bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Ba2NaNb5O15 Film by RF Magnetron Sputtering Method
Authors: Masuda Yoichiro , Masumoto Hiroshi , Baba Akira , Goto Takashi , Hirai Toshio
Published: February 2005

A film with tungsten-bronze structure was formed on a Pt/Al2O3 substrate by a RF msagnetron sputtering method. The deposition ratio of the films (Ba:Na:Nb) depended on the sputtering gas pressure. When the deposition rates were 10 nm/min at 10-1 Pa and 5 nm/min at 8 Pa, the dielectric constant and the dielectric loss factor were 141 and 0.02 at room temperature, respectively, and the remanent polarization P
r and the coercive field E
c were 32 µC/cm2 and 576 V/mm, respectively.
Preparation of Pb(Zr, Ti)O3 Thin Films by Multi-Target Sputtering
Authors: Hase Takashi , Sakuma Toshiyuki , Miyasaka Yoichi , Hirata Kazuo , Hosokawa Naokichi
Published: February 2005

Lead zirconate titanate (PZT) thin films have been prepared with a multi-target sputtering system onto Pt-coated Si substrates. Structure, composition and dielectric properties have been investigated on films ranging in thickness from 60 nm to 1400 nm. The dominant phase of PZT thin films varied from pyrochlore to perovskite with increasing film thickness. An interface PZT layer with about 100 nm thickness, which was confirmed to mainly consist of pyrochlore phase grains, was observed at the PZT/Pt interface in a cross-sectional transmission electron microscopy (TEM) image of an 850 nm thick film. That is, the pyrochlore grains preferentially grow at the early stage of deposition and do not change their structure during subsequent deposition. Dielectric constant and remnant polarization were degraded with decreasing thickness. This can be explained in view of the existence of the interface layer with a low dielectric constant.
Structural and Electrical Characterization of SrTiO3 Thin Films Prepared by Metal Organic Chemical Vapor Deposition
Authors: Yamaguchi Hiromu , Lesaicherre Pierre-Yves , Sakuma Toshiyuki , Miyasaka Yoichi , Ishitani Akihiko , Masaji Yoshida Masaji Yoshida
Published: February 2005

SrTiO3 thin films were prepared on Si and Pt/TaO
x
/Si substrates by Sr(DPM)2/Ti(i-OC3H7)4/O2/Ar chemical vapor deposition (CVD), using a simple vaporizing-and-transport source delivery system. A thickness uniformity of ±5.6% and a composition uniformity of ±2.7% were obtained. The dielectric constant was 210 for 110 nm thick SrTiO3 films (Sr/(Sr+Ti)=0.5) annealed at 600°C for 2 hours. An SiO2 equivalent thickness of 1.1 nm was obtained for 40 nm thick SrTiO3 films, and leakage current densities were 6×10-8 A/cm2 at 1.0 V and 5×10-7 A/cm2 at 1.65 V. The structural and electrical properties were affected by the film composition.
Preparation of Tetragonal Perovskite Single Phase PbTiO3 Film Using an Improved Metal-Organic Chemical Vapor Deposition Method Alternately Introducing Pb and Ti Precursors
Authors: Hirai Tadahiko , Goto Takaaki , Matsuhashi Hideki , Tanimoto Satoshi , Tarui Yasuo
Published: February 2005

Perovskite single-phase PbTiO3 films consisting of both a- and c-axis-oriented grains were prepared on a single-crystalline MgO substrate at a low substrate temperature of 510°C with an improved MOCVD (metal-organic chemical vapor deposition) method using tetra-ethyl-lead, titanium-iso-propoxide and ozone oxidant. Pb and Ti precursor vapors are alternately introduced into the reactor through different inlets, so that complicated vapor-phase reactions between the precursors and the reactions of which were unavoidable in conventional MOCVD, can be significantly inhibited in the inlet manifold. It is probable that this inhibition contributed to the present accomplishment of low-temperature epitaxial growth since it suppresses the vapor-phase generation of various Ti-Pb intermediates and oxides which are considered to greatly impede the flexibility in epitaxy.
Switching and Fatigue Characteristics of (Pb, La)(Zr, Ti)O3 Thin Films by Metalorganic Chemical Vapor Deposition
Authors: Tominaga Kouji , Shirayanagi Atsuhiro , Takeshi Takagi Takeshi Takagi , Masaru Okada Masaru Okada
Published: February 2005

Lanthanum-modified lead zirconate titanate (PLZT) thin films (0.3∼0.4 µm) have been prepared on Pt/SiO2/Si substrates at 650°C by the metal-organic chemical vapor deposition (MOCVD) method. The electrical properties of the films were examined as a function of lanthanum content. The relative dielectric constants increased as the La content increased to about 5 at%, and beyond this value, it became constant at 600. The remanent polarization and coercive field decreased from 22 to 1 µC/cm2 and from 90 to 20 kV/cm with increasing La content in the range of 0∼11 at%, respectively. The leakage current density decreased considerably with the addition of La, and was 8×10-9 A/cm2 at an applied voltage of 5 V. The switched charge densities of PLZT films showed almost no change up to switching cycles of 1×1012 at a bipolar pulse of ±5 V.
Preparation of C-Axis-Oriented Bi4Ti3O12 Thin Films by Metalorganic Chemical Vapor Deposition
Authors: Nakamura Takashi , Muhammet Rusul , Shimizu Masaru , Shiosaki Tadashi
Published: February 2005

Bi4Ti3O12 thin films were prepared on Pt/SiO2/Si(100), Pt/Ti/SiO2/Si(100) and sapphire (R-cut) by metalorganic chemical vapor deposition (MOCVD). Bi(C6H5)3 and Ti(i-OC3H7)4 were chosen as the metalorganic precursors. C-axis-oriented Bi4Ti3O12 thin films were grown on Pt/SiO2/Si (100) at 550°C. These films deposited directly on the substrates exhibit high loss and exhibit very rough surface morphology.
However, a Bi4Ti3O12 film with a Bi2Ti2O7 buffer layer on Pt/SiO2/Si(100) exhibits very smooth morphology and are highly c-axis-oriented. This film shows remanent polarization of 0.6 µC/cm2, coercive field of 13 kV/cm and dielectric constant of 180.
Epitaxial BaTiO3/MgO Structure Grown on GaAs(100) by Pulsed Laser Deposition*
Authors: Nashimoto Keiichi , Fork David K. , Ponce Fernando A. , Tramontana Joseph C.
Published: February 2005

