bluuebunny/crossref_metadata_2025 huggingface dataset:
Prebreakdown Phenomena and Formation Processes of Low-Pressure Glow Discharges in Ar, Ar/N2 and Ar/O2 Mixtures
Authors: Hosokawa Tatsuzo , Goto Kazuhiro , Ohuchi Mikio , Ichinose Kensuke , Funato Yasuyuki , Kaneda Teruo
Published: October 2002

In this research, both the prebreakdown phenomena and the transient processes from the prebreakdown phenomena to the glow discharge in low-pressure Ar gas, Ar/N2 and Ar/O2 mixtures were investigated by electrical and optical methods. The prebreakdown phenomenon in the Ar/N2 mixture was similar to that of Ar gas, and a pulseless component has been observed. The prebreakdown phenomenon in the Ar/O2 mixture differed from those in the Ar gas and Ar/N2 mixture, and formed a pulse discharge. Thus, the prebreakdown phenomenon in the Ar gas has been changed to pulse discharge by mixing a small amount of O2 gas which played an important role in the formation of pulse discharge.
A Surface-Silylated Single-Layer Resist Using Chemical Amplification for Deep Ultraviolet Lithography: II. Limited Permeation of Si Compounds from Liquid Phase*
Authors: Sugita Kazuyuki , Yamashita Masahiro , Liew Chan Ming , Harada Kieko , Kushida Masahito , Saito Kyoichi
Published: October 2002

A single thick layer of poly(vinyl phenol) containing onium salt was surface-silylated uniformly through contact with hexamethyl-cyclotrisilazane or hexamethyl-disilazane in solution to obtain a bilevel structure, similarly to a previous silylation study in the vapor phase. Silicon atoms were effectively incorporated into the surface sublayer by limited permeation of the solute and reaction with –OH to form –O–SiR3. The O2 reactive ion etching (RIE) durability of the silylated sublayer of 170–220 nm thickness was 15–38 times as high as that of the unsilylated bulk layer. The resist layer was patterned by 5–10 mJ/cm2 deep ultraviolet exposure, chemically amplified desilylation during postexposure baking, and wet development with alkali to remove the surface sublayer in the exposed area, forming a shallow, recessed image. When the layer, particularly that silylated with hexamethyl-disilazane, was plasma-developed by O2 RIE, the bulk layer in the exposed area was clearly blanked to the substrate to give a positive-tone image with a high aspect ratio.
Ferroelectricity of YMnO3 Thin Films on Pt(111)/Al2O3(0001) and Pt(111)/Y2O3(111)/Si(111) Structures Grown by Molecular Beam Epitaxy
Authors: Shogo Imada Shogo Imada , Takuya Kuraoka Takuya Kuraoka , Eisuke Tokumitsu Eisuke Tokumitsu , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

Ferroelectric YMnO 3 (YMO) thin films were grown on Pt/Al2O3 (0001) and Pt/Y2O3/Si (111) structures using Y2O3 buffer layers by molecular beam epitaxy (MBE). In situ reflection high-energy electron diffraction (RHEED) analyses and X-ray diffraction (XRD) analyses showed that both Y2O3 and YMO films were epitaxially grown on both substrates. Capacitance–voltage (C–V) measurement for a YMO film on the Pt/Al2O3 structure showed a butterfly-type curve with a memory window of 0.85 V. The remanent polarization (2P
r) of the film was determined to be larger than 0.7 µC/cm2 from Sawyer-Tower measurement. Ferroelectricity of a YMO film in the Al/YMO/Y2O3/Pt/Y2O3/Si(111) structure was almost the same as that on Pt/Al2O3, which indicated that the effect of the different thermal expansion coefficients of the substrates was not significant.
Chemical Treatment Effects on Si(111) Surfaces in Aqueous NaF Solution
Authors: Tomita Noriko , Adachi Sadao
Published: October 2002

Chemically treated Si(111) surfaces in aqueous NaF solution have been investigated using spectroscopic ellipsometry (SE), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and wettability measurements. The SE data indicate that the solution causes the removal of the native oxide upon immersing the sample in the solution. After the native oxide is etched away completely, the SE data yield the spectrum of a slightly roughened surface. The SE-estimated roughness is ∼ 0.64 nm, which is considerably larger than the AFM determined rms value (∼ 0.26 nm); the difference is considered to be due to the SE technique being sensitive not only to the surface microroughness but also to the adsorbed chemical species. The XPS data support the fact that the native oxide is removed upon immersing the sample in the solution. It is also shown that the Si LMM signal at ∼ 1160 eV can provide direct information regarding the relative quality of surface regions prepared by different methods. The wettability measurements show that the as-degreased surface is hydrophilic (θ∼35°), while the NaF-etched surface is hydrophobic (θ∼70°).
Latent Damage Generation in Thin Oxides of Metal-Oxide-Semiconductor Devices under High-Field Impulse Stress and Damage Characterization Using Low-Frequency Noise Measurement
Authors: Chim Wai Kin , Lim Peng Soon
Published: October 2002

Latent damage generation in thin oxides of metal-oxide-semiconductor (MOS) devices, caused by high-field impulse or electrostatic discharge (ESD) stress applied to the gate electrode, can lead to increased trap generation during subsequent hot-carrier stressing. However, the charge-to-breakdown (Q
bd) of such impulse prestressed devices is not significantly affected by the latent damage, and hence it is difficult to characterize such damage using Q
bd measurements. Monitoring of the latent damage can be carried out by detecting the change in an appropriate electrical parameter of the device or by extracting the generated interface states and oxide trap charges. However, such electrical measurements have their own limitations. It was found that low-frequency noise measurement is a more sensitive method than the above-mentioned electrical measurements for characterizing the ESD stress-induced latent damage in thin oxides.
Effects of Negative Ions in Aqueous Ti Solution on Formation of Ultrafine TiO2 Powder by Low Temperature Homogeneous Precipitation
Authors: Kim Sun-Jae , Park Sung
Published: October 2002

