bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal Changes of LC Molecular Alignments Dependent on Applied AC Frequency
Authors: Yamashita Masafumi , Tako Toshiharu
Published: February 2005

Temporal changes of molecular alignments in a twisted nematic liquid crystal (TNLC) cell with 10- µm thickness were studied by a measurement of transmitted light intensities using the Wollaston prism. Intensity I
//, whose wave vibrates in the direction parallel to the director, approached zero at first after the alternating electric field at 16 volts and at 480 Hz was applied, but I
⊥ increased conversely. Within 1 ms after applying the electric fied, the sum of I
// and I
⊥ decreased. There would be a scattering loss of transmission intensity caused by the turbulence of molecular alignments. The molecules in the middle portion of a TN LC cell will begin to be realigned within a few milliseconds after the electric field is applied or removed.
Thermal Stability of the AlN/a-Si/GaAs MIS Diodes with Different GaAs Surface Stoichiometry
Authors: Fujieda Shinji
Published: February 2005

The thermal stability of AlN/a-Si/GaAs MIS diodes with an a-Si interlayer deposited on (a) As-rich, (b) As-dimerstabilized and (c) Ga-stabilized GaAs surfaces was investigated. In n-type diodes, the accumulation-side capacitance of the C-V curve increased drastically by elevating the annealing temperature to above 650°C in (c), while the capacitance decreased rapidly at 600°C in (a) and slowly above 600°C in (b). The p-type diodes exhibited no distinct change in (a) and (b), but degradation occurred in (c) above 650°C. Diffusion of As into the a-Si layer and formation of interfacial free As are suggested to occur, resulting in generation of donor- and acceptor-type levels, respectively.
Open-Tube Zn Diffusion Method for InGaAsP/InP Heterojunction Bipolar Transistors
Authors: Ohishi Toshiyuki , Ohtsuka Ken-ichi , Abe Yuji , Sugimoto Hiroshi , Matsui Teruhito
Published: February 2005

An open-tube Zn diffusion method using solid sources of Zn3P2 and InP has been developed and applied to the fabrication of InGaAsP/InP heterojunction bipolar transistors (HBTs). The diffusion depth was accurately controlled by the diffusion time. A sharp change in Zn concentration was observed at the diffusion front. The external base of InGaAsP/InP HBT was formed by means of the present method; both good current/voltage characteristics of the base-collector junction and a large direct current gain of 112,000 were obtained.
Determination of the Crystallographic Polarity of Zincblende Structure by Using Ion-Induced Secondary Electrons
Authors: Kudo Hiroshi , Shima Kunihiro , Ishihara Toyoyuki , Seki Seiji
Published: February 2005

By using keV electron yields induced by 60-MeV S7+ in GaP and InP crystal targets, we have carried out high sensitivity measurements of the preferential collision effect which is known to occur when the incident direction of the ions is slightly off from the <110 > axis of zincblende lattice. The results demonstrate the quick and simple determination of the crystallographic polarity of zincblende structure crystals using this method.
Hydrogen-Radical Annealing of Chemical Vapor-Deposited Amorphous Silicon Films
Authors: Uchida Yasutaka , Kanoh Hiroshi , Sugiura Osamu , Matsumura Masakiyo
Published: February 2005

This letter describes that photogenerated hydrogen-radical annealing (HRA) is very effective for improving the electric properties of chemical-vapor-deposited amorphous silicon films. The ratio of photoconductivity to dark conductivity (at a light intensity of 100 mW/cm2) changed from 100 to 6×104 upon annealing in a hydrogen-radical-rich ambient at 280°C. Thin-film transistor (TFT) characteristics were also improved by HRA.
Annealing Effect of (Pb/Cu)SrLaCuOy Superconductor
Authors: Adachi Seiji , Setsune Kentaro , Wasa Kiyotaka
Published: February 2005

The annealing effects of a “1201” superconductive lead cuprate, (Pb/Cu)SrLaCuO
y
, were investigated. A single-phase ceramic sample with good superconductivity was obtained by annealing at 500°C for 24 h in nitrogen, and its fractured surface was transgranular. This sample exhibited T
c(onset)=38 K, T
c(zero resistivity)=33 K and T
c(Meissner)=36 K. Its volume fraction of the superconductive phase was approximately 30% at 4.2 K.
Properties of Y1Ba2Cu3O7-x Superconducting Thin Films Prepared by Reactive Evaporation Method
Authors: Chang Ho Jung , Watanabe Yasuhiro , Doshida Yutaka , Shimizu Kenji , Okamoto Yoichi , Akihama Ryozo , Song Jin Tae
Published: February 2005

The superconducting YBa2Cu3O7-x
(YBCO) thin films on MgO(100) substrates were prepared by a reactive evaporation method. Superconducting transition temperature and crystal quality were examined as a function of the substrate temperature (T
s) and the oxygen partial pressure (P
O2
). The as-grown thin films at the substrate temperature of 620°C exhibited a zero resistance temperature (T
czero
) of 83 K with the onset (T
conset
) temperature of 88 K under the P
O2
of 2×10-3 Torr. The lattice parameter c was about 11.74 Å for the as-grown film with T
czero
of 80 K and was shortened to about 11.70 Å by the post-annealing at 900°C for 10 min in O2 flow, although T
czero
was not changed. This phenomena may be ascribed to the deficiency of oxygen in the CuO2 plane of the YBCO layered perovskite structure.
Ar Ion Laser-Assisted MOVPE of ZnSe Using DMZn and DMSe as Reactants
Authors: Yoshikawa Akihiko , Okamoto Tamotsu , Fujimoto Tsuyoshi , Onoue Kozo , Yamaga Shigeki , Kasai Haruo
Published: February 2005

Growth of ZnSe layers by Ar ion laser-assisted MOVPE using DMZn and DMSe has been investigated. It is shown that an Ar ion laser can be a useful light source for the photoassisted MOVPE of ZnSe. By utilizing several Ar ion laser emission lines near the absorption edge of ZnSe as the irradiation light, it has been reconfirmed that the absorption of photons by the ZnSe layer is essential for the growth rate enhancement in the photoassisted MOVPE of ZnSe. Furthermore, it has been found for the first time that hydrogen gas plays a very important role in the reaction between DMZn and DMSe to form ZnSe under photoirradiation.
Initial Stages of Epitaxial Growth of GaP on Si with AsH3 Preflow
Authors: Kohama Yoshitaka , Kadota Yoshiaki , Ohmachi Yoshiro
Published: February 2005

