bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Stability of Metal-Insulator-Diamond Semiconductor Interface by Employing CaF2/Thin BaF2 Composite Insulator Film
Authors: Ito Akihiro , Tsuji Kiyoshige , Hosomi Takeshi , Maki Tetsuro , Kobayashi Takeshi
Published: October 2002

This letter presents a possible technical solution to obtain a mechanically and chemically tough BaF2/diamond interface for use in a metal/insulator/semiconductor (MIS) structure with excellent electrical properties. Presently, BaF2/diamond structures suffer from cracks and deterioration problems, although the interfaces are electrically stabilized to an acceptable quality. In the present work, we employed a composite film structure (CaF2/thin BaF2) as a gate insulator and its electrical properties were closely investigated by means of capacitance–voltage measurements. As long as BaF2 is thinner than 50 nm, the diamond MIS structure was electrically, chemically and mechanically stabilized. No particular difference was found in the surface state distributions between the BaF2/diamond and (CaF2/thin BaF2)/diamond interfaces.
Spin-coated Films of Squarylium Dye J-Aggregates Exhibiting Ultrafast Optical Responses
Authors: Tatsuura Satoshi , Tian Minquan , Furuki Makoto , Sato Yasuhiro , Pu Lyong Sun , Wada Osamu
Published: October 2002

The formation of J-aggregates of squarylium dye derivatives in spin-coated films is reported. Squarylium dye derivatives with dipropylamino bases are found to spontaneously aggregate in a spin-coated film. Aggregation is promoted when dye molecules are dispersed in a poly(vinyl alcohol) film, and when a spin-coated film of dye molecules is heated in the presence of acid vapor. In particular, J-aggregates formed by exposure to acetic acid vapor show the narrowest spectral width. J-aggregates formed by the acid treatment method are stable at room temperature and the spectral full-width at half maximum of the J-band is 20 nm. Optical response of the acid-treated film is confirmed to exhibit a short relaxation time of bleached absorption of 300 fs.
Three-Dimensional Display System with Dual-Frequency Liquid-Crystal Varifocal Lens
Authors: Suyama Shiro , Date Munekazu , Takada Hideaki
Published: October 2002

A new volumetric three-dimensional (3-D) display system that provides all the
visual cues to depth perception has been developed. This system provides flicker-free,
large 3-D images of 250 mm in both diameter and depth with a viewing cone from
-10° to +10°. The system is simply composed of a dual-frequency
liquid-crystal (LC) varifocal lens (the key device), a two-dimensional display, and two
fixed lens. The focal length of the LC varifocal lens can be continuously varied from
-1.2 to +1.5 diopters (1/m) by changing the effective refractive index of LC.
Using a dual-frequency LC for the varifocal lens achieves sufficiently fast operation of
at least 60 Hz for flicker-free moving 3-D images. The simple structure of our
varifocal lens facilitates the fabrication of a large-diameter lens, resulting in large
3-D images with a sufficient viewing cone.
Low Temperature Heteroepitaxial Growth of a New Phase Lead Zirconate Titanate Film on Si Substrate with an Epitaxial (ZrO2)1-x(Y2O3)xBuffer Layer
Authors: Susumu Horita Susumu Horita , Mami Aikawa Mami Aikawa , Tetsuya Naruse Tetsuya Naruse
Published: October 2002

We investigated the crystalline and electrical properties of heteroepitaxial lead zirconate titanate (PZT) films grown on Si covered with epitaxial (100) (ZrO2)1-x(Y2O3)x(YSZ) buffer layers. The PZT films were prepared by reactive sputtering. When the substrate temperature was between 400 and 485°C, we obtained a heteroepitaxial (110) oriented monoclinic PZT (m-PZT) film which was metastable. The lattice parameters were as follows:a=b=0.379 nm,c= 0.521 nm and γ=81.3°. The m-PZT film had a larger oxygen composition ratio O/(Zr+Ti) of 3.2 to 3.8 than the perovskite phase. Although the resistivity of the as-grown m-PZT film was much lower than that of the normal perovskite phase, it was increased by two to five orders of magnitude by a step-annealing process of 300°C for 120 min, 325°C for 120 min and 350°C for 180 min in sequence. From theC–Vcharacteristics of the step-annealed m-PZT/YSZ/Si structure, the relative dielectric constant was estimated to be about 45.
Superiority of an AlN Intermediate Layer for Heteroepitaxy of Hexagonal GaN
Authors: Sasaki Masahiro , Nakayama Tomoo , Shimoyama Norio , Suemasu Takashi , Hasegawa Fumio
Published: October 2002

The superiority of AlN as an intermediate layer during heteroepitaxy of GaN on GaAs substrates is demonstrated on the basis of growth rates, surface reactivity and crystallography. Although GaN growth on GaAs using monomethyl-hydrazine (MMHy) as a nitrogen source shows a long lag time to start growth, this lag time disappears upon the insertion of an AlN intermediate layer. Based on mass spectrometric analysis, these growth behaviors are attributed to the decomposition of MMHy which is enhanced by the Al source injection onto GaAs surfaces. The growth mechanism is explained within a framework of simple bond behavior. Further, it is confirmed by pole figure X-ray diffraction observations that a single phase hexagonal GaN layer is grown on GaAs(111)B substrates when the AlN intermediate layer is inserted, while a cubic phase is included in the GaN grown directly on the GaAs(111)B surface.
Shock and Static Compression of Nitrobenzene
Authors: Naoshi Kozu Naoshi Kozu , Mitsuru Arai Mitsuru Arai , Masamitsu Tamura Masamitsu Tamura , Hiroshi Fujihisa Hiroshi Fujihisa , Katsutoshi Aoki Katsutoshi Aoki , Masatake Yoshida Masatake Yoshida
Published: October 2002

