bluuebunny/crossref_metadata_2025 huggingface dataset:
Emission Characteristics of Poly[(tetraalkyldisilanylene)-p-oligophenylene]s
Authors: Katsumi Yoshino Katsumi Yoshino , Kazuya Tada Kazuya Tada , Masaharu Hirohata Masaharu Hirohata , Rahmat Hidayat Rahmat Hidayat , Satoshi Tatsuhara Satoshi Tatsuhara , Masanori Ozaki Masanori Ozaki , Akinobu Naka Akinobu Naka , Mitsuo Ishikawa Mitsuo Ishikawa
Published: October 2002

Optical absorption spectrum, photoluminescence (PL) and electroluminescence (EL) in poly[(tetraalkyldisilanylene)-p-oligophenylene]s (PDSiOP) are found to be dependent on the length of the oligophenylene but not on the length of the short alkyl substituents such as methyl and ethyl substituents. Spectral narrowing of the blue PL was observed in poly[(tetraalkyldisilanylene)-p-oligophenylene]s upon intense optical excitation due to stimulated emission. PL quenching and photoconductivity (PC) enhancement upon C60 doping are commonly observed in these polymers. These characteristics were explained taking the important role of oligophenylene units in the main chain into consideration.
A Model Experiment of Electromagnetic Wave Propagation over Long Distances using Waveguide Terminology
Authors: Motoji Ikeya Motoji Ikeya , Yoshihisa Kinoshita Yoshihisa Kinoshita , Hiroshi Matsumoto Hiroshi Matsumoto , Shunji Takaki Shunji Takaki , Chihiro Yamanaka Chihiro Yamanaka
Published: October 2002

Electromagnetic (EM) waves observed by telecommunication engineers ahead of earthquakes are controversial because they should not propagate over long distances from the hypocenter due to dissipation in the conductive Earth. A model of an earth crust dielectric waveguide was proposed and discussed with an earth atmospheric waveguide and tested in a laboratory scaling simulation experiment using a granite slab and an EM generator antenna at the hypocenter for the Kobe Earthquake. The mappings of evanescent and wave-ripple standing waves were obtained by scanning a detector antenna over the Japanese island archipelago model. Theoretical relations of the field intensity ΔV, such as log
ΔV =0.375M
W + c, where M
W and c are the moment magnitude and a constant, respectively have been derived by considering EM waves from an ensemble of dipolar charges at a fault zone. The theoretical scaling law is consistent with the empirical one.
Growth of High-Quality AlN, GaN and AlGaN with Atomically Smooth Surfaces on Sapphire Substrates
Authors: Ohba Yasuo , Hiroaki Yoshida Hiroaki Yoshida , Rie Sato Rie Sato
Published: October 2002

Metalorganic chemical vapor deposition (MOCVD) growth of AlN, GaN and AlGaN on sapphire substrates was investigated, with the aim of realizing high-quality heterostructures with atomically smooth interfaces. AlN with surfaces constructed of single-atomic-layer steps was grown by the two-step growth technique, in which the thin first layer was grown at a low temperature (1250° C) and then the second layer was grown at a high temperature (1350° C). GaN with surfaces consisting of simple atomic-layer steps were successively grown on the AlN layer by optimizing the growth conditions. Marked degradation of surface flatness was not observed for Al0.2Ga0.8N grown on GaN.
Bandgap Energy of GaNAs Alloys Grown on (001) GaAs by Metalorganic Molecular Beam Epitaxy
Authors: Katsuhiro Uesugi Katsuhiro Uesugi , Ikuo Suemune Ikuo Suemune
Published: October 2002

GaNAs layers have been successfully grown on GaAs(001) substrates by metalorganic molecular beam epitaxy using monomethylhydrazine (MMHy) as a N source. The N composition in GaNAs increased with decreasing growth temperature and with the increasing MMHy precursor ratio in the group-V precursors. We obtained a N composition of 7.2% in GaNAs. With the increased N composition, the absorption spectra shifted to lower energy and the absorption coefficient increased by one order of magnitude. When the N composition in GaNAs is less than 1%, the measured bandgap energy is very close to the theoretical bandgap energy based on the dielectric model. However, for N composition larger than 1%, the bandgap energy deviated considerably from the dielectric model, and approached the theoretical bandgap energy based on the first-principles supercell models.
Femtosecond Free Induction Decay Beats in Nd3+:YAG Crystal
Authors: Ryuzi Yano Ryuzi Yano , Naoshi Uesugi Naoshi Uesugi
Published: October 2002

Femtosecond free induction decay (FID) beats were observed for the 4F3/2 - 4I9/2 transition of Nd3+ ions doped in Y3Al5O12 (YAG) crystal at room temperature using a mode-locked Ti3+:Al2O3 laser. This is the first observation of room-temperature dephasing processes in the time domain for rare-earth ion doped materials. The FID beat signal shows a dip structure produced by the interference between the pump pulse and the FID signal, and a quantum beat. The FID signal became large and comparable to the pump pulse as the crystal length was increased. The FID intensity evolution due to the pulse propagation is explained well by phenomenological equations.
Molecularly Flat Films of Linear Polyions and Proteins Obtained by the Alternate Adsorption Method
Authors: Onda Mitsuhiko , Lvov Yuri , Katsuhiko Ariga Katsuhiko Ariga , Toyoki Kunitake Toyoki Kunitake
Published: October 2002

Alternately assembled films of poly(ethyleneimine) (PEI) and poly(styrenesulfonate) (PSS), as examined by non-contact atomic force microscopy (AFM), provided molecularly flat surfaces with height difference of several Å. Similar observations on alternate protein films of PEI-glucose oxidase, PEI-ferritin and PSS-peroxidase showed that films with outermost protein layers gave well-packed island structures and that the size of the island and the film roughness were related to the size of proteins used. Subsequent adsorption of a polyion layer decreased the surface roughness of protein layers significantly probably due to bridging of protein molecules by polyion chains.
Measurement of Einstein's A Coefficient of the 296.7 nm Transition Line of the Carbon Atom
Authors: Haruhiko Ito Haruhiko Ito , Masafumi Ito Masafumi Ito , Masaru Hori Masaru Hori , Akihiro Kono Akihiro Kono , Takashi Takeo Takashi Takeo , Terumasa Kato Terumasa Kato , Toshio Goto Toshio Goto
Published: October 2002