A previous paper reported that when GaP epilayers are grown on Si substrates, an As-stabilized surface made by AsH3 preflow before growth prevents many defects from generating at the GaP/Si interface, and that consequently, the crystalline quality of GaP epilayers is markedly improved. This letter describes the AsH3 preflow effect on the initial stages of GaP epitaxial growth. The relative ease with which As or P atoms are absorbed onto Si surfaces is observed using X-ray photoelectron spectroscopy. Although preflow before GaP growth causes As or P atoms to absorb onto Si surfaces, As atoms are absorbed more easily than P atoms. The initial stages of GaP epitaxial growth on Si substrates with and without AsH3 preflow are investigated using high-resolution scanning electron microscopy and transmission electron microscopy. This confirms that AsH3 preflow suppresses island growth, allowing GaP epilayers to grow two-dimensionally, and also reduces the GaP-Si interfacial energy.
The Optimum Design of Thin Film Transistors by Dynamic Characteristics Measurement
Authors: Yamada Tsutomu , Ohima Susumu , Kihara Katsuya , Jinno Yushi , Okita Yuji , Arioka Teijiro , Yamaguchi Takao , Nakakado Takashi
Published: February 2005

By measuring the voltage from the source electrode of the TEG-TFTs, the dynamic characteristics of TFT-LCDs have been analysed. It was clearly determined that the V
rms decrement depends on the increase in the delay time of the gate signal. Under the H-reversed half-line driving method, both the time lag between the drain and the gate signal and the size of TFTs were both optimized. We were able to obtain these results on the condition that τdelay was equal to 1/3 of the on-time of the gate signal.
Temperature Dependence of the Output of a Stacked and Amplified Image Sensor
Authors: Huang Zhong-Shou , Ando Takao
Published: February 2005

This study analyzes the ambient temperature dependence of the output of a proposed image sensor. A self-compensation effect of the output current with temperature has been observed. Simulation results give the operation condition under which output of the sensor exhibits a zero temperature coefficient. Experimental results show that increase of the dark current from a hydrogenated amorphous silicon (a-Si:H) photodiode can be reduced by the effect up to about 75°C.
Mechanochemical Effects of Grinding on the Bi-Pb-Sr-Ca-Cu-O Superconductor
Authors: Awano Masanobu , Kani Keiko , Kodama Yasuharu , Takagi Hiroyoshi , Kuwahara Yoshitaka
Published: February 2005

The effects of mechanical grinding on the powder of the Bi-Pb-Sr-Ca-Cu-O superconductor (so-called “high T
c phase”) were examined. The grain size of the powders decreased with increased grinding time accompanied by the degradation of crystallinity. Powders involving relatively lower crystal strain recovered their crystallinity as “high T
c phase” by postheat treatment. But powders having relatively excessive crystal strain recrystallized as “low T
c phase” and others. Such an effect reveals the metastability of the high T
c phase under the condition of excessive crystal strain.
Preparation and Properties of Superconducting [La1/6Ln1/3Ba1/6Sr1/6Ce1/6]8Cu6Oz (Ln=Eu, Gd, Dy, Ho and Y)
Authors: Wada Takahiro , Ichinose Ataru , Yaegashi Yuji , Yamauchi Hisao , Tanaka Shoji
Published: February 2005

We have prepared two series of samples of [La1/6Ln1/3Ba1/6Sr1/6Ce1/6]8Cu6O
z
(Ln=Eu, Gd, Dy, Ho and Y) by annealing at the two different oxygen partial pressures [P(O2)] of 3 and 200 atm. The crystal structures of all the samples were of the (Eu, Ce)4(Eu, Ba)4Cu6O
z
type. Only samples with Ln=Eu, Gd and Dy when annealed at P(O2)=3 atm exhibited superconductivity with T
c's in a range of 10–35 K, while all the samples with Ln=Eu, Gd, Dy, Ho and Y became superconductors with T
c's in a range of 5–40 K when annealed at P(O2)=200 atm.
Transmission Electron Microscopy of Modulated Structures in Pb-Doped BSCO Superconductors, Bi2.1-xPbxSr1.9CuOy (x=0 to 0.3)
Authors: Matsui Yoshio , Maeda Atsutaka , Uchinokura Kunimitsu , Takekawa Shunji
Published: February 2005

Crystal structures of Pb-doped BSCO superconductors, Bi2.1-x
Pb
x
Sr1.9CuO
y
with x=0 to 0.3, are examined by transmission electron microscopy. Compounds with x from 0.05 to 0.2 exhibit satellite reflections in b
*-c
* electron diffraction patterns in a different manner from the x=0 compound, indicating formation of modulated structures similar to those observed in Pb-doped BSCCO superconductors. Modulation periodicity increases with increase of Pb content x. The compound with x=0.3, however, shows no satellite reflections suggesting the absence of modulation at high Pb content.
Preparation of Bicrystal in a Bi-Sr-Ca-Cu-O Superconductor
Authors: Tomita Naruaki , Takahashi Yutaka , Ishida Yoichi
Published: February 2005

A [001]-twist bicrystal was prepared by sintering single crystal sheets of an 80 K Bi-Sr-Ca-Cu-O superconductor Resistivity measurement showed that the transition temperature of the bicrystal agreed with that of the single crystal. However, a large shoulder was observed in the current-voltage measurement suggesting weak coupling of the grain boundary.
Photoluminescence of Eu2+ Ion Doped into Ca1-xSrxF2 Mixed Crystals
Authors: Kawano Katsuyasu , Tominaga Jun'ichi , Satoh Hiroyuki , Nakata Ryouhei , Sumita Minoru
Published: February 2005

