshold wavelength to the band edge and the longer optical path.
Nondestructive Detection of Small Internal Defects in Carbon Steel by Laser Ultrasonics
Authors: Tanaka Takao , Izawa Yasukazu
Published: October 2002

A small internal defect 100 µm in diameter in a carbon steel sample was successfully detected by the laser ultrasonic technique. Irradiation of a Q-switched Nd:YAG laser was used for ultrasonic generation, and a frequency-doubled CW Nd:YAG laser combined with a Fabry-Perot etalon was used for detection of ultrasonic vibration on the carbon steel surface. The ratio of the internal defect diameter to the ultrasonic wavelength (d/λ) was estimated to be about 0.07. The dependence of the normalized amplitude of the defect signal on the defect diameter was measured, and the ultrasonic reflectance by the cylindrical internal defect was roughly evaluated using the experimental results. It is considered that the laser ultrasonic technique has the ability to detect internal defects in industrial components and engineering structures, which is comparable to that of the conventional ultrasonic testing technique.
TiN Films Prepared by Flow Modulation Chemical Vapor Deposition using TiCl4 and NH3
Authors: Hirotaka Hamamura Hirotaka Hamamura , Hiroshi Komiyama Hiroshi Komiyama , Yukihiro Shimogaki Yukihiro Shimogaki
Published: October 2002

We propose a new chemical vapor deposition (CVD) process, the flow modulation chemical vapor deposition (FMCVD) process, to obtain high quality titanium nitride (TiN) films at low deposition temperature in a single CVD chamber. FMCVD uses sequential deposition and reduction processes, such as the deposition of TiN films followed by chlorine reduction. This cycle was repeated to achieve sufficient film thickness. By decreasing the thickness in one cycle, the residual chlorine concentration and the resistivity of the films decreased. Using FMCVD process, we could achieve low resistivity (250 µΩcm), low residual chlorine concentration (2 at.%) with uniform step coverage at low deposition temperature (380°C).
Hydrothermal Reaction of Copper and Water
Authors: Fujikawa Takao , Yoshikawa Tetsuya
Published: October 2002

Experiments to investigate the reaction between copper and water were carried out. A copper powder sample was encapsulated with water in a Cu capsule and annealed at 120 MPa, 9000 s, at temperatures from 300°C to 400°C. Observation of the processed sample using an optical microscope and X-ray diffraction analysis showed that copper and water react and form Cu(OH)2 and Cu2O. To date the mechanisms of the reaction are not clear, however the dissipation of hydrogen and oxygen appears to play an important role.
Photoinduced Valence Changes of Samarium Ions Inside a Silica-Based Glass with Near- Infrared Femtosecond-Laser Pulses: Materials for Three-Dimensional Optical Memory
Authors: Koji Fujita Koji Fujita , Kazuyuki Hirao Kazuyuki Hirao
Published: October 2002

We report photoinduced valence changes of samarium ions inside a silica-based glass using focused femtosecond-laser pulses of 800 nm wavelength. Photoluminescence spectra reveal that femtosecond-laser irradiation reduces Sm3+ in the vicinity of the focal point of the laser beam to Sm2+. The mechanism of the photoinduced reduction of Sm3+  is discussed based on optical absorption and electron spin resonance spectra.
A Polarization Readout Method Applied to a Groove Baseband Recording Optical Read-Only Memory Discs
Authors: Kobayashi Seiji , Yamatsu Hisayuki , Takemoto Yoshihiro
Published: October 2002

In our pervious papers, we proposed a method named groove baseband recording (GBR), to record a multilevel signal onto optical read-only memory discs. We use signal processing to generate a multilevel recording signal, which satisfies the DC-free and zero-intersymbol interference condition. The resultant multilevel signal is emboss-recorded as position displacement of groove walls. In this study, we use the polarization effect to detect the position displacement of the groove walls. By our experiments, we confirmed sufficient signal-to-noise ratio and full bandwidth given by the optical transfer function. We also encountered a strong signal distortion, for which we introduced a feedback to reduce nonlinear characteristics existing in the recording and playback systems. An experimental disc of 0.7 micron track pitch and 0.194 micron/bit density is fabricated. When a magneto optical equivalent optical pickup is used to playback this disc, we confirm a 2-dimensional eye pattern of 16 levels is clearly observed.
25 GB Read-Only Disk System using the Two-Dimensional Equalizer
Authors: Tomita Yoshimi , Nishiwaki Hiroshi , Miyanabe Shogo , Kuribayashi Hiroki , Yamamoto Kaoru , Yokogawa Fumihiko
Published: October 2002