The Hugoniot and static compression curve (isotherm) were investigated using explosive plane wave generators and diamond anvil cells, respectively. The obtained Hugoniot from the shock experiments is represented by two linear lines: U
s=2.52+1.23 u
p (0.8<u
p<2.2) and U
s=3.63+0.935 u
p (2.3<u
p<3.6), where U
s and u
p are the shock velocity and the particle velocity in km/s, respectively. A kink exists at around 15 GPa. The line for the higher particle velocities agrees well with the Hugoniot of detonation products calculated by the CHEETAH code. This suggests that nitrobenzene detonates in this range. Under static high pressure over 7 GPa, nitrobenzene undergoes a reaction that is expected to be polymerization. Considering the Hugoniot and the isotherm, it is plausible that shocked nitrobenzene (<15 GPa) is in the liquid state.
Relation between the Radius of Tip Curvature and the Light Emission Efficiency from Scanning Tunneling Microscope
Authors: Iwami Masayuki , Uehara Yoichi , Ushioda Sukekatu
Published: October 2002

The relation between the efficiency of scanning tunneling microscope light emission (STM-LE) and the radius of tip curvature has been studied using silver tips. The emission efficiency increases with decreasing radius of tip curvature ρ for ρ>80 nm. This result agrees qualitatively with the prediction of a theory that includes the effect of electromagnetic retardation.
Anomalous Cross-Field Transport of Electrons Driven by the Electron-Ion Hybrid Instability Due to the Velocity Shear in a Magnetized Filamentary Plasma
Authors: Matsubara Akihiro , Tanikawa Takao
Published: October 2002

The effect of cross-field velocity shear of electrons on the plasma transport has been experimentally investigated in a steady-state filamentary plasma whose effective column radiusrpis smaller than the ion Larmor radius ρiand much larger than the electron Larmor radius ρe(ρe≪rp<ρi). When the shear frequency ωS(=v0/LE, wherev0is the maximum flow velocity in the sheared flow andLEis the shear scale length), which is the measure of the strength of the velocity shear, becomes much larger than the lower hybrid frequency, electrostatic plasma fluctuations of the lower hybrid range of frequency are excited in the significantly sheared flow. It is observed that these enhanced fluctuations induce the anomalous, non-ambipolar diffusion of electrons across magnetic field lines. The estimated cross-field diffusion coefficient of electrons obeys the Bohm scaling. The observed instability can be identified as the electron-ion hybrid shear instability through comparison between experimental and numerically obtained results.
La–Ca–Mn–O Thin Film based Thermistor for Measuring Low Temperature of 77–230 K
Authors: Jae-Hoon Song Jae-Hoon Song , Kyoung-Kook Kim Kyoung-Kook Kim , Hyung-Jin Jung Hyung-Jin Jung , Duck-Kyun Choi Duck-Kyun Choi , Won-Kook Choi Won-Kook Choi
Published: October 2002

Perovskite manganite La–Ca–Mn–O (LCMO) thin films were deposited on LaAlO3 (001) single crystal substrate by radio-frequency magnetron sputtering at room temperature. After annealing at 800–1000°C in O2 atmosphere for 1 h, sheet resistance (R) of the LCMO thin films was measured by van der Pauw method in the range of 77–300 K. The characteristic resistance-temperature curves of all the annealed films showed typical insulator to metal transition behavior of colossal magnetoresistance (CMR) materials on cooling. The sheet resistance of LCMO films changes with temperature, conforming to a function of exp
(βT) in the temperature range from 77 K to 230 K, which is applicable to an oxide thin film thermistor.
Room-Temperature Mid-Infrared Light-Emitting Diodes from Liquid-Phase Epitaxial InAs/InAs0.89Sb0.11/InAs0.80P0.12Sb0.08 Heterostructures
Authors: Gong Xiu Ying , Kan Hirofumi , Makino Takamitsu , Iida Takefumi , Watanabe Kenzo , Gao Yu Zhu , Aoyama Mitsuru , Rowell Nelson L. , Yamaguchi Tomuo
Published: October 2002

Light-emitting diodes (LEDs) in the 3 to 5 µm wavelength range have been fabricated from InAs/InAsSb/InAsPSb heterostructures grown by liquid-phase epitaxy (LPE) between 520 and 500°C. Temperature dependence of the performance for the LEDs was studied using a Fourier transform infrared (FTIR) measurement system with double modulation. Room-temperature operation of LEDs was realized. Under a peak current of 5 A (2% duty cycle), the output powers of the diodes were between 150 and 500 µW indicating their potential applications for CO2 and CO gas sensors.
Preparation of Bi–Pb–Sr–Ca–Cu–O Thin Films by RF Magnetron Sputtering
Authors: Sakamoto Shinichi , Okamoto Taichi , Saito Yukinori
Published: October 2002

Bi-based superconducting films were prepared by rf magnetron sputtering. Effects on the transition temperature of in situ annealing at 730°C and subsequent ex situ annealing from 800 to 900°C were examined. Films treated with only in situ annealing at 730°C showed a T
c0 of 65 K. As the temperature of ex situ annealing increased, T
c0 increased gradually and a T
c0 of 92.4 K was obtained for the films annealed at 880°C for 12 h in air.
Excitation Migration from Photoexcited Tris(8-hydroxyquinolino)aluminium to Quinacridone in Codeposited Thin Films
Authors: Kundu Santi , Fujihara Kan , Okada Tadashi , Matsumura Michio
Published: October 2002

Absorption, fluorescence, and time-resolved fluorescence measurements have been carried out to demonstrate the energy transfer from photoexcited tris(8-hydroxyquinolino)aluminium (ALQ) to quinacridone (QA) in codeposited thin films. All the results indicate that the excitation energy is transferred from ALQ to QA, which distribute randomly in three dimensions in the thin films, by the Förster mechanism. From the analyses of the fluorescence decay of ALQ, the critical distance for the energy transfer between ALQ and QA molecules is determined to be 26 Å. This value is in good agreement with that calculated from the fluorescence spectra of ALQ, the absorption spectra of QA, and the fluorescence quantum efficiency of ALQ. This agreement also indicates that energy migration among ALQ molecules is not an efficient process.
Thickness Dependence of Characteristics for (Ba, Sr)TiO3 Thin Films Prepared by Metalorganic Chemical Vapor Deposition
Authors: Takeshima Yutaka , Tanaka Katsuhiko , Sakabe Yukio
Published: October 2002