The spectral peak, linewidth and quantum efficiency of the luminescence band of Eu2+(4f65d) ions in Ca1-x
SF
x
F2 mixed crystals were studied for different x-values. With increasing x, the absorption peak shifted linearly to that of SrF2:Eu2+, while the luminescence peak varied in a parabolic manner with a minimum around x=0.5. In addition, the half-width broadened remarkably, and the activation energy for the nonradiative relaxation was minimized down to 0.4 eV. The temperature dependences of the half-width and the quantum efficiency agreed well with the calculated results on the basis of electron-phonon interaction.
Layer Structure of Antiferroelectric Liquid Crystal MHPOBC Studied by X-Ray Diffraction
Authors: Suzuki Atsushi , Orihara Hiroshi , Ishibashi Yoshihiro , Yamada Yuichiro , Yamamoto Norio , Mori Kahoru , Nakamura Koji , Suzuki Yoshiichi , Hagiwara Takashi , Kawamura Ichiro , Fukui Minoru
Published: February 2005

The layer structure of the antiferroelectric liquid crystal MHPOBC was studied by X-ray measurements. We observed a thermal hysteresis in the layer structure; i.e., a chevron structure was formed in the cooling process, and a bookshelf structure in the heating process. It was found that the layer spacing decreases discontinuously at the Sm C*-Sm CA
* transition point for an enantiomeric mixture in the cooling process. The result is discussed on the basis of a phenomenological theory.
Preparation of Fe-Ni-Based Metal-Metalloid Amorphous Alloys by Mechanical Alloying and Mechanical Grinding Methods
Authors: Miura Harumatsu , Isa Shigeteru , Omuro Keisuke
Published: February 2005

Using a high energy ball mill, alloys of Fe40Ni40P14B6 and Fe40Ni40B20 were synthesized from crystalline, elemental iron and nickel metals and iron-metalloid alloys such as Fe-B and Fe-P by mechanical alloying (MA). Powders of the Fe40Ni40P14B6 alloy were also prepared from the cast ingot products by mechanical grinding (MG). Each of the MA and MG powder products showed a halo pattern typical of amorphous materials in the X-ray diffraction trace, and the crystallization enthalpy of the Fe40Ni40P14B6 MA powder, measured by differential scanning calorimetry, was almost the same as that of the melt-quenched sample of the same composition.
Control of the Electrical Properties of AlN/thin-a-Si/GaAs MIS Diodes by GaAs Surface Pretreatments
Authors: Fujieda Shinji , Mochizuki Yasunori , Akimoto Koichi , Hirosawa Ichiro , Matsumoto Yoshishige , Matsui Junji
Published: February 2005

The influence of GaAs surface stoichiometry was investigated on the electrical properties of AlN/thin-a-Si/GaAs MIS diodes which have an amorphous Si interlayer. The structures were fabricated by an MOCVD method with surface stoichiometry control by AsH3, H2 and TMG (trimethylgallium) pretreatments. These procedures are expected to result in As-rich, As-dimer-stabilized and Ga-stabilized GaAs surfaces, respectively. For n-GaAs, the AsH3 and H2 pretreatments suppressed the frequency dispersion of the accumulation-side capacitance, while the TMG pretreatment caused increase of the dispersion. The opposite behavior was observed for p-GaAs. These facts indicate that the function of a-Si interlayers is influenced by the initial stoichiometry of GaAs surfaces.
Electrical, Magnetic and Superconducting Properties in Bi2-xPbxSr2CaCu2O8+δ
Authors: Koyama Kuniyuki , Kanno Satoshi , Noguchi Seiichiro
Published: February 2005

Samples of the Bi2-x
Pb
x
Sr2CaCu2O8+δ system are prepared to be almost a single phase of the Bi2Sr2CaCu2O8+δ structure for a region of 0≦x≦0.15. Substitution of Pb for Bi ions is observed by EPMA at grain level. The T
c decreases linearly with x in this region. Comparison with the results for the Bi2Sr2Ca1-x
Nd
x
Cu2O8+δ shows that the hole concentration in [Cu-O] plays a most significant role in determining the T
c in the Bi2Sr2CaCu2O8+δ system. The universal relationship between the hole concentration in [Cu-O] and T
c is determined in a wide range of concentration in this system.
Electron Irradiation Effects on a Bi1.4Pb0.6Sr2Ca2Cu3O10 Superconductor
Authors: Shiraishi Kensuke , Itoh Hiroshi , Kato Takahiko
Published: February 2005

Sintered Bi1.4Pb0.6Sr2Ca2Cu3O10 pellets were sequentially irradiated with 1 or 3 MeV electrons up to 8×1019 m-2 at ambient temperature, and the electrical resistivity was measured as a function of temperature. The superconducting transition (zero resistance) temperature decreased almost linearly with electron dose after a transient regime concurrently with a linear increase in the resistivity. The zero resistance temperature measured with 120 kA ·m-2 current density was increased from 96.5 to 102.8 K by 3 MeV electron irradiation to 1.0×1019 m-2, and then decreased upon further irradiation.
Preparation of Mostly Single High-Tc Phase Thin Films in Bi, Pb-Sr-Ca-Cu-O by Pyrolysis of Organic Acid Salts
Authors: Nasu Hiroyuki , Nonogawa Hideki , Nozue Akiyoshi , Kamiya Kanichi
Published: February 2005

Bi, Pb-Sr-Ca-Cu-O thin films of mostly single high-T
c phase were successfully obtained by pyrolysis of organic acid salts. The highest T
c(end) was 101 K, and film thickness was nearly 1 µm. The superconducting transition temperature was strongly dependent on heat-treatment procedures and time. The 24-hour firing was sufficient to raise T
c(end) above 100 K.
Phase Locking of SWL Array Junctions in Submillimeter Mixing
Authors: Kodaira Shinji , Inatani Junji , Sakai Kiyomi , Fukushima Toshiaki
Published: February 2005

We have fabricated a submillimeter mixer with two SWL (short-weak-link) junctions connected in series. This mixer has been used for a 337 GHz fundamental mixing. It has been found that these two junctions independently contribute the IF (intermediate frequency) output when the applied LO (local oscillator) power is small, but that they behave just as a single junction for the increased LO power.
Application of MoO3 Electron Resist to Lift-Off Process
Authors: Okamoto Masaaki , Baba Mamoru , Ikeda Toshio
Published: February 2005