BaTiO3 thin films on MgO encapsulated GaAs(100) were prepared epitaxially, in condition ranging from 600°C to 800°C and from 2×10-4 Torr O2 to 1×10-2 Torr O2, by pulsed laser deposition. The epitaxial relationship between all materials was cube-on-cube. BaTiO3 thin films obtained were c axis oriented tetragonal phase and showed ferroelectric properties. Epitaxial BaTiO3 had quite smooth surface of less than 100 Å in roughness. BaTiO3 grown on 40-Å-thick epitaxial MgO was also epitaxial although defect density in BaTiO3 looked higher than that in BaTiO3 grown on 400-Å-thick MgO. The interfaces of BaTiO3/40-Å-thick MgO/GaAs structure were abrupt and free of secondary phases in spite of the quite thin MgO layer.
Preparation of PbTiO3 Thin Film on Si by ArF Excimer Laser Ablation
Authors: Okuyama Masanori , Asano Jun-ichi , Imai Tadayuki , Don-Hee Lee Don-Hee Lee , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

Deposition behavior of PbTiO3 thin films on Si substrates having native oxide has been investigated by the laser ablation method using an ArF excimer laser. Atomic ratio Pb/Ti in the film decreases with increase of substrate temperature and laser shot period, but only changes slightly with increase of laser fluence. Preferentially c-axis-oriented film on Si substrate is obtained during the deposition in O2 gas of 13 Pa at the substrate temperature of 500°C and low laser repetition rate. The change of Pb/Ti and the origin of the preferential orientation are explained by Pb reevaporation from the substrate and successive deposition of Pb and Ti layers. Dielectric constant and the remanent polarization are about 130 and 30 µC/cm2, respectively.
Dielectric Properties of (Ba, Sr)TiO3 Thin Films Deposited by RF Sputtering
Authors: Horikawa Tsuyoshi , Mikami Noboru , Makita Tetsuro , Tanimura Junji , Kataoka Masayuki , Kazunao Sato Kazunao Sato , Masahiro Nunoshita Masahiro Nunoshita
Published: February 2005

Thin films of (Ba0.65Sr0.35)TiO3 (BST) have been prepared by an rf-sputtering method at substrate temperatures of 500 to 700°C. The dielectric constant of these films ranges from 190 to 700 at room temperature. This value changes with the grain size rather than the film thickness. The dielectric constant of about 300 and leakage current density of about 1×10-8 A/cm2 are obtained in the 65-nm-thick film deposited at a substrate temperature of 600°C. This shows the BST film can be applied to dielectrics of dynamic random access memory (DRAM) capacitors.
Energetic O- Ions and O Atoms in Planar Magnetron Sputtering of ZnO Target
Authors: Tominaga Kikuo , Sueyoshi Yasuhiko , Chong Munfei Chong Munfei , Yoshihiro Shintani Yoshihiro Shintani
Published: February 2005

Energetic negative ions and neutral atoms were observed by a time-of-flight apparatus for the sputtering of a ZnO target in Ar, Ar+O2 and O2 gases by a conventional DC planar magnetron system. Gas pressure dependence of energetic ions such as O-, O2
- and neutral O atoms was measured. The relative intensity of the flux of energetic O- ions and O atoms in each sputtering gas was estimated, and the production mechanism of the energetic O- ions was discussed. The O- ions were mainly produced by the sputtering of oxygen atoms by Ar+ ions. It was also confirmed that there exists a fairly strong flux of O- ions at excited states.
Preparation and Properties of PbTiO3 Films by Sol-Gel Processing
Authors: Maeda Masaki , Ishida Hiroshi , Ko Ko Kyaw Soe Ko Ko Kyaw Soe , Ikuo Suzuki Ikuo Suzuki
Published: February 2005

Thin films of PbTiO3 were fabricated by sol-gel processing. The optimum route and the conditions for preparing homogeneous and crack-free thin films were systematically investigated. Thin films were deposited on substrates by the dip-coating method. The films processed on silica glass and the (100) plates of SrTiO3 exhibit preferential orientation of the (001) axis perpendicular to the substrates. The spontaneous polarization and coercive field for the films deposited on indium-tin oxide-coated (ITO) glass were 3.5 µC/cm2 and 50 kV/cm, respectively.
Preparation of <100>-oriented Lead-Zirconate-Titanate Films by Sol-Gel Technique
Authors: Aoki Katsuhiro , Yukio Fukuda Yukio Fukuda , Akitoshi Nishimura Akitoshi Nishimura
Published: February 2005

A sol-gel technique to control the crystalline orientation of lead-zirconate-titanate (PZT) films on Pt/Ti/SiO2/Si substrates has been studied. It is found that crystalline orientations of sintered films show strong dependence on their thicknesses and <100>-oriented films can be obtained by limiting their thicknesses to 100 nm. It is also found that thicker oriented films can be obtained by stacking up these oriented films. The scanning electron microscopy observation reveals that a well-oriented film surface is smoother than those of non oriented ones. The leakage current of the 240-nm-thick oriented film is about 7 nA/cm2 at 3 V, which is an order of magnitude lower than the best reported lanthanum and iron-doped PZT film.
Ferroelectric Properties of Sol-Gel Derived Pb(Zr, Ti)O3 Thin Films
Authors: Amanuma Kazushi , Mori Toru , Hase Takashi , Sakuma Toshiyuki , Atsushi Ochi Atsushi Ochi , Yoichi Miyasaka Yoichi Miyasaka
Published: February 2005