(Ba0.6, Sr0.4)TiO3 thin films were prepared by metalorganic chemical vapor deposition (MOCVD) using bisdipvaloylmethanatobarium tetraethylenepentamine adduct (Ba(C11H19O2)2(C8H23N5)2), bisdipvaloylmethanatostrontium tetraethylenepentamine adduct (Sr(C11H19O2)2(C8H23N5)2), and titanium isopropoxide (Ti(i-OC3H7)4) as starting materials. The thickness dependence of permittivity and other characteristics were investigated for epitaxially grown barium strontium titanate (BST) thin films on Pt(100)/MgO(100) substrates and nonepitaxially grown BST films on Pt(111)/MgO(100) substrates. The epitaxially grown films had a high relative permittivity (1200) at thicknesses greater than 120 nm. Permittivity decreased with the film thickness when the thickness was less than 120 nm, but remained constant at thicknesses between 50 and 80 nm. The nonepitaxially grown films had a relative permittivity of 600 at a thickness greater than 100 nm and decreased with decreasing film thickness when the thickness was below 100 nm. In this paper, the origin of thickness dependence is discussed in terms of the grain-size effect and the strain effect.
Effect of Pb Content in Target on Electrical Properties of Laser Ablation Derived Lead Zirconate Titanate Thin Films
Authors: Wang Zhan-Jie , Kikuchi Kaoru , Maeda Ryutaro
Published: October 2002

Thin films of Pb(Zr0.52Ti0.48)O3(PZT) 1.8–2.0 µm thick on a Pt/Ti/SiO2/Si substrate were prepared by excimer laser ablation and were crystallized by subsequent annealing. Crystalline phases in the PZT films were investigated by X-ray diffraction analysis (XRD). The microstructure and composition of the films were studied by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA), respectively. The effect of the Pb content of the target on electrical properties of PZT thin films was investigated. The PZT films with a well-crystallized perovskite phase were obtained by adding 20 wt.% excess PbO to the target and annealing at 750°C for 90 min. The remanent polarization and the coercive field of this 0.8 µm think film were 23.6 µC/cm2 and 60.0 kV/cm, while the dielectric constant and loss values measured at 1 kHz were approximately 935 and 0.04, respectively.
Evaluation of Pb(Zr, Ti)O3 Films Derived from Propylene-Glycol-Based Sol-Gel Solutions
Authors: Maki Kazunari , Soyama Nobuyuki , Mori Satoru , Ogi Katsumi
Published: October 2002

Crack-free PbZr0.52Ti0.48O3 (PZT) films up to almost 1 µm thick have been prepared on Pt/Ti/SiO2/Si substrates from stable propylene-glycol (diol)-based sol-gel solutions by a single coating. We have studied the film thickness dependence of various properties such as microstructure, crystal orientation, ferroelectric properties, and leakage current density for the PZT single-coated films. It was found that the 0.22-µm-thick PZT single-coated film was a dense film with (111)-orientation and exhibited good ferroelectric properties. In order to thicken the PZT dense film, we have studied a sol-gel technique involving multiple coatings of 0.22-µm-thick layers. Finally, the 0.66- and 1.10-µm-thick PZT multicoated films have been prepared on platinized silicon substrates by three and five coatings of 0.22-µm-thick layers. Various properties of the multicoated films have also been evaluated.
Increase in Switching Charge of Ferroelectric SrBi2Ta2O9 Thin Films with Polarization Reversal
Authors: Soichiro Okamura Soichiro Okamura , Masaki Takaoka Masaki Takaoka , Takashi Nishida Takashi Nishida , Tadashi Shiosaki Tadashi Shiosaki
Published: October 2002

The increase in switching charge of as-grown SrBi2Ta2O9 (SBT) capacitors with polarization reversal was investigated. We call this phenomenon wake-up. The switching charge was increased and the rectangularity of the D-E hysteresis loops was improved with polarization reversal. The switching pulse with larger amplitude, longer width and shorter period generated a larger increase in the switching charge with polarization reversal. At the same time, the capacitors came to exhibit a rapid increase in leakage current at a certain applied field after the switching. Furthermore, the D-E hysteresis loop of the capacitors with wake-up shifted toward the positive- or negative-bias field according to the sweeping direction of the applied voltage. We have concluded that some spontaneous polarizations locked by localized space charges at the interface layer in the wake-up-exhibiting SBT capacitors were freed by the application of numerous switching pulses, and trap levels generated in the interface layer by the switching rendered the rapid increase in leakage current and the voltage shift of D-E hysteresis easy.
Epitaxial Growth of Bi4Ti3O12/CeO2/Ce0.12Zr0.88O2 and Bi4Ti3O12/SrTiO3/Ce0.12Zr0.88O2 Thin Films on Si and Its Application to Metal-Ferroelectric-Insulator-Semiconductor Diodes
Authors: Migita Shinji , Xiong Si-Bei , Sakamaki Kazuo , Ota Hiroyuki , Tarui Yasuo , Sakai Shigeki
Published: October 2002