Ultrafine crystalline TiO2 powder was prepared by homogeneous precipitation by heating aqueous TiOCl2 solution below 70°C. The TiO2 powder was formed even at room temperature. By spontaneous hydrolysis of the aqueous TiOCl2 solution, all the precipitates were completely crystallized in the rutile phase. These, however, were transformed into the anatase phase by adding more TiOSO4 solution to the aqueous TiOCl2 solution. The formed secondary particles consisted of needle-shaped, spherical and mixed primary particles corresponding to the rutile, anatase and mixed phases, respectively. It seems that the formation and phase determination of crystalline TiO2 powder during the precipitation may be affected by capillary pressure. This pressure probably depends on the shape of the primary particles.
Theoretical Analysis of The threshold Current Density in BeMgZnSe Quantum-Well Ultraviolet Lasers
Authors: Takeo Maruyama Takeo Maruyama , Naoto Nakamura Naoto Nakamura , Masahiro Watanabe Masahiro Watanabe
Published: October 2002

A II–VI semiconductor laser using Be-chalcogenide semiconductor material which is lattice-matched to silicon was proposed and its threshold current density was estimated based on the density-matrix theory. The threshold current density was calculated to be below 1 kA/cm2 in a single quantum-well (QW) less than 7 nm thick.
New Methods to Achieve High Sensitivity of Objective Lens Actuator in Optical Disc System
Authors: Huang Lei , Gong Mali , Jia Weipu , Yan Ping , Cui Ruizhen , Zhang Haitao
Published: October 2002

In order to reduce the cross-coupled vibration and improve the driving sensitivity of lens actuator, in this paper, we present some important factors that affect this sensitivity and propose new methods that can be conveniently adopted for existing product lines. Experimental results verify the validity of these proposed methods.
Grain Size Dependence of High Power Piezoelectric Characteristics in Nb Doped Lead Zirconate Titanate Oxide Ceramics
Authors: Sakaki Chiharu , Newalkar Bharat L. , Komarneni Sridhar , Uchino Kenji
Published: October 2002

The grain size dependence of high power piezoelectric properties and their variation upon heat generation for Nb doped lead zirconate titanate oxide (PZT)-based ceramics were investigated under high AC electric fields. The temperature rise was found to decrease linearly upon reduction in grain size and was about 40% lower for fine grained ceramic (0.9 µm) compared to coarse grained one (3.0 µm) near the maximum vibration velocity level (0.30 m/s) whereas coercive field displayed a linear increase upon lowering the grain size. Furthermore, a rise in vibration velocity and mechanical quality factor (Q
m) under low electric fields was found to correlate with decreasing grain size. Such a trend was explained in terms of the pinning effect of grain boundaries, which is observed to be critical for suppressing heat generation in high power ceramic applications.
SrTa2O6 Thin Films Deposited by Plasma-Enhanced Atomic Layer Deposition
Authors: Lee Won-Jae , You In-Kyu , Ryu Sang-Ouk , Yu Byoung-Gon , Cho Kyoung-Ik , Yoon Soon-Gil , Lee Chun-Su
Published: October 2002

SrTa2O6 (STO) thin films were prepared by plasma-enhanced atomic layer deposition (PEALD) with an alternating supply of reactant sources, Sr[Ta(C2H5O)5(C4H10NO)]2 {strontium bis-[tantalum penta-ethoxide dimethyllaminoethoxide]; Sr(Ta(OEt)5·dmae)2} and O2 plasma. It was observed that the uniform and conformal STO thin films were successfully deposited using PEALD and the film thickness per cycle was saturated at approximately 0.8 Å at 300°C. Electrical properties of STO thin films prepared on Pt/SiO2/Si substrates at various annealing temperatures were investigated. While the grain size and dielectric constant of STO films increased with increasing annealing temperature, the leakage current characteristics of STO films slightly deteriorated. The leakage current density of a 40 nm STO film annealed at 600°C was approximately 5×10-8 A/cm2 at 3 V.
Formation and Characterization of Aggregates of Merocyanine Dyes in Vacuum-Deposited Thin Film
Authors: Ueda Yasukiyo , Nitta Kuniyuki
Published: October 2002

Thin films of merocyanine (MD) dyes substituted with alkyl chains of various lengths at the benzothiazol ring are prepared by vacuum evaporation. The structure and aggregate formation upon dimethylamine vapor treatment are discussed based on the kind of substituent at the rhodanine ring, crystallinity and alkyl chain length. It is found that the introduction of a carboxymethyl group at the rhodanine ring and the fabrication of amorphous films are very important in aggregate formation. MD-2, -5 and -6 films, which the numbers indicate the number of carbon atoms in the alkyl chain, form H-aggregates, and MD-10 and amorphous MD-18 form J-aggregates. The difference in aggregate structure according to the alkyl chain length positioned at the benzothiazol ring depends on the degree of steric hindrance between alkyl chains. The activation energies of H- and J-aggregate formation are estimated to be 4.46 kJ mol-1 and 11.07 kJ mol-1, respectively.
C-Axis-Oriented Ru Thin Films Prepared by Sputtering in Ar and O2 Gas Mixture
Authors: Abe Yoshio , Kaga Yukinao , Kawamura Midori , Sasaki Katsutaka
Published: October 2002

C-axis-oriented Ru thin films were deposited on glass substrates by sputtering a Ru target in Ar and O2 gas mixture with O2 flow ratios which were lower than that required for RuO2 formation. A minimum value of 3.5° was obtained for the full-width at half maximum (FWHM) of the rocking curve of a Ru (002) peak for the Ru film deposited at a substrate temperature of 500°C and O2 flow ratio of 4%. The c-axis-oriented Ru films were observed to be formed from the initial stage of crystal growth and became continuous even at a film thickness of 3 nm. Two-dimensional crystal growth of the single-axis-oriented Ru films was suggested.
Approach to Patterning of Extreme Ultraviolet Lithography Masks using Ru Buffer Layer
Authors: Lee Byoung Taek , Hoshino Eiichi , Takahashi Masashi , Yoneda Takashi , Yamanashi Hiromasa , Hoko Hiromasa , Ryoo ManHyoung , Chiba Akira , Ito Masaaki , Sugawara Minoru , Ogawa Tarou , Okazaki Sinji
Published: October 2002