Pb(Zr, Ti)O3 thin films of thickness ranging from 55 nm to 625 nm were synthesized on Pt/Ti/SiO2/Si substrates using a sol-gel process. The film thickness dependence of both microstructure and electrical properties was investigated. The synthesized films showed columnar structure. The diameter of each column was around 100 nm regardless of the film thickness. The 328 nm-thick film exhibited a dielectric constant (ε) of 1000, remanent polarization (P
r) of 20 µC/cm2, and coercive field (E
c) of 47 kV/cm. Both ε and P
r decreased and E
c increased with decreasing film thickness. This behavior is attributed to the existence of a low-dielectric-constant interface layer. The results of leakage current measurement were in good agreement with the model of space-charge-limited current.
Development of (Pb, Nb)(Zr, Sn, Ti)O3 Film Using a Sol-Gel Process and Resulting Antiferroelectric Properties
Authors: Akiyama Yoshikazu , Sachiko Kimura Sachiko Kimura , Itaru Fujimura Itaru Fujimura
Published: February 2005

(Pb, Nb)(Zr, Sn, Ti)O3 films are developed on Pt-coated Si substrates using a sol-gel process and their electronic properties are studied. An excessive amount of Pb in precursor solution is necessary to obtain films with good crystallinity. A 2.4-µm-thick film annealed at 650°C shows a dielectric constant of about 400 at room temperature. Electric field intensity at the antiferroelectric-to-ferroelectric phase transition is 80 kV/cm. Spontaneous polarization is 28 µC/cm2. Spontaneous polarization in this film is close to that observed in bulk samples (sintered at 1270°C). The electric field intensity, however, is approximately twice that of bulk samples.
Ion Channeling Study of SrTiO3Substrates and As-Deposited YBa2Cu3OxThin Films
Authors: Watamori Michio , Shoji Fumiya , Bando Yoshichika , Terashima Takahito , Oura Kenjiro
Published: February 2005

The crystalline quality (perfection or imperfection) of SrTiO3substrates and subsequent as-deposited YBa2Cu3Oxsuperconducting films has been investigated by a high-energy ion channeling technique. Analysis was performed as a function of depth, especially at 3 typical depth regions (surface, inside, interface), to clarify junction ordering features between substrates and films. Based on ion channeling measurements, it has been found that (1) disorders of substrates affect crystalline quality of films greatly at the interface regions, (2) the film reorders over a proper amount of YBa2Cu3Oxdisordered layers (as in buffer layers), (3) the film consists of an almost single domain. The crystalline quality of some SrTiO3substrates widely used in Japan has also been investigated and the common characteristics of distortions along thec-axis have been found.
High-Sensitivity Accelerometer Using Multilayer Piezoelectric Ceramics
Authors: Ohtsuki Yasunori , Yoshiaki Fuda Yoshiaki Fuda , Tetsuo Yoshida Tetsuo Yoshida
Published: February 2005

A high sensitivity accelerometer using multilayer piezoelectric ceramics including internal electrodes has been developed. The sensitivity of this accelerometer is about 900 pC/G at the frequency range from 0.01 to 10 Hz. Because the circuit was structed to cancel pyroelectric voltages, the output voltage changes of this accelerometer were decreased to 1/10 compared with the case of a noncanceling circuit.
Effects of Porosity on Dielectric, Elastic and Electromechanical Properties of Pb(Zr, Ti)O3 Ceramics with Open Pores: A Theoretical Approach
Authors: Hisao Banno Hisao Banno
Published: February 2005

Theoretical equations for dielectric, elastic and electromechanical properties of PZT (Pb(Zr, Ti)O3) ceramics with open pores are derived as afunction of porosity based on the 3-3 model. This theory is applied to previous obtained experimental results. Some of them agree well with the theoretical results based on the 3-3 model, while the others agree well with theoretical results based on the 3-0 model rather than on the 3-3 model. This is considered to be due to differences in the structure of the porous PZT ceramics.
Mechanism of Temperature Dependence of Piezoelectric Properties for Pb(Zr, Ti)O3
Authors: Kamiya Toshio , Mishima Ryuuichi , Tsurumi Takaaki , Nishimura Masaki Daimon
Published: February 2005

Temperature dependence of piezoelectric properties was measured for a tetragonal and a rhombohedral Pb(Zr, Ti)O3 (denoted as t-PZT and r-PZT, respectively). A least squares fitting of complex admittance data was employed in order to precisely determine various electromechanical constants. It was confirmed that the piezoelectric constant d
31 of the t-PZT was thermally stable while that of the r-PZT largely increased with temperature. It was clarified that the elastic compliance s
11
E and the electromechanical coupling factor k
31 decreased and the dielectric constant ε33
T increased with temperature in the t-PZT, giving rise to the thermally stable behavior of d
31. In the case of the r-PZT, the increase in ε33
T dominated the temperature dependence of the d
31. From the XRD analysis, it seemed that the increase in ε33
T of the r-PZT originated from a large thermal expansion of the unit cell volume.
Electrical and Mechanical Properties of Pb(Zr, Ti)O3 Ceramics Related to Mn Ion Diffusion
Authors: Hase Kiyoshi , Saitoh Masahiro , Toshihiko Kittaka Toshihiko Kittaka , Kunisaburo Tomono Kunisaburo Tomono
Published: February 2005

The electrical and mechanical properties of Pb(Zr, Ti)O3 (PZT) ceramics with Mn ions injected by diffusion at high temperature were studied. The rise of mechanical quality factor (Q
m) and the change of fracture mechanism from intergranular fracture to transgranular fracture was observed with increased diffusion temperature. These changes are related to the diffusion of Mn ions from the grain boundaries into the grains.
Low-Firing Y5P Relaxor Dielectric Material for Multilayer Ceramic Capacitor
Authors: Yamashita Yohachi , Furukawa Hideyuki Kanai
Published: February 2005

