bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Hydrogen in Dry Etching of Silicon Carbide Using Inductively and Capacitively Coupled Plasma
Authors: Mikami Hidenori , Hatayama Tomoaki , Yano Hiroshi , Uraoka Yukiharu , Fuyuki Takashi
Published: July 2005

We investigated the etching mechanism of SiC using inductively and capacitively coupled plasma with CHF3 and SF6 gases. We discussed the effects of O2 and H2 gases on etching properties. By optimizing the conditions of H2 flow rate, we could confirm the improvement in etching rates. Surface roughness was also improved by the optimum addition of H2 gas. Analysis by XPS revealed that a fluorocarbon film was formed on the surface after etching with SF6 gas. Surface fluoride atomic concentration was reduced from 28 to 8 at.% by the addition of H2 gas. A H2 annealing suppressed the fluoride concentration of surface to less than 3 at.%. This processing technique is very effective for the fabrication of SiC devices.
Molecular Beam Epitaxial Growth of Al-doped ZnMgO Alloy Films for Modulation-doped ZnO/ZnMgO Heterostructures
Authors: Koike Kazuto , Hama Kenji , Nakashima Ippei , Sasa Shigehiko , Inoue Masataka , Yano Mitsuaki
Published: July 2005

In this paper, we describe the characteristics of Al-doped n-type Zn1-x
Mg
x
O alloy films grown on a-plane sapphire substrates by molecular beam epitaxy, and the application of the films in modulation-doped ZnO/Zn1-x
Mg
x
O quantum wells (QWs). The results of Hall measurement for the Al-doped Zn0.8Mg0.2O alloy films revealed an excellent doping efficiency that the resistivity at 300 K decreased from 3.8×10-1 Ω·cm at 1.0×1018 cm-3 to 8.0×10-4 Ω·cm at 3.5×1020 cm-3. Although Al doping at higher than 1020 cm-3 resulted in a reduction in intensity and a broadening of the peak width of near-band-edge emission in cathodoluminescence with an increase in absorption-edge energy induced by the Burstein–Moss shift in optical transmittance, highly c-axis-oriented films without rotational domains were obtained in a wide range of doping levels. Such a successful doping was also confirmed for Zn1-x
Mg
x
O alloy films with a Mg content as high as 0.4. By applying Al doping to modulation-doped ZnO/Zn0.6Mg0.4O QWs, the sheet carrier density of the ZnO well was found to be proportional to the doping level in the Zn0.6Mg0.4O barrier layer.
Investigation of Chemical Vapor Deposition (CVD)-Derived Cobalt Silicidation for the Improvement of Contact Resistance
Authors: Kim Hyun-Su , Yun Jong-Ho , Moon Kwang-Jin , Sohn Woong-Hee , Jung Sug-Woo , Jung Eun-Ji , Kim Se-Hoon , Bae Nam-Jin , Choi Gil-Heyun , Kim Sung-Tae , Chung U-In , Moon Joo-Tae , Ryu Byung-Il
Published: July 2005

The improved contact resistance was obtained by the new barrier metal scheme such as CVD-Co/Ti/TiN process in the level of about half of that from CVD-Ti/TiN process. And the mechanism of contact silicidation of CVD-Co/Ti/TiN was investigated. Because Co silicide may prohibit the Si diffusion into Ti silicide and Si recess during TiCl4-based CVD-Ti process, and the inertness of Co silicide to the dopants, the improved contact resistance with uniform silicide morphology was obtained. Therefore, CVD-Co/Ti/TiN contact silicide process can be regarded as the next generation contact silicidation process.
Degradation of Low-Frequency Noise in Partially Depleted Silicon-on-Insulator Metal Oxide Semiconductor Field-Effect Transistors by Hot-Carrier Stress
Authors: Chen Kun-Ming , Hu Hsin-Hui , Huang Guo-Wei , Chang Chun-Yen
Published: July 2005

In this study, we determined the effects of hot-carrier stress on the low-frequency noise characteristics of partially depleted metal–oxide–semiconductor field-effect transistors (MOSFETs) in silicon-on-insulator (SOI) technology. In devices with a floating-body configuration, kink-related excess noise was observed due to the floating-body effect. The level of this excess noise decreased after normal-mode stress, while it was masked by 1/ f noise after reverse-mode stress. The effects of stress-generated interface traps on the drain-to-body leakage current and the floating-body effect were also determined and used to explain the noise behavior. Moreover, the stress-induced 1/ f noise degradation in floating-body devices and body-contact devices was studied. It was found that the 1/ f degradation of body-contact devices is more significant than that of floating-body devices after hot-carrier stress.
Micromachined Piezoelectric Microspeaker
Authors: Yi Seung Hwan , Kim Eun Sok
Published: July 2005

