bluuebunny/crossref_metadata_2025 huggingface dataset:
Exchange Coupling in NiO/Ni Double Layer Films
Authors: Shimazawa Koji , Baba Toshinori , Kobayashi Koji , Shinagawa Kiminari , Toshiaki Saito Toshiaki Saito , Tachiro Tsushima Tachiro Tsushima
Published: October 2002

NiO/Ni double layer films were prepared by partial oxidation of Ni films deposited on MgO(100) substrates by a vacuum evaporation method, and the exchange coupling field H
ex and the easy coercive force H
ce in the films were studied in relation to the substrate temperature T
s and the oxidation temperature. As a result, it is found that (1) Ni films deposited at low T
s (100° C) are easily oxidized at low temperatures (∼450° C), compared with those deposited at higher T
s (200° C or 300° C), (2) H
ex and H
ce in NiO/Ni double layer films prepared at low temperatures are large compared with those in films prepared at high temperatures. The reasons for the increase of H
ex and H
ce in NiO/Ni films prepared at low temperatures are discussed.
High-Performance Characteristics of Bonded Magnets Produced Using Sm2Fe17Nx Powder Stabilized by Photoinduced Zinc Metal Coating
Authors: Izumi Hirokazu , Machida Ken-ichi , Shiomi Atsushi , Masayuki Iguchi Masayuki Iguchi , Gin-ya Adachi Gin-ya Adachi
Published: October 2002

The surface of Sm2Fe17N

x

fine powder was stabilized by coating with zinc metal produced by the photodecomposition of diethylzinc (Zn(C2H5)2). The remanence (B
r) and coercivity (H
cj) values of the resulting Zn/Sm2Fe17N

x

powder were changed little by zinc coating, and remained at high levels even after heat treatment at 423 K, since the oxidation-resistance was improved by the zinc coating. Epoxy resin bonded magnets prepared using the Zn/Sm2Fe17N

x

powder had a maximum energy product ( BH
m
a
x
) value of 176 kJ·m-3, which did not change greatly after exposure to air. The irreversible flux loss of the bonded Zn/Sm2Fe17N

x

magnet was smaller than that of the uncoated Sm2Fe17N

x

magnet.
Generation of Tunable Pulses below 345 fs Using a Passively Mode-Locked Fiber Ring Laser with Bulk Components
Authors: Endo Michiyuki , Ghosh Gorachand , Tanaka Yuichi
Published: October 2002

A stable, passively mode-locked erbium-doped silica fiber ring resonator is fabricated to generate tunable optical pulses with durations of 270–345 fs in the 1.55 µ m band pumped by a 1.48 µ m semiconductor laser diode. The lasing wavelength is tuned continuously over a wavelength range of 60 nm from 1.532 to 1.594 µ m by rotating a bulk band-pass filter inserted in the resonator with a repetition rate of 45.4 MHz.
New Realization Method for Three-Dimensional Photonic Crystal in Optical Wavelength Region
Authors: Noda Susumu , Noritsugu Yamamoto Noritsugu Yamamoto , Akio Sasaki Akio Sasaki
Published: October 2002

A new realization method for three-dimensional photonic crystals in the optical wavelength region is proposed. Microfabrication techniques using wafer-bonding, selective etching, and laser beam deflection pattern observation techniques are successfully combined, and the feasibility of the proposed method is experimentally demonstrated.
Low-Temperature Growth of ZnS by Photoassisted Metalorganic Chemical Vapor Deposition
Authors: Yasuhisa Fujita Yasuhisa Fujita
Published: October 2002

Low-temperature growth of ZnS on quartz and GaAs substrates has been carried out by photoassisted metal-organic chemical vapor deposition (MOCVD) using an ArF excimer laser. Hydrocarbon incorporation in the films, however, makes it difficult to perform crystal growth at temperatures of less than 400° C. This hydrocarbon incorporation was prevented by decomposition of metalorganics on the substrate by simultaneous irradiation of an ultrahigh-pressure mercury lamp on the substrate surface. Using this technique, crystal growth of ZnS was achieved at growth temperatures in the range of 100–150° C.
Growth of SrCuO2 Thin Films on Oxygen-Annealed SrTiO3 (100) Substrates
Authors: Kawayama Iwao , Masaki Kanai Masaki Kanai , Tomoji Kawai Tomoji Kawai
Published: October 2002

The effect of annealing on the surface of SrTiO3 (100) substrates and initial growth of SrCuO2 thin films on the SrTiO3 were studied by reflection high-energy electron diffraction (RHEED) and atomic force microscopy (AFM). The terraces of SrTiO3 (100) substrates annealed at 1000° C in O2 atmosphere has atomically flat surfaces with high crystallinity and steps one unit cell high (3.9 Å) . The deposition of SrCuO2 on the annealed substrates forms islands near the steps with a height of 4–7 Å resulting in surface roughening in spite of the flat substrate surface. By depositing Sr as a buffer layer on the annealed substrates, the flatness of SrCuO2 thin films was improved.
A Digital Method of Gas Laser Etching for Oxide Superconductors
Authors: Oohira Tsunehiro , Sakai Shigeki , Kasai Yuji , Tetuo Shimizu Tetuo Shimizu , Hiroshi Tokumoto Hiroshi Tokumoto , Keizo Shimizu Keizo Shimizu
Published: October 2002

Using a gas-assisted laser etching system, a digital etching method was demonstrated for Bi-Sr-Ca-Cu-O superconducting thin films. The etched surface was examined using an atomic force microscope. When NF3 was used as the reactive gas, there was a laser fluence region in which the etching rate was nearly constant. This result suggests the existence of a self-stopping mechanism in the etching process, indicating the possible development of this method into a precise layer-by-layer etching technology for high-T
c superconducting materials.
Improvement of Hot-Electron Hardness in Metal-Oxide-Semiconductor Devices by Combination of Gate Electrode Deposited Using Amorphous Si and Gate Oxide Grown in N2O
Authors: Kuei-Shu Chang-Liao Kuei-Shu Chang-Liao , Tang-Yuan Lan Tang-Yuan Lan
Published: October 2002