In order to achieve a higher density disk system, we applied a two-dimensional equalizer along with a limit equalizer to an optical disk drive system which has an objective lens with a numerical aperture of 0.85 and a thin transparent cover layer of 0.1 mm thickness. Consequently we realized the 25 GB read-only disk system with sufficient margins against disk tilt and defocus. The two-dimensional equalizer is composed of a cross-talk cancel system and a tangential adaptive equalizer, and could prevent deterioration due to inter-symbol interference and cross-talk from adjacent tracks. Using the limit equalizer could prevent deterioration due to disk noise. By measuring the jitter with the limit equalizer, which has an ability to expand the system margin almost equivalent to that of the Viterbi decoder, we could evaluate the disk quality for standardization and verification.
Ultraviolet Light Generation in a Periodically Poled MgO:LiNbO3 Waveguide
Authors: Sugita Tomoya , Mizuuchi Kiminori , Kitaoka Yasuo , Yamamoto Kazuhisa
Published: October 2002

We demonstrated the highly efficient UV light generation of 386 nm wavelength in a periodically poled MgO:LiNbO3 waveguide. Utilizing multiple short pulses for electric poling to off-cut MgO:LiNbO3, we succeeded in fabricating a uniform periodically poled structure with a period of 2.2 µm and a thickness of 1.5 µm over a 10 mm interaction length. By using this structure with a waveguide, the harmonic ultraviolet light generation with a high conversion efficiency of 1000 %/W was achieved in a single-pass configuration.
High-Numerical-Aperture Objective Lens for Blue Laser Disk System
Authors: Sato Makoto , Ezuka Toshiharu , Koike Katsuhiro , Murao Noriaki , Kikuchi Ikuya , Maeda Takanori
Published: October 2002

The authors have developed and prototyped an adjustment-free two-component objective lens for a blue laser disk system (numerical aperture = 0.85, disk thickness = 0.1 mm). The lens is designed to be sufficiently tolerant to the relative position, i.e., the decentering, tilt and spacing inaccuracy between the two lenses, and does not require adjustment of the two lenses. We have carried out some experiments and the tolerance of our newly developed objective lens has been experimentally verified.
Confinement and Transfer of a Two-Dimensional Wave Packet under Crossed Electric and Magnetic Fields
Authors: Hidetoshi Takagi Hidetoshi Takagi , Mitsuru Ishida Mitsuru Ishida , Nobuhiko Sawaki Nobuhiko Sawaki
Published: October 2002

The motion of a two-dimensional Gaussian wave packet was analyzed under crossed electric and magnetic fields by solving the time-dependent Schrödinger equation numerically. It was found that the perpendicular magnetic field prevents the expansion of the wave packet and the in-plane electric field transfers the wave packet. The possibility of trapping and transfer of the wave packet is discussed by introducing a phenomenological decay term into the partial waves.
Excited-State Magnetoluminescence of InAs/GaAs Self-Assembled Quantum Dots
Authors: Paskov Plamen P. , Holtz Per-Olof , Monemar Bo , Garcia Jorge M. , Schoenfeld Winston V. , Petroff Pierre M.
Published: October 2002

The magnetoluminescence of InAs/GaAs self-assembled quantum dots (QDs) is studied. Using different excitation intensities, the dots are filled with up to 11–12 electron-hole pairs and the magnetic field evolution of the excited-state emissions is revealed. The magnetoluminescence spectra resemble very well the spectra of uncorrelated electro-hole pairs. A splitting of the states with a nonzero angular momentum quantum number is observed and the in-plane reduced electron-hole mass is determined. The experimental value is found to be in a good agreement with the theoretical predictions based on the eight-band k ·p model including both strain effect and band nonparabolicity.
Fabrication Technologies for Double-SiO2-Barrier Metal-Oxide-Semiconductor Transistor with a Poly-Si Dot
Authors: Hatano Tsuyoshi , Ito Yuhei , Nakajima Anri , Yokoyama Shin
Published: October 2002