A diaphragm-based piezoelectric microspeaker is fabricated on a heavily compressive silicon–nitride film, and is compared to commercial speakers. The largest sound pressure level (SPL) produced by the fabricated microspeaker is 92 dB (when measured 2 mm away from the microspeaker in open field) at around 3 kHz for 6 Vpeak-to-peak input. The microspeaker produces a comparable sound output as a commercial piezo-ceramic and electro-dynamic speaker used in current cellular phones. The keys to this success are as follows: (1) the usage of a diaphragm that has a very high compressive residual stress, high enough to cause the diaphragm to be wrinkled and (2) the usage of high quality ZnO film deposited by two-step deposition technique.
Modulation Effects of Photocarriers on the Terahertz Plasma-Wave Resonance in High-Electron-Mobility Transistors under Interband Photoexcitation
Authors: Hanabe Mitsuhiro , Otsuji Taiichi , Ishibashi Takuma , Uno Tomohiro , Ryzhii Victor
Published: July 2005

Two-dimensional (2-D) electron plasma in a submicron channel of a high-electron mobility transistor (HEMT) is excited by interband photoexcitation, resulting in performing the photomixing function. The injected photoelectrons modulate the total 2-D electron density, affecting the plasma resonant properties. The modulation depth of the density of 2-D electrons by the photoelectrons deeply relates to the resonant intensity and f
r. This effect was modeled analytically in the 2-D plasma hydrodynamic equation. In order to validate the analytical calculation, the plasma-wave resonance was experimentally observed for a 0.15-µm gate-length InGaP/InGaAs/GaAs pseudomorphic HEMT in the terahertz range. At the modulation depth of 30%, the resonance was clearly observed with a double peak (the peak at 1.9/5.8 THz corresponding to the fundamental/third harmonic resonance). The resonant frequencies slightly shifted downward and the intensity attenuated with decreasing the modulation depth. Observed resonant frequencies support the analytical calculation.
Reliability of Strained SiGe Channel p-Channel Metal–Oxide–Semiconductor Field-Effect Transistors with Ultra-Thin (EOT=3.1 nm) N2O-Annealed SiN Gate Dielectric
Authors: Chen Ching-Wei , Chien Chao-Hsin , Chen Yi-Cheng , Hsu Shih-Lu , Chang Chun-Yen
Published: July 2005

The p-channel metal–oxide–semiconductor field-effect transistor (pMOSFET) with 50-nm-thick Si0.85Ge0.15 channel and ultra-thin (EOT=3.1 nm) N2O-annealed SiN gate dielectric has been shown to have well-performing on/off and output characteristics. Several methodologies for the device reliability characterization, such as stress-induced-leakage-current (SILC), drain-avalanche-hot-carrier (DAHC) injection, channel hot-carrier (CHC) injection and negative-bias-temperature-instability (NBTI), have been used and the results were compared. In terms of the long-term degradation, the excellent quality of the N2O-annealed SiN gate dielectric can be firmly obtained because only negligible degradations have been found after stressing no matter which technique was employed. Even so, the experimental results have been compared and we found that the HC degradation is worse than the NBTI degradation and the channel-hot-carrier (CHC) stressing is the worst case for all kinds of reliability testing. Meanwhile, we have also verified that the interface state generation is the dominant mechanism responsible for the HC-induced degradation while the electron trapping dominates the device degradation for the NBTI stressing.
General Analytical Relationship for Electric Field of Gated Field Emitters
Authors: Nicolaescu Dan , Nagao Masayoshi , Filip Valeriu , Kanemaru Seigo , Itoh Junji
Published: July 2005