A new technique, namely the combination of a gate electrode deposited using amorphous-Si and a gate oxide grown in N2O, is proposed and shown to improve the hot-electron hardness in metal-oxide-semiconductor (MOS) devices. It is found experimentally that MOS capacitors fabricated using this technique exhibit excellent charge-to-breakdown performance. The number of hot-electron-induced interface traps and the flat-band voltage shift are also reduced. The hardness improvement can be explained using a mechanism based on the increase in compressive stress in the oxide, the suppression of hydrogen effects, and the relaxation of SiO2/Si interfacial strain.
High Tc Superconducting Flash A/D Converter Using Planar Quasi-One Junction Superconducting Quantum Interference Devices (SQUIDs)
Authors: Umezawa Toshimasa , Tadashige Fujita Tadashige Fujita , Yasushi Higashino Yasushi Higashino
Published: October 2002

We have designed and fabricated a planar HTS (DyBaCuO) superconducting quasi-one junction (QOS) Superconducting Quantum Interference Device (SQUID) for a flash A/D converter using step-edge Josephson junctions. The simulation suggests that the HTS QOS bandwidth is limited with 2.6 GHz by an external shunted capacitor. To fabricate a 1–2 µ m size SQUID inductance hole and step-edge junctions, a stepper photo-lithography process was employed. To make a sensitive comparator, a flux transformer was directly installed on the QOS, whose magnetic field gain of 833 was in agreement with the designed value of 828. The basic analog to digital conversion test of the QOS comparator was confirmed at a frequency of 10 kHz–1 MHz at 77 K. The dynamic range was estimated as 2Φ0.
Role of E/Z Photoisomerization of Cinnamate Side Chains Attached to Polymer Backbones in the Alignment Photoregulation of Nematic Liquid Crystals*1
Authors: Ichimura Kunihiro , Akita Yasuhiro , Akiyama Haruhisa , Yuko Hayashi Yuko Hayashi , Kazuaki Kudo Kazuaki Kudo
Published: October 2002

The mechanism of azimuthal reorientation of nematic liquid crystals induced by linearly polarized light irradiation of thin films of polymers with cinnamate side chains has been discussed. It has been concluded that the photoalignment is induced not by the polarized photodimerization, but by polarized photoisomerization, based on the following results. First, spectral analysis of olefinic chromophores upon UV irradiation has shown that a predominant photochemistry in films is the E/Z photoisomerization which results in the dichroism of the chromophores. Second, the alignment direction can be altered by subsequent irradiation with polarized light with a different electric vector. Photodimerization plays a role in enhancing the thermal stability of photoalignment.
Characteristics of the Electric Capacitance and Dielectric Loss of the Thermal Oxide of Porous Silicon Formed Using Highly Phosphorus Diffused Silicon
Authors: Kuranari Yoshinobu Arita
Published: October 2002

The anodic reaction condition dependence and the oxidation time dependence of the electric capacitance and the dielectric loss factor have been investigated for the thermal oxide of porous silicon formed with highly phosphorus diffused silicon. A high degree of phosphorus diffusion in the anodic reaction region in advance of the reaction is an effective way to decrease oxide capacitance produced by the oxidation of porous silicon formed using n-type silicon. The frequency dependence of the electric capacitance and the dielectric loss are discussed. A model based on interstitial conduction is investigated to explain the experimental results regarding the frequency dependence of capacitance and tan δ.
Atmosphere Dependence in Phosphorus Pileup at the Silicon Surface during Isochronal Heating
Authors: Yoshiyuki Sato Yoshiyuki Sato , Manabu Itsumi Manabu Itsumi
Published: October 2002

The heating atmosphere dependence of the amount of implanted phosphorus that piles up at the silicon surface during a 3-min heating at 800–1000 °C is investigated. The amount is found to be larger in oxygen than in nitrogen at 900 °C. It is concluded this is due to a larger amount of phosphorus coming to the surface from inside the silicon in oxygen as a result of oxidation enhanced diffusion and transient enhanced diffusion. Phosphorus depth profiles support this conclusion.
Proposal of Semiconductor Directional-Coupler-Type All-Optical Switch with Tapered-Waveguide Structures
Authors: Toshiyuki Takizawa Toshiyuki Takizawa , Akira Uchino Akira Uchino , Shigehisa Arai Shigehisa Arai
Published: October 2002

We propose a semiconductor directional-coupler-type all-optical switch with tapered structures which is based on the nonlinear refractive index variation induced by photoexcited carriers. A recurrence equation describing the device is derived from “Marcatili's” coupling mode theory and studied by numerical simulations. It is shown that the introduction of tapered structures is effective for improving the extinction ratio. It is also found that this device can drive a signal light at a power about 17 dB higher than the control light power.
Reflective Direct-View Display using a Mixed-mode Twisted Nematic Cell
Authors: Kuo Chen-Lung , Wei Chung-Kuang , Wu Shin-Tson , Wu Chiung-Sheng
Published: October 2002

A new reflective direct-view display using a mixed-mode twisted-nematic liquid crystal cell is demonstrated. This display mode exhibits high contrast, wide viewing angle, fast response time, good gray scale, good colorimetry performance while eliminating parallax. Computer simulations and confirming experimental results are presented.
Numerical Investigation and Model Approximation for the Hysteretic Current-Voltage Characteristics of Josephson Junctions with Nonlinear Quasiparticle Resistance
Authors: Yoshinao Mizugaki Yoshinao Mizugaki , Koji Nakajima Koji Nakajima
Published: October 2002