A double-tunnel-barrier (1.7-nm-thick SiO2) metal-oxide-semiconductor (MOS) transistor with a poly-Si dot was proposed as a single-electron transistor (SET). The simulation results indicated that room-temperature operation of the SET is possible when the poly-Si dot size is in the order of ∼10 nm. Technologies for the fabrication of the MOS transistor were developed. We have evalulated plasma-induced damage at the sidewall of the Si trench in which a poly-Si dot is embedded. It was found that a sacrificial oxidation of 20 nm is necessary to remove the plasma-induced damage. In order to assure complete electrical isolation of the source and the drain by the trench, simulation of the impurity (arsenic, phosphorous and boron) profiles for the MOS transistor with a trench (200 nm length×200 nm depth) were carried out. Test MOS transistors with a poly-Si dot (200 nm length×200 nm height×50–100 nm width) were fabricated. However, the device showed an abnormally large current which may be ascribed to the residual poly-Si in the trench outside of the dot region.
New Technique to Determine Gettering Efficiency of Heavy Metals and Its Application to Carbon-Ion-Implanted Si Epitaxial Wafers
Authors: Itoga Toshihiko , Hozawa Kazuyuki , Takeda Kazuo , Isomae Seiichi , Ohkura Makoto
Published: October 2002

Using a newly developed method to evaluate the gettering efficiency of Si wafers, we found that C-ion implantation prior to epitaxial growth greatly improves the gettering efficiency of heavy metals in epitaxial Si wafers. The gettering efficiency was evaluated through direct observation by total X-ray reflection fluorescence (TXRF) by counting the number of heavy metal atoms that diffused from the back to the front surface of wafers. Heavy metals were deposited on the backside surface of Si wafers from metal-dissolved aqua solution. Two-step annealing was carried out after the deposition. The first step caused metal diffusion and the second produced precipitation from the front surface of the wafers. The effectiveness of the method was confirmed by comparing the results obtained from as-received and intrinsic (or internal) gettering (IG)-processed Czochralski-grown Si wafers. The method was applied to C-ion-implanted epitaxial Si wafers to confirm the improvement in gettering efficiency in accordance with the implanted C dose. The effectiveness of the C-ion implantation was also confirmed by evaluating the electrical characteristics of the oxide grown on the Si wafers.
Electron Motion Three-Dimensional Confinement for Microelectronic Vacuum Gauges with Field Emitters
Authors: Nicolaescu Dan , Kanemaru Seigo , Filip Valeriu , Itoh Junji
Published: October 2002

Novel microelectronics vacuum gauges using field emitters are proposed and the three-dimensional (3D) confinement of electron motion is numerically analyzed. For the case of magnetron and inverted-magnetron structures, the two-dimensional (2D) confinement of electron motion takes place when the electrons move subject to crossed electric E and magnetic B fields. The radial electric field is applied between two cylindrical surfaces coaxial around the X axis, which is also the direction of the applied magnetic field B. A similar structure named “orbitip” is used for electron 2D confinement without magnetic fields for special conditions concerning the electron launching. For all above-mentioned devices, designs involving a region of minimal potential energy for the electron along the axial X direction may ensure the electron motion confinement along this direction. Such configurations are obtained if the inner cylindrical electrode (or the outer one, or both) has a variable radius and also an external planar electrode is used.
High-Performance Epoxy-Resin-Bonded Magnets Produced from the Sm2Fe17Nx Powders Coated by Copper and Zinc Metals
Authors: Noguchi Kenji , Machida Ken-ichi , Adachi Gin-ya
Published: October 2002

Fine powders of Sm2Fe17N
x
coated with copper metal reduced from CuCl2 and/or zinc metal subsequently derived by photo-decomposition of diethylzinc [Zn(C2H5)2] were prepared, and their magnetic properties were characterized in addition to those of epoxy-resin-bonded magnets produced from the coated powders (Cu/Sm2Fe17N
x
, Zn/Sm2Fe17N
x
and Zn/Cu/Sm2Fe17N
x
). The remanence (B
r) and maximum energy product [(BH)max] of double metal-coated Zn/Cu/Sm2Fe17N
x
powders were maintained at higher levels than those of single Zn metal-coated Sm2Fe17N
x
ones (Zn/Sm2Fe17N
x
) even after heat treatment at 673 K since the oxidation resistance and thermal stability were effectively improved by formation of the thick and uniform protection layer on the surface of Sm2Fe17N
x
particles. Moreover, the epoxy-resin-bonded magnets produced from the Zn/Cu/Sm2Fe17N
x
powders possessed good corrosion resistance in air at 393 K which it resulted in the smaller thermal irreversible flux loss than that of uncoated and single Zn metal-coated Sm2Fe17N
x
powders in the temperature range of above 393 K.
Numerical Analysis of Optical Modes in Two-Dimensionally Ordered Polystyrene Spheres in Attenuated Total Reflection Geometry
Authors: Haraguchi Masanobu , Fukui Masuo , Nakai Teruo , Okamoto Toshihiro , Shinya Akihiko , Koda Takao , Shimada Ryoko , Ohtaka Kazuo
Published: October 2002