We measured Einstein's A coefficient of the transition line of the C atom at 296.7 nm (2s2p
3
5S2 - 2s
22p
2
3P2), which is useful for the absorption spectrocopic measurement of C atom density in processing plasmas. Einstein's A coefficient was evaluated from the emission decay rate of the 296.7 nm line in an electron cyclotron plasma employing CO gas. The obtained value of 3.9×104 s-1 is almost 2000 times as large as the reported theoretical A coefficient [G. H. Garstang: The Observatory 82 (1962) 50].
Single-Electron Tunneling through Amorphous Carbon Dots Array
Authors: Miura Naruhisa , Numaguchi Tetsuyuki , Yamada Akira , Shirakashi Makoto Konagai
Published: October 2002

Minute amorphous carbon dots were fabricated by electron-beam-induced deposition (EBID) carried out in a scanning electron microscope (SEM) system. The use of residual hydrocarbon molecules as a precursor enabled easy nanostructure fabrication. By optimizing electron-beam conditions, dots with a diameter of as small as 40 nm were successfully obtained. They were arranged in series between fine metal electrodes to form a device with multiple-tunnel junctions. Single-electron charging effects, such as the Coulomb blockade and the Coulomb staircase, were clearly observed at 9.4 K.
Refractive Index Distribution in Photoresist Thin Film Formed by the Spin Coating Method
Authors: Wakamiya Wataru , Hirayama Makoto , Kawai Akihiko Yasuoka
Published: October 2002

By measuring refractive index distribution in a wafer, we discuss the characteristic change of resist film. By various treatments including baking and dipping into a solution, the refractive index distribution differs slightly from that of the resist thickness in a wafer. We analyze the refractive index variation based on the Clausius-Mossotti relation of a solid.
Controlled Carrier Depletion around Nano-Scale Metal Discs Embedded in GaAs
Authors: Wernersson Lars-Eric , Litwin Andrej , Lars Samuelson Lars Samuelson , Wermer Seifert Wermer Seifert
Published: October 2002

Matrices of uncontacted, nano-scale, tungsten discs, embedded in GaAs by epitaxial overgrowth, have been characterised electrically. By varying the spacing between the discs, it is demonstrated that when the disc separation is smaller than 300 nm (for a doping level of 1016 cm-3), the conductance drops by seven orders of magnitude and the material becomes semi-insulating. The presence of the metal-induced barrier is deduced from the temperature dependence of the current transport. These results are discussed in terms of overlapping Schottky depletion regions around the discs.
Nanosecond AgGaS2 Optical Parametric Oscillator with More Than 4 Micron Output
Authors: Poh Boon Phua , Rui Fen Wu , Tow Chong Chong , Bao Xi Xu
Published: October 2002

This paper reports on a mid infra-red AgGaS2 optical parametric oscillator (OPO) pumped by nanosecond 1.064 micron Nd:YAG laser. Its wavelength tuning range is from 2.8 to more than 4.2 micron. Using singly resonating (SRO) configuration, the maximum absolute conversion efficiency obtained is about 10% (slope efficiency ∼16%) which is equivalent to a pump depletion of 30–40%. A comparison is also made between the oscillation threshold of the single and double pump pass version of this SRO. In addition, the variation of the oscillation threshold with its output wavelength is also discussed.
Determination of the Design Parameters for the Optical Second Harmonic Generation Efficiency in Organic Crystal-Cored Fibers
Authors: Celal Yildiz Celal Yildiz , Sedat Özsoy Sedat Özsoy
Published: October 2002

The second harmonic power generation efficiency (SHPGE) obtained under the phase-matching conditions in the 4-N,N-dimethylamino-3-acetamidonitroberzene (DAN) crystal-cored fibers having different cladding materials has been investigated. It has been found that a very high SHPGE can be obtained under the certain conditions. For the crystal-cored fiber having the core diameter of 0.52 µ m, the length of 2 cm, and the input beam power 3 mW, the efficiency of about 100% has been estimated for all of the cladding materials employed in this paper.
Characteristics of Heterojunction Utilizing Conducting Polymer and Diamond Film on Si
Authors: Kazuya Tada Kazuya Tada , Yoshihiro Yokota Yoshihiro Yokota , Koji Kobashi Koji Kobashi , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

An organic heterojunction utilizing conducting polymer, poly(2-methoxy-5-dodecyloxy-1,4-phenylenevinylene) (MDDO-PPV), and diamond film with the structure of Al/MDDO-PPV/diamond/Si has been fabricated. The device exhibits current rectification characteristics. The electroluminescence (EL) from MDDO-PPV on the diamond film has been observed. The rectifying junction and EL characteristics have been revealed and explained by taking hole injection from diamond film into consideration.
The Hysteresis Caused by Interface Trap and Anomalous Positive Charge in Al/CeO2–SiO2/Silicon Capacitors
Authors: Roh Yonghan , Jung Kyunghae Kim
Published: October 2002

We report the hysteresis induced by two similar defects located at and near the SiO2–Si interface in the Al/CeO2–SiO2/Si capacitor. We find that the hysteresis are generated directly due to the presence of interface trap and anomalous positive charge. Electrical characteristics of the hysteresis are, however, distinct and are strongly dependent on the type of defects. For example, the hysteresis caused by interface traps disappeared after passivating the Si dangling bonds by a post metallization annealing, while only a bias-temperature annealing causes the reduction of the hysteresis generated by anomalous positive charge. We suggest the mechanisms of the hysteresis generation in the Al/CeO2–SiO2/Si capacitor.
Observation of Purifier Performance to Reduce Moisture in Hydrogen Chloride by Near Infrared Laser Absorption Spectrometry
Authors: Morishita Jun-ichi , Wu Shang-Qian , Yoshio Ishihara Yoshio Ishihara , Tetsuya Kimijima Tetsuya Kimijima
Published: October 2002