A new lift-off process using an inorganic MoO3 electron resist is proposed and applied to the fabrication of openings in sputter-deposited SiO2 and SiO films. A MoO3 mask pattern with overhang structure is fabricated by the two-step sputter-deposition of MoO3 and a subsequent electron-lithographic technique. The MoO3 mask pattern has a heat-resistive property and can be successfully used to lift off the sputter-deposited SiO2 and SiO films.
Epitaxial Growth of Al on (NH4)2Sx-Treated GaAs
Authors: Oigawa Haruhiro , Fan Jia-Fa , Nannichi Yasuo , Kawabe Mitsuo
Published: February 2005

Epitaxial growth of Al film on the (NH4)2S
x
-treated surface of (100) GaAs was investigated by means of reflection high-energy electron diffraction (RHEED). A single crystal of epitaxial (110) Al film was obtained on the treated surface with heat treatment at 300°C prior to Al deposition, while Al film became polycrystalline without heat treatment. The effect is explained in terms of the alignment of S atoms on GaAs. The (NH4)2S
x
-treated surface seems to be useful in the wide range of GaAs processes.
Pulsed Laser-Induced Amorphization of Polycrystalline Silicon Film
Authors: Sameshima Toshiyuki , Hara Masaki , Usui Setsuo
Published: February 2005

A 20 nm-thick polycrystalline silicon film was completely amorphized through laser-induced melt-regrowth using a 30 ns XeCl excimer laser pulse at an energy density of over 240 mJ/cm2. Moreover, the amorphized silicon was recrystallized by irradiation by a single pulse at an energy density below 240 mJ/cm2. The transition from the amorphous to the crystalline state was reversible and governed by the laser energy density. The laser-induced amorphized film had a low optical band gap of 1.4 eV. Its electrical conductivity was characterized by variable-range hopping.
Millimeter-Wave Surface Resistance of EuBa2Cu3O7-y Film on MgO Substrates
Authors: Konaka Tsuneo , Sato Makoto , Asano Hidefumi
Published: February 2005

We have measured the surface resistance of c-axis-oriented EuBa2Cu3O7-y
thin films grown in situ onto (100)MgO by magnetron sputtering. The measurements were made at 50 GHz between 20 and 300 K in a TE013 gold-plated invar cavity by replacing the endplate with a film. The surface resistance decreases sharply at 87 K to 40 m Ω at 77 K, becomes lower than that of an OFHC copper plate below 74 K, and lies within the measurement sensitivity range of 2 m Ω below 60 K. This low surface resistance suggests that MgO-based films are very suitable for high-frequency applications.
Properties of Yb-Ba-Cu-O Superconductors Prepared by a Plasma-Arc Melting and Rapid Quenching Method
Authors: Kamino Maruo , Takahashi Kazuhiko , Yokoo Toshiaki , Yoshisato Yorinobu , Nakano Shoichi
Published: February 2005

A PMQ (plasma-arc melting and rapid quenching) method has been successfully developed to obtain homogeneous and highly dense Yb-Ba-Cu-O compounds through the crystallization of the superconducting phase from the amorphouslike state. The maximum T
c of 91 K and packing density of 7.14 g/cm3 (98% of the theoretical density 7.27 g/cm3) were produced by this method. Furthermore, a large activation energy of 1.5 eV was observed by magnetic relaxation measurements.
A New Family of Copper Oxide Compounds with a Tl-O Monolayer: (Tl1-zPbz)(Sr1-xLax)2(Ln1-yCey)2Cu2O9
Authors: Mochiku Takashi , Nagashima Toshio , Saito Yoshio , Watahiki Masaya , Asano Hajime , Fukai Yuh
Published: February 2005

We have discovered a new family of copper oxide compounds (Tl1-z
Pb
z
)(Sr1-x
La
x
)2(Ln1-y
Ce
y
)2Cu2O9 (Ln=lanthanoid atoms) with a Tl-O monolayer. The crystal structure of these compounds was determined by Rietveld analysis of X-ray powder diffraction data. Its structure can be derived by stacking TlBa2CaCu2O7- and Nd2CuO4-type slabs alternately along the c-axis; they are joined by conductive CuO2 sheets. These compounds do not exhibit superconductivity down to 10 K.
Effect of Discharge Gas Pressure on YBaCuO Epitaxial Film Formation by Reactive RF Magnetron Sputtering
Authors: Sakuta Ken , Iyori Masahiro , Katayama Yoshitomo , Kobayashi Takeshi
Published: February 2005

The in situ epitaxial growth of the YBaCuO film was carried out by the reactive magnetron sputtering under discharging gas pressures ranging from 4–120 Pa. It appeared that the pressure strongly affected not only the deviation of the film composition from the target but also the film crystallinity which is in turn closely correlated to the superconductivity and its stability. In the plasma emission spectra, we found a reduction in the Ar spectrum intensities relative to those of the metal components with increasing pressure.
A New Technique to Produce Clean and Thin Silicon Films In Situ in a UHV Electron Microscope for TEM-TED Studies of Surfaces
Authors: Ozawa Soh-ichiro , Yamanaka Akira , Kobayashi Kunio , Tanishiro Yasumasa , Yagi Katsumichi
Published: February 2005

A new technique of in situ oxygen gas reaction thinning of Si films at around 750–800°C in an ultrahigh-vacuum electron microscope was developed. The technique produced films as thin as 10 to 20 nm. Such a thin film allows us to observe surface atomic steps, out-of-phase boundaries and {1/7 0}, {1/7 1/7} and {2/7 0} spots from the Si(111)7×7 surface. These spots were not observed in previous studies, having been masked by strong inelastic scattering. The technique is useful not only for detecting clear diffraction spots of kinematical intensity for surface structure analysis but also for observation of high-resolution plan-view structure images of clean and adsorbed surfaces.
High-Power Microwave-Induced Plasma Source for Trace Element Analysis
Authors: Okamoto Yukio , Yasuda Makoto , Murayama Seiichi
Published: February 2005