The sintering and electrical properties of the ceramic dielectric material, (Pb0.65Ba0.35)(Zr0.7Ti0.3)O3-Ba(Cu1/2W1/2)O3 have been studied. A small amount of Ba(Cu1/2W1/2)O3 drastically decreases the sintering temperature and increases the electrical resistivity of the ceramic. The dielectric material fired at 1,050-1,080°C, had a fired grain size of about 3 µm, a dielectric constant of 4,000-4,500, and a capacitance resistivity product of 10,000 Ω·F at room temperature and 8,000 Ω·F at 125°C. A multilayer ceramic capacitor made with such a ceramic dielectric and with 70Ag/30Pd internal electrodes satisfied the Y5P (ΔC<±10%, -30-+85°C) specifications of the EIA (Electronic Industries Association) Standards.
Enhancement of Time Response of Self-Pumped Phase-Conjugate Mirror in KNSBN:Cu Crystal Using Cylindrical Lenses
Authors: Gao Xin , Zheng Akira Sasaki
Published: February 2005

In this study we investigate the effect of incident beam diameters and profiles on time response and phase-conjugate reflectivity in a KNSBN:Cu crystal self-pumped phase-conjugate mirror. The time response of a self-pumped phase-conjugate mirror can be effectively enhanced by using two cylindrical lenses to increase incident light density without reduction of coupling strength. In maximum phase-conjugate reflectivity, the time response obtained using two cylindrical lenses is 4 times faster than that using a spherical lens.
Microwave Dielectric Properties of Lanthanide Titanate Ceramics
Authors: Takahashi Junichi , Kageyama Keisuke , Kouhei Kodaira Kouhei Kodaira
Published: February 2005

Microwave dielectric property changes with substitution of La3+ by Nd3+ and/or Sm3+ ions are studied for La2Ti2O7 and La4Ti9O24 ceramics. For the monoclinic La2Ti2O7, the substitution causes a considerable decrease in the permittivity (εr) of the material from εr=47 (La) to εr=36 (Nd), with a simultaneous variation in the Q·f value from 8500 to 16000 GHz. In La4Ti9O24-type dielectrics, only a slight change is observed in both the εr(≈37) and Q·f values (≈24000 GHz) by lanthanide substitution. The effects of mixing of different dielectric materials on the microwave properties are also examined for La2Ti2O7-La4Ti9O24 and Nd2Ti2O7-Nd4Ti9O24 composites. The permittivity and temperature coefficient of resonant frequency of the composite ceramics can be controlled using Lichteneker's rule, whereas the mixing of the different dielectrics results in the substantial lowering of the Q·f value.
Anomaly of Dielectric Constant of (Ba1-xSrx)(Mg1/3Ta2/3)O3 Solid Solution and Its Relation to Structural Change
Authors: Masaaki Sugiyama Masaaki Sugiyama , Toru Nagai Toru Nagai
Published: February 2005

The temperaure dependence of the dielectric constant has been studied in the (Ba1-x
Sr
x
)(Mg1/3Ta2/3)O3 solid solution. It is found by transmission electron microscopy and Raman spectroscopy that a new low-temperature phase exists in materials with strontium-rich compositions, and it is transformed into the ordered hexagonal perovskite phase with increasing temperature. The structural change is reversible by cooling and heating treatments. Because the dielectric constant of the low-temperature phase becomes large with increasing temperature, it is explained that materials with strontium-rich compositions have a negative temperature coefficient of resonant frequency. The anomaly of the dielectric constant with increasing temperature is discussed in relation to phase transformation.
Mode of Occurrence and Cause of Cracking of Li2B4O7 Single Crystals during Growth by Czochralski Method
Authors: Komatsu Ryuichi , Satoshi Uda Satoshi Uda , Kazuyasu Hikita Kazuyasu Hikita
Published: February 2005

The mode of occurrence and the origin of cracking of lithium tetraborate (Li2B4O7) single crystals during growth have been investigated. The melt temperature dependence and the origin of crystal cracking have been explained in terms of activation enthalpy change for viscous flow in Li2B4O7 melt associated with temperature distribution in the melt.
Simulations of Switching Characteristics in Ferroelectrics
Authors: Omura Masayoshi , Ishibashi Takashi Mihara
Published: February 2005

Simulations of switching characteristics in ferroelectrics have been carried out using a two-dimensional lattice model in ferroelectrics, in which latent nuclei are randomly distributed. The obtained results show that the remanent polarization P
r, the coercive field e
c and the rectangular ratio R of hysteresis loops depend on the interaction coefficient between neighboring dipole moments κ and the latent-nucleus density N. It is also found that as N increases, decreases the critical pulse width t
*, for which the system returns to the initial polarization state after the removal of the narrow applied pulse field. The information is collected to examine the possibility of nondestructive readout in ferroelectric memory.
Stress-Enhanced Diffusion of Boron at the Interface of a Directly Bonded Silicon Wafer
Authors: Ishigami Shun-ichiro , Kawai Yukio , Hisashi Furuya Hisashi Furuya , Takayuki Shingyouji Takayuki Shingyouji
Published: February 2005

We have investigated the interface of Si/Si directly bonded wafers using X-ray topography (XRT), spreading resistance (SR), and secondary ion mass spectroscopy (SIMS). The residual stress induced at the interface of the bonded wafer was observed as ring patterns by XRT when the two wafers, flat and convex, were bonded. It appears that the residual stress enhanced the diffusion of boron atoms and aggregated them near the bonded interface. However, the resistivity increased in the region under the compressive stress in spite of the aggregation of boron.
Role of Carbon and Hydrogen in Reactive Ion Etching of InP by Gas Mixture of Ethane and Hydrogen
Authors: Ohtsuka Ken-ichi , Sugimoto Hiroshi , Matsui Toshiro Isu
Published: February 2005

InP crystals were etched by reactive ion etching (RIE) with ethane and hydrogen (C2H6/H2). Etched crystals and gas species were characterized by photoluminescence and mass spectroscopic measurements. Evaporation of phosphorus is induced by hydrogen, mainly originating from H2 gas. Incorporation of C increases with the gas species of hydrocarbon having multiple bonds. Near-bandgap emission with intensities greater than before RIE, which shows the hydrogen passivation, and defect-complex-related emission bands at 1.06-1.07 eV enhanced by RIE were observed. The role of gas species and the identification of defects are discussed on the basis of the experimental results.
Metalorganic Vapor Phase Epitaxy Growth and Characterization of (AlxGa1-x)0.5In0.5P/Ga0.5In0.5P (x=0.4, 0.7 and 1.0) Quantum Wells on 15°-Off-(100) GaAs Substrates at High Growth Rate
Authors: Jou Ming-Jiunn , Lin Jyh-Feng , Chang Chuan-Ming , Lin Chun-Hung , Wu Meng-Chyi , Biing-Jye Lee Biing-Jye Lee
Published: February 2005