Insulating buffer layers, CeO2/Ce0.12Zr0.88O2 and SrTiO3/Ce0.12Zr0.88O2 films, are grown on Si(001) substrates by the pulsed laser deposition technique, and ferroelectric Bi4Ti3O12 films are grown on these buffer layers by the molecular beam epitaxy technique. X-ray diffraction data show that the c-axes of the Bi4Ti3O12 films grown on CeO2/Ce0.12Zr0.88O2 and SrTiO3/Ce0.12Zr0.88O2 buffer layers are normal and inclined 45° to the buffer layer surface, respectively. Memory windows appearing in capacitance and voltage characteristics of diode structures with Pt top electrodes are 1.2 V for a Pt/Bi4Ti3O12/CeO2/Ce0.12Zr0.88O2/Si diode, and 3.5 V for a Pt/Bi4Ti3O12/SrTiO3/Ce0.12Zr0.88O2/Si diode. This difference in magnitude may be due to the different growth orientation and strongly anisotropic polarization of Bi4Ti3O12.
Low-Temperature Preparation of Sr2(Ta1-x, Nbx)2O7 Thin Films by Pulsed Laser Deposition and its Electrical Properties
Authors: Toshiyuki Nakaiso Toshiyuki Nakaiso , Hideki Sugiyama Hideki Sugiyama , Minoru Noda Minoru Noda , Masanori Okuyama Masanori Okuyama
Published: October 2002

Sr2(Ta1-x
, Nbx)2O7(STN) ferroelectric thin films were prepared on Pt/Ti/SiO2/Si and SiO2/Si(100) substrates by the pulsed laser deposition (PLD) method. (151)-oriented STN thin films were deposited at a low temperature of 600°C in N2O ambient gas at 0.08 Torr for composition ratios of x=0.2, 0.3 and 0.4. A symmetrical polarization hysteresis loop of the STN film was observed for the composition ratio of x=0.3, where the remanent polarization was 0.4 µC/cm2 and the coercive force was 30 kV/cm. The dielectric constant at room temperature was as low as 55. The remanent polarization of postannealed films was not changed after 1010 cycles of polarization reversal. A counterclockwise capacitance–voltage (C–V) hysteresis was observed in the metal-ferroelectric-insulator-semiconductor (MFIS) structure using Sr2(Ta0.7,Nb0.3)2O7 on SiO2/Si at a deposition temperature of 600°C. The C–V curve spreads symmetrically in both positive and negative directions when applied voltage is increased and the window did not change in sweep rates ranging from 0.1 to 5.0 V/s.
Poling Field Dependence of Crystal Orientation and Ferroelectric Properties in Lead Titanate Ceramics
Authors: Ogawa Toshio
Published: October 2002

Domain switching and rotation in lead titanate ceramics were evaluated by investigating the poling field dependence of the relative intensity of the X-ray diffraction (002) peak and the electrical properties. Although the lead titanate ceramic surface was highly oriented in the direction of the c-axis by the poling field, it was difficult to align the crystal orientation of the ceramic bulk because of the large anisotropy of the crystal structure. The effect of domain clamping on the planar coupling factor and dielectric constant at coercive fields was confirmed in lead titanate ceramics as well as in the case of soft and hard tetragonal lead zirconate titanate ceramics. The peaks of frequency constant due to domain clamping were not observed in lead titanate ceramics. Further, it was thought that domain rotations occurred at the fields required to obtain the minimum frequency constant.
Low-Temperature Preparation of Lead-Based Ferroelectric Thick Films by Screen-Printing
Authors: Futakuchi Tomoaki , Nakano Kunitaka , Adachi Masatoshi
Published: October 2002

Low-temperature preparation of ferroelectric Pb[Zr0.2Ti0.3(Mg1/3Nb2/3)0.3(Zn1/3Nb2/3)0.1(Mg1/2W1/2)0.1]O3 thick films by a screen-printing method on ZrO2 ceramic substrates and Si substrates was examined. The influence of excess PbO as a sintering aid was investigated in comparison with bulk ceramics. The remanent polarization and coercive field of the thick film fired at 850°C on Si substrate were 8.1 µC/cm2 and 5.7 kV/cm, respectively. The low-temperature process using this ferroelectric thick film is very promising for the development of advanced microactuators.
Compositional Homogeneity and Electrical Properties of Lead Magnesium Niobate Titanate Single Crystals Grown by a Modified Bridgman Technique
Authors: Luo Haosu , Xu Guisheng , Xu Haiqing , Wang Pingchu , Yin Zhiwen
Published: October 2002

Relaxor ferroelectric single crystals Pb((Mg1/3Nb2/3)1-x
Ti
x
)O3 (PMNT 100(1-x)/100x) were grown directly from melt by a modified Bridgman technique. The segregation during the growth of PMNT single crystals was studied by means of differential thermal analysis (TGA), thermogravimetric analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence analyzer (XRFA). The results show that PbTiO3 content increases throughout the crystal growth. The segregation coefficient is about 0.95 during the growth of PMNT 76/24 directly from melt. Therefore, the electric properties of PMNT single crystals vary even in the same boule. It was demonstrated that the homogeneity of PMNT single crystals can be improved by optimizing growth parameters, but it cannot be eliminated because of the effect of segregation during the crystal growth. We have recently improved the growth process of the modified Bridgman technique to increase the homogeneity of the crystals. Good-quality single crystals with a boule size of more than φ40×80 mm or 30×30×1 mm plates have been achieved. For PMNT 67/33 crystals, their coupling factors are k
33≈94% for the longitudinal mode, k
33
′≈86% for the beam mode, and k
t≈62% for the thickness mode, and they have the piezoelectric constant d
33=1500–3000 pC/N, and dielectric constant ε
33/ε
0=3500–5500.
Piezoelectric Characterization of Low-Temperature-Fired Pb(Zr, Ti)O3–Pb(Ni, Nb)O3 Ceramics
Authors: Shiratsuyu Kosuke , Hayashi Koichi , Ando Akira , Sakabe Yukio
Published: October 2002

The compositional design of Pb(Zr, Ti)O3–Pb(Ni, Nb)O3 ceramics to lower the sintering temperature and improve their piezoelectric properties was investigated. The nonstoichiometric composition containing excess NiO or PbO and NiO can be densified at 800°C. The excess NiO composition can be fabricated in the firing temperature range of 900 to 1050°C without decreasing the electromechanical coupling factor. Using the new techniques, PZT–Pb(Ni, Nb)O3 ceramics prepared by the conventional powder process can be fired at low temperatures below 1000°C.
Study of Three Different Relaxor Ferroelectrics by High Resolution Micro-Brillouin Scattering
Authors: M. Jiang Fuming , Seiji Kojima Seiji Kojima
Published: October 2002