The properties of Ru film were examined to determine its suitability as a repair buffer layer for the patterning of extreme ultraviolet lithography (EUVL) masks. Ru is etched more slowly than a conventional SiO2 buffer layer by a focused ion beam (FIB) for mask repair, which makes it more suitable as a sacrificial layer during repair. When etched in an O2/Cl2 gas mixture with a high Cl2 content at a low total gas flow rate, Ru exhibited a high etching selectivity with respect to Si, the top layer of a Mo/Si multilayer reflector. This could enable use of a simpler mask patterning process without any damage to the multilayer. In addition, the use of Ru rather than SiO2 for the buffer layer improved the deep ultraviolet (DUV) inspection contrast before and after buffer layer etching. The patterning of a mask with a TaN absorber layer and a Ru buffer layer was demonstrated.
Positive Charge Increase in Plasma Deposited Oxides Induced by Low Pressure Chemical Vapor Deposition of Silicon Nitride
Authors: Fay Jean Luc , Beluch Jean , Despax Bernard , Sarrabayrouse Gérard
Published: October 2002

The origin of the positive charge observed in an interlayer dielectrics made of a silicon-oxide layer deposited by plasma enhanced chemical vapor deposition (PECVD) from an O2/tetraethoxysilane (TEOS) mixture covered by a silicon-nitride layer obtained by low pressure chemical vapor deposition (LPCVD) is studied. Charge creation during silicon-nitride deposition is evidenced. Even though NH3 thermal decomposition is one of the main parameters of both hydrogen incorporation and the charge creation in the oxide layer, the increase in hydrogen content and charge trapping after nitride deposition is not only due to the diffusion of hydrogen originating from ammonia fragmentation. The results show that the charge decrease observed when increasing the O2/TEOS ratio and boron doping is partly related to the decrease of the carbon content in the oxide.
Synthesis of Carbon Nanotubes by Laser Ablation of Graphites at Room Temperature
Authors: Kuo T. F. , Chi C. C. , Lin I. N.
Published: October 2002

We successfully synthesized carbon nanotubes with very small diameters (5–10 nm) at room temperature by using high energy laser pulses (193 nm, 5 J/cm2 and 20 ns duration time) to re-excite the carbon species contained in the laser ejected plume. The carbon nanotubes, which presumably formed in gas phase, were preferentially collected by electro-statically biasing (∼ 5 kVDC) the substrates. High resolution transmission electron microscopic analysis reveals that thus obtained materials are multiwall carbon nanotubes.
A Study of Photoelectrochemical Oxidation of GaN Epilayers by Extrinsic Photoconductivity
Authors: Fu Dejun , Yuldashev Shavakat U. , Kim Nam Hwa , Ryu Young Sun , Yun Jae Sung , Park Seung Ho , Kang Tae Won , Chung Kwan Soo
Published: October 2002

GaN epilayers grown on sapphire substrates by molecular-beam epitaxy were oxidized by photoelectrochemical (PEC) treatment in KOH. The effect of the oxidation on the GaN surface was investigated by extrinsic photoconductivity. The PEC-treated samples show decreased photoresponse and relaxation time compared with those of the as-grown sample. The concentration of deep states in the epilayers as determined from the light-intensity dependence of rise and decay times is reduced after PEC oxidation. The results suggest that the defective bonds at the surface are effectively saturated by oxygen coverage during PEC growth of the oxide layer. Results of temperature-dependent photoconductivity measurement reveal that shallow levels are also passivated within a short time of PEC treatment.
Optical Gain and Optical Internal Loss of GaN-Based Laser Diodes Measured by Variable Stripe Length Method with Laser Processing
Authors: Kimura Yoshinori , Ito Atsuya , Miyachi Mamoru , Takahashi Hirokazu , Watanabe Atsushi , Ota Hiroyuki , Ito Norikazu , Tanabe Tetsuhiro , Sonobe Masayuki , Chikuma Kiyofumi
Published: October 2002

We demonstrate a new technique for the variable stripe length (VSL) method by which the optical gain and optical internal loss of GaN-based laser diodes (LDs) can be directly measured. In the technique, the laser processing is utilized for varying the excitation length. The excitation length of GaN-based LDs can be varied by directly processing its p-electrode with high-power laser irradiation. From the results of the measurements, it was revealed that the optical internal loss of GaN-based LDs was strongly affected by the layer structure.
Surface Wave Plasma Production Employing High-Permittivity Material for Microwave Window
Authors: Kusaba Kouta , Shinagawa Keisuke , Furukawa Masakazu , Kawamura Katsufumi , Shindo Haruo
Published: October 2002

As a novel method of large-diameter plasma production for ultralarge-scale integrated (ULSI) circuit processes, microwave plasma production employing a high-permittivity material window is proposed. A systematic plasma density enhancement is found to occur in conjunction with increase in the permittivity value of the dielectric window material. The results are shown to be due to the surface wave, and the microwave power consumption mainly occurs near the window in the high permittivity. This plasma production can provide a good downstream plasma with a large diameter for ULSI processes.
Application of Bessel Beams for Microfabrication of Dielectrics by Femtosecond Laser
Authors: Marcinkevičius Andrius , Juodkazis Saulius , Matsuo Shigeki , Mizeikis Vygantas , Misawa Hiroaki
Published: October 2002

We demonstrate a novel approach to femtosecond microfabrication of transparent dielectrics, which employs nondiffracting Bessel beams instead of the conventionally used Gaussian beams. The main advantage of Bessel beams is the possibility of recording linear photomodified tracks, extending along the lines of nondiffractive beam propagation without sample translation, as would be required for Gaussian beams. Recording of patterns with an aspect ratio of up to 102–103 in vitreous silica using amplified femtosecond Ti:saphire laser pulses is demonstrated.
Toward Standard Method for Microelectromechanical Systems Material Measurement through On-Chip Electrostatic Probing of Micrometer Size Polysilicon Tensile Specimens
Authors: Minotti Patrice , Le Moal Patrice , Joseph Eric , Bourbon Gilles
Published: October 2002