We have numerically calculated attenuated total reflection (ATR) signals due to two-dimensionally ordered (2D) spheres on a glass substrate for both TE- and TM-polarized incident light beams using a finite difference time-domain method. The calculated ATR spectra are in good agreement with the experimental ones reported previously by us. From the ATR spectra and the spatial distribution of light intensity, it has been found that the ATR dips are due to the excitation of the optical modes in the 2D spheres. The propagation length of the optical modes is confirmed to be comparable to the diameter of the sphere. It indicates that the optical modes propagate in a variety of fashions and the light intensity in the 2D spheres takes a maximum value at the contact points between the spheres.
Modulation Coding for Digital Holographic Memory Using Strontium Barium Niobate
Authors: Kume Tatsuya , Yagi Shogo , Imai Tadayuki , Yamamoto Manabu
Published: October 2002

We discuss modulation coding for a digital holographic memory that uses highly sensitive strontium barium niobate. We observed degradation of the reconstructed images near the beginning of multiplexing. Concluding that the degradation was caused by medium saturation, we reduced it by using a 2:4 modulation code, which reduces the average intensity of the coded pattern and the clustering of bright bits. As a result, we improved the signal-to-noise ratios of the reconstructed images and hence the bit error rates of the system. We obtained bit error rates of less than 10-3, which can be eliminated by conventional error correction, in 50-times-multiplexing.
Ultraviolet Femtosecond Pulse Amplification with High Gain Using Solid-State, Broad-Band Gain Medium Ce3+:LiCaAlF6
Authors: Liu Zhenlin , Kozeki Toshimasa , Suzuki Yuji , Sarukura Nobuhiko , Shimamura Kiyoshi , Fukuda Tsuguo , Hirano Masahiro , Hosono Hideo
Published: October 2002

Femtosecond pulse amplification with high gain in the ultraviolet region has been demonstrated using the solid-state, broad-band crystal Ce3+:LiCaAlF6. With the seed pulses coming from the third harmonic generation of a cw mode-locked Ti:sapphire laser, the confocal, four-pass amplifier pumped by 15-mJ, 266-nm, 10-ns pulses from a Q-switched Nd:YAG laser demonstrates 60-dB gain and delivers 54-µJ, 289-nm, 200-fs, 10-Hz pulses. There is almost no satellite pulse even without any special single-pulse selection.
Thermal Stability of Liquid Crystal Alignment Layers Prepared by In-Situ Ultra-Violet Exposure during Imidization of Polyimide
Authors: Kim Jae-Hoon , Acharya Bharat R. , Agra D\~ena Mae , Kumar Satyendra
Published: October 2002

A novel method for liquid crystal alignment using in-situ exposure to linearly polarized ultra-violet (LPUV) light during imidization of polyimide has been devised. The alignment layers prepared by this method exhibit higher thermal stability than the conventional method that employs LPUV exposure after imidization. Multi-domain cells can be easily fabricated with the use of a photo mask and multi-step in-situ LPUV exposure during hard bake. With this method, it is also possible to generate pretilt angle using two-step LPUV exposure during imidization.
Profile Control of SiO2 Trench Etching for Damascene Interconnection Process
Authors: Seta Shoji , Sekine Makoto , Hayashi Hisataka , Yoshida Yukimasa
Published: October 2002

The purpose of the present study is to reveal a microtrench generation mechanism in the damascene trench etch process for SiO2 film. Experiments are discussed for the CO gas flow and the pressure change, employing a C4F8/CO magnetron etch system. Increasing the CO gas flow or the pressure prevents the microtrench generation. Moreover, the microtrench ratio A/B that is defined by the depth at the edge of the trench bottom, A and the trench depth at the center of the trench bottom, B becomes higher in accordance with increasing larger space size. In previous reports, the main effect of CO gas and pressure increase is identified as decreasing CF
x
radical density by dilution of C4F8 or by increasing the residence time. The reduction of CF
x
radical flux may prevent microtrench generation by decreasing the formation of fluorocarbon film at the trench bottom. These results suggest that the microtrench generation is caused by thicker formation of fluorocarbon films at the center of the trench bottom which has a larger solid angle than at the edge of the trench bottom.
Radiative Laser Cooling in an Electron Storage Ring
Authors: Yoshihiro Shobuda Yoshihiro Shobuda
Published: October 2002