A high-power microwave-induced plasma source (2.45 GHz, 1.2 kW) for trace element analysis is presented. The plasma is generated by a circularly polarized wave induced by a helical coil with a mode transformer. The sample introduction system consists of a pneumatic nebulizer with no dehydration system, i.e., utilizing direct introduction of aqueous solutions. An annular-shaped argon plasma was generated at atmospheric pressure in a 2.3–4.2-mm i.d. quartz discharge tube with a low gas flow rate (2 l/min). Preliminary analytical results were otained using an aqueous Ca(10 ppm)+Zr(200 ppm) solution sample and compared to those obtained with the argon inductively coupled plasma.
Surface Diffusion of Al Atoms on GaAs Vicinal Surfaces in Molecular Beam Epitaxy
Authors: Tanaka Masaaki , Suzuki Takashi , Nishinaga Tatau
Published: February 2005

We have studied the surface diffusion in molecular beam epitaxial growth of AlAs on GaAs vicinal surfaces by observing intensity oscillations of reflection high-energy electron diffraction (RHEED). By measuring the critical temperature where the RHEED oscillation begins to appear, the critical condition for the growth mode transition was determined. Combining the experimental results with the theory taking into account the surface diffusion and supersaturation ratio of adatoms on the terraces, the surface diffusion length of Al atoms is estimated and compared with that of GaAs.
Suppression of Beryllium Diffusion by Incorporating Indium in AlGaAs for HBT Applications using Molecular Beam Epitaxy
Authors: Tomioka Takeshi , Fujii Toshio , Ishikawa Hideaki , Sasa Shigehiko , Endoh Akira , Bamba Yasuo , Ishii Kazuaki , Kataoka Yuji
Published: February 2005

We developed a molecular beam epitaxy technique to suppress Be diffusion by incorporating In in the AlGaAs epilayer. Diffusion coefficients of Be-doped In
y
(Al0.1Ga0.9)1-y
As (p: 7×1019 cm-3) grown at 600°C were reduced from 1×10-14 cm2/s to 2×10-15 cm2/s when the InAs mole fraction y was increased from 0 to 0.07, indicating that compressive stress in the epilayer caused by incorporating In plays an important role in suppressing Be diffusion. We fabricated a heterojunction bipolar transistor with a 100-nm-thick p+-In0.055(Al
x
Ga1-x
)0.945As base layer (x: 0 to 0.1), and obtained a DC current gain of 27.
Preparation and Crystallization Process of High-Tc Superconducting Bi,Pb-Sr-Ca-Cu-O Film (Tc=101 K) by Melt-Quenching and Annealing Techniques
Authors: Ibara Yoshikazu , Inoue Katsuto , Osaka Yukio
Published: February 2005

Thin films (about 1 µm) with the dominant high-T
c phase of Bi,Pb-Sr-Ca-Cu-O have been prepared by pyrolysis (melt-quenching and postannealing) of 2-ethylhexanoates. The critical temperature T
c was approximately 101 K for the specimen annealed at 850°C for 10 h.
It was found that annealing conditions (annealing temperature and atmosphere) are effective in increasing the volume fraction, which was determined by X-ray diffraction, of the high-T
c phase (Bi2-x
Pb
x
Sr2Ca2Cu3O
y
). It was suggested that the high-T
c phase on a MgO(100) substrate is thermally a stable phase at 850°C.
Water Vapor Detection by Means of Middle-Infrared Emitting, Er3+-Activated Phosphors
Authors: Mita Yoh , Ohata Kiyoshi , Shionoya Shigeo
Published: February 2005

Luminescence characteristics have been investigated for various Er3+-activated phosphors having emission at wavelength regions of 2.6 to 2.8 µm. Efficient luminescent emissions have been observed for phosphors having fluoride lattices such as YF3 and doped with high Er+3 concentration. Combined with a GaAs:Si near-infrared light emitting diode, a simple and quantitative water vapor detecting device has been obtained. Optimization procedures for luminescence characteristics as well as those for device properties are discussed.
Plasma Irradiation Effects on Nd-Ce-Cu-O and La-Sr-Cu-O Thin Films
Authors: Kamada Takeshi , Hayashi Shigenori , Kohiki Shigemi , Adachi Hideaki , Kitagawa Masatoshi , Hirao Takashi , Wasa Kiyotaka
Published: February 2005

Hydrogen- and oxygen-plasma irradiation effects on Nd-Ce-Cu-O and La-Sr-Cu-O thin films were studied with the use of electron cyclotron resonance (ECR). Superconductivity was induced for the Nd1.85Ce0.15CuO4-y
films after the hydrogen plasma irradistion. X-ray photoelectron spectroscopy (XPS) revealed that it was due to the reduction (Cu2+→Cu1+) by the hydrogen plasma. In contrast, the superconducting properties of the La1.87Sr0.13CuO4-y
thin films were found to be deteriorated by the hydrogen plasma and to be improved by the oxygen plasma.
Reduction of Textural Drift in a Laser Recrystallized Silicon-on-Insulator Structure Employing Liquid Encapsulation
Authors: Doi Atsutoshi , Meguro Takashi , Aoyagi Yoshinobu
Published: February 2005

Textural drift in the laser recrystallized silicon-on-insulator (SOI) structure is successfully reduced by using a liquid encapsulation technique. Liquid encapsulation with polyethylene gylcol during the laser recrystallization provides an effective heat release from the surface as compared with the conventional technique. Therefore, thermal gradient in the vertical direction of the silicon film can be controlled by this method. An improved thermal profile in the vertical direction is considered to be a main reason for the reduced textural drift.
Electric Field Effect on the Al-MgO-YBa2Cu3Oy Structure
Authors: Kabasawa Uki , Asano Katsunori , Kobayashi Takeshi
Published: February 2005

The electric field effect on YBa2Cu3O
y
was investigated at room temperature by using the Al-MgO-(001)YBa2Cu3O
y
metal-insulator-superconductor (MIS) structure. Special care was taken for preparation of a good interface: heteroepitaxial growth technology was employed for MgO-YBa2Cu3O
y
successive growth. A typical MIS capacitance-voltage (C-V) curve was obtained under the condition of the reduced carrier concentration, suggesting that the existing band diagram could be applicable to YBa2Cu3O
y
as well as to semiconductors.
Preparation of Tl-Ca-Ba-Cu-O High-Temperature Superconducting Thin Films by Flash Evaporation
Authors: Verma K. K. , Verma G. D. , Tiwari R. S. , Srivastava O. N.
Published: February 2005