Three different relaxor ferroelectrics, 0.65PMN-0.35PT, Sr0.61Ba0.39Nb2O6(SBN), and Pb0.85La0.1Zr0.65Ti0.35O3have been studied by Brillouin scattering using a microscope with a focal point of 1–2 µm. Relaxation modes have been directly observed for the first time for all three samples. They form at a temperature much higher than the reported dielectric maximum temperature Tm. Thermal evolution of the polar microregions has been illustrated by the temperature dependence of the relaxation time. By scanning the microprobe over the 0.65PMN-0.35PT crystals, local distortions differing from the global symmetry were found due to microregions. A modified superparaelectric model has been proposed to describe the relaxation behavior in 0.65PMN-0.35PT. Comparison of the Raman and Brillouin results for SBN shows that the origins of relaxation modes are the dipolar relaxation associated with the polar vibration modes. Phase transition behaviors are discussed.
Observation of Crystallization Process from Amorphous Bi4Ti3O12 Prepared by Rapid Quenching Method
Authors: Masaaki Takashige Masaaki Takashige , Sinichi Hamazaki Sinichi Hamazaki , Yoshio Takahashi Yoshio Takahashi , Fuminao Shimizau Fuminao Shimizau , Toshihisa Yamaguchi Toshihisa Yamaguchi , Min-Su Jang Min-Su Jang , Seiji Kojima Seiji Kojima
Published: October 2002

We studied the crystallization of amorphous samples of Bi4Ti3O12 prepared by rapid quenching. Differential thermal analysis, powder X-ray diffraction and Raman spectral measurements revealed that the amorphous sample first crystallizes at approximately 610°C to a metastable Bi2Ti2O7 phase and then transforms irreversibly to the stable Bi4Ti3O12 phase at approximately 830°C.
Characterization of Proton-Irradiated InGaAs/GaAs Multiple Quantum Well Structures by Nonresonant Transient Four-Wave Mixing Technique
Authors: Jarasiunas Kestutis , Mizeikis Vygantas , Iwamoto Satoshi , Nishioka Masao , Someya Takao , Fukutani Katsuyuki , Arakawa Yasuhiko , Shimura Tsutomu , Kuroda Kazuo
Published: October 2002

Effects of proton irradiation and thermal annealing on free carrier lifetime and transport in a InGaAs/GaAs multiple quantum well (MQW) structure and its substrate have been studied by using the nonresonant transient four-wave mixing technique. Under the excitation of the surface region of the structure by 0.53 µm wavelength, we determined the carrier lifetime τ=150–600 ps, bipolar diffusion coefficientD=24–26 cm2s-1, and mobility-lifetime product µτ≈(2–6)×10-7cm2V-1in 3 MeV proton irradiated and annealed MQW samples. At excitation by 1.06 µm wavelength, we studied the full proton penetration range, including the substrate. We found an unexpected twofold increase in carrier bulk lifetime with increasing irradiation dose. Features of this effect at low photoexcitation and its absence at high photoexcitation are attributed to carrier separation by potential fluctuations in the vicinity of irradiation-created deep defects. These features indicate that proton-irradiated semi-insulating GaAs exhibits properties of mesoscopic pointlike defects, similar to those previously reported in nonstoichiometric crystals of GaAs. This result is important to understand the mechanism of carrier compensation in proton-irradiated semiconductors.
Low Leakage TiO2 Gate Insulator Formed by Ultrathin TiN Deposition and Low-Temperature Oxidation
Authors: Matsuo Kouji , Nakajima Kazuaki , Omoto Seiichi , Nakamura Shinichi , Yagishita Atsushi , Minamihaba Gaku , Yano Hiroyuki , Suguro Kyoichi
Published: October 2002

A new method of forming TiO2 gate insulators is proposed. It was found that ultrathin TiN deposition on ultrathin SiO2 and low-temperature thermal oxidation resulted in smaller TiO2 grains surrounded by amorphous boundaries. The gate leakage current was effectively reduced by applying ultrathin TiO2/SiO2 stacked insulators to metal-oxide-semiconductor (MOS) capacitors and Damascene gate metal-oxide-semiconductor-field-effect-transistors (MOSFETs) with good characteristics were successfully fabricated.
Suppression of the Josephson Current in Normal-Distribution-Shaped Tunnel Junctions
Authors: Katsuya Kikuchi Katsuya Kikuchi , Hiroaki Myoren Hiroaki Myoren , Takeshi Iizuka Takeshi Iizuka , Susumu Takada Susumu Takada
Published: October 2002

The magnetic field dependence of the Josephson current of a Josephson tunnel junction whose shape was a normal distribution is analyzed for superconducting tunnel junction (STJ) photon detector applications. It was found that the Josephson current of a normal distribution junction is very sensitive to the external magnetic field and follows a function of exp
(-B
2), while a conventional rectangular STJ exhibits the well-known Fraunhofer pattern of sin
x/x. Numerical calculations show that the Josephson current of the normal distribution junction can be suppressed by an external magnetic field that is one tenth of that needed for conventional rectangular junctions. Calculations of a normal distribution junction approximated with a 1 µm mesh also show that the Josephson current is sufficiently suppressed by a small magnetic field. The effect of the misalignment of the angle between the junction and the magnetic field was evaluated. It was found that for a normal-distribution-shaped junction, misalignment of the magnetic field is allowed within ± 5°, suppressing the Josephson effect by two orders of magnitude more than that of a rectangular junction.
Photo-Induced Liquid Crystal Alignment with Discotic Films
Authors: Wu Long-Hai , Lee Wen-Chin , Hsu Chain-Shu , Wu Shin-Tson
Published: October 2002