Polysilicon deposited by low pressure chemical vapor deposition is the most widely used structural material for surface-micromachined microelectromechanical systems. Thus, investigations are still needed in order to identify polysilicon mechanical characteristics as a function of the deposition conditions. The following work focuses on new micrometer size monolithic test cells combining polysilicon tensile specimens and ultra-high driving force electrostatic actuators fabricated from a common process flow. The proposed approach allows intrinsic material properties such as polysilicon tensile fracture to be measured through electrostatic probing, using on-chip micrometer size uniaxial tensile test cells.
Photoconductivity in Semiconducting Single-Walled Carbon Nanotubes
Authors: Fujiwara Akihiko , Matsuoka Yasuyuki , Suematsu Hiroyoshi , Ogawa Naoki , Miyano Kenjiro , Kataura Hiromichi , Maniwa Yutaka , Suzuki Shinzo , Achiba Yohji
Published: October 2002

We have observed the photoconductive response of film samples of single-walled carbon nanotubes for the first time.
Two peaks in the photoconductivity excitation spectra around 0.7 and 1.2 eV are observed at room temperature, which can be interpreted as a photocurrent in semiconducting nanotubes. At a low temperature, we found a marked change in the intensity of the spectrum. In this paper, we discuss this temperature dependence and the mechanism of photoconductivity.
Characteristics of Metal/Ferroelectric/Insulator/Semiconductor Using La2O3 Thin Film as an Insulator
Authors: Won Dong-Jin , Wang Chae-Hyun , Choi Doo-Jin
Published: October 2002

We fabricated a novel metal/ferroelectric/insulator/semiconductor (MFIS) structure using the PbTiO3 film and La2O3 film prepared by metal organic chemical vapor deposition as a ferroelectric and an insulator, respectively. The dielectric constant (k) of the 420 Å La2O3 film was about 28. The leakage current density was about 3×10-6 A/cm2 at +5 V. The MFIS using an Al/PbTiO3 (3600 Å)/La2O3 (280 Å)/Si configuration showed clockwise C–V hysteresis. The memory window increased from 0.3 to 2.6 V with increasing bias from 2 to 10 V. In this letter we propose the La2O3 film as an alternative insulator layer in the MFIS structure.
Microstructural Investigation of Pulsed-Laser-Deposited SrRuO3 Films on Si with SrO Buffer Layers
Authors: Chen Yuxi , Koike Junichi , Higuchi Takamitsu , Iwashita Setsuya , Ishida Masaya , Shimoda Tatsuya
Published: October 2002

Conductive SrRuO3 films were deposited on {001} Si substrates by pulsed-laser deposition using SrO as buffer layers. The microstructure and orientation relationships (ORs) of the constituting layers were investigated by X-ray diffraction, transmission electron microscopy, high-resolution electron microscopy and energy dispersive X-ray spectroscopy. Good epitaxial growth of SrO and SrRuO3 films on the Si substrates was achieved. Multiple domains were formed in the SrRuO3 films. The domain boundaries were nearly perpendicular to the interface between the SrRuO3 films and the SrO buffer layers. Three ORs among Si, SrO and SrRuO3 were observed, indicating a new OR between Si and SrO.
On-Wafer Monitoring of Vacuum-Ultraviolet Radiation Damage in High-Density Plasma Processes
Authors: Samukawa Seiji , Ishikawa Yasushi , Kumagai Shinya , Okigawa Mitsuru
Published: October 2002

Vacuum-ultraviolet (VUV) radiation damage was investigated in inductively coupled Ar, He, and O2 plasmas by measuring the hole currents generated in SiO2 film. The hole currents strongly depended on the irradiated plasma VUV wavelength and photon flux (electron density). When the electron density was increased, larger hole currents were observed in the SiO2 film. A VUV wavelength of 58.4 nm in the He plasma and of 130.5 nm in the O2 plasma generated more holes in the SiO2 film than that of 104.8 and 106.6 nm in the Ar plasma did. That is believed to be due not only to the photon energy but also to the dependence of VUV transmittance in SiO2 films on the VUV wavelength. We found that pulse-time-modulated plasma is very effective in reducing the number of holes generated in SiO2 film by plasma VUV irradiation. Compared to the result obtained in the cw plasma, the VUV spectrum intensities and hole currents in the pulse-time-modulated plasma decreased drastically when the electron density was maintained.
Growth of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 Single Crystals Directly from Melt
Authors: Fang Bijun , Luo Haosu , Xu Haiqing , He Tianhou , Yin Zhiwen
Published: October 2002

Piezoelectric Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT 91/9) single crystals were grown directly from melt by a modified Bridgman method. X-ray diffraction confirms that the crystals are of pure perovskite structure. The obtained crystals have piezoelectric constant d
33 in the range of 1800–2000 pC/N, which is comparable to that of the PZNT crystals grown from flux. However, compared with the flux-grown PZNT 91/9 crystals, there is a broad diffused peak on the curve of temperature dependence of the dielectric constant, and a lower dielectric peak at 105°C. Domain observation shows that both the rhombohedral and tetragonal orientation states coexist in the morphotrpic PZNT 91/9 crystals.
Interaction of SF6 Cluster Ion Beams with Si Surface
Authors: Takaoka Gikan H. , Nakamura Shigeru , Seki Toshio , Matsuo Jiro
Published: October 2002

The etching process of Si surfaces by irradiation of SF6 cluster ions has been investigated using a quadrupole mass spectrometer (QMS) and a time-of-flight (TOF) method. The fluoride reaction is enhanced after impact of the cluster ions, and SiF4 particles are evaporated from the surface. In contrast, after impact of SF6 monomer ions on the Si substrate, physical sputtering occurs under a binary collision process, and the sputtered atoms are mainly Si atoms. In the reactive cluster ion beam process, high energy density in a local area on the surface results in a considerable increase in equivalent temperature inside the cluster, which is very effective for the enhancement of the chemical reaction. Thus, fluoride etching of Si at a high sputtering rate has been achieved by irradiation of SF6 cluster ions but not SF6 monomer ions.
Simultaneous Observation of Millisecond Dynamics in Atomistic Structure, Force and Conductance on the Basis of Transmission Electron Microscopy
Authors: Kizuka Tokushi , Ohmi Hajime , Sumi Takao , Kumazawa Katsuyoshi , Deguchi Shunji , Naruse Mikio , Fujisawa Satoru , Sasaki Shinya , Yabe Akira , Enomoto Yuji
Published: October 2002