The performance of a purifier in reducing moisture in hydrogen chloride (HCl) was evaluated using near-infrared laser absorption spectrometry. The moisture concentration in HCl passed through the purifier was lower than the detection limit (3σ) which was estimated to be 95 ppb. Despite the fact that the moisture concentration in the inlet stream increased from 1 ppm to 11 ppm, the moisture concentration in the outlet stream was maintained below the detection limit. Therefore, it is quite important to use the purifier in order to obtain dry HCl in a stable manner.
Optical Properties of Strained AlGaN and GaInN on GaN
Authors: Takeuchi Tetsuya , Takeuchi Hideo , Sota Shigetoshi , Sakai Hiromitsu , Hiroshi Amano Hiroshi Amano , Isamu Akasaki Isamu Akasaki
Published: October 2002

The composition of alloys in strained ternary alloy layers, Al

x

Ga1-
x

N (0<x<0.25) and Ga1-
x

In

x

N (0<x<0.20), on thick GaN was precisely determined using the high-resolution X-ray diffraction profile. The band gap of strained AlGaN is found to increase almost linearly according to the AlN molar fraction, while that of strained GaInN has a large bowing parameter of 3.2 eV.
Observation of Intrinsic Josephson Junction Properties on (Bi,Pb)SrCaCuO Thin Films
Authors: Akihiro Odagawa Akihiro Odagawa , Masahiro Sakai Masahiro Sakai , Hideaki Adachi Hideaki Adachi , Kentaro Setsune Kentaro Setsune , Tetsuji Hirao Tetsuji Hirao , Kunio Yoshida Kunio Yoshida
Published: October 2002

We have fabricated intrinsic Josephson junctions for (Bi,Pb)2Sr2Ca2Cu3O
x
thin films and investigated their electronic characteristics. Mesa structures with the junctions are fabricated on the surface of high-quality films prepared by rf-sputtering and subsequent heat treatment. The junctions show distinct hysteresis and a multiple branching structure with a periodic voltage jump at a current-voltage response. These results demonstrate that the fabricated mesas consist of stacked series SIS junctions. From this periodic structure, a voltage jump of 26–28 mV is obtained for the 2223 phase at 4.2 K.
Selective Lateral Etching of Al0.3Ga0.7As/GaAs Heterojunction Structure Using the Redox Solution of I2/KI
Authors: Dong Hyun Kim Dong Hyun Kim , Hee Chul Lee Hee Chul Lee
Published: October 2002

Selective lateral etching for an Al0.3Ga0.7As/GaAs system was conducted with iodine-potassium iodide ( I2/KI) redox solution having high preferential etching characteristics. The selectivity of Al0.3Ga0.7As relative to GaAs varied with the molar ratio of I2/KI, pH, stripe direction, and stirring speed of the solution. The undercut widths of Al0.3Ga0.7As below the GaAs layer were measured by observing the etched cross-section with a scanning electron microscope. For the [100] directional stripe, the undercut width of Al0.3Ga0.7As was measured up to about 3 µ m after etching for 1 min under the etching conditions of [I2]/[KI]=0.67 and pH=2.76. As a new application to the Al

x

Ga1-
x

As/GaAs heterojunction bipolar transistor (HBT) with x≤0.3, selective lateral etching was carried out to reduce the extrinsic base-collector capacitance of the HBT. As the result of capacitance-voltage (C-V) measurement, the base-collector capacitance of the lateral etched HBT was reduced to about 50% of that of the conventional HBT.
Optical Signal Inverter Using Injection Locking of Coupled Semiconductor Lasers
Authors: Takehiro Fukushima Takehiro Fukushima , Toyokazu Sakamoto Toyokazu Sakamoto
Published: October 2002

We propose and demonstrate a unique optical signal inverter using injection locking in coupled semiconductor lasers with a narrow-band Fabry-Perot (F-P) etalon. In this method, one laser diode is operated as a master laser to control the injection locking and the other is operated as a slave laser. By setting of the F-P etalon inside the coupled cavity, the locking and unlocking states can be allocated to the low and high levels for the output power, respectively. Under direct modulation of the master laser, the inverted light signal is available from the output port. This optical inverter can be operated at an output power of ∼7 mW.
Electron-Hole Recombination Range under the Control of a Langmuir-Blodgett Film Barrier
Authors: Wang Mingde Jin
Published: October 2002

In organic electroluminescent (EL) devices, the barrier layer performs the role of controlling the electron-hole recombination range. Organic EL devices have been fabricated with single 8-hydroxyquinoline Zinc (Znq2) layer and double layers for the Znq2 layer deposited on poly(methylmethacrylate) (PMMA) Langmuir-Blodgett films as a barrier layer, respectively. The organic layers were sandwiched between indium/tin oxide (ITO) and aluminum electrodes in EL organic devices. The experimental results suggest that the LB films perform an important role in enhancing the Znq2 EL efficiency.
Very High Hole Mobility in P-Type Si/SiGe Modulation-Doped Heterostructures
Authors: Tsai Wen-Chung , Chang Chun-Yen , Huang Guo-Wei , Fang Frank-Fu , Chang Yang-Hueng , Huang Chen-Feng
Published: October 2002

In this study, high-quality Si/Si1-
x

Ge

x

/Si p-type modulation-doped heterostructures were grown by ultrahigh-vacuum/chemical vapor deposition (UHV/CVD). High-field magnetotransport measurements revealed Shubnikov-de Hass oscillations in the longitudinal magneto resistance and the integer quantum Hall effect in transverse magnetoresistance illustrating the presence of a well-confined two-dimensional hole gas. The mobilities of the two-dimensional hole gas, as high as 12500 cm2/V·s at 0.65 K, were obtained for normal (doped layer at surface side) modulation-doped heterostructures with x = 0.12 at a sheet carrier concentration of 3.45 ×1011 cm-2. In addition, for this heterostructure, temperature-dependent measurements of Shubnikov-de Hass oscillations in the range 0.65 K–2.4 K were taken and the hole effective mass of 0.295 m
0 ±0.01 m
0 was obtained.
Formation of Metal-Insulator-Semiconductor Structure (B/Hexagonal BN/Graphite) by Plasma Chemical Vapor Deposition
Authors: Osaka Yukio , Nakagawa Nahotoshi , Kenji Kohno Kenji Kohno
Published: October 2002