We present a model analysis for the current-voltage (I-V) characteristics of Josephson junctions having superconductor-insulator-superconductor (SIS) structure. The numerical result for the V
m value, which is the product of the maximum supercurrent and the observed subgap resistance, shows a marked decrease with increasing junction critical current density (J
c). The marked decrease is independent of leak current. Increasing J
c reduces the junction capacitance C
J and enlarges the amplitude of the junction voltage oscillation. Nonlinearity of the quasiparticle resistance restricts the voltage oscillation amplitude to the gap voltage, which results in the rapid decrease of the V
m value. In this paper, we introduce a sinusoidal oscillation model for the junction voltage, and derive the approximated expressions for the V
m value. The model approximation results agree well with the numerical results.
Hydrogen-related Degradation and Recovery Phenomena in Pb(Zr,Ti)O 3 Capacitors with a Platinum Electrode
Authors: Hiroshi Miki Hiroshi Miki , Keiko Kushida-Abdelghafar Keiko Kushida-Abdelghafar , Kazuyoshi Torii Kazuyoshi Torii , Yoshihisa Fujisaki Yoshihisa Fujisaki
Published: October 2002

Pb(Zr,Ti)O3 capacitors with top platinum electrodes area subjected to hydrogen annealing from 300°C to 450°C. Both the remnant polarization and breakdown voltage were drastically degraded after hydrogen annealing, whereas the dielectric constant was found to be relatively stable. Capacitors recovered their characteristics before annealing after re-oxidation treatment. An interfacial degradation model with a platinum-catalysis reduction is proposed to explain these notable degradation phenomena.
Preparation of Piezoelectric Thick Films using a Jet Printing System
Authors: Adachi Hideo , Kuroda Yoshimi , Takuya Imahashi Takuya Imahashi , Kazuhisa Yanagisawa Kazuhisa Yanagisawa
Published: October 2002

Pb(Zr, Ti)O3 piezoelectric thick films were prepared on Pt/Cr/SiO2/Si substrate using an improved jet printing system (JPS). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis and measurements of electrical properties, including dielectricity, ferroelectricity and piezoelectricity, were carried out on these films. A very high deposition rate of 3 µm/min and films with thicknesses above 100 µm were obtained without peeling. However, the films prepared in this fashion demonstrate lower piezoelectric behavior than bulk PZT ceramics. The reason for this has been explored using element analysis. Furthermore, we have developed a mask depositing technique as a surface leveling.
Effects of LaNiO3 Conductive Buffer Layer on The Structural and Electrical Characteristics of Ba0.4Sr0.6TiO3 Thin Films Prepared by RF Magnetron Sputtering
Authors: Chii-Ming Wu Chii-Ming Wu , Tai-Bor Wu Tai-Bor Wu
Published: October 2002

Sputter-deposited LaNiO3 (LNO) was used as a conductive buffer layer for the deposition of 80-nm-thick Ba0.4Sr0.6TiO3 (BST) thin films on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering. Smooth and highly (100)-oriented perovskite films of BST were grown on the (100)-textured LNO by deposition at temperatures ≧200 °C. However, a relatively rough and weakly crystallized BST film was obtained by deposition directly on Pt/Ti/SiO2/Si substrates at 500 °C. Satisfactory dielectric constants of 160 to 320 were achieved for films deposited on LNO at temperatures from 350 to 550 °C, while a low dielectric constant of 120 was obtained for the film deposited on Pt at 500 °C. All the films in a Pt/BST/LNO or Pt/BST/Pt capacitor configuration basically showed a similar ohmic conduction characteristic of low conductivity in low bias regime up to a transition voltage around 1–3 V, and beyond that a nonohmic conduction with current rapidly increasing against the applied bias occurred. However, the films deposited on LNO would have a more moderate nonohmic conduction than that of the film deposited on Pt.
Microstructures and Electrical Properties of V2O5-based Multicomponent ZnO Varistors Prepared by Microwave Sintering Process
Authors: Chen Chang-Shun , Kuo Cheng-Tzu , Wu Tai-Bor , Lin I-Nan
Published: October 2002

The V2O5-based ZnO varistor materials were successfully densified using microwave sintering process. The materials can reach a high density as 94.6% T.D. (theoretical density) when sintered at 800 °C (10 min) but the grain growth was initiated only when sintered at a higher temperature than 1000 °C (10 min). The varistor characteristics, including breakdown voltage (V
bk), nonlinear coefficient (α) and leakage current density (J
L), degraded markedly for the samples sintered at too high temperature (i.e., T≥1000 °C) and for too long period (i.e., t≥10 min) that was ascribed to the occurrence of abnormal grain growth. Contrarily, the intrinsic characteristics, including potential barrier height (φ b) and donor density (N
d), varied only moderately with these sintering conditions. The V2O5-based ZnO materials sintered at 1000 °C (5 min) possessed good varistor characteristics as V
bk=248 V/mm, α=31 and J
L=4.6×10-5 A/cm2. The corresponding intrinsic parameters are φ b=0.63 eV and N
d=2.37×1024 m-3.
Molecular Orientations and Optical Transmission Properties of Liquid Crystal Cells with Slit-Patterned Electrodes
Authors: Zhan He Zhan He , Toshiaki Nose Toshiaki Nose , Susumu Sato Susumu Sato
Published: October 2002

The molecular orientations in slit-patterned electrode liquid crystal (LC) cells with homogeneous initial alignment parallel to the slit pattern are investigated in detail using a 3-dimensional polarization observation method. In addition to conventional observations of interference fringes, we study the molecular orientations from cross sections of the LC cells using photoelasticity experimental techniques and a UV-curable LC material. A model of LC molecular orientations referred to as the electrically induced hybrid twisted nematic (EHTN) molecular orientation, is proposed. Moreover, optical transmission properties of such LC cells with different structural parameters are measured as a function of the applied voltage. The possibility of application of these kinds of LC cells to LC display devices is discussed.
Prephotobleaching Process in Polysilane Films
Authors: Hideki Hayashi Hideki Hayashi , Tetsuya Kurando Tetsuya Kurando , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