High-resolution transmission electron microscopy (HRTEM) has been developed to possess functions of atomic force microscopy and scanning tunneling microscopy. Dynamics of subnano Newton-scale force and conductance were simultaneously observed at intervals of 1/30–1/3840 s during HRTEM imaging of contact, deformation and fracture processes between nanometer-sized tips. The experimental basis of the atomic-scale mechanics of materials was developed on the basis of the present microscopy.
Fabrication of <111>-Oriented Si Film with a Ni/Ti Layer by Metal Induced Crystallization
Authors: Minagawa Yasushi , Yazawa Yoshiaki , Muramatsu Shin-ichi
Published: October 2002

We used metal-induced-crystallization (MIC) to crystallize amorphous silicon (a-Si) films over 1 µm thick. We employed a Ni/Ti layer for MIC. The a-Si films with the Ni/Ti layer were annealed at 550°C. We found that a 6-µm-thick Si film was oriented in the <111> direction by inserting a Ti layer between Ni and the glass substrate. If the thicknesses of the Ni and Ti layer were nearly the same, the peak intensity ratio of the (220) to (111) planes was 3%. This oriented growth tendency is maintained from the beginning of crystallization to the full-crystallized stage.
Growth of Crystal Silicon Films from Chlorinated Silanes by RF Plasma-Enhanced Chemical Vapor Deposition
Authors: Liu Haiping , Jung Sughoan , Fujimura Yukihiro , Toyoshima Yasutake , Shirai Hajime
Published: October 2002

Low-temperature growth of crystal silicon films is demonstrated from chlorinated silane, i.e., SiH2Cl2, SiHCl3 and SiCl4, with hydrogen dilution by a RF glow-discharge method. Low-temperature crystallization is significantly enhanced on amorphous substrates such as glass from the initial growth stage in all systems. In the SiH2Cl2 system, however, the film crystallinity strongly depends on deposition parameters, i.e., substrate temperature, T
s, and the flow rate of hydrogen, Fr(H2). On the other hand, it is almost independent of T
s and Fr(H2) in the SiCl4 system. This difference originates from the chemical reactivity of deposition precursors and the corresponding surface reaction. Low-temperature crystallization from SiH2Cl2 and SiCl4 systems is discussed through studies on the film growth combined with the in situ monitoring of the surface reaction using Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS).
YBa2Cu3O7-δ/NdBa2(Cu1-xNix)3O7-δ Double Layers by Liquid-Phase Epitaxial Growth
Authors: Yao Xin , Izumi Toru , Hobara Natsuro , Nakamura Yuichi , Izumi Teruo , Shiohara Yuh
Published: October 2002

Our present investigation has answered questions pertaining to the REBa2Cu3O7-δ (RE123, RE=rare-earth elements)-coated conductor application when NdBa2(Cu1-x
Ni
x
)3O7-δ (Ni–NdBCO) solid solution is used as a buffer layer by the liquid-phase epitaxy (LPE) process. The NiO/Ni substrate has no substantial reaction in the Ni-saturated Nd–Ba–Cu–O liquid. There is no essential Ni interdiffusion between YBa2Cu3O7-δ (YBCO) and Ni–NdBCO LPE thick films as evident from T
c values of 90 K obtained from multilayer YBCO/Ni–NdBCO samples.
Catalytic Chemical Sputtering: A Novel Method for Obtaining Large-Grain Polycrystalline Silicon
Authors: Matsumura Hideki , Kamesaki Koji , Masuda Atsushi , Izumi Akira
Published: October 2002

A novel method, called the catalytic chemical sputtering method, is proposed. In this method, hydrogen atoms generated by the catalytic cracking reaction between a heated tungsten catalyzer and hydrogen gas, react with solid silicon to draw out silicon-hydride species from it chemically, and such species are again decomposed by the catalytic cracking reaction or directly transported to form silicon films on substrates. Thus, silicon films are prepared at low substrate temperatures without using silane or disilane gases. By this method, polycrystalline silicon with a grain size larger than 1 µm is obtained at substrate temperatures of approximately 400°C.
Luminescence Intensity Reduction in Mg-Doped GaN Grown by Metalorganic Chemical Vapor Phase Epitaxy
Authors: Chen-Ke Shu Chen-Ke Shu , Hsiao-Hui Chen Hsiao-Hui Chen , Wen-Hsiung Lee Wen-Hsiung Lee , Yung-Chung Pan Yung-Chung Pan , Huai-Ying Huang Huai-Ying Huang , Jehn Ou Jehn Ou , Wei-Kuo Chen Wei-Kuo Chen , Wen-Hsiung Chen Wen-Hsiung Chen , Ming-Chih Lee Ming-Chih Lee
Published: October 2002

Photoluminescence dynamic responses of a heavily Mg-doped GaN grown by metalorganic chemical vapor phase epitaxy have been investigated. As the probe power density increased from 2.5 to 925 W/cm2, a Mg-related emission band shifted from 2.82 to 3.16 eV revealing characteristics of donor-acceptor pair recombination. The intensity evolution also showed slow decay that suggests the metastable emission behavior. A simple potential barrier model was proposed to occur between the Mg related deep levels and common Mg acceptor level, which impedes electron relaxation and thus slows down the luminescence decay. From the variation of decay time constant with temperature, a barrier energy was deduced to be about 69 meV which is very close to the electrical result of 68 meV.
In Situ Monitoring of GaN Reactive Ion Etching by Optical Emission Spectroscopy
Authors: Yoshida Harumasa , Urushido Tatsuhiro , Miyake Hideto , Hiramatsu Kazumasa
Published: October 2002