A new technique for fabrication of a metal-insulator-semi-conductor (MIS) structure (B/hexagonal BN/graphite) on graphite is presented. Hexagonal BN(h-BN) and B films were deposited by plasma chemical vapor deposition (CVD). The B films were n-type semiconductors. Raman measurement of the B film showed that the B-configuration of these films is similar to the one in tetragonal B crystal. The capacitance-voltage (C-V) characteristics of the MIS structure at 100 kHz with a 47 nm thick h-BN layer showed inversion behavior. This behavior seems to be due to the small energy gap (0.6 eV) of B films.
Vertical Microcavity Lasers with InGaAs/GaAs Quantum Dots Formed by Spinodal Phase Separation
Authors: Schur Richard , Sogawa Fumihiro , Nishioka Masao , Satomi Ishida Satomi Ishida , Yasuhiko Arakawa Yasuhiko Arakawa
Published: October 2002

We report the growth, characterization and lasing of vertical microcavity lasers with an active layer of self-organized InGaAs/GaAs quantum dots. The quantum dots are formed by spinodal phase separation in low-In-content (x=0.03) In

x

Ga1-
x

As epilayers deposited with decreasing growth temperature in a hot-wall metalorganic chemical vapor deposition reactor. Optical transitions involving ground and excited states of the quantum dots were investigated using photoluminescence at moderately high excitation densities. Lasing oscillation was observed at 77 K by optical pumping. The coupling parameter β of the spontaneous emission into the lasing mode was estimated to be ∼8×10-3.
Effects of C 60 Doping on Electrical and Optical Properties of Poly[(disilanylene)oligophenylenes]
Authors: Kazuhisa Hosoda Kazuhisa Hosoda , Kazuya Tada Kazuya Tada , Mitsuo Ishikawa Mitsuo Ishikawa , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Photoluminescence (PL) of poly[(disilanylene)quaterphenylene] (PDSiQP) has been markedly quenched upon introduction of several mol% of C60, whereas photoconductivity of PDSiQP has been drastically enhanced upon doping with a small amount of C60 at the excitation with a photon energy exceeding the band gap energy of PDSiQP. We interpreted these results taking the electronic energy states of both PDSiQP and C60 and the role of oligophenyl units in the main chain of PDSiQP into consideration.
Quantum-Confined Stark Effect due to Piezoelectric Fields in GaInN Strained Quantum Wells
Authors: Takeuchi Tetsuya , Sota Shigetoshi , Katsuragawa Maki , Komori Miho , Takeuchi Hideo , Hiroshi Amano Hiroshi Amano , Isamu Akasaki Isamu Akasaki
Published: October 2002

We have studied the influence of piezoelectric fields on luminescence properties of GaInN strained quantum wells. Our calculation suggests that an electric field of 1.08 MV/cm is induced by the piezoelectric effect in strained Ga0.87In0.13N grown on GaN. The photoluminescence peak energy of the Ga0.87In0.13N strained quantum wells showed blue shift with increasing excitation intensity. Moreover, the well-width dependence of its luminescence peak energy was well explained when the piezoelectric fields were taken into account. These results clearly showed that the piezoelectric field induced the quantum-confined Stark effect.
Fabrication of Homojunction Using Spray Pyrolised CdS Thin Film by Copper Diffusion
Authors: K. P. Varkey K. P. Varkey , K. P. Vijayakumar K. P. Vijayakumar
Published: October 2002

PN homojunction has been fabricated for the first time in spray pyrolised CdS thin film. This is achieved by annealing CdS/Cu bilayer film. J-V characteristics of the homojunction are drawn; fill factor and efficiency are calculated to be 0.44% and 0.73% respectively. It is observed that there exists a minimum temperature at which the CdS/Cu bilayer has to be annealed for the formation of the junction. Interestingly increasing the annealing temperature does not result in any appreciable variations of open circuit voltage and short circuit current.
Unipolar Darlington Infrared Phototransistor
Authors: Victor Ryzhii Victor Ryzhii
Published: October 2002

A novel unipolar infrared photodetector – the Darlington infrared phototransistor (DIPT) – is proposed and evaluated. The DIPT is the integration of a quantum-well infrared photodetector, utilizing the electron intersubband transitions, and a hot-electron transistor. The operation principle of the DIPT is considered. Its performance is estimated using an analytical model. It is shown that the DIPT can exhibit very large responsivity. DIPTs may be useful for new detectors of infrared radiation of wavelength longer than 2 µm.
Light Emitting Diode with Porous Silicon/Conducting Polymer Heterojunction
Authors: Kazuya Tada Kazuya Tada , Maki Hamaguchi Maki Hamaguchi , Akihiko Hosono Akihiko Hosono , Shinsuke Yura Shinsuke Yura , Hiroshi Harada Hiroshi Harada , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

A light emitting diode (LED) with a Au/porous Si/poly(2-methoxy-5-dodecyloxy-1,4-phenylene vinylene) (MDDO-PPV)/Au structure has been fabricated and characterized. Red light emission with nonlinear emission intensity-current characteristic has been observed in this device. The observed light emission should originate from the radiative recombination in the porous Si layer.
Absolute Fluorine Atom Densities in Fluorocarbon High-Density Plasmas Measured by Appearance Mass Spectrometry
Authors: Keiji Nakamura Keiji Nakamura , Kazunori Segi Kazunori Segi , Hideo Sugai Hideo Sugai
Published: October 2002