Current–voltage I(V) measurements are used for the characterization of metallic Spindt-type and Si gated emitters, in conjunction with the Fowler–Nordheim (FN) current density–electric field J(E) relationship describing the local tunneling process. For proper device modeling, the electric field on the emitter should be linked to the applied voltage. A general analytical relationship for computing the electric field on the emitter apex for planar and volcano-shaped gated emitters has been derived. The relationship is valid for a wide range of the parameters, taking into account the emitter radius and cone angle as well as the gate aperture radius. An example of device modeling concerning HfC-coated poly-Si gated emitters is presented.
Contact Resistance Reduction Using Vacuum Loadlock System and Plasma Dry Cleaning
Authors: Miya Hironobu , Shingubara Shoso , Sakaue Hiroyuki , Takahagi Takayuki
Published: July 2005

The contact resistance between Si substrates and P-doped poly-Si films was investigated using a vacuum loadlock system with various wafer transfer environments. When compared to that in air atmosphere, the contact resistance was reduced by 40% and 50% in nitrogen atmosphere and under vacuum, respectively. Furthermore, the use of a plasma dry cleaning method to remove the native oxide before P-doped poly-Si deposition decreased the contact resistance by 60% compared with that in air. The surface treated with plasma dry cleaning was analyzed by secondary-ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS) and was found to be terminated by SiO
x
F
y
or SiF
x
, which suppressed the formation of an interface oxide and the adsorption of organic compounds.
Adsorption of Dibutyl Phthalate and Dioctyl Phthalate on Si Substrate
Authors: Miya Hironobu , Sasajima Ryota , Takami Eiko , Nakamura Naoto , Takahagi Takayuki
Published: July 2005

The behaviors of organic compounds such as dibutyl phthalate (DBP) or dioctyl phthalate (DOP) on a Si substrate are investigated by gas chromatograph and mass analysis (GC–MS). DBP or DOP source is set in a chemically clean booth, and organic amount is measured in air and on the substrate. At various concentrations of DBP or DOP, organic adsorption amount is measured and this amount is expressed by the Langmuir equation. In a mixed-gas atmosphere, the amounts of DBP and DOP are measured and it is clear that DBP concentration decreases when the total organic amount exceeds the saturated adsorption amount on the substrate. This phenomenon is understood as the replacement of DBP by DOP. In this paper, we describe the adsorption amount quantitatively in individual atmosphere of DBP or DOP and a mixed-gas atmosphere.
Precise Depth Control of Silicon Etching Using Chlorine Atomic Layer Etching
Authors: Park Sang-Duk , Min Kyung-Suk , Yoon Byoung-Young , Lee Do-Haing , Yeom Geun-Young
Published: July 2005

In this study, the atomic layer etching (ALE) of Si was carried out using Cl2 adsorption followed by Ar+ ion beam irradiation with a low energy Ar+ ion beam generated by an inductively coupled plasma ion gun. A saturated silicon etch rate due to chlorine ALE could be obtained when the Ar+ ion acceleration voltage of the ion gun was in the range of 70 to 90 V, as a result of the preferential etching of silicon chloride formed during the chlorine adsorption period by the Ar+ ions while the silicon sputter etch rate remains insignificant. This was attributed to the differences in the silicon-to-silicon and silicon-to-silicon chloride binding energies. The saturated silicon etch rate by ALE was dependent on the chlorine flow rate, i.e. the surface coverage of chlorine and the Ar+ ion irradiation time. In this experiment, a silicon etch rate of 1.36 Å/cycle, which is a (100) silicon monolayer per cycle, could be obtained by flowing more than 10 sccm chlorine gas followed by bombarding the surface by Ar+ ions with an acceleration voltage of 70 V for more than 40 seconds. Under this condition, when a 30 nm scale silicon etch profile was examined after 200 cycles, a silicon etch profile with no undercut could be obtained.
An Evaluation Process of Polymeric Adhesive Wafer Bonding for Vertical System Integration
Authors: Kwon Yongchai , Seok Jongwon
Published: July 2005

Bonding of wafers using dielectric polymer thin films as bonding adhesives is one of key approaches to monolithic vertical system integration. As the first step for the integration, properties of the polymer desired for baseline adhesive material are studied, followed by the evaluations on bonding results obtained from wafer pairs bonded between a silicon and a glass wafers. Four sequential evaluation procedures are performed after bonding; (1) optical inspection is made to measure the fraction of bonded area, (2) a razor blade test is taken to separate the bonded wafers, (3) a four-point bending method is used to measure bonding strength quantitatively, (4) FTIR is applied to analyze changes in chemical structure. Bonding integrity is evaluated