Radiative laser cooling is one way to reduce the horizontal emittance of an electron beam. When an electron collides head-on with a laser beam, the electron's energy spread can be very large. In order to store an electron beam, it is desirable to reduce its energy spread. By changing the collision angle, we can decreace the horizontal emittance while reducing the energy spread. Radiative laser cooling is an efficient method to reduce the horizontal emittance which is increased by the intrabeam scattering.
Simulation of Multilayer Defects in Extreme Ultraviolet Masks
Authors: Ito Masaaki , Ogawa Taro , Otaki Katsura , Nishiyama Iwao , Okazaki Shinji , Terasawa Tsuneo
Published: October 2002

We have employed a scalar simulation based on Fresnel formulas to predict approximately how strongly a multilayer defect in a reflective mask affects the aerial image in extreme ultraviolet lithography. This method enables us to obtain the field reflected from a defective mask, using considerably fewer computational resources than those required for a rigorous electromagnetic simulation. This method was applied to two-dimensional masks with multilayer defects modeled by a simple structure in which the coverage profile was identical throughout the layers. For such defects, we confirmed the validity of the scalar simulation by comparing the normalized peak intensity to that obtained from an electromagnetic simulation. The dependence of the printability of a defect on its size and position is also discussed.
A Large-Scale Packet Switch System and 60-Gbps Pulse Arbitration Circuit Operation Using Single Flux Quantum Technology
Authors: Yorozu Shinichi , Kameda Yoshio , Tahara Shuichi
Published: October 2002

We evaluate the performance of a single flux quantum (SFQ) circuit and discuss its possible system-level application. First, we describe an optical-electrical-SFQ hybrid router system that is divided into three functions: an SFQ packet-routing function, a control function, and an optical transmission function. For the packet-switching core, we have developed a packet-switching architecture based on an internal speedup time-shifted Batcher Banyan approach. Our simulated results show that this architecture should provide good scalability and a low packet-loss rate. Additionally, we have fabricated an asynchronous pulse arbitration circuit. This circuit is a key component in our
packet-switching system. The circuit synchronizes two asynchronous incoming signals without any global clock signals. It consists of a clock generator based on a ring oscillator and data latches. By measuring the average output voltage of the Josephson junction, we confirmed the output signal control by the clock at over 60 Gbps throughput.
70 nm NMOSFET Fabrication with 12 nm n+-p Junctions Using As2
+ Low Energy Implantations
Authors: Choi Byung Yong , Sung Suk Kang , Park Byung-Gook , Lee Jong Duk
Published: October 2002

Nano-scale gate length metal oxide semiconductor field effect transistor (MOSFET) devices require extremely shallow source/drain extension regions with junction depth of 20–30 nm [The International Technology Roadmap for Semiconductors: Semiconductor Industry Association (1998)]. In this work, 12 nm n+-p junctions that are realized by using As2
+ low energy (≤10 keV) implantation show the low sheet resistance of 1.0k Ω/□ after a rapid thermal annealing process. The As2
+ implantation and RTA process make it possible to fabricate the nano-scale n-type metal oxide semiconductor field effect transistor (NMOSFET) with gate length of 70 nm. The As2
+ 5 keV NMOSFET shows a small threshold voltage roll-off and a DIBL effect of 30 mV at 100 nm gate length NMOSFET devices.
Formation of SiGe on Insulator Structure and Approach to Obtain Highly Strained Si Layer for MOSFETs
Authors: Sugiyama Naoharu , Mizuno Tomohisa , Suzuki Masamichi , Takagi Sin-ichi
Published: October 2002