The Tl-Ca-Ba-Cu-O thin films conforming to 2122 composition have been deposited by a comparatively simple and viable process, the thermal flash evaporation of the Ca-Ba-Cu-O precursor flux followed by diffusion of Tl derived by vapourising Tl2O3. The films have been characterised by R-T monitoring, XRD, SEM and EDAX. The films have been found to have T
c (R=0) of 88 K for ZrO2 and 97 K for MgO substrates. The films have been found to be partially oriented with the c axis perpendicular to the film surface.
Phase Stability and Decomposition of Superconductive (Y1-xCax)Ba2Cu4O8 (0≦x≦0.1)
Authors: Wada Takahiro , Suzuki Nobuo , Ichinose Ataru , Yaegashi Yuji , Yamauchi Hisao , Tanaka Shoji
Published: February 2005

The stability of (Y1-x
Ca
x
)Ba2Cu4O8 has been studied as a function of Ca content, temperature and oxygen partial pressure, P(O2), by means of thermogravimetry and differential thermal analysis. When heated at P(O2)=1 atm, YBa2Cu4O8 decomposed into YBa2Cu3.5O7.5-Y
(1-2-3.5) and CuO above 899°C and the resultant 1-2-3.5 phase decomposed into YBa2Cu3O7-z
(1-2-3) and CuO above 926°C. As the Ca content increased, the decomposition temperatures of both 1-2-4 and 1-2-3.5 phases were decreased and they tended to merge. Actually, when the Ca content was as high as 10% of the Y content, the 1-2-4 phase decomposed directly into a 1-2-3 phase and CuO at 884°C.
Ge K-Edge Extended X-Ray Absorption Fine Structure Study of the Local Structure of Amorphous GeTe and the Crystallization
Authors: Yoshihito Maeda Yoshihito Maeda , Masatoshi Wakagi Masatoshi Wakagi
Published: February 2005

The local structure and crystallization of amorphous GeTe (a-GeTe) were examined by means of Ge K-edge EXAFS. In a-GeTe, both Ge-Ge and Ge-Te bonds were observed to exist in nearest neighbors of Ge. The average coordination number around Ge is 3.7, which is close to the tetrahedral structure. A random covalent network (RCN) model seems to be suitable for the local Structure. After a-GeTe crystallizes at 129°C, the Ge-Ge bond disappears and the Ge-Te bond length increases considerably. As temperature rises, in a-GeTe the Debye-Waller factor of the Ge-Te bond increases greatly, while that of the Ge-Ge bond increases only slightly. At the crystallization, it is found that the fluctuation of the Ge-Te bond length plays a major role in the change of the local structure and bonding state around Ge.
Effects of Oxygen Concentration and Annealing Sequence on Microstructure of Separation by Implanted Oxygen Wafer with High-Temperature Annealing
Authors: Kawazu Satoru , Miyatake Hiroshi , Yamaguchi Yasuo , Nishimura Tadashi , Koyama Hiroshi
Published: February 2005

We investigate the influence of oxygen concentration and annealing sequence on the microstructure of the SIMOX (separation by implanted oxygen) wafer. Samples with different oxygen contents are compared. Higher oxygen concentration causes higher density of dislocations in the top silicon layer by the growth and dissolution of precipitates. The two-step annealing, consisting of annealing at 600°C for 8 h and 1350°C for 30 min, increases the density of dislocations because the nuclei of precipitates may effectively be formed before the high-temperature annealing. Another procedure consisting of laser annealing and 1350°C annealing causes no significant effect on the dislocation density.
Characterization of Boron-Doped Diamond Epitaxial Films
Authors: Shiomi Hiromu , Yoshiki Nishibayashi Yoshiki Nishibayashi , Naoji Fujimori Naoji Fujimori
Published: February 2005

Boron-doped diamond epitaxial films were characterized on the dependence of boron concentration by an optical microscope, reflection high-energy electron diffraction, secondary ion mass spectrometry, Hall effect measurement and metal contacts. These films were grown on synthesized single-crystal diamonds(100) by microwave plasma chemical vapor deposition (CVD) using H2, CH4and B2H6at a CH4concentration of CH4/H2=6% and at doping gas ratios of B2H6/CH4=0.83 ppm, 8.3 ppm, and 167 ppm. They were all epitaxially grown and had smooth surfaces. Hall effect measurements were performed in the temperature range of 300 K to 773 K. They indicated that there existed acceptorlike centers other than boron in the films synthesized in the vapor phase. Fermi degeneracy was found to occur at a boron concentration of 3×1020cm-3. Schottky diodes were fabricated using Al for Schottky contacts and Ti for ohmic contacts. Rectifying properties were degraded at high boron concentration.
Photoreflectance Spectra from GaAs Buffer Layer of GaAs/AlAs Multiple Quantum Well/GaAs Buffer/GaAs Substrate
Authors: Haraguchi Masanobu , Nakagawa Yoshinori , Muto Masuo Fukui
Published: February 2005

We have measured photoreflectance spectra from a GaAs buffer of a GaAs/AlAs multiple quantum well (MQW)/GaAs buffer/GaAs substrate. In order to interpret our experimental results, we have tried to modify Aspnes's low field limit theory for electroreflectance. From this treatment, the built-in electric field at the interface between the MQW layer and the GaAs buffer layer is estimated to be 35 kV/cm. It has been shown that PR spectra at various points on the sample surface resolve the question on the homogeneity of the MQW layer thickness.
Fundamental Absorption Spectrum of MgS
Authors: Nobuhiko Yamashita Nobuhiko Yamashita
Published: February 2005

The diffuse absorption spectra of pure MgS powder at 80 and 293 K are obtained from the diffuse reflection spectra by using Kubelka's formula. The fundamental absorption spectrum is also obtained from the high-energy part of the excitation spectrum of the MgS:Sb3+ phosphor. The fundamental absorption edge of MgS is near 4.6 eV, which is relatively near that (near 4.5 eV) of CaS.
Internal Reflection Method for Measuring Optical Constants of Deposited Films
Authors: Kondo Shin-ichi , Kataoka Yoshiharu , Tadaaki Saito Tadaaki Saito , Mamoru Mekata Mamoru Mekata
Published: February 2005