We report absolute fluorine atom (F) density measurements based on appearance mass spectrometry (AMS). A liquid nitrogen cold trap installed in a mass spectrometer dramatically reduces background noise at m/e=19 (F+), enabling reliable AMS measurement of F density. The F density reaches ∼1019 m-3 in high-density inductively coupled plasmas in 100 % CF4 or C4F8 while addition of 50 % hydrogen decreases the F density by one order of magnitude. A conventional actinometry technique results in a factor of ∼4 greater reduction of F density in comparison with the AMS result. High etch selectivity of SiO2 to Si is achieved for the radical density ratio CFxF larger than 25 (x=1–3).
Influence of Ce Content on Crystal and Electrical Properties of CexZr1-xO2 Thin Films on Si(100) Substrates
Authors: Koike Hiroshi , Uesugi Takumi , Hirai Tadahiko , Yasuo Tarui Yasuo Tarui
Published: October 2002

We report on the crystalline and electrical properties of Ce

x

Zr1-
x

O2 thin films having various Ce content. The Ce

x

Zr1-
x

O2 thin films were deposited on Si(100) substrates by electron-beam evaporation. X-ray diffraction (XRD) and inductively coupled plasma emission spectroscopy (ICPES) analysis revealed that the crystal structure and lattice constants of Ce

x

Zr1-
x

O2 thin films depend on the Ce content. An increased Ce content brings about the (111)-preferred orientation structure. Capacitance-voltage (C-V) measurements results indicate that the interface state density decreased with increasing Ce content to bring about good electrical properties of Ce

x

Zr1-
x

O2/Si interface as a gate oxide.
Broadband Double-Layer Antireflection Coatings for Semiconductor Laser Amplifiers
Authors: Lee Jungkeun , Tanaka Toshiki , Uchiyama Seiji , Masahiro Tsuchiya Masahiro Tsuchiya , Takeshi Kamiya Takeshi Kamiya
Published: October 2002

We have investigated a double-layer antireflection (AR) coating for semiconductor lasers, which consists of TiO2 and SiO2 with non-quarter-wave thicknesses. In order to precisely control refractive indices, an electron-beam evaporator with oxygen pressure control was applied. Film thicknesses were accurately measured using the spectroellipsometric technique. Calculations show that the double-layer coating has much enhanced error margins, as well as broader bandwidths, which allows the performance of a double-layer coating even with ±1.6% of thickness errors in both layers to be comparable to or better than that of an ideal single-layer coating. By applying the double-layer coating design to a 1.55 µm GaInAs/AlGaInAs semiconductor laser amplifier, a minimum reflectivity of 5.3×10-3 and bandwidths of 140 nm for R<10-3 and 31 nm for R<10-4 were experimentally obtained.
Control of the Orientation of Photosynthetic Reaction Center Proteins Using an Applied Bias-Voltage Langmuir-Blodgett Technique
Authors: Yasuda Yoshiaki , Hara Masayuki , Miyake Jun , Hideki Toyotama Hideki Toyotama
Published: October 2002

We investigated the orientation control of photosynthetic reaction center proteins (RCs) by preparing RC Langmuir-Blodgett films in which a DC bias voltage ranging from -0.5 V to +0.5 V was applied (using a potentiostat) during film deposition. The bias voltage was applied between a conductive indium-tin-oxide coated glass substrate and a subphase through a helical platinum counter electrode. The orientation was evaluated using displacement-current measurement and photoelectron spectroscopy. Our results confirm that molecular orientation of RCs in the films was controlled by the polarity of the applied voltage.
Effect of Reducing Process Temperature for Preparing SrBi2Ta2O9 in a Metal/Ferroelectric/Semiconductor Structure
Authors: Nagashima Kazuhito , Koike Tadahiko Hirai , Fujisaki Yoshihide , Hase Takashi , Miyasaka Yoichi , Yasuo Tarui Yasuo Tarui
Published: October 2002

A SrBi2Ta2O9 (SBT) thin film was prepared on a CeO2/Si(100) substrate at a process temperature of 700° C. In the X-ray photoelectron spectroscopy (XPS) analysis, no diffusion of Si, which had been observed in the 800° C process sample, was detected in this 700° C process sample. In the capacitance-voltage (C-V) measurement, the width of the threshold hysteresis (“memory window”) was observed to be 1.0 V. In the curve fitting of the C-V characteristics, the measured characteristics fit the calculated characteristics fairly well. It is considered that this fairly good fit is due to prevention of the diffusion of Si and SBT elements caused by reducing the process temperature for preparing the SBT thin film.
FeCl3-Doping of a Polymer Containing Thiophene Hexamers in the Main Chain
Authors: Sato Masa-aki , Miwa Masayuki , Mune-aki Sakamoto Mune-aki Sakamoto , Masao Hiroi Masao Hiroi
Published: October 2002

A soluble polymer with a limited π-conjugation length, containing thiophene hexamers in the main chain, was prepared by reductive condensation. The obtained polymer was soluble in common organic solvents and cast to films. The films doped with FeCl3 showed considerable conductivities, 0.4–0.2 S/cm. The absorption spectra of the FeCl3-doped films indicated the predominant presence of one-electron oxidized species (polarons) and the instability of plural-electron oxidized species on the polymer chain in the atmosphere.
TlGaP Layers Grown on GaAs Substrates by Gas Source Molecular Beam Epitaxy
Authors: Fushida Masahiro , Asahi Hajime , Yamamoto Kazuhiko , Koh Hideki , Asami Kumiko , Oe Shun-ichi Gonda
Published: October 2002