Photo-induced liquid crystal alignment using cross-linked discotic compounds was demonstrated. These discotic compounds exhibit good solubility in common organic solvents, 60°C processing temperature and excellent thermal stability. A linearly polarized long wave ultraviolet light (λ=350 nm) was used to initiate the cross-linking process which, in turn, induces liquid crystal alignment on the discotic film surface. The polarity of discotic compounds plays an important role in affecting the pretilt angle of the liquid crystal alignment. A pretilt angle of 1±0.4° was obtained using single exposure at oblique angle. Potential application of this new photo-alignment film for low temperature poly-silicon thin-film-transistor liquid crystal display is foreseeable.
Second Harmonic Generation in CdTe Plate by Free Electron Laser
Authors: Yamauchi Toshihiko , Kikuzawa Nobuhiro , Minehara Eisuke , Nagai Ryoji , Nishimori Nobuyuki , Sawamura Masaru , Hajima Ryoichi , Shizuma Toshiyuki , Hayakawa Takehito
Published: October 2002

The second harmonic generation (SHG) signal converted from the 22 µm input wavelength of free electron laser (FEL) is observed using a non-birefringent CdTe crystal. The conversion efficiency of SHG is experimentally obtained to be ∼3×10-5%/(MWcm-2).
Equivalent Circuit Model of an Inductive RF Discharge with a Helical External Coil
Authors: Yoshiki Hiroyuki
Published: October 2002

An inductive RF discharge with a helical external coil has been analyzed
by an equivalent circuit model including both the inductive and capacitive
coupling branches. A true inductive discharge is considered as a co-axial
one-turn secondary winding of an air-core transformer, while a capacitive
current is assumed to flow from a high voltage coil plate to a grounded
electrode via a quartz glass and sheaths. The dependence of the plasma
density on antenna coil voltage is calculated as a function of the excitation frequency and gas pressure. It is shown that the mechanism of the E-H mode
jump, accompanied by the hysteresis phenomenon, can be attributed to the
nonlinear dependence of the inductively absorbed power on the plasma
density.
Solid-State Pulser Development for High Power Dense Plasma Focus X-Ray Sources
Authors: Petr Rodney , Reilly Dennis , Freshman Jay , Orozco Nelson , Pham Dan , Ngo Long , Mangano Joseph
Published: October 2002

Solid-state pulsed power technology has been successfully
applied to a high average power dense plasma focus (DPF) X-ray point
source. In the past, electrode erosion and associated insulator
lifetime have been the primary limiting factors for implementing a DPF
X-ray source in a practical X-ray lithographic tool. The solid-state
pulsed power supply described here uses fast-switching thyristors,
diodes, and saturable magnetics to eliminate current reversal through
the DPF electrodes. Anode erosion measurements show a mass loss of
25 µg/C with the solid-state driver, which indicates that an
electrode set can last more than 5 million shots before
refurbishment. The DPF source produces an average energy of 7.3 J per
pulse into 4π steradians at 1.1 keV effective wavelength in
∼1 Torr of neon gas at pulse repetition rates up to
60 Hz. The X-ray yield efficiency is nominally 0.6%.
Effect of Oxygen Deficiency on the Magnetic, Electrical, and Magnetoresistive Properties of La0.7Sr0.3CoO3-δ
Authors: Hsu Hai-Wen , Chang Yen-Hwei , Chen Guo-Ju
Published: October 2002

This study investigates the magnetic, electrical, and
magnetoresistive properties of the oxygen-deficient compositions of
La0.7Sr0.3CoO3-δ. Experimental results indicate
that the La0.7Sr0.3CoO3-δ (0≦δ≦0.15) compositions are all ferromagnetic and exhibit a
metal-insulator (M-I) transition. The magnetization decrease and
resistivity increase depend on the oxygen deficiency. Our results
further suggest that the oxygen nonstoichiometry facilitates the
cooling of the T
C and T
P. At a low
temperature, the magnetoresistance depends heavily on magnetization. A
large MR effect is observed in a larger oxygen deficiency. Moreover,
this study also discusses possible mechanisms.
Fabrication of Nanoscale Cubic SiC Particle Film
Authors: Yong Sun Yong Sun , Kenta Kirimoto Kenta Kirimoto , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

Nanoscale cubic SiC particle film is grown on Si substrate by hydrogen plasma sputtering of a SiC target. Before the film growth an amorphous SiC buffer layer of about 100 nm thickness is prepared on the Si substrate. By annealing the buffer layer in hydrogen atmosphere, the nanoscale cubic SiC particle film can be grown on the buffer layer on Si. Particle size, composition and crystallinity of the film depend on the composition, the crystallinity and the surface morphology of the buffer layer.
Absolute Beam-Charge Measurement for Single-Bunch Electron Beams
Authors: Tsuyoshi Suwada Tsuyoshi Suwada , Satoshi Ohsawa Satoshi Ohsawa , Kazuro Furukawa Kazuro Furukawa , Nobumasa Akasaka Nobumasa Akasaka
Published: October 2002

The absolute beam charge of a single-bunch electron beam with a pulse width of 10 ps and that of a short-pulsed electron beam with a pulse width of 1 ns were measured with a Faraday cup in a beam test for the KEK B-Factory (KEKB) injector linac. It is strongly desired to obtain a precise beam-injection rate to the KEKB rings, and to estimate the amount of beam loss. A wall-current monitor was also recalibrated within an error of ±2%. This report describes the new results for an absolute beam-charge measurement for single-bunch and short-pulsed electron beams, and recalibration of the wall-current monitors in detail.
Effect of Ar+ Ion Bombardment During Hydrogenated Amorphous Silicon Film Growth in Plasma Chemical Vapor Deposition System
Authors: Kato Isamu , Nakano Yuuki , Yamaguchi Nobuhiko
Published: October 2002