It has been found that the absorption of incident ultraviolet (UV) light by polysilane films with thicknesses comparable to the penetration depth of UV light does not decrease for a while and then decreases rapidly according to a power law under prolonged exposure to UV light, indicating the occurrence of the prephotobleaching process in the period of no change in the absorption. The transition time, when the absorption of UV light begins to decrease significantly, is inversely proportional to the incident photon flux, obeys a power law as a function of the film thickness and is temperature dependent. We explain the prephotobleaching process using the thermally assisted photoscission model where the σ bonds between domainlike σ-conjugated segments of silicon chains have lower activation energy than the σ bonds in the segments contributing to the absorption of UV light and are photoscissored first. The exponential distribution of activation energy is assumed for the two kinds of σ bonds. The minimum activation energy of the intrasegment σ-bonds has been estimated to be 75 meV as a result of the analysis of the experimental results obtained using this model.
Optimum Gaseous Pressure for Measurement of the X-Ray Excited Scanning Tunneling Microscope Tip Current
Authors: Kouichi Tsuji Kouichi Tsuji , Kazuaki Wagatsuma Kazuaki Wagatsuma
Published: October 2002

When X-rays irradiate a sample surface of a scanning tunneling microscope (STM), a current between the STM tip and the sample is detected. This current originates from the electron emission from the sample surface, and can be used for surface analysis. The STM tip current was amplified using gaseous molecules; however, the direct ionization of molecules in the air affected the tip current measurement at normal air pressure. It was found that the optimum gaseous pressure was near 5 kPa, where the influence of the direct ionization could be ignored, although the amplification effect still occurred.
Characteristics of 1-MHz Discharges in SF 6/Ar and CF 4/Ar Mixtures in a Parallel-Plate System
Authors: Kenji Aoyagi Kenji Aoyagi , Itsuo Ishikawa Itsuo Ishikawa , Hideki Kusunoki Hideki Kusunoki , Yukinori Saito Yukinori Saito , Shinji Suganomata Shinji Suganomata
Published: October 2002

In SF6/Ar and CF4/Ar mixtures at a total pressure of 0.5 Torr, the discharge characteristics at 1-MHz have been investigated as a function of the mixing ratio. In the case of the SF6/Ar mixture, discharge parameters, such as discharge-sustaining voltage and discharge current, suddenly decrease by mixing only 5% SF6 with Ar, and the plasma exists uniformly only inside the gap between electrodes. By increasing the SF6 ratio, the electron temperature rises, and tends to saturate at large SF6 ratios. In the case of the CF4/Ar mixture, the plasma density near the discharge axis is lower than that around the edge of the electrode at small CF4 ratios. At a CF4 ratio of 20%, in particular, the plasma density in the interelectrode gap becomes very low, and the spatiotemporal emission profile across the gap around the edge of the electrode is different from that at the axis. At CF4 ratios greater than 60%, the discharge parameters suddenly change due to the electronegativity of CF4. These characteristics are synergistic.
Polysilicon Encapsulated Local Oxidation of Silicon for Deep Submicron Lateral Isolation
Authors: Gonçal Badenes Gonçal Badenes , Rita Rooyackers Rita Rooyackers , Ingrid De Wolf Ingrid De Wolf , Ludo Deferm Ludo Deferm
Published: October 2002

In this paper it will be shown that polysilicon encapsulated local oxidation of silicon (PE-LOCOS) is a feasible lateral isolation technique for quarter-micron or smaller complementary metal-oxide-semiconductor (CMOS) technologies. This isolation technique features limited process complexity and very good manufacturability and reproducibility, together with excellent bird's beak and active area dimension control. Electrical measurements performed on perimeter intensive gate oxide capacitors and diodes show no isolation-edge-related degradation, which is confirmed by Raman spectroscopy and emission microscopy measurements. Transistor narrow-channel data from devices fabricated with PE-LOCOS are presented and discussed.
Effects of Electrode Materials and Annealing Ambients on the Electrical Properties of TiO2 Thin Films by Metalorganic Chemical Vapor Deposition
Authors: S. C. Sun S. C. Sun , T. F. Chen T. F. Chen
Published: October 2002

In this work, we investigate the effects of the top electrode materials and annealing ambients on the electrical properties of chemical-vapor-deposited (CVD) TiO2 films. Experimental results indicate that the leakage current is mainly determined by the work function of electrode materials before sintering. The capacitor with TaN top electrode reveals the least leakage. After 450° C and 800° C sintering in N2, owing to its thermal stability, WN is found to be the optimal material for withstanding high-temperature thermal treatment. From the annealing ambient results, N2O was more effective than O2 in reducing leakage current, and furnace annealing in N2O ( FN2O) produces the smallest leakage. Such a phenomenon is primarily owing to the reduction of oxygen vacancies and carbon concentration in TiO2 by the atomic oxygen generated by the dissociation of N2O during the thermal cycle, thereby improving film quality.
Local Atomic Bonding in Fluorinated Silicon Oxides: Bond-Ionicity-Controlled Contributions of Infrared-Active Vibrations to the Static Dielectric Constant
Authors: Yang Gerald Lucovsky
Published: October 2002