A novel method, the internal reflection method, was applied to the measurement of optical constants associated with fundamental electronic transitions in deposited films. This method is based on the attenuated total reflection spectroscopy using a prism of a low refractive index and was found to give optical constants consistent with the results furnished by other methods. The internal reflection method is advantageously applicable to deposited films of semiconductors and ionic compounds as compared with the conventional free-surface reflection methods such as spectroscopic ellipsometry and the Kramers-Kronig analysis method. The present method is also applicable to liquid samples because of its simple optical configuration. A possible extension of the method to the measurements on films of layer compounds is discussed.
Charge Buildup in Magnetized Process Plasma
Authors: Namura Takashi , Okada Hiroyuki , Naitoh Yasushi , Yoshihiro Todokoro Yoshihiro Todokoro , Morio Inoue Morio Inoue
Published: February 2005

The charge buildup in a magnetron etcher has been studied experimentally for two different magnet arrangements and theoretically on the basis of an equivalent circuit model. Wafer charging measured with a metal-Si3N4-SiO2-Si (MNOS) capacitor is negative along the centerline of the magnet poles and positive between the magnets in both cases. Wafer charging is explained either by curtent crowding at the center of the magnet poles or by the nonambipolar diffusion effect.
Transmission Electron Microscopy Observation of Defects Induced by Fe Contamination on Si(100) Surface
Authors: Sadamitsu Shinsuke , Sasaki Ayako , Hourai Masataka , Shigeo Sumita Shigeo Sumita , Nobukatsu Fujino Nobukatsu Fujino
Published: February 2005

The behavior of Si(100) surface defects induced by Fe contamination was studied with transmission electron microscopy. After annealing at 1150°C for 1 hour and a subsequent heat treatment at 850°C for 2 hours, Fe-containing precipitates were observed in Si substrate in close vicinity to the interface of Si and SiO2 formed during the annealing. One of these precipitates is identified as FeSi-type silicide. In addition, the inclusions which were confirmed to be Fe3O4 or γ-Fe2SiO4 were observed in the surface thermal SiO2 layer. These results demonstrate that Fe atoms diffuse into the Si substrate during annealing at 1150°C and precipitate at a Si/SiO2 interface, while Fe atoms left on the surface form inclusions in the surface SiO2 layer. Under an additional thermal oxidation at 1000°C, oxidation-induced stacking faults were formed. They were not decorated at all in contrast with those induced by Cu or Ni contamination.
Preparation of Y-Cu-O/Ba-Cu-O Multilayered Thin Films and Thermal Diffusion Behavior of the Interface
Authors: Asakawa Toshiaki , Shiraishi Tadashi , Nakanishi Shinya , Hirayama Tohru , Sakata Hironobu , Amano Masatake , Nagata Hirotoshi , Takano Akihiko , Hashimoto Takuya , Mamoru Yoshimoto Mamoru Yoshimoto , Hideomi Koinuma Hideomi Koinuma
Published: February 2005

Y-Cu-O and Ba-Cu-O layers were sequentially deposited by the plasma-controlled sputtering method and their interface structure was investigated. A binary target composed of YCuO
x
and BaCuO
y
pellets was sputtered under alternatingly varying magnetic fields to deposit films, which were supposed to consist of Y1Ba0.07Cu1.14 and Y0.15Ba1Cu1.13 periodic oxide layers. At deposition rates ranging between 0.13 and 0.16 nm, the formation of multilayered structures was clearly observed at a substrate temperature of 300°C and below, whereas the interface apparently diffused during the deposition to form a compositionally homogenous film at temperatures above 300°C. This thermal fluctuation at the interface was consistently interpreted in terms of a diffusion equation applied to the interface of semi-infinite solids.
Properties of Superconductive Strip-line Resonators Fabricated Using EuBaCuO Films on MgO (100)
Authors: Nagai Yasuhiro , Sato Makoto , Asano Hidefumi , Konaka Shugo Kubo
Published: February 2005

This paper reports on the properties of superconductive strip-line resonators fabricated using EuBaCuO superconducting films on MgO (100) substrates. A high loaded-Q of 22000 and an unloaded-Q of 24000 are realized at 35.5 K and 5.55 GHz. The surface resistance is calculated as 160 µΩ without any correction and 50 µΩ with t/λ correction. In addition, a resonant frequency shift of 40 MHz occurs in the measurement range. This shift can be mainly explained by the reduction in penetration depth due to the decrease in temperature. From this shift, penetration depth at 0 K is estimated to be 0.75 µm. Furthermore, there is no change in the unloaded-Q in the power region below -10 dBm, but then the unloaded-Q gradually decreases as the input power is increased although the penetration depth hardly varies. This limitation does not indicate that the whole superconductive phase is weakened. The influence of air spacing on resonant frequency is also discussed for MgO and LaAlO3 substrates.
Magnetic Properties of Amorphous (Tb1-xGdx)30Fe70 Thin Films
Authors: Takeno Yukio , Kazuhiro Kaneko Kazuhiro Kaneko , Kimiyoshi Goto Kimiyoshi Goto
Published: February 2005

Amorphous (Tb1-x
Gd
x
)30Fe70 thin films were prepared at various substrate temperatures (T
sub) and with various thicknesses, and their magnetic properties were investigated. The films prepared at T
sub=77 K show only in-plane anisotropy, and those prepared at T
sub=473 K only perpendicular anisotropy. The films prepared at T
sub=300 K are found to simultaneously have two components of anisotropy, the in-plane and the perpendicular. Since the absolute value of K
u decreases linearly with the fraction of Gd substitution for Tb, the single-ion anisotropy of Tb is considered to be closely connected with the anisotropy of these films. Thickness dependence of perpendicular anisotropy and that of angular dispersion of the easy axis of the local anisotropy of amorphous Tb15Gd15Fe70 films suggest the formation of small microcrystals in the films to produce the perpendicular anisotropy.
Sources of Inhomogeneity and Their Effects on the Asymmetry of the Ferromagnetic Resonance Lineshapes of Single Crystal Nickel Films
Authors: Abdulabbas Abdullah Hussain Abdulabbas Abdullah Hussain
Published: February 2005