High-quality bulk layers of (Al
x
Ga1-x
)0.5In0.5P (x=0 to 1.0) and (Al
x
Ga1-x
)0.5In0.5P/Ga0.5In0.5P (x=0.4, 0.7 and 1.0) quantum wells (QWs) have been grown on 2°- and 15°-off-(100) GaAs substrates by means of low-pressure metalorganic vapor phase epitaxy at a high growth rate of 9 Å/s. The high-resolution transmission electron microscopic (TEM) image indicates the interfacial abruptness to be on the order of one monolayer. Photoluminescence (PL) results indicate an increase in peak energy and a decrease in full width at half-maximum (FWHM) for samples grown on 15°-off substrates, due to the suppression of sublattice ordering. For QWs with a direct barrier, an intense and distinct PL peak can be clearly observed for well thickness as thin as 9 Å. However, no emission is observed for the 9 Å well in the Al0.5In0.5P/Ga0.5In0.5P QWs, due to the indirect transition from the X-valley in AlInP to the heavy hole valence band of GaInP. For the first time, (Al0.7Ga0.3)0.5In0.5P/Ga0.5In0.5P multiple quantum wells (MQWs) with well widths of 9 Å have been obtained. The 20 K PL peak energy corresponds to a wavelength of 545 nm, the shortest ever reported for (Al
x
Ga1-x
)0.5In0.5P/Ga0.5In0.5P MQWs.
High-Pressure Synthesis of Mo-Containing 1212 and 1222 Compounds, (Cu, Mo)Sr2YCu2Oz and (Cu, Mo)Sr2(Y, Ce)2Cu2Oz
Authors: Akira Ono Akira Ono
Published: February 2005

A new “1222” compound (Cu, Mo)Sr2(Y, Ce)2Cu2O
z
is prepared at ambient pressure. After treatment under high oxygen pressure, the sample exhibits a sharp superconducting diamagnetic signal below the critical temperature (T
c) which varies depending on oxygen pressure. The highest value of T
c is 50 K. It is 22 K lower than the maximum T
c for the 1212 phase, (Cu, Mo)Sr2YCu2O
z
. The fluorite-type slab in the crystal structure is unfavorable for superconductivity in comparison with the Y layer. The T
c for the 1222 phase is not enhanced by the partial replacement of Sr by Ba, although approximately 25% of Sr can be replaced by Ba.
Nature of Preferred Orientation of YBa2Cu3Ox Thin Films
Authors: Masashi Mukaida Masashi Mukaida , Shintaro Miyazawa Shintaro Miyazawa
Published: February 2005

To clarify a preferential orientation of YBa2Cu3O
x
thin films, the growth parameters of a- and c-axis oriented thin films are investigated. YBa2Cu3O
x
thin films are grown on different lattice-mismatching substrates, such as Nd: YAlO3 (001), LaAlO3 (100), NdGaO3 (110), PrGaO3 (001), SrTiO3 (100) and MgO (100) by pulsed laser deposition (PLD) to determine the a- and c-axis preferential orientation phase diagrams. These a- and c-axis preferential orientations are controlled by the lattice constant of the substrate, the substrate temperature during deposition, the oxygen pressure in the growth chamber, and the laser power. The existence of a
c-axis oriented YBa2Cu3O
x
layer between the substrate
and a-axis oriented YBa2Cu3O
x
thin films is explained.
Detection of Compositional Separation in Co-Ru Alloy Magnetic Films
Authors: Maeda Yasushi , Koji Takei Koji Takei , David J. Rogers David J. Rogers
Published: February 2005

We examined the possible occurrence of compositional separation (CS) in hcp Co-Ru alloy magnetic films. Using spin echo 59Co NMR and transmisson electron microscopy, we found that CS, which produces a Co-rich component (≈10 at.%Ru), occurs in sputtered Co-≈33 at.%Ru films when substrate temperature is elevated to 400°C. The results suggest that the origin of CS lies in magnetically induced phase separation during film growth.
Photoluminescence Studies in CuAlS2:Zn
Authors: Aksenov Igor , Matsui Masahiro , Tetsuya Kai Tetsuya Kai , Katsuaki Sato Katsuaki Sato
Published: February 2005

Photoluminescence properties of Zn-doped CuAlS2 crystals have been studied in connection with the composition and crystal phases of the samples. It has been found out that Zn at relatively low concentration introduces a deep donor-like defect in the band gap of a host compound, whereas doping with Zn in a high concentration results in a formation of a multiphase structure on the surface and in the presurface region of the samples, this structure resulting in an enhancement of blue and green luminescence inherent to the lightly Zn-doped CuAlS2 phase.
Infrared Photoresponse in Semi-Insulating GaAs Diode
Authors: Hirohata Toru , Suzuki Tomoko , Kazutoshi Nakajima Kazutoshi Nakajima , Yoshihiko Mizushima Yoshihiko Mizushima
Published: February 2005

In semi-insulating GaAs (SI GaAs) photodiodes, an IR
photoresponse for longer wavelength beyond the energy gap
threshold is observed. The sensitivity is analyzed by
classifying electrode types and configurations. The IR
sensitivity originates from the optical hole injection. When a
cathode has an ohmic contact, the IR sensitivity is enhanced
exponentially with the bias voltage. The enhancement of the IR
sensitivity corresponds to the negative differential resistance
in SI GaAs. The mechanism of the IR sensitivity is discussed
in terms of the avalanche injection.
Crystal Growth of Huntite-Borates Doped with Li+, Si4+, Ge4+, Ti4+, V5+, Cr3+, Mn4+ and Nd3+ from Highly Concentrated Molten Fluxes
Authors: Chani Valery I. , Shimamura Kiyoshi , Keiji Inoue Keiji Inoue , Tsuguo Fukuda Tsuguo Fukuda
Published: February 2005