There is considerable interest in insulating films with static dielectric constants lower than that of SiO2. One alloy system that has attracted much recent attention is F-doped SiO2 or Si–O–F. This paper i) reviews the published experimental results for the infrared optical properties of Si–O–F alloys, ii) discusses the bonding arrangements of F atoms in the SiO2 network structure, iii) develops a procedure for characterizing the composition of these materials in a pseudo-binary alloy notation, iv) explains the reductions in the dielectric constant induced by F atoms in terms of bond-ionicity-controlled contributions from electronic and vibrational dipole transitions, and v) addresses briefly the chemical stability of the films.
A Novel Optical Adaptive Neuro-Device Using a Split-Gate MOS Transistor
Authors: Shin Jang-Kyoo , Io Eiji , Tsuji Kiyotaka , Sugiura Takayasu , Hiroo Yonezu Hiroo Yonezu , Naoki Ohshima Naoki Ohshima
Published: October 2002

An optical adaptive neuro-device in which a split-gate MOS transistor is used to generate and inject hot electrons is presented. The proposed adaptive neuro-device has been fabricated by a double poly Si n-channel MOS process, and its operation has been experimentally verified. It has also been successfully applied to a synaptic connection circuit keeping the sum of synaptic weights in a neuron constant with time. Since it occupies much less area than previous adaptive neuro-devices based on electron tunneling and possesses promising characteristics, this device may be suitable as a fundamental synaptic connection device for the hardware implementation of large-scale artificial neural networks.
Performance of a Novel Optical Compensation Film Based on Negative Birefringence of Discotic Compound for Wide-Viewing-Angle Twisted-Nematic Liquid-Crystal Displays
Authors: Mori Hiroyuki , Itoh Yoji , Nishiura Yosuke , Nakamura Taku , Yukio Shinagawa Yukio Shinagawa
Published: October 2002

The performance of a novel optical compensation film utilizing a negatively birefringent discotic compound was optimized by both simulation and experiment to achieve wide-viewing-angle characteristics of twisted-nematic liquid-crystal displays (TN-LCDs). It was shown that the film remarkably enlarges the viewing angle of TN-LCDs when the discotic compound layer has hybrid molecular orientation which is a similar structure to that of on-state liquid crystals of TN-LCDs.
Characterization of Interface Electronic Properties of Low-Temperature Ultrathin Oxides and Oxynitrides Formed on Si(111) Surfaces by Contactless Capacitance-Voltage and Photoluminescence Methods
Authors: Yoshida Toshiyuki , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Using contactless capacitance-voltage (C-V), photoluminescence surface state spectroscopy ( PLS3) and X-ray photoelectron spectroscopy techniques, interface electronic properties of ultrathin-insulator films formed on Si (111) surfaces at low temperatures were characterized, paying particular attention to the effect of nitrogen-related plasmas. Hydrogen termination was used as the initial surface treatment. Low-temperature (400° C) thermal oxidation processes produced oxide/Si interfaces with a high-density of interface states that caused limited C-V variation and low PL efficiency. Treatment of low-temperature thermally grown oxides in electron cyclotron resonance (ECR) N2 plasma had no effect on the interface properties. On the other hand, marked enhancement of C-V variation and PL efficiency was achieved at the surface after ECR N2O-plasma oxynitridation at 400° C. The correlation between chemical and electronic properties of the interfaces is discussed.
Excimer Laser Induced Crystallization of Polycrystalline Silicon Films by Adding Oxygen
Authors: Jun Hong-Seok Choi , Park Cheol-Min , Byung-Hyuk Min Byung-Hyuk Min , Min-Koo Han Min-Koo Han
Published: October 2002

We have investigated the behaviors of the grain-growth and the electrical properties in excimer laser-induced polycrystalline silicon films by adding oxygen (poly- SiO
x
). The melting and solidification times in laser-induced crystallization were increased by adding oxygen into amorphous silicon films which promoted the grain-growth. The dark conductivity of poly- SiO
x
films was decreased with the increase of oxygen concentration up to 6.32×1020 cm-3. However, the degradation of dark conductivity by light stress was improved in poly- SiO
x
films probably due to the stable silicon networking. We have also observed that the electrical stability was enhanced in the poly- SiO
x
films with oxygen concentration of 9.1×1019 cm-3 without much decrease of dark conductivity.
Proposal and Demonstration of AlAs-Oxide Confinement Structure for InP-Based Long Wavelength Lasers
Authors: Ohnoki Noriyuki , Mukaihara Toshikazu , Hatori Nobuaki , Mizutani Akimasa , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

We have demonstrated an AlAs oxidation process for current and light confinement in the AlGaInAs/InP system for the first time. A lattice-mismatched 200-Å-thick AlAs layer grown on an InP substrate by metalorganic chemical vapor deposition (MOCVD) was selectively oxidized. The temperature dependence of the oxidation rate was examined. The oxidized AlAs showed good electric isolation characteristics for lateral current confinement. The proposed AlAs-oxide confinement structure formed on an InP substrate may facilitate fabrication and threshold reduction of long wavelength lasers including vertical-cavity surface-emitting lasers.
Two-Dimensional Analytical Subthreshold Model and Optimal Scaling of Fully-Depleted SOI MOSFET Down to 0.1 µm Channel Length
Authors: Sergey Pidin Sergey Pidin , Mitsumasa Koyanagi Mitsumasa Koyanagi
Published: October 2002

New two-dimensional analytical model for the potential distribution and the subthreshold factor in SOI MOS field-effect transistor (SOI MOSFET) is developed. The model accounts for the nonlinear potential distribution inside the buried oxide without use of any fitting parameters. The analytical model is compared to the numerical device simulation results and a good agreement is found. Our model accurately describes the effect of the subthreshold factor decrease with increasing the substrate doping concentration in thin-film fully-depleted SOI MOSFETs. The model can be utilized to predict design criteria for scaling down thin-film fully depleted SOI MOSFETs and is suitable for use in circuit simulators such as SPICE.
Analysis of The Threshold Voltage Adjustment and Floating Body Effect Suppression for 0.1 µm Fully Depleted SOI-MOSFET
Authors: Risho Koh Risho Koh , Hiroshi Matsumoto Hiroshi Matsumoto
Published: October 2002