The optical emission during GaN reactive ion etching (RIE) using Cl2 plasma was monitored in situ by optical emission spectroscopy (OES). The optical emission intensity of atomic Ga is in proportion to the etch rate, and the time-integrated values of the optical emission intensities from atomic Ga and molecular N2 are proportionally correlated to the etched volumes of GaN. It is found that monitoring of the Ga and N2 optical emissions allows in situ control of the etching depth of GaN even if the etch rate fluctuates during the etching process.
Low Temperature Deposition of Pb(Zr,Ti)O3 Film by Source Gas Pulse-Introduced Metalorganic Chemical Vapor Deposition
Authors: Aratani Masanori , Ozeki Tomohiko , Funakubo Hiroshi
Published: October 2002

We prepared Pb(Zr,Ti)O3 [PZT] thin films on (111)Pt/Ti/SiO2/Si substrates at 395 to 580°C by metalorganic chemical vapor deposition (MOCVD). PZT thin films with Zr/(Zr+Ti)=0.62 prepared by conventional continuous source gas introduction (continuous-MOCVD) and pulse introduction (pulse-MOCVD) were compared. Film with higher crystallinity and smoother surfaces were obtained by pulse-MOCVD compared with continuous-MOCVD. Moreover, the leakage current density of the film decreased and ferroelectricity increased with pulse-MOCVD. Ferroelectricity decreased with decreasing the deposition temperature, but the remanent polarization (Pr) value was 22.5 µC/cm2 for the film with a 5 nm-thick PbTiO3 buffer layer deposited at 395°C by pulse-MOCVD, while ferroelectricity was not obtained for the film deposited by continuous-MOCVD at the same deposition temperature.
Technique for Local Pretilt Measurement in Nematic Liquid Crystals
Authors: Lamarque-Forget Sandrine , Martinot-Lagarde Philippe , Dozov Ivan
Published: October 2002

We propose a simple technique for local measurement of the nematic pretilt on a solid substrate, using standard planar orientation on the opposite surface. We obtain the pretilt from the variation of the cell birefringence under weak electric field. We apply experimentally the proposed technique to measure the pretilt of the nematic 5CB on various substrates. We discuss the advantages and the limitations of our technique.
Integrated Sculptured Thin Films
Authors: Motofumi Suzuki Motofumi Suzuki , Yasunori Taga Yasunori Taga
Published: October 2002

We have demonstrated the integration of various morphologies generated by dynamic oblique deposition, during which the deposition angle and the azimuth of the substrate are varied. The layers with zigzag, helicoidal and cylindrical columns have been successfully stacked on a substrate without using any etching process. In addition, the uniform and flat layer is formed on porous layers by a gradual change in the deposition geometry. Therefore, shape-related physical anisotropies and the chemical activity due to high porosity can be integrated in one thin film, making it applicable to devices such as solar cells and chemical sensors.
Characteristics of YBa2Cu3O7 Thin Films Deposited on Substrates Buffered by Various TiO2 Layers
Authors: Po-Iem Lin Po-Iem Lin , Chia-Wen Liu Chia-Wen Liu , Chich-Chang Hsieh Chich-Chang Hsieh , Kaung-Hsiung Wu Kaung-Hsiung Wu , Jenh-Yih Juang Jenh-Yih Juang , Tseng-Ming Uen Tseng-Ming Uen , Jiunn-Yuan Lin Jiunn-Yuan Lin , Yih-Shung Gou Yih-Shung Gou
Published: October 2002

Titanium nitride (TiN) and superconducting YBa2Cu3O7 (YBCO) thin films have been deposited sequentially on SrTiO3(STO)(100) substrates by in situ pulsed laser ablation. The TiN films were originally intended to serve as the lower contact electrode of the c-axis YBCO thin films. It was found that, although high-quality YBCO films could be obtained with the YBCO/TiN/STO(100) bilayer structure, the TiN(100) layer was oxidized which changed the structure into YBCO/TiO2/STO(100) during YBCO deposition. Comparative studies of depositing YBCO films directly onto a dc-sputtered TiO2/STO(100) template conventionally used in the selective epitaxial growth (SEG) process have, however, resulted in formation of a nonsuperconducting YBCO top layer. The characteristics of the resultant TiO2 layers obtained using various processes were analyzed to delineate the apparent discrepancies.
Time-Domain Terahertz Spectroscopy of (100) (LaAlO3)0.3-(Sr2AlTaO6)0.7 Substrate
Authors: Toshihiko Kiwa Toshihiko Kiwa , Masayoshi Tonouchi Masayoshi Tonouchi
Published: October 2002

We measured terahertz (THz) properties of high-T
c superconductor's (HTS's) substrates, (100) MgO and (100) (LaAlO3)0.3-(Sr2AlTaO6)0.7 (LSAT), at frequencies between 0.5 THz and 2 THz using time-domain terahertz spectroscopy (TDTS). The complex refractive index \tilden and dielectric function \tildeε of the MgO substrate were independent of frequencies; those of LSAT slightly increased with increasing frequency. It was determined that \tilden=3.17+i0.004 and \tildeε=10.1+i0.06 for the MgO substrate and \tilden=4.8+i0.02 and \tildeε=24+i0.2 for the LSAT substrate at 1 THz. The LSAT values were almost independent of the temperature at these frequencies. The dielectric loss tan
δ's of the LSAT and the MgO substrates were less than 0.01. The tan
δ's of LSAT were several times larger than those of MgO, and increased with an increase of frequency.
Dendrite Growth Observed in Pb(Mg1/3Nb2/3)O3–PbTiO3 Single Crystals Prepared by the Bridgman Process
Authors: Xu Guisheng , Luo Haosu , Xu Haiqing , Qi Zhenyi , Yin Zhiwen
Published: October 2002

Several patterns of dendritic crystals of Pb(Mg1/3Nb2/3)O3–PbTiO3 grown by the Bridgman process have been identified. This phenomenon arose from constitutional supercooling of the pseudo binary solid solution system. Therefore, macroscopic segregation and constitutional supercooling should be simultaneously restrained during crystal growth in order to obtain uniform crystals in composition and structure. A high growth temperature, larger temperature gradient and slower growth rate should be adopted to maintain stable a growth interface.
Metalorganic Vapor Phase Epitaxial Growth of High-Quality AlInN/AlGaN Multiple Layers on GaN
Authors: Kosaki Masayoshi , Mochizuki Shingo , Nakamura Tetsuya , Yukawa Yohei , Nitta Shugo , Yamaguchi Shigeo , Amano Hiroshi , Akasaki Isamu
Published: October 2002