TlGaP layers are grown on GaAs substrates by gas source molecular beam epitaxy. TlGaP is a constituent ternary alloy of the new III–V compound semiconductor TlInGaP, a material which can be used for 0.9 µ m to over 10 µ m laser diodes and for temperature-insensitive-wavelength laser diodes. TlGaP on GaAs shows phase separation into three stable compositions: TlGaP nearly lattice-matched to GaAs, GaP-like TlGaP and TlP-like TlGaP. By adjusting Tl and Ga fluxes, TlGaP layers without phase separation are grown. Photoconductance measurement on TlGaP shows absorption in the 1.3 µ m wavelength region as well as the small temperature variation of band-gap energy, as expected.
Electron Temperature and Density Profiles in a Neutral Loop Discharge Plasma
Authors: Sakoda Tatsuya , Iwamiya Hironori , Uchino Kiichiro , Muraoka Katsunori , Itoh Masahiro , Uchida Taijiro
Published: October 2002

Thomson scattering measurements of electron temperature and density in a neutral loop discharge (NLD) plasma were performed in order to reveal electron behavior around the neutral loop. The method yielded unambiguous and reliable results, enabling quantitative analyses of particle balance to be made. The results showed that the electron temperature had a peak on the neutral loop and, in contrast, the electron density had a peak at a position radially inward from the neutral loop. We suggest that charged particles are produced by electron impact ionization of argon atoms on the neutral loop and then flow radially inward. The effect of the magnetic field strength on the NLD plasma formation is also discussed.
Development of High Field Heat-Treatment Equipment and Relevant Applications
Authors: Watanabe Kazuo , Kimura Satoshi Awaji
Published: October 2002

High field and high temperature heat-treatment equipment was developed, using an 11 T liquid helium-free superconducting magnet with a 52 mm diameter room temperature bore. The newly developed heat-treatment system enables us to carry out an experiment, continuously, at 10 T and at temperatures up to 1200° C for a few weeks or months. As a performance test, a high field seeding process for YBa2Cu3O7 bulk at 10 T and about 1000° C for 3 days is developed, to improve the crystallinity of the YBa2Cu3O7 bulk.
Bleaching and Spectral Shape Modification of CdS Photocurrent due to He–Ne Laser Pumping
Authors: Ullrich Bruno , Natalia Mitkova Dushkina Natalia Mitkova Dushkina , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

The influence of He-Ne laser pumping on the photocurrent of a CdS single crystal was studied in the range 450–700 nm at room temperature. It was observed that the photocurrent was extremely dependent on laser irradiation. A low pump intensity of 64 mW·cm-2quenches the photocurrent by more than three orders of magnitude. The pumping also induces a spectral shape modification, i.e., a reduction of the gap photoconductivity at 500 nm below the photocurrent due to trap levels at 540 nm. The phenomena are explained in terms of two-photon absorption.
Fabrication of 5 nm Resolution Electrodes for Molecular Devices by Means of Electron Beam Lithography
Authors: Fabrizio Enzo Di , Grella Luca , Gentili Massimo , Baciocchi Marco , Morales Luigi Mastrogiacomo
Published: October 2002

Electron beam lithography is used to fabricate two-metal electrode tip-shaped structures. The distance between the tips is continuously controlled to be between 5 and 70 nm. The electron beam lithography process is robust and the tip separation is well controlled in the sense that the smallest distance between the tips is a consequence of the design and not a consequence of randomly distributed metal spots around the tip area. Interest in these structures is due to the fact that they can be used to fabricate rectifiers, working with single molecule, designed to exhibit semiconductor properties.
InAlAs/AlAsSb Type II Multiple Quantum Well Layers Lattice-Matched to InP Grown by Molecular Beam Epitaxy
Authors: Kawamura Yuichi , Kurisu Hirokazu , Yoshimatsu Kiyotsune , Kamada Akihiro , Naito Yoshihiro , Naohisa Inoue Naohisa Inoue
Published: October 2002

In0.52Al0.48As/AlAs0.56Sb0.44 type II multiple quantum well (MQW) layers lattice-matched to InP substrates were grown by molecular beam epitaxy (MBE). High quality InAlAs/AlAsSb MQW layers were obtained by controlling As/Sb beams precisely and optimizing the V/III ratio during growth. Below-gap light emission at 0.90–0.97 µ m was observed at 77 K, which arises from the recombination between electrons in the InAlAs layers and holes in the AlAsSb layers across the type II heterointerface. The valence band discontinuity ΔE
v is estimated to be 0.28 eV from the InAlAs well width dependence of the emission energy.
Triangular-Facet Lasers Coupled by a Rectangular Optical Waveguide
Authors: Ando Seigo , Naoki Kobayashi Naoki Kobayashi , Hiroaki Ando Hiroaki Ando
Published: October 2002

The coupled structure of two triangular prism-shaped micro-ring cavity lasers with a rectangular optical waveguide is achieved by selective area metalorganic vapor phase epitaxy (MOVPE), and its preliminary lasing characteristics are measured by optical pumping. This coupled laser structure consists of a (111)B growth plane and perpendicular (110) sidewall facets on a (111)B GaAs substrate. By using these coupled lasers as an oscillator and a modulator, the lasing light from the oscillator can be modulated at the modulator by changing the optical pumping power of the modulator. The carrier lifetime in the active layer of the triangular laser can also be estimated with this laser configuration. The sidewall of the triangular laser covered with an AlGaAs layer exhibits a longer carrier lifetime (∼560 ps) and lower threshold (E
th=8 pJ) because of the reduced surface recombination at the edge of the GaAs active layer.
Proposed Photon Momentum Detector and Application to a Phototransistor
Authors: Yoshihiko Mizushima Yoshihiko Mizushima
Published: October 2002

Photon momentum can be converted into electron momentum by the occurrence of mirror reflection. Electron momentum can be measured at the reflecting interface of a metal-semiconductor junction. A theory explaining the possibility of a photon momentum detecting device with an implemented amplification mechanism for practical sensitivity is proposed. The phototransistor theory is compared to recent experimental reports on GaAs photodiodes. It is shown that the proposed theory for the photon momentum detection is consistent with the experimental facts.
Helicoid-Stabilized Tristable Switching in Ferroelectric Liquid Crystal Mixtures with Ultrashort Pitch
Authors: Itoh Keizo , Takanishi Yoichi , Yokoyama Jun , Ishikawa Ken , Takezoe Hideo , Fukuda Atsuo
Published: October 2002