The short channel effect for the fully depleted silicon-on-the-insulator metal-oxide-silicon field-effect-transistor (SOI-MOSFET) is analyzed based on a simple analytical model (capacitance network model). It is found that the origin of the short channel effect can be separated into two components. One is the potential modification due to the electric field between the gate electrode and S/D (source and the drain electrode), and the other is the degradation in the vertical component of the electric field of the acceptor. The capacitance network model considering the above two components explains the short channel effect down to the 0.1 µ m regime. The dopant concentration required to adjust threshold voltage is also given by this model. Moreover, based on the above analysis, a new structure to reduce the short channel effect with suppressing the floating body effect is proposed.
Correlation of W-Si-N Film Microstructure with Barrier Performance against Cu Diffusion
Authors: Shimooka Yoshiaki , Iijima Tadashi , Nakamura Shinichi , Kyoichi Suguro Kyoichi Suguro
Published: October 2002

The relationship between the microstructure of WSi0.6N films and the barrier property against Copper (Cu) diffusion is discussed in this paper. While WSi0.6N is amorphous below 850° C, W microcrystals in amorphous WSiN occur at 850° C. Their average grain sizes increase from 3 nm to 8 nm and their numerical densities also increase from 200/µ m2 to 7400/µ m2 at temperatures ranging from 850° C to 880° C. From the X-ray photoelectron spectroscopy (XPS) measurements, it is thought that the W of Si–W bonds in WSiN films is transformed into metallic W. The amount of Cu that diffused through the WSiN layer into Si was calculated by integrating the depth profiles of Cu measured using secondary ion mass spectroscopy (SIMS). The activation energy of the diffused Cu was constant at 2.8 eV in the temperature range of 700–900° C. Consequently, the excellent barrier property is thought to be due to the absence of continuous grain boundaries throughout the film where Cu atoms can easily migrate. That is, the W microcrystal formation does not change the Cu diffusion mechanism up to 900° C, and the Cu diffusion is controlled by diffusion of it in an amorphous matrix.
In-Situ Fabrication of Gate Oxide and Poly-Si Film by XeCl Excimer Laser Annealing
Authors: Park Cheol-Min , Min Byung-Hyuk , Yoo Juhn-Suk , Hong-Seok Choi Hong-Seok Choi , Min-Koo Han Min-Koo Han
Published: October 2002

We have proposed a new method to form the gate oxide and recrystallize the polycrystalline silicon (poly-Si) active layer simultaneously. During the irradiation of excimer laser, the poly-Si film is recrystallized while the oxygen ion impurities, which are injected into the amorphous silicon (a-Si) film, are activated by laser energy and react with silicon atoms to form SiO2. Our experimental results show that a high quality oxide, a poly-Si film with fine grain, and a smooth and clean interface between oxide and poly-Si film have been successfully obtained by the proposed fabrication method. The maximum oxide breakdown electric field which exceeds 7 MV/cm is obtained.
Suppressing Ion Implantation Induced Oxide Charging by Utilizing Physically Damaged Oxide Region
Authors: Takase Michihiko , Koji Eriguchi Koji Eriguchi , Bunji Mizuno Bunji Mizuno
Published: October 2002

We report effects of ion implantation induced damage on gate leakage current in Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) without sidewall-oxidation. It is found that the region of “physical damage” induced by the 10 keV arsenic ions implantation process is the depth of 10 nm. A “oxide charging” has been suppressed by utilizing the physical damage as “a path of the conduction current from the plasma” which can be removed by means of wet etching after the ion implantation process. This newly developed technique is able to prevent both oxide charging of the gate oxide and direct ion impact damage of gate oxide.
Effective KOH Etching Prior to Modified Secco Etching for Analyzing Defects in Thin Bonded Silicon on Insulator (SOI) Wafers
Authors: Mitani Kiyoshi , Hiroji Aga Hiroji Aga , Masatake Nakano Masatake Nakano
Published: October 2002

The modified Secco etching which was developed for detecting threading dislocations in separation by implanted oxygen (SIMOX) wafers showed etch pits with a density of 103–106/ cm2 when it was applied to bonded silicon on insulator (SOI) wafers thinner than 1 µ m produced by the plasma assisted chemical etching (PACE) process including touch polishing. When these pits were observed, a group of pits appeared as a scratch pattern. Also the density of pits was dependent on the remaining SOI thickness after the first diluted Secco etching in the modified Secco etching process. These results indicated that the density of defects had a certain distribution in the SOI thickness direction and that the defects were different from threading dislocations which reached buried oxides from the surface. In order to observe the distribution of defect density in the SOI depth direction, KOH etching was utilized prior to the modified Secco etching. Using this method, it was found that surface defects were predominant and bulk defects were also present in thin bonded SOI layers.
New Electrically Thinned Intrinsic-Channel SOI MOSFET with 0.01 µm Channel Length
Authors: Tamio Shimatani Tamio Shimatani , Sergey Pidin Sergey Pidin , Mitsumasa Koyanagi Mitsumasa Koyanagi
Published: October 2002

In an ultrasmall device with a channel length of 0.01 µm, only one impurity atom on the average exists in the channel region even though the impurity concentration is higher than 5.0×1018 cm-3. Therefore, the device characteristics significantly change from device to device within a wafer, or even within a chip, due to the statistical variation of the impurity concentration. We investigated the influences of isolated atoms in the channel region on the device characteristics based on a Monte Carlo simulation and propose a new 0.01 µm silicon-on-insulator metal oxide semiconductor field-effect transistor (SOI MOSFET) with undoped channel to suppress the influences of statistical variation and the short channel effect.
Dual-Gate Shorted Anode SOI Lateral Insulated Gate Bipolar Transistor Suppressing the Snap-Back
Authors: Lee Byeong-Hoon , Byeon Dae-Seok , Kim Doo-Young , Lee Won-Oh , Choi Min-Koo Han
Published: October 2002