Al1-x
In
x
N epilayers with a thickness of 20 nm grown on GaN were characterized. It was found that the surface roughness of very thin Al1-x
In
x
N is more sensitive to the growth temperature than to the lattice mismatch to GaN. Multiple layers of (Al0.95In0.05N/Al0.10Ga0.90N)5 were grown at different temperatures. X-ray diffraction measurement revealed that the sample grown at 800°C is of high quality, showing up to five orders of sharp satellite peaks, while no clear satellite peaks are observed from the sample grown at 720°C. Transmission electron microscopy observation revealed that multiple layers grown at 800°C exhibit very sharp interfaces.
Experimental Determination of Valence Band Discontinuities at Cu(Al,Ga)(S,Se)2/GaAs(001) Heterointerfaces Using Ultraviolet Photoemission Spectroscopy
Authors: Mutsumi Sugiyama Mutsumi Sugiyama , Hisayuki Nakanishi Hisayuki Nakanishi , Shigefusa F. Chichibu Shigefusa F. Chichibu
Published: October 2002

Ultraviolet photoemission spectroscopy measurement was carried out for c(001) plane Cu(Al,Ga)(S,Se)2 chalcopyrite structure epilayers grown on GaAs(001) substrates to determine valence band discontinuities, ΔE
v, at the heterointerfaces. The values of ΔE
v were estimated to be about 1.2 eV for CuAlS2/GaAs, 1.0 eV for CuAlSe2/GaAs, 1.1 eV for CuGaS2/GaAs and 0.3 eV for CuGaSe2/GaAs. From these values and bandgap energies of the corresponding compounds, Cu(Al,Ga)(S,Se)2 system is considered to offer the TYPE-I heterostructures between the corresponding narrow bandgap materials and wide bandgap ones.
In situ X-Ray Diffraction Investigation of Elastic Behavior of YNbO4-Modified ZrO2(3Y) Using Synchrotron Radiation
Authors: Sheng-Dih Yuh Sheng-Dih Yuh , Chen-Chia Chou Chen-Chia Chou
Published: October 2002

The effect of 5 mol% YNbO4 addition on the non-tetragonal-to-monoclinic phase transformation characteristics and the elastic behavior of ZrO2(3Y) ceramics was investigated using an in situ compression-diffraction technique employing synchrotron radiation in the present work. The heavily overlapping diffraction patterns between cubic, orthorhombic and/or nontransformable tetragonal (t′) reflections of the present YNbO4-modified ZrO2(3Y) can be distinguished and the fracture toughness can be increased effectively by sintering at 1550°C for 1 h. The observed stress-induced phase transformation of cubic-to-t′ or cubic-to-orthorhombic plays a primary role in energy absorption and the intriguing stress-strain characteristics of the present material system under an elastic loading-unloading process.
Fabrication and Optical Characteristics of Electrodeposited Conducting Polymer Thin Film Based on Poly(p-phenylene vinylene) Derivative
Authors: Takeshi Fujisawa Takeshi Fujisawa , Ryutaro Ootake Ryutaro Ootake , Yusuke Nishihara Yusuke Nishihara , Akihiko Fujii Akihiko Fujii , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Ultrathin films based on a poly(p-phenylene vinylene) derivative were fabricated successfully by an electrodeposition method. A luminescent polyanion, poly(1,4-(2-(5-carboxypentyloxy)-5-methoxyphenylene)vinylene) (CPMOPPV) was adsorbed onto substrates with an electrode under an applied electrical potential. The film thickness was controlled by adjusting the deposition time, the applied working potential or the CPMOPPV concentration in ethanol solution. The thin film could be formed onto even a semiconducting polymer film or an insulator polymer film, as well as onto a metal electrode. The optical properties of the electrodeposited thin films were also studied. Electroluminescent (EL) devices with the single-layered structure of CPMOPPV were fabricated and strong yellow EL was observed.
Back-Illuminated GaN Metal-Semiconductor-Metal UV Photodetector with High Internal Gain
Authors: Jiang Hao , Nakata Naoyuki , Zhao Guang Yuan , Ishikawa Hiroyasu , Shao Chun Lin , Egawa Takashi , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

Back illuminated metal-semiconductor-metal photodetectors based on GaN grown on (0001) sapphire were fabricated and characterized. The photodetector with a thin GaN layer of 0.3 µm exhibited low dark current with a saturation value of 2.06 pA. A visible rejection of more than four orders of magnitude was observed in the spectral responsivity under 5 µW/cm2 irradiance at 5 V bias. The responsivity was 16.5 A/W at a wavelength of 350 nm, which is 55 times that of the top illumination case. The results imply the presence of high internal gain under back illumination, due to the high density of charge generation.
Scanning Electron Microscope Observation of Heterogeneous Three-Dimensional Nanoparticle Arrays Using DNA
Authors: Takayuki Takahagi Takayuki Takahagi , Gen Tsutsui Gen Tsutsui , Shujuan Huang Shujuan Huang , Hiroyuki Sakaue Hiroyuki Sakaue , Shoso Shingubara Shoso Shingubara
Published: October 2002

DNA oligonucleotides are considered to be as a useful tool for fabricating complex structures on a nanometer scale because of their selective reactivity. Herein, we describe a fabrication technique for heterogeneous three-dimensional nanoparticle arrays composed of gold nanoparticles of two different sizes linked by thiol-synthesized DNA oligonucleotides. Each size of the gold nanoparticles was encapsulated by complementary DNA oligonucleotides. DNA hybridization occurs upon their mixing, resulting in the construction of a three-dimensional nanostructure. Scanning electron microscope (SEM) observation and UV spectroscopy were performed to confirm the construction of the nanostructure. This fabrication technique will be crucial for the advancement of nanotechnology in the next ten years.
Spin-Dependent Luminescence of Highly Polarized Electrons Generated by Two-Photon Absorption in Semiconductors
Authors: Matsuyama Tetsuya , Horinaka Hiromichi , Wada Kenji , Kondo Takashi , Hangyo Masanori , Nakanishi Tsutomu , Okumi Shoji , Togawa Kazuaki
Published: October 2002