The ferromagnetic resonance technique has been used to study the asymmetry of the main resonance line in single crystal nickel films prepared under different deposition conditions. All resonance experiments were performed at about 17 GHz, at room temperature. It is demonstrated that in both the perpendicular and parallel configurations, a contribution to the asymmetry comes from certain types of inhomogeneity in the internal field. Magnetic inhomogeneities and both surface and volume structural imperfections are the main sources of the inhomogeneities in the present samples. The origin of these inhomogeneities is discussed.
Second-Harmonic Generation in Noncentrosymmetric p-Nitroaniline Spontaneously Crystallized by Quenching from Lyotropic Liquid Crystalline Poly(γ-benzyl-L-glutamate)
Authors: Kamio Yuichi , Watanabe Junji , Kajikawa Kotaro , Takezoe Hideo , Fukuda Atsuo , Toyooka Takehiro , Ishii Takafumi
Published: February 2005

We have found a new crystal structure of p-nitroaniline (pNA) formed by quenching a mixture of poly(γ-benzyl-L-glutamate) (PBLG) and pNA in its lyotropic cholesteric liquid crystalline phase. Strong second-harmonic generation (SHG) has been observed in this quenched material, indicating the formation of a noncentrosymmetric structure of pNA. The maximum SH light intensity observed in PBLG/pNA=3:2 is as large as 3.6 times that of 2-methyl-4-nitroaniline (MNA) powder. We have confirmed, on the basis of X-ray and differential scanning calorimetry (DSC) measurements, that the SHG-active crystal of pNA is segregatedly formed from the crystal domain consisting of α-helical PBLG.
Preparation of AlN-Al2O3 Composite Films by Microwave Plasma Chemical Vapor Deposition
Authors: Someno Yoshihiro , Sasaki Makoto , Hirai Toshio
Published: February 2005

AlN-Al2O3 composite films were prepared by microwave plasma chemical vapor deposition using an AlBr3-H2-N2-N2O-Ar gas mixture on a Si substrate. They were examined with respect to their deposition rate, microstructure, compositions, and refractive indices. Four crystallinity phase regions were observed by X- ray diffractometer as a function of N2O gas flow rate and substrate temperature: A, c-axis oriented AlN; B, lower-oriented AlN; C, amorphous; and D, amorphous +β-NH4Br. Composite films composed of AlN and Al2O3 microcrystals having an average grain size of 50 nm were detected by transmission electron microscopy observation. Refractive indices, optical band gaps, and surface roughness were also determined.
Driving Force of Electromigration on Semiconductor Surfaces for Ag/Si(111)
Authors: Hitoshi Yasunaga Hitoshi Yasunaga , Shouzou Yoda Shouzou Yoda
Published: February 2005

A scanning Auger electron microscopic investigation was made on the electromigration of Ag thin film patch with a coverage of several monolayers deposited on Si(111) substrates with a variety of dope levels ranging up to 3×1019 cm-3. Electromigrative velocity of the Ag patch decreased in the same way as the electric field applied to the substrate with increasing extrinsic dope level. Thus, the driving force is directly proportional to the electric field, which strongly suggests that the electrostatic force dominates the electromigration of Ag on Si(111).
Morphological Transformation of Palladium Caused by Measurement of a Scanning Tunneling Microscope
Authors: Ohmori Takashi , Kazuhito Hashimoto Kazuhito Hashimoto , Akira Fujishima Akira Fujishima
Published: February 2005

It was observed that scanning the surface of palladium (Pd) for imaging with a scanning tunneling microscope (STM) caused the morphological change of the surface: The morphology of Pd was transformed from a rough surface to a flat one. This observation suggests that the surface was changed so as to reduce the surface energy. In the case of platinum, the morphology also changed to a certain degree. However, the change was not as drastic as compared with that of Pd. It is supposed that this morphological transformation was due to an electrostatic force (image force) between the STM tip and the metal surface.
A Study on Energy Distributions of Oxygen Ions Desorbed from CO-Adsorbed Ni(110) by Time-of-Flight Electron-Stimulated Desorption (TOF-ESD)
Authors: Akemi Takano Akemi Takano , Kazuyuki Ueda Kazuyuki Ueda
Published: February 2005

Ion energy distributions (IED's) of oxygen ions desorbed from a CO-adsorbed Ni(110) surface by electron stimulation of various primary energies between 200 and 900 eV have been studied using a time-of-flight electron-stimulated desorption (TOF-ESD) apparatus. The IED's represent different profiles for different desorption mechanisms. The IED of O+ ions stimulated by a shake-off mechanism was Gaussian distribution with a peak at 3.6 eV and a half width at a half maximum (HWHM) of 2 eV, while the IED by direct ionization of the valence electron is asymmetric and distributed from 3 to 10 eV with a peak at about 5 eV which seems to be decomposed into two Gaussian distributions.
In Situ Observation of Particle Behavior in rf Silane Plasmas
Authors: Shiratani Masaharu , Syohichiroh Matsuo Syohichiroh Matsuo , Yukio Watanabe Yukio Watanabe
Published: February 2005

In situ observation of growth and behavior of particles formed in rf discharges of silane gas is carried out by using a Mie scattering method together with an rf modulation method, in which the applied voltage is modulated by a low-frequency square wave. The observation reveals that particles have a growth time quite longer than their extinction time and also are charged up negatively to be trapped in the discharging space. The drastic suppression of the particle growth realized in square-wave-amplitude-modulated rf discharges can be explained by taking into account the above features and further falloff of time-averaged densities of short lifetime species by the rf modulation.
Deposition Pressure Effects on the Laser Plume of YBa2Cu3O7-δ
Authors: Izumi Hirohiko , Ohata Katsumi , Sawada Takashi , Tadataka Morishita Tadataka Morishita , Shoji Tanaka Shoji Tanaka
Published: February 2005

The control of the preferential orientation in oxide superconducting films, which is generally done by deposition temperatures, was achieved by choosing the oxygen pressures during the deposition. Time-resolved optical observations of the laser plume were carried out at the same time with the film deposition. Upon increasing the oxygen pressure, the velocities of the emissive species ablated from the target were decreased. The kinetic energy effects of the ablated species on the film orientation are discussed, and the orientation change can be qualitatively understood by a surface migration model as well as the case of the deposition temperature dependence.