A new dual gate shorted anode silicon on insulator (SOI) lateral insulated gate bipolar transistor (LIGBT), which suppresses effectively the snap back without sacrificing the forward voltage drop, the switching speed and the breakdown voltage, is proposed and verified by numerical simulation. The numerical simulation results show that the snap-back is reduced less than the anode voltage of 2.5 V while the snap-back occurs at anode voltage of about 4 V for the conventional structure with the drift length of 35 µ m. We have verified that the snap-back is suppressed due to the enhancement of the hole injection and investigated the snap-back as a function of the device parameters such as the n- drift region doping concentration and drift region length.
Fabrication and Characterization of GaAs Single Electron Devices Having Single and Multiple Dots Based on Schottky In-Plane-Gate and Wrap-Gate Control of Two-Dimensional Electron Gas
Authors: Kasai Seiya , Jinushi Kei-ichiroh , Hidemasa Tomozawa Hidemasa Tomozawa , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Single-dot and multiple (2, 3, 18, and 37)-dot single electron transistors (SETs) based on the control of a two-dimensional electron gas (2DEG) with a recently proposed Schottky in-plane gate (IPG) and a newly introduced Schottky wrap gate (WPG) were successfully fabricated on AlGaAs/GaAs wafers using electron beam (EB) lithography and their transport properties were investigated. Each of the fabricated SETs showed Coulomb blockade-like conductance oscillation. In single-dot SETs, a strong correlation was found between the device dimensions and the temperature limit of the conductance oscillation. Conductance oscillation characteristics of multiple-dot SETs were complicated, and were not explained by the classical Coulomb blockade theory. Based on a simplified theoretical analysis using computer simulation, it was shown that quantized energy due to electron confinement and dot-coupling can dominate the charging effect in the fabricated SETs.
Luminescent Properties of ZnxSr 1-xS:Ce Thin Film Phosphors for Electroluminescent Devices
Authors: Tae Lee Sang , Masahiko Kitagawa Masahiko Kitagawa , Kunio Ichino Kunio Ichino , Hiroshi Kobayashi Hiroshi Kobayashi
Published: October 2002

The dependence of the luminescent properties of Ce-doped Zn
x
Sr1-x
S thin films on composition and annealing temperature is investigated. It has been found that the emission intensity of Ce3+ photoluminescence is enhanced by the incorporation of an optimum amount of Zn and by the increase of the post-annealing temperature. The luminescent intensity depends strongly on the crystallinity of the films and on the valence state of Ce ions. Fabrication of electroluminescent devices introducing Zn
x
Sr1-x
S as a host material has been attempted.
Boron Implantation into GaAs/Ga0.5In0.5P Heterostructures
Authors: Henkel Achim , Delage Sylvain Laurent , di Forte-Poisson Marie Antoinette , Hartnagel Hervé Blanck
Published: October 2002

The electrical effect of implantation of boron ions with energies from 100 keV to 360 keV into GaAs and Ga0.5In0.5P has been studied. The implantation dose varied from 5×1011 cm-2 to 5×1013 cm-2. Resistivities higher than 1×105 Ω cm for both n-type GaAs and n-type GaInP were measured. C–V and breakdown voltage measurements were used to characterize the electrical properties of implanted n GaInP. GaInP appears to be more sensitive to boron implantation than GaAs, and higher resistivities can be obtained with lower boron doses. Boron implantation at 200 keV followed by a 10-min annealing (T=416 ° C) generates a mid-gap trap level at 1.04±0.02 eV below the GaInP conduction band for Q=2×1012 cm-2 and a trap level at 0.92±0.02 eV for Q=5×1012 cm-2. Low-dose boron ion implantation can give rise to a GaInP passivation-like layer.
Successful Surface Passivation of Air-Exposed AlGaAs by a Silicon Interface Control Layer-Based Technique
Authors: Ikeya Kengo , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

In order to make the silicon interface control layer (Si ICL)-based surface passivation technique applicable to air-exposed AlGaAs surfaces, various surface treatments were systematically studied. The treatments investigated include UHV thermal cleaning, ( NH4)2 S
x
treatment, HCl treatment and H2 plasma treatment. Chemical status and quality of the treated surfaces were evaluated by in-situ and ex-situ X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements. A strong correlation was found between the band-edge PL intensity and the amount of surface oxide components, in particular Al-oxides. Marked reduction of the amount of oxide components and enhancement of PL intensity were realizable by a combination of HCl surface treatment and Si ICL formation.
Dominant Electron Trap with Metastable State in Molecular Beam Epitaxial GaAs Grown at Low Temperatures
Authors: Hashizume Tamotsu , Shunsuke Shiobara Shunsuke Shiobara , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Photocapacitance transient behavior of the dominant S1 electron trap with an activation energy of 0.64 eV in low-temperature GaAs (LT-GaAs) grown by molecular beam epitaxy (MBE), which we recently detected by deep-level transient spectroscopy, was investigated in detail. It was found that the S1 trap has metastable properties causing a marked photoquenching behavior. Transition processes between the ground state and the metastable state were found to be very different from those of EL2, indicating that the dominant S1 trap is not EL2, but a new deep level peculiar to the LT-GaAs layer.
Octahedral Void Structure Observed in Grown-In Defects in the Bulk of Standard Czochralski-Si for MOS LSIs
Authors: Ueki Takemi , Itsumi Manabu , Takeda Tadao
Published: October 2002