Bi-containing crystals of YbAl3(BO3)4 and ErAl3(BO3)4 with the huntite structure doped with Si4+, Ge4+ and transition metal cations Ti4+, V5+, Cr3+ and Mn4+ have been grown by spontaneous crystallization from fluxes based on Bi2O3-B2O3-Li2O. The Li+ cation was used for charge compensation of the crystal structure. The concentration of crystal-formed oxides was 43-96 mol% and the achieved productivity (crystal/melt weight ratio) was about 77 wt%. The dependences of crystal stability and chemical properties of prepared materials on crystal composition were discussed.
Nucleation and Film Growth in Photochemical Vapor Deposition of Aluminum Thin Film Using Dimethylaluminum Hydride
Authors: Takao Kawai Takao Kawai , Mitsugu Hanabusa Mitsugu Hanabusa
Published: February 2005

In the deposition of aluminum thin films on silicon oxide via a photochemical surface reaction of dimethylaluminum hydride (DMAH) induced by a deuterium lamp, the initial nucleation period was independent of gas pressure and became shorter with increasing UV intensity, whereas the rate of subsequent film growth on underlying aluminum layers increased with gas pressure, but it became indcpcndent of UV intcnsity and growth continued even without irradiation. We concluded that on the substrate surface photodissociation of adsorbates took place more slowly than adsorption of DMAH, while on growing aluminum layers the thermal decomposition of source molecules was dominant.
Characteristics of Nitrogen-Doped ZnTe Films and ZnTe-ZnSe Superlattices Grown by Hot Wall Epitaxy
Authors: Sakakibara Shingo , Amano Noriyasu , Ishino Kenei , Akihiro Ishida Akihiro Ishida , Hiroshi Fujiyasu Hiroshi Fujiyasu
Published: February 2005

Nitrogen-doped (N-doped) p-type ZnTe films have been prepared on GaAs(100) substrates by hot wall epitaxy (HWE) for the first time. To obtain high-quality films with high hole concentrations, optimum growth conditions such as the substrate temperature and the growth rate were studied by X-ray and Photoluminescence (PL) measurements. The hole concentration and Hall mobility were 1.1×1017cm-3and 52 cm2V-1s-1, respectively. The PL spectra of these films had a excitonic emission (I1), indicating high crystalline quality. The activation energy of the nitrogen acceptor was calculated, for the first time, to be 51 meV from the donor-acceptor (DA) emission energy. The existence of nitrogen in the films was confirmed by secondary ion mass spectroscopy (SIMS). The N-doped ZnTe-ZnSe SL's were also prepared and the hole concentration and Hall mobility were 2.3×1018cm-3and 36 cm2V-1s-1, respectively.
Thirty-Meter X-Ray Pencil Beam Line at the Institute of Space and Astronautical Science
Authors: Kunieda Hideyo , Tsusaka Yoshiyuki , Suzuki Hisanori , Ogasaka Yasushi , Awaki Hisamitsu , Tawara Yuzuru , Yamashita Koujun , Yamazaki Takashi , Itoh Masayuki , Kii Tsuneo , Makino Fumiyoshi , Ogawara Yoshiaki , Tsunemi Hiroshi , Hayashida Kiyoshi , Nomoto Susumu , Wada Mikio , Miyata Emi , Hatsukade Isamu
Published: February 2005

A 30-m-long X-ray beam line has been built at the Institute of Space and Astronautical Science (ISAS) to evaluate the performance of X-ray optical instruments for space programs, in particular for the X-ray telescope onboard the Astro-D (Asca) satellite. This beam line consists of an X-ray generator, a 30-m-long vacuum duct, and measuring chambers. Strong and stable X-ray pencil beams from Al, Ti, Cu, Mo and W targets are available with the parallelism of several arcs [full width at half maximum (FWHM)]. Three kinds of detectors are prepared: a conventional gas proportional counter equipped with a thin plastic window, a one-dimensional position-sensitive proportional counter with a Be window, and a charge-coupled device (CCD) modified for X-ray measurements. At the present compact beam line, instead of giant systems of hundreds of meters, the combination of a strong X-ray (0.2-10 keV) pencil beam and translation stages enables us to examine the entire aperture of large X-ray optical instruments of up to 40 cmφ and 1 m in length.
Characterization of Antiphase Domain in GaP on Misoriented (001) Si Substrate Grown by Metalorganic Chemical Vapor Deposition
Authors: Soga Tetsuo , Nishikawa Hironobu , Jimbo Takashi , Umeno Masayoshi
Published: February 2005

Antiphase domains (APD's) in GaP grown on (001) Si with different misorientation angles (0-6?) have been characterized by transmission electron microscopy (TEM) and etch pit observation. The self-annihilation of APD during growth is observed for GaP grown on exactly (001), 1?-off (001) and 2?-off (001) Si substrates, using TEM. A part of the APD is propagated to the surface in the case of exactly (001) and 1?-off (001) Si substrates. All the APD's are annihilated in the early stage of growth for GaP grown on 2?-off Si. On the other hand, no APD has been detected for GaP grown on 4?-off and 6?-off Si. The GaP surface morphology and the etch pit density are greatly affected by the APD's generated at the interface even if they are annihilated during the growth.
Low Resistance NiAuGe/Au Ohmic Contacts on N-Type (111)A GaAs
Authors: Lovell David R. , Takebe Toshihiko , Yamamoto Teiji , Inai Makoto , Kikuo Kobayashi Kikuo Kobayashi , Toshihide Watanabe Toshihide Watanabe
Published: February 2005