Antiferroelectric-like tristable switching was observed in smectic liquid crystal mixtures containing chiral dopants derived from trifluoromethylated pyranose. The results of transmittance measurement with obliquely incident light clearly indicate that the phase showing the tristable switching is not antiferroelectric but ferroelectric. The helicoidal pitch quadratically changes with the amount of dopant and seems to attain about 50 nm in the mixtures with a dopant content of more than 40 wt%. The quadratic dependence originates from the flexoelectric effect with negligible inter-molecular chiral interaction. Mechanisms for the tristable switching are proposed on the basis of the ultrashort pitch.
Size Effect on Thermal Conduction in Silicon-on-Insulator Devices under Electrostatic Discharge (ESD) Conditions
Authors: Yongho Sungtaek Ju Yongho Sungtaek Ju , Kenneth Eugene Goodson Kenneth Eugene Goodson
Published: October 2002

Previous experimental work has shown degradation in the electrostatic discharge (ESD) failure voltage for silicon-on-insulator (SOI) devices compared to that of devices made from bulk silicon substrates. Understanding of this trend requires simulations of temperature fields in SOI devices using accurate thermal property values. The present work predicts the in-plane lattice thermal conductivity of thin silicon films at temperatures up to 1000 K considering the size effect due to phonon-boundary scattering. For silicon layers thinner than 0.2 µm, a significant reduction in the thermal conductivity is expected even at temperatures as high as 700 K. A compact expression for the thermal conductivity of thin silicon films can be readily used in device simulations. Temperature field predictions for a simplified SOI device show the impact of the size effect and motivate discussion of its implications for ESD buffer design.
Analyses of Diamond Nucleation Processes on Carbonized Substrates
Authors: Xi Li Xi Li , Tadashi Miyagi Tadashi Miyagi , Yasuaki Hayashi Yasuaki Hayashi
Published: October 2002

The formation of carbonized interface layers is a spontaneous stage in the nucleation process of the chemical vapor deposition (CVD) of diamond onto substrates, however, the relationship between the carbonization and nucleation stages has not been well understood to date. This paper will discuss diamond nucleation mechanisms in relation to the carbonization of silicon substrates. For this purpose the silicon substrates are first carbonized using direct resistive heating. Then, diamonds are deposited on the substrates using a hot-filament CVD (HF-CVD) method. The experimental results reveal that when no ion effects exist, the solid-phase carbon reaches the same thermal equilibrium state as in the gas-phase during diamond deposition, and that the formation of the carbonized interface layers has no immediate relationship to diamond nucleation.
Formation of Si(111)–6×6–Au Structure without Using a Vacuum Evaporation Technique Observed by Reflection High-Energy Electron Diffraction
Authors: Tomohide Takami Tomohide Takami , Shozo Ino Shozo Ino
Published: October 2002

We have demonstrated the formation of the Si(111)–6×6–Au surface structure without using a vacuum evaporation technique. Au multiply-twinned particle micelles, comprised of a Au multiply-twinned particle and mercaptopropionic acid, in water were put on a thermally oxidized Si(111) substrate. After drying and introduction into a vacuum chamber, the Si(111) substrate was flashed at 900°C. Then the 6×6 surface structure was observed by reflection high-energy electron diffraction. A novel technique for metal deposition at a coverage of several monolayers or at sub–monolayer coverage can be predicted from the result.
Relation between ESR and Hydrogen in Magnetron-Sputtered a-Ge:H
Authors: Hoonkee MIN Hoonkee MIN , Shoichi UEDA Shoichi UEDA , Minoru KUMEDA Minoru KUMEDA , Tatsuo SHIMIZU Tatsuo SHIMIZU
Published: October 2002

On the basis of ESR measurements, the g-value between 2.019 and 2.023 and peak-to-peak linewidth (ΔH
pp) between 35 and 50 G have been reported in a-Ge and a-Ge:H. However, we observed a smaller g-value of 2.014 in hydrogen-rich a-Ge:H. Such a small g-value in hydrogen-rich a-Ge:H is thought to arise from a different local structure around the Ge dangling bond than that in previously reported samples. In order to clarify the reason for the small g-value in hydrogen-rich a-Ge:H, we investigated the change in the g-value under various deposition conditions and with increasing annealing temperature.
Evaluation of Phase Coherent Length of Hot Electrons Based on Wigner Distribution Function
Authors: Hideaki Tsuchiya Hideaki Tsuchiya , Tanroku Miyoshi Tanroku Miyoshi
Published: October 2002

A new methodology for evaluation of the phase coherent length of hot electrons is proposed based on the Wigner distribution function. In our approach, the coherent length can be evaluated directly from the resonant width in the momentum-space of the Wigner distribution function under the influence of electron-electron interactions and phonon scattering. In this paper, a coherent length of hot electrons created in a double barrier resonant tunneling structure is studied. It is found that the electron coherency deteriorates in the quantum well layer due to the interaction with the accumulated electrons, and that consequently to obtain hot electrons with longer coherency from the resonant tunneling structure it should be biased near the valley region of the I-V curve rather than at the peak voltage.
Dependence of Frequency and Pressure on Electron Energy Distribution Functions in Low Pressure Plasma
Authors: Haruaki Akashi Haruaki Akashi , Seiji Samukawa Seiji Samukawa , Nobuaki Takahashi Nobuaki Takahashi , Tai Sasaki Tai Sasaki
Published: October 2002