We have developed the double tubed coaxial line type microwave plasma chemical vapor deposition (MPCVD) system to fabricate hydrogenated amorphous silicon (a-Si:H) films. We have studied the influence of Ar+ ion bombardment during a-Si:H film growth and clarified that the ion bombardment causes film surface heating effect and ion implanting effect. It is not sufficient to discuss only whether films are of good quality or not, when the ion bombardment energy is increased. In this study, we show that the effect of ion bombardment can be separated into the film surface heating effect and the ion implanting effect and discuss the influence of each effect on the film properties. We also show that the film surface temperature can be expressed as a function of the sheath voltage. It is clarified that a film with low dangling bond density can be fabricated at low temperatures if there is no ion bombardment.
Application of Monte Carlo Simulation to a Structural Analysis for Two-Layered/Substrate System
Authors: Kinoshita Akimasa , Hirai Masaaki , Kusaka Masahiko , Iwami Motohiro , Yokota Yasuhiro
Published: October 2002

Monte-Carlo simulation (MCS) using X-ray emission due to
electron beam excitation is applied to determine the film thickness of
a one-layer/substrate system. So far, the characteristic X-ray
intensity has been used in this kind of simulation. However, it is
difficult to utilize this method for a complicated system such as a
multilayered structure. We succeeded in determining the layer
thicknesses for a two-layered system, by a new method using
characteristic Si-L2,3 soft X-ray emission band spectra. This
method is shown to be promising for the quantitative analysis of
multilayer and complicated systems. In this study, a quantitative
analysis using both MCS and Si-L2,3 emission band spectra is
demonstrated for the NiSi/NiSi2/Si system.
Preparation of Gelatin Layer Film with Gold Clusters in Using Photographic Film
Authors: Kuge Ken'ichi , Arisawa Michiko , Aoki Naokazu , Hasegawa Akira
Published: October 2002

A gelatin layer film with gold clusters is produced by taking advantage of the photosensitivity of silver halide photography. Through exposure silver specks, which are called latent-image specks and are composed of several reduced silver atoms, are formed on the surface of silver halide grains in the photographic film. As the latent-image specks act as a catalyst for redox reaction, reduced gold atoms are deposited on the latent-image specks when the exposed film is immersed in a gold (I) thiocyanate complex solution for 5–20 days. Subsequently, when the silver halide grains are dissolved and removed, the gelatin layer film with gold clusters remains. The film produced by this method is purple and showed an absorption spectrum having a maximum of approximately 560 nm as a result of plasmon absorption. The clusters continued to grow with immersion time, and the growth rate increased as the concentration of the gold complex solution was increased. The cluster diameter changed from 20 nm to 100 nm. By this method, it is possible to produce a gelatin film of a large area with evenly dispersed gold clusters, and since it is produced only on the exposed area, pattern forming is also possible.
Dependence of Light-Leakage Caused by Spherical Spacers on Liquid Crystal Mixture in Super Twisted Nematic Liquid Crystal Displays
Authors: Utsumi Yuka , Komura Shinichi , Iwakabe Yasushi , Matsuyama Shigeru , Kondo Katsumi
Published: October 2002

The dependence of light-leakage caused by domain formation around spacers on liquid crystal mixture is observed. It is found that the surface alignment of liquid crystal molecules on the spacer depends on the liquid crystal mixture, which affects the light-leakage intensity. We propose models of the surface alignment, one is a vertical alignment on the spacer and the other is a tangential alignment on the spacer that decreases and increases the light-leakage intensity, respectively. These models are confirmed by observing their extinction patterns under crossed polarizers.
Screening Effects on Electron-Longitudinal Optical-Phonon Intersubband Scattering in Wide Quantum Well and Comparison with Experiment
Authors: Park Seoung-Hwan , Ahn Doyeol , Lee Yong-Tak
Published: October 2002

Screening effects on the electron-longitudinal optical (LO)-phonon intersubband scattering in a wide quantum well are investigated. The scattering rate is significantly reduced by the screening effects around the well width with ΔE
21 = E
LO. From a comparison with experimental results, it is found that the electron temperature estimated with screening effects is higher than that estimated without screening effects. This is due to the fact that the intrasubband relaxation time with screening effects is longer than that without screening effects. With screening effects, the lifetime significantly decreases with increasing applied electric field. On the other hand, the lifetime calculated without screening effects is nearly independent of any applied electric field. The results calculated with screening effects agree well with the experimental results.
High Efficiency Excitation of Cylindrical Optical Near Fields for Atom Guidance
Authors: Akifumi Takamizawa Akifumi Takamizawa , Haruhiko Ito Haruhiko Ito , Motoichi Ohtsu Motoichi Ohtsu
Published: October 2002

We describe coupling of light beams to a micron-sized hollow fiber used for atom guidance. In particular, we deal with an annular light beam produced by means of a hollow fiber. The coupling efficiency of the annular light beam to the LP01 mode with a cylindrical optical near field is compared to that of a Gaussian light beam. Next, we examine optical pumping and heating effects of the light beams on atoms before they enter the hollow fiber. From these results, we find that the use of the annular light beam is more advantageous than the use of the Gaussian light beam for both high efficiency excitation of the LP01 mode and suppression of the preinteraction between atoms and leaked light at the entrance. The spatial intensity distribution of an annular light beam is measured with a protrusion-type fiber probe. This method is useful for observing fine structures of light beams with high spatial resolution.
Highly Accurate and Precise Measurement Technique for Effective Exposure Dose
Authors: Izuha Kyoko , Fujisawa Tadahito , Asano Masafumi , Inoue Soichi
Published: October 2002