The first demonstration of the generation of highly spin-polarized electrons in semiconductors using two-photon excitation was performed by measuring the spin-dependent luminescence. Bulk p-GaAs samples were excited by circularly polarized light with wavelength of 1.5 µm from an optical parametric oscillator and the luminescence polarization spectrum was measured. The experimental results showed that the highly spin-polarized electrons were generated by the circularly polarized two-photon excitation of the bulk p-GaAs. The initial spin polarization of conduction band electrons was estimated to be 95% from the spin relaxation time and the lifetime obtained by the time-resolved luminescence measurement.
Mechanism of Leakage Current Reduction by Adding WO3 to Crystallized Ta2O5
Authors: Manabe Kenzo , Kobayashi Kenji , Fujieda Shinji , Tatsumi Toru
Published: October 2002

The addition of WO3 to Ta2O5 suppresses the formation of oxygen vacancies during crystallization and reduces the leakage current of crystallized Ta2O5. By adding 3.8 at% WO3 to crystallized Ta2O5, a leakage current reduction of four orders of magnitude was achieved. This leakage current reduction is due to the replacement of Ta5+ ions by smaller W6+ ions, which relaxes the stress induced by extension and distortion along the c-axis on crystallization and thereby suppresses the formation of oxygen vacancies in β-Ta2O5.
Fabrication and Characterization of Sub-Micron Metal-Ferroelectric-Insulator-Semiconductor Field Effect Transistors with Pt/Pb5Ge3O11/ZrO2/Si Structure
Authors: Zhang Fengyan , Hsu Sheng Teng , Ono Yoshi , Ulrich Bruce , Zhuang Weiwei , Ying Hong , Stecker Lisa , Evans David R. , Maa Jershen
Published: October 2002

The first metal-ferroelectric-insulator-semiconductor field effect transistors (MFIS FETs) using Pt/Pb5Ge3O11/ZrO2/Si structure has been successfully fabricated. The integration process is simple and reliable, and it is fully compatible with conventional complementary metal oxide semiconductor (CMOS) process. The smallest working device obtained is 0.3 µm×0.5 µm (L×W). The memory window is as large as 3 V and it is not dependent on device size. The endurance of the device is at least 108 cycles without degradation. The memory window decreased to 80% and 75% of initial values after 104 seconds retention tests at room temperature and 100°C respectively.
Particle Image Velocimetry Investigation of N2-Air Convection Induced by Magnetic Fields
Authors: I. Wakayama Xiaodong Ruan , Xiangqun Song Xiangqun Song , Fujio Yamamoto Fujio Yamamoto
Published: October 2002

The particle image velocimetry (PIV) technique was used to investigate the N2-air convection caused by the application of magnetic field gradients. When the magnetic field was applied (1.5 T at the center of an electromagnet) and N2 gas was injected into air toward a weaker magnetic field, the surrounding air was found to be drawn toward a stronger magnetic field forming a vortex, while the N2 gas was pushed out. The maximum velocity of the N2 gas with the field was about five times larger than that without the field. These results agree well with the results of numerical simulations.
Effects of B-Site Disorder in Sr2FeMoO6 with Double Perovskite Structure
Authors: Moritomo Yutaka , Shimamoto Naoyuki , Xu Sheng , Machida Akihiko , Nishibori Eiji , Takata Masaki , Sakata Makoto , Nakamura Arao
Published: October 2002

Heat treatment effects on the physical properties have been investigated for Sr2FeMoO6 single crystals with double perovskite structure. We have evaluated the occupancy g of the Fe3+ ion on one sublattice of the perovskite-B site by Rietveld refinement of the synchrotron-radiation X-ray powder patterns. Both the saturation magnetization M
s and critical temperature T
c for the ferrimagnetic transition decrease linearly with g in the large-g region (g ≥∼ 0.84), but begin to deviate from the empirical relations for g ≤∼ 0.84. We interpreted this behavior in terms of variation of the correlation length of the spin ordering.
Impact Excitation of Carriers in Diamond under Extremely High Electric Fields
Authors: Watanabe Tomokatsu , Irie Masatake , Teraji Tokuyuki , Ito Toshimichi , Kamakura Yoshinari , Taniguchi Kenji
Published: October 2002

Impact ionization process in diamond under extremely high electric fields (EFs) has been investigated. The impact-ionization rate was calculated theoretically from Fermi's golden rule using the full band structure. It is found from Monte Carlo simulations that the impact ionization of carriers occurs at high EFs above 1×106 V/cm. The threshold EF for ionization is smaller for hole than for electron. Current(I)–voltage(V) characteristics measured for p-i-p diamond stacking structures revealed that I is approximately proportional to V
2 with substantial electroluminescence at EFs higher than 5×106 V/cm, being in good agreement with the theoretically predicted values.
Lasing Characteristics of Low-Threshold GaInNAs Lasers Grown by Metalorganic Chemical Vapor Deposition
Authors: Kawaguchi Masao , Miyamoto Tomoyuki , Gouardes Eric , Schlenker Dietmar , Kondo Takashi , Koyama Fumio , Iga Kenichi
Published: October 2002

We report on the lasing characteristics of low-threshold long-wavelength GaInNAs double quantum well (DQW) lasers grown by metalorganic chemical vapor deposition (MOCVD). We have achieved a threshold current density of 450 A/cm2 for a 1.28-µm-emitting laser. This is the lowest value for 1.3-µm-range GaInNAs lasers grown by MOCVD. We also observed high characteristic temperatures (T
0) of 210 K and 130 K for 1.25 µm and 1.28 µm lasers, respectively. In addition, we investigated the gradual change in lasing characteristics under pulsed operation. The blue shift of an emission wavelength and a threshold current reduction were observed, which is similar to that observed in the thermal annealing of GaInNAs.