The formation of a SiGe layer on insulators, which can be realized by applying the separation by implanted oxygen (SIMOX) technique to SiGe layers, is essential for fabricating strained silicon on insulator (SOI) metal oxide semiconductor field effect transistors (MOSFETs). In this study, the SIMOX process for SiGe films is examined in terms of Ge diffusion during SIMOX annealing and the annealing temperature. It is found that the SIMOX annealing at temperature above 1300°C is necessary to realize uniform buried oxides, even though the melting point of SiGe crystal decreases with the Ge content. Ge diffusion during high-temperature annealing must also be taken into account when preparing the SiGe layer for SIMOX. These facts indicate that the realization of a SiGe layer on buried oxides is difficult with the simple SIMOX process for SiGe crystal, particularly so in the case of high Ge content. In order to overcome this problem, the double layer SiGe structure on an insulator is proposed and the effectiveness of this structure on the increase of strain in Si is verified experimentally. The strain relaxation of the SiGe layer with higher Ge content, which is grown on the SiGe layer with lower Ge content, is observed with expanding of the under-layer.
A Novel Simulation Program with Integrated Circuit Emphasis (SPICE) Model of Ferroelectric Capacitors Using Schmitt Trigger Circuit
Authors: Shuu'ichirou Yamamoto Shuu'ichirou Yamamoto , Takumi Kato Takumi Kato , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

We have proposed a novel parallel-element simulation program with integrated circuit emphasis (SPICE) model for ferroelectric capacitors, in which Schmitt trigger circuits are used for representing dipoles in the ferroelectric films. It is found that the model expresses the hysteretic characteristics of polarization accurately, even when voltages are applied asymmetrically to the capacitors. We have also proposed a method to introduce the polarization reversal time in the proposed model and demonstrated the circuit response for high-speed pulses in which the polarization reversal time cannot be neglected.
A Body-Effect-Assisted NOR-type (BeNOR) Multilevel Flash Memory
Authors: Wang Yen-Sen , Tsai Hong-Ping , Yang Evans Ching-Song , King Ya-Chin , Chen Steve , Hsu Charles Ching-Hsiang
Published: October 2002

We propose a new Body-Effect-assisted NOR-type (BeNOR) flash memory for multilevel storage application. Body effect assisted self-convergent programming employs secondary electron injection but a different operation bias from the CHannel Initiated Secondary ELectron (CHISEL) flash. Accurately programmed states are accomplished by the linear dependence of V
TH on the bit-line voltage; therefore, parallel multilevel programming and elimination or reduction of bit-by-bit verification can be achieved. In this paper, programming power consumption and reliability considerations are also assessed for efficient and long-term operation.
In-Diffusion and Annealing Processes of Substitutional Nickel Atoms in Dislocation-Free Silicon
Authors: Tanaka Shuji , Ikari Tetsuo , Kitagawa Hajime
Published: October 2002

In-diffusion and annealing processes of substitutional nickel atoms in dislocation-free silicon are studied in the temperature range from 940 to 1020°C to distinguish between the site exchange mechanisms of nickel atoms. The concentration of substitutional nickel atoms varies with time according to the theoretical prediction of the dissociative mechanism. It is found that the in-diffusion and annealing rates are accelerated by nickel precipitation in the bulk. The relationship between the time constant of the two processes and the volume density of the precipitates is discussed.
Direct Observation of Polytype Domains in GaN using a Cryogenic Scanning Photoluminescence Microscope with Sub-Micron Spatial Resolution
Authors: Yoshimoto Masahiro , Goto Motoki , Saraie Junji
Published: October 2002

Cubic and hexagonal domains with sizes of 1–10 µm in GaN were visualized using a newly developed cryogenic scanning photoluminescence (PL) microscope with a sub-µm spatial resolution. PL emissions at wavelengths of 358 and 380 nm were used to discriminate the polytype. The coverage of the hexagonal phase on the surface changes in accordance with the volume fraction of the polytype as determined by X-ray diffraction.
Wall Heating Effect on Crystallization of Low-Temperature Deposited Silicon Films from an Inductively-Coupled Plasma
Authors: Kojima Tetsuya , Ohishi Akihiro , Toyoda Hirotaka , Goto Masashi , Nishitani Mikihiko , Sugai Hideo
Published: October 2002

The influence of vessel-wall temperature T
w on the grain size of poly-Si films deposited on a low-temperature (300°C) substrate by an inductively-coupled SiH4/H2 plasma is investigated. The grain size is reduced after a clean vessel wall at T
w ∼100°C experiences long SiH4/H2 discharge. This reduction in the grain size due to SiH4/H2 discharge duration can be suppressed by heating the wall to T
w ∼300°C. To understand the mechanism, the H atom density in the plasma is measured from the ratio of Hα/Hβ emission intensities. The H atom density is found to decrease monotonically with the discharge time at T
w ∼100°C, and this H density decrease is suppressed by increasing the wall temperature to ∼300°C.