The electron energy distribution functions (EEDF), ionization frequency R
i and mean electron energy ε in a low pressure high frequency (13.56 MHz–1 GHz) discharge in Ar gas have been examined using Monte Carlo method. The dependence of driving frequency on the EEDF, R
i and ε is calculated. As the frequency increases, the lower energy electrons increase significantly because they can not follow the applied high frequency electric field. Then, R
i and ε decrease with increasing frequency. The dependence of pressure on EEDF, R
i and ε under applied frequencies of UHF (500 MHz) and RF (13.56 MHz) is also investigated for actual etching pressures. The EEDF, R
i and ε in the UHF plasma do not depend on the pressure, whereas those in the RF plasma are strongly influenced by the pressure. It is considered that the driving frequency (UHF) is higher than the electron collision frequency in the plasma.
Improving Gate Oxide Integrity of Cobalt Silicided P-Type Polysilicon Gate Using Arsenic Implantation
Authors: Sun Wein-Town , Liaw Wei-Wu , Liaw Ming-Chi , Hsieh Kuang-Chien , Charles Ching-Hsiang Hsu Charles Ching-Hsiang Hsu
Published: October 2002

The gate oxide integrity degradation due to the thermal instability of cobalt silicide ( CoSi2) in p-type polysilicon gate metal-oxide-semiconductor (MOS) capacitors is alleviated by arsenic implantation into p-type poly-Si gate. The thin gate oxides of p+-poly MOSFETs were severely degraded due to agglomeration of cobalt silicide at high temperature after silicidation. The degradation of thin gate oxide was found to be suppressed by the implantion of arsenic into p-type polysilicon gate. This is due to the fact that arsenic atoms segregate simultaneously into grain boundary and interface, and diffusion of decomposed cobalt along grain boundary was then retarded during agglomeration.
Electrical Characterization of Silicon Dioxide Thin Films Prepared by Chemical Vapor Deposition from Tetrakis(diethylamino)silane and Ozone
Authors: Toshiro Maruyama Toshiro Maruyama
Published: October 2002

Silicon dioxide thin films were prepared by a low-temperature atmospheric-pressure chemical vapor deposition method from tetrakis(diethylamino)silane-ozone at a substrate temperature above 200° C. The relative dielectric constants of the films prepared in this study were lower than those for the films prepared from tetraethoxysilane-ozone. The relative dielectric constants for both films were nearly proportional to the absorbance of Si–O· bonds at about 950 cm-1, indicating that an ionic polarization due to the nonbridging oxygen was closely connected with the relative dielectric constant of the film prepared using ozone at a low substrate temperature.
High Efficiency Electron-Emission in Pt/SiOx/Si/Al Structure
Authors: Negishi Nobuyasu , Chuman Takashi , Iwasaki Shingo , Yoshikawa Takamasa , Hiroshi Ito Hiroshi Ito , Kiyohide Ogasawara Kiyohide Ogasawara
Published: October 2002

A high efficiency electro-emission device (HEED) has been developed with a structure of Pt/SiO

x

/Si/Al on a thermally-oxidized Si substrate. The thicknesses of the SiO

x

and Si films were 400 nm and 5 µ m, respectively. Electron emission characteristics of the HEED are reported. It was found that the HEED has an electron-emission efficiency as high as 28% and a high brightness of 80 kcd/m2 using phosphor ZnS:Cu,Al. This high electron-emission efficiency was obtained in a range of applied voltage in which negative resistance occurred.
Improvement in the Detection Limits of Elastic Recoil Detection Analysis (ERDA) Using a Time-of-Flight Detection
Authors: Hong Wan , Hayakawa Shinjiro , Maeda Kuniko , Fukuda Shigekazu , Yanokura Minoru , Aratani Michi , Kimura Kazuie , Yohichi Gohshi Yohichi Gohshi , Isao Tanihata Isao Tanihata
Published: October 2002

The detection limits of oxygen and silicon in a SiO2 sample were compared between a time-of-flight elastic recoil detection analysis (TOF-ERDA) and conventional ERDA using a 41.5 MeV 40Ar ion beam. With TOF-ERDA, an energy spectrum of each mass can be extracted by measuring both the flight time and the energy of each recoil particle while conventional ERDA provides an overlapped energy spectrum fo all masses. It was found that the oxygen can be detected at areal densities of as low as 6.62×1013 atoms/cm2 by TOF-ERDA, and that the detection limits can be improved by the factor of 5 compared to conventional ERDA.
Investigation on the Surface Electronic States of the Si(001) c(4×2) and c(8×8) Surfaces: An Electron Energy Loss Spectroscopy Study
Authors: Toshitaka Kubo Toshitaka Kubo , Tetsuya Aruga Tetsuya Aruga , Noriaki Takagi Noriaki Takagi , Mitsuaki Nishijima Mitsuaki Nishijima
Published: October 2002

The surface electronic states of the clean (and CO-covered) Si(001) c(4×2) and c(8×8) surfaces at 90 K have been studied by using high resolution electron energy loss spectroscopy. On the clean c(8×8) surface, the loss peaks are observed at 0.3, 0.7 and 1.2 eV. The 1.2 eV loss is sensitive to the CO adsorption, whereas the 0.3 and 0.7 eV losses are not sensitive. These suggest that the c(8×8) structure contains the defects which are not understood by the dimer vacancy model.
Ballistic Electron Emission Microscopy Studies of Inhomogeneity in Au/CaF2/n-Si(111) Interfaces
Authors: Sumiya Touru , Fujinuma Haruko , Tadao Miura Tadao Miura , Shun-ichiro Tanaka Shun-ichiro Tanaka
Published: October 2002

We have performed ballistic electron emission microscopy (BEEM) measurements on the Au/ CaF2/n-Si(111) system in which calcium fluoride ( CaF2) (about 2 monolayers (ML)) was introduced at the Au/Si interface. A BEEM image clearly shows the coexistence of two types of terrace for each of which the BEEM I-V spectrum has a different shape. A typical threshold voltage of the BEEM current for one type is about 0.75 V. In contrast, the second type shows a threshold voltage of about 3.5 V, which is much higher than the value of the first type. Furthermore, the BEEM current on the second type is significantly reduced and saturates above about 6 V. We attribute the coexistence of the two types of terrace in the BEEM image to the different degrees of coverage of the CaF2 intralayers between them. At the second type of terrace, a Au/2 ML CaF2/1 ML CaF/Si(111) interface exists, although the first type has a Au/1 ML CaF/Si(111) interface without a CaF2 intralayer.