A highly accurate and precise measurement technique for effective exposure dose in optical microlithography has been developed. The effective exposure dose can be obtained by a dose monitor mark in a photomask, called the effective dose meter, which consists of multiple segments including grating patterns with a pitch below the resolution limit and different duty ratios gradually. Since the residual thickness of the photoresist after development changes according to the duty ratio, the effective exposure dose can be obtained by monitoring the film thickness for each segment of effective dose meter. It was found that an extremely high dose resolution of less than 0.01% was achieved in this technique. A dynamic range expansion technique has been also proposed, which has wide measurement range and improved repeatability. Across-wafer variation of the effective exposure dose in the current krypton fluoride excimer laser lithography process was measured as a demonstration of these technologies.
A 100-kV, 100-A/cm2 Electron Optical System for the EB-X3 X-Ray Mask Writer
Authors: Saito Kenichi , Kato Junichi , Matsuda Tadahito , Nakayama Yoshinori
Published: October 2002

In order to increase the throughput of the EB-X3 variably shaped electron beam writing system, a method of increasing the current density with a zoom lens was introduced into the electron optical system. The electron optical characteristics were measured at current densities of 50 and 100 A/cm2 under various zoom-lens conditions, and the results show that this method can increase the current density to 100 A/cm2 without any change in the major electron optical characteristics. At this current density, the patterning resolution was estimated to be 55 nm, and no melting of the first shaping aperture and no microdischarges in the 100-kV electron gun were observed. This confirms that the current density of the EB-X3 can in fact be extended to 100 A/cm2 for the fabrication of X-ray masks with a minimum feature size of 100 nm and below.
Nanoindentation of Polycarbonate Using Carbon Nanotube Tip
Authors: Seiji Akita Seiji Akita , Hidehiro Nishijima Hidehiro Nishijima , Takayoshi Kishida Takayoshi Kishida , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

We have demonstrated nanoindentation by a nanotube tip on a polycarbonate surface. The indentation was performed with a force curve measurement using a tapping-mode atomic force microscope in air at room temperature. A nanotube with high buckling force larger than 1 µN is required for the formation of the indent on the polycarbonate. The indent widths are comparable to the nanotube diameter and their spacing is ∼50 nm. Although excess force during the indentation induces plastic deformation of the nanotube cap, the body of the nanotube retains its original shape because of the high axial strength of the nanotube. The ability to fabricate a nanometer-scale dot array in air without any chemical reactions demonstrates potential for use in information storage with high density.
Study of the Superlattice-Like Phase Change Optical Recording Disks
Authors: Chong Tow Chong , Shi Lu Ping , Miao Xiang Shui , Tan Pik Kee , Zhao Rong , Cai Zhong Ping
Published: October 2002

Superlattice-like phase change optical disks, where the
recording layer consists of alternating thin layers with two
different phase change materials of GeTe and Sb2Te3, have
been fabricated. The optical and thermal properties were simulated
and measured. Samples were measured by X-ray diffraction (XRD) after
annealing. The peaks of Ge2Sb2Te5 were observed,
which indicates that Ge2Sb2Te5 was formed at the
interface between GeTe and Sb2Te3. The recording, erasing
and overwriting properties were investigated. The signal
differentiation in writing, reading and erasing was observed at the
pulse width of 7 ns, which indicates that the superlattice-like
structure can effectively shorten the crystallization time. The
overwriting cycle was measured using a static tester. Within 10000
times no significant change in the modulation amplitude was observed.
Deep UV Mastering with a Write Compensation Technique Realizing over 20 GB/layer Capacity Disc
Authors: Takeda Minoru , Furuki Motohiro , Ishimoto Tsutomu , Kondo Kenji , Yamamoto Masanobu , Kubota Shigeo
Published: October 2002

Recent progress in blue laser diodes has necessitated the development of ultra-high density mastering
corresponding to a density several times higher than that of the digital versatile disk (DVD). As reported earlier,
we developed a deep UV master recorder using an all-solid-state 266 nm laser, and confirmed an acceptable RF
signal read-out quality from 20 Gbytes capacity with CD disc size, of which the bit density is equal to 14 Gbit/inch2. Here, we report the improvement of RF signal jitter utilizing a write compensation technique for the
mastering process. In this technique, the positions of the leading and trailing edges of the signal are shifted by pit
signal processing (PSP). We confirmed an improved quality read-out signal of which the bottom jitter value is less
than 8% from the 20 Gbytes disc, and also analyzed the signal jitter elements. In addition, experimental results of
significantly higher densities of up to 30 Gbytes
(21 Gbit/inch2) are demonstrated.
Near-Field Optical Head for Disc Mastering Process
Authors: Imanishi Shingo , Ishimoto Tsutomu , Aki Yuichi , Kondo Takao , Kishima Koichiro , Yamamoto Kenji , Yamamoto Masanobu
Published: October 2002

Near-field recording for the disc mastering process was realized. A high-numerical-aperture (NA)
objective (NA=1.4) composed of an aspherical lens and a solid immersion lens (SIL) was driven by an
air pad and a piezotransducer. The gap between the SIL and the glassmaster was controlled by a new
gap detection method using the totally internally reflected beam from the bottom surface of the SIL. In
the near-field operation, the gap was maintained at 100 nm with a residual error of ±4.8 nm. In the DC
exposure with a laser beam of 413 nm, a narrower groove structure could be formed almost at the
inverse rate of NA expansion. In the read-only memory (ROM) exposure with an eight to fourteen
modulation plus (EFM+) signal, signal bottom jitter values of 9.8% for an 18 GB disc and 10.9% for a
20 GB disc were obtained.
Synchronous Trigger Detection for Pulse Laser Readout on Super Resolution Erasable Optical Disks
Authors: Yin Gung-Chian , Chen Bing-Mau , Tai Chia-Ping , Shieh Han-Ping D.
Published: October 2002

The laser pulse readout scheme is advantageous in reading
thermal super resolution disks, but the light modulation on the RF
signal confuses the detection channel. A synchronous trigger detection
scheme, using the pulse laser trigger signal to pick up the desired
signal, is proposed to suppress the adverse effects of the light
modulation. A 5-dB increase of the signal on an magneto-optical super
resolution center aperture detection disk by the synchronous detection
system was demonstrated experimentally.