The resistance of NiAuGe/Au ohmic contacts on n-type GaAs, grown by molecular beam epitaxy, on (111)A GaAs substrates which are misoriented by 5? toward [100] has been studied. The ohmic contacts were formed by simultaneously evaporating Ni and a eutectic alloy of AuGe and then evaporating a layer of Au. The contacts were alloyed at 450?C. Contact resistances (R
c) from 0.035 ??mm to 0.056 ??mm are observed.
Optimum Bias Conditions for K-Band Microwave Mixing Using YBaCuO Step-Edge Microbridge Josephson Junction
Authors: Fukumoto Yoshito , Rikuo Ogawa Rikuo Ogawa , Yoshio Kawate Yoshio Kawate
Published: February 2005

Characteristics of the K-band microwave mixing using a YBaCuO step-edge microbridge Josephson junction were systematically investigated, and the optimum bias conditions were experimentally determined. A large intermediate frequency (IF) output signal was observed at every midway between the Shapiro steps, and the maximum IF output was obtained between the 0th and 1st steps (0-1) for the local oscillation (LO) power level of I
0/I
c=0.2-0.3 (absolute LO power of -49.9 dBm). The maximum conversion efficiency was estimated to be -26.6 dB. Although the IF output (0-1) was observed for a wide range of LO power, it vanished or decreased radically under some peculiar conditions (I
0/I
c?0 and ?(I
0/I
c)/?I
LO?0). These characteristics were qualitatively accounted for by the basic Josephson-mixing theory.
Possible Configurations for All-Optical Ultrafast Photonic Switching*
Authors: Shimizu Kazuhito Fujii
Published: February 2005

We discuss the feasibility of various configurations for ultrafast all-optical-switching elements (AOSEs) using third-order optical nonlinearities. The band-gap nonlinearities, in which the pump- and signal-photon energies are both close to the band-gap energy, do not satisfy basic requirements of the ultrafast AOSEs. Possible configurations to fulfill the requirements are suggested.
Optical Constants of Cubic ZnS
Authors: Shunji Ozaki Shunji Ozaki , Sadao Adachi Sadao Adachi
Published: February 2005

The real (?1) and imaginary (?2) parts of the dielectric function of cubic ZnS have been measured by spectroscopic ellipsometry in the 1.2-5.6 eV photon-energy range at room temperature. The measured dielectric-function spectra reveal distinct structures at energies of E
0/(E
0+?0) critical points. These data are analyzed on the basis of a simplified model of interband transitions. Results are in satisfactory agreement with the experimental data over the entire range of photon energies. Dielectric-related optical constants of cubic ZnS, such as the complex refractive index (n
*=n+ik), the absorption coefficient (?) and the normal-incidence reflectivity (R), are presented and analyzed.
Liquid Crystal Alignment on Polymer Films:Changes of the Pretilt Angles Due to the Thermal Treatment of Polyalkylene Pyromellitimides
Authors: Myrvold Bernt O. , Iwakabe Yasushi , Shuichi Oh-hara Shuichi Oh-hara , Katsumi Kondo Katsumi Kondo
Published: February 2005

Two polyimides have been cured at different temperatures and some samples further annealed at different temperatures after rubbing. It is found that the pretilt angles on these films increase with increasing curing temperature and/or increasing curing time. There is a further increase in the preiilt angle after annealing, but this effect is dependent on the structure of the polyimide as well as the pretreatment conditions of the sample. All these observations can be explained by considering the change in the alignment of the polyimide and thus the induced in-plane order of the liquid crystalline layer.
Field Evaporation of Ge(111) Surfaces in Presence of Hydrogen
Authors: Sakata Toyo , Block Jochen. H. , Matthias. Naschitzki Matthias. Naschitzki , Werner. A. Schmidt Werner. A. Schmidt
Published: February 2005

Field evaporation of Ge(111) surfaces in the presence of hydrogen was studied by field ion microscopy. The evaporation rate decreased exponentially with decreasing field strength and increased almost linearly with increasing hydrogen pressure below 1?10-4 Torr, above which it tended to saturate. In the investigated temperature range, 80-274 K, the evaporation rate approached constant values below 100 K and above 170 K, while it increased exponentially with the reciprocal value of temperature in the range 100-170 K. The evaporation voltage was constant below 100 K and above 250 K, while it decreased linearly with increasing reciprocal value of temperature in the range 100-250 K. The process of field evaporation was discussed from the viewpoint of surface hydride formation and hydride desorption to explain the experimental results.
Sheath Width in Negative-Ion-Containing Plasma
Authors: Horiike Haruo Shindo
Published: February 2005

Sheath width in negative-ion-containing plasma, which is important in plasma etching, is numerically investigated on the basis of Poisson's equation. With the aid of the previously reported Bohm criterion voltage, the negative ion term is consistently incorporated into the sheath equation. One of the important findings is that the sheath width increases with an increase in the negative ion density. This is simply because the positive-ion current decreases with negative-ion density even under the condition of a constant plasma density. The positive-ion density in the sheath front must decrease to keep neutrality with negative charges when the negative ions with low temperature are introduced, provided that the Bohm criterion voltage is not greatly different.
Plasma Oscillation Method for Measurements of Absolute Electron Density in Plasma
Authors: Teruyuki Shirakawa Teruyuki Shirakawa , Hideo Sugai Hideo Sugai
Published: February 2005

A new and simple method for precise measurements of electron density in a plasma with use of plasma oscillations is described. A weak electron beam is injected from a hot filament and excites electron waves oscillating at the plasma frequency ?p, whose sharp spectrum, obtained using a detector, gives the electron density. This plasma oscillation method is free of many difficulties often encountered with a Langmuir probe, such as thin film deposition, plasma potential fluctuation, and magnetic fields. The measurement technique is theoretically analyzed and experimentally demonstrated in the density measurements of an inductively coupled rf plasma, together with a comparison with the Langmuir probe method.
Trapping of Multiply Charged Ta Ions produced by Laser Ablation in an Ion Trap
Authors: Kitazawa Sin-iti , Okada Kunihiro , Nakamura Takashi , Shunsuke Ohtani Shunsuke Ohtani , Hiroshi Takuma Hiroshi Takuma
Published: February 2005