We analyzed the structure of octahedral voids in the bulk of standard silicon wafers. They are often twin type and are about 100 nm in size. The structure of the defect is incompletely octahedron, and is mainly surrounded by { 111 } planes. Our electron diffraction and energy-dispersive X-ray spectroscopy analyses suggest that the octahedron defect is void. A 2-nm-thick layer exists on each of the side walls of the void defect. Our auger electron spectroscopy analysis suggests that the 2-nm-thick layer is SiO2. It is believed that the void structure is formed during Si-ingot growth.
Extremely Flat Interfaces in InxGa 1-xAs/Al 0.3Ga 0.7As Quantum Wells Grown on (411)A GaAs Substrates by Molecular Beam Epitaxy
Authors: Tatsuya Saeki Tatsuya Saeki , Takeharu Motokawa Takeharu Motokawa , Takahiro Kitada Takahiro Kitada , Satoshi Shimomura Satoshi Shimomura , Akira Adachi Akira Adachi , Yasunori Okamoto Yasunori Okamoto , Naokatsu Sano Naokatsu Sano , Satoshi Hiyamizu Satoshi Hiyamizu
Published: October 2002

Effectively atomically flat interfaces over a macroscopic area (super-flat interfaces) have been achieved in pseudomorphic In
x
Ga1-x
As/Al0.3Ga0.7As (x = 0.0, 0.04, 0.07) quantum wells (QWs) with well widths (L
w) of 1.2–11.8 nm grown on (411)A GaAs substrates at 520°C by molecular beam epitaxy (MBE). A single, sharp photoluminescence (PL) peak was observed for each QW over the large area of the wafer (8 mm ×5 mm). The linewidths for narrow QWs (L
w = 2.4 nm) were 8.9 meV (x = 0.04) and 9.9 meV (x = 0.07) at 4.2 K, which were about 30% smaller than those of QWs simultaneously grown on conventional (100) GaAs substrates.
Sidegating-Induced Negative Differential Resistance in MBE-Grown InAs/AlSb HFETs
Authors: Bolognesi Colombo R. , Dvorak Martin W. , Chow David H.
Published: October 2002

We report sidegating measurements on mesa-isolated InAs/AlSb-based heterojunction field effect transistors (HFETs) grown on GaAs semi-insulating substrates with thick strain-relaxed AlSb buffer layers. We find that the AlGaSb/AlSb buffer layers provide adequate inter-device isolation for low sidegate voltages |V
SG|<5 V. For sidegate electrode voltages of ±20 V, the substrate leakage current remains lower than 100 nA for a sidegate separation of only 4 µ m from the active channel. For large positive sidegate voltages, a marked sidegating-induced negative differential resistance (SINDR) appears in the drain characteristics. The peculiar frequency and temperature dependencies of the SINDR effect indicate that the negative differential resistance is caused by a transient occupation of deep level centers by holes injected into the buffer layers from the sidegate electrode. In contrast, large negative sidegate voltages have a negligible impact on the HFET drain characteristics. The present results illustrate the importance of buffer layers in InAs/AlSb HFETs and call for a deep level transient spectroscopy characterization of deep centers in InAs/AlSb HFET buffer layers.
Dependence of Resonant Interband Tunneling Current on Barrier and Well Width in InAs/AlSb/GaSb/AlSb/InAs Double-Barrier Structures
Authors: Hiroto Kitabayashi Hiroto Kitabayashi , Takao Waho Takao Waho , Masafumi Yamamoto Masafumi Yamamoto
Published: October 2002

Dependence of the peak current densities (I
p) on AlSb barrier and GaSb well widths (L
b and L
w) in InAs/AlSb/ GaSb/AlSb/InAs double-barrier resonant interband tunneling diodes was systematically investigated. We found that I
p increases exponentially and reaches 7.5×104 A/cm2, which is the highest value ever reported, as L
b decreases from 7 to 3 ML. We also found that I
p increases monotonically as L
w decreases from 46 to 10 ML. When L
w is less than 10 ML, however, I
p decreases with the decrease in L
w and thus has a maximum value for L
w of 10 ML. This behavior can be explained well in terms of one dominant resonance level. Agreement between the behaviors of the dominant resonance level and the calculated energy level for the ground state of light holes in the well indicates that I
p is mainly dominated by interband tunneling through the ground state of light holes.
Large Schottky Barrier Heights on Indium Phosphide-Based Materials Realized by In-Situ Electrochemical Process
Authors: Sato Taketomo , Uno Shouichi , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Pt Schottky barriers were formed on InP-based materials by a novel in-situ electrochemical process. The electrical characteristics, surfaces and interfaces of the Schottky diodes were investigated by current-voltage (I-V), capacitance-voltage (C-V), deep-level transient spectroscopy (DLTS) and atomic force microscopy (AFM) measurements. The mechanism for increasing the Schottky barrier heights (SBH) was explained in terms of possible ordered interface formation from the viewpoint of the disorder induced gap state (DIGS) model.
InAlAs/InGaAs HEMTs with Uniform Threshold Voltage Fabricated by Selective Wet-Etching Using Adipic Acid
Authors: Higuchi Katsuhiko , Uchiyama Hiroyuki , Shiota Takashi , Makoto Kudo Makoto Kudo , Tomoyoshi Mishima Tomoyoshi Mishima
Published: October 2002

Highly selective wet-etching of InGaAs on InAlAs was demonstrated using pH-controlled adipic acid, NH4OH, and H2O2solutions. A maximum selectivity of 250 was obtained by controlling the etching mechanism of InGaAs and InAlAs. This highly selective etching was applied to the fabrication of InAlAs/InGaAs high electron mobility transistors (HEMTs). The standard deviations of the threshold voltage (Vth) and peak extrinsic transconductance (gm) were as low as 38 mV and 11 mS/mm, respectively, in a 3-inch diameter wafer. The averagegmwas as high as 726 mS/mm which is comparable to or higher than that of conventional InAlAs/InGaAs HEMTs fabricated by non-selective etching.