Multiply charged ions of Ta were produced by using laser ablation,and were stored in a radio-frequency ion trap. The charge states of the ions stored range from q=+1 to +6 for tantalum. The experimental apparatus for trapping and probing multiply charged ions is described, and results for the measurements on the charged-state spectra of trapped ions and storage time are presented.
Detection of Bulk Microdefects underneath the Surface of Si Wafer Using Infrared Light Scattering Tomography
Authors: Furukawa Jun , Hisashi Furuya Hisashi Furuya , Takayuki Shingyouji Takayuki Shingyouji
Published: February 2005

A new method has been developed to detect bulk microdefects (BMD) underneath the surface of a Si wafer using infrared light scattering tomography. In this method, infrared light enters from the cleaved surface obliquely and is totally reflected at the surface of the wafer, in order to eliminate the effect of scattering at the surface. BMD not only underneath the surface of the polished silicon wafer, but also underneath the wafer surface on which devices are fabricated, are easily detected by this method.
Effect of an External Magnetic Flux on Antitumor Antibiotic Neocarzinostatin Yield by Streptomyces carzinostaticus var. F-41
Authors: Kudo Kozo , Yoshida Yuko , Yoshimura Noboru , Ishida Nakao
Published: February 2005

The yield of the antitumor antibiotic neocarzinostatin (NCS), produced by Streptomyces carzinostaticus var. F-41, was sensitive to an external magnetic flux. When this strain was cultivated at 28?C in a NCS-producing medium under various magnetic flux densities, good NCS yield was observed at below 250 G magnetic flux density during the exponential growth phase as compared with that obtained in the same medium without magnetic flux, but was not observed at more than 500 G. However, no definite effect on the physiological characteristics and carbohydrate utilization of this strain, and primary physicochemical properties of NCS from magnetic flux could be detected.
Future Generation Magneto-Optical Media from a Manufacturing Point of View
Authors: Norio Ohta Norio Ohta
Published: February 2005

Future-generation magneto-optical (MO) media are studied from a manufacturing point of view. The first priority to expand MO media application is to realize low-cost technology. Of course, high capacity and high-speed capability are necessary to compete with other memories. Non-overwriting media provide a major stream for higher capacity disks such as 2× (two times the memory capacity of the first-generation disk) and 3×, because of their cost-effective production line using fine-tuned, already-repaid sputtering machines. Concerning overwriting schemes, field modulation media are very attractive in terms of media cost and high-density recording, but is limited to a single-sided disk. Light intensity modulation has an advantage for high-speed overwriting. In this paper, I propose an attractive scheme for a drastic reduction of cost per MByte. Field modulation writing and magnetic superresolution (MSR) readout are combined to increase memory density. More than 700 MB is possible on a 3.5-inch single-sided disk using a 780 nm current-generation laser.
Thin Injection-Molded Substrate for High Density Recording Phase-Change Rewritable Optical Disk
Authors: Ohta Takeo , Inoue Kazuo , Ishida Takashi , Gotoh Yoshikazu , Satoh Isao
Published: February 2005

A thin disk substrate was examined for use as a high-density recording optical disk. An injection-molded polycarbonate thin disk substrate of 0.6 mm thickness showed birefringence under 60 nm and small tilt angle under 5 mrad. The track pitch was 1.0 µm and the diameter was 86 mm. The laser source was visible light at wavelength 680 nm, and the numerical aperture (NA) of the optical head was as large as 0.6. This new high-density disk and drive system had the characteristics of wide tilt angle tolerance, equivalent to conventional thick substrates of 1.2 mm, and high-density small mark length of 0.52 µm, giving a carrier-to-noise (C/N) ratio beyond 48 dB. We found that for new high-density disk generation, thin disk substrates were suitable.
Write-Once Optical Disk Using Ge-Sb-Te/Bi-Te Bilayer Film for Mark-Edge Recording
Authors: Matsubara Motonari , Ohkawa Hideki , Yoshimaru Tomohisa , Koyahara Nobuhisa Yoshida
Published: February 2005

The Ge-Sb-Te/Bi-Te bilayer has been developed as a recording layer for a write-once optical medium. Mark-edge recording is carried out using the bilayer, and the (1, 7) run-length-limited code is employed for mark-edge recording. Without waveform equalization, the bilayer has a wide recording power tolerance of ±33% with a linear density of 0.68 µm/bit. This linear density corresponds to ∼9 Gbytes for both sides of a 300-mm disk with a modified constant angular velocity mode. Furthermore, the alloying states along the cross section of the bilayer are measured by energy-dispersive X-ray spectroscopy after laser recording at 9 and 15 mW.
Compact Optical Light Paths
Authors: Willem G. Ophey Willem G. Ophey
Published: February 2005

Possible integration steps of optical pickups for read-only, recordable and magneto-optical applications are presented with the Laser Detector Grating Unit as the universally applicable component.
Rapid-Access System for Optical Disk Drive Using Feedforward Brake Pulse
Authors: Ogawa Masaharu , Nakajima Yoshiki , Koyanagi Kimiyuki , Teruo Furukawa Teruo Furukawa
Published: February 2005

A rapid-access control method for optical disk drives has been developed. A brake pulse is fed forward to the objective lens actuator to rapidly reduce track crossing velocity of the light spot when in the close vicinity of the destination track during macro seeking. At the instant the light spot reaches the destination track, the track-following operation is performed by only the objective lens actuator until the linear motor stops. This rapid-access system was applied to a 3.5” optical disk drive, and it was found to provide a seek time for 256 tracks, excluding rotational latency, 30% shorter than a conventional direct access system.
Optical Filtering in the Collection Path of a Data Storage Device
Authors: Milster Tom D. , Wang Mark S. , Li Weiquan , Walker Ed
Published: February 2005

The effects of placing a shading band in the collection path of a magneto-optical data storage device are presented. The shading band consists of an opaque region in the center of the collection aperture, which reduces the low-frequency response of the system without affecting the high-frequency response. This partially equalizes the system transfer function. Dynamic measurements indicate that the noise is also reduced in the low-frequency region, thus not significantly affecting the narrow-band carrier-to-noise ratio (CNR). The integrated signal-to-noise ratio (SNR) shows slight improvement in the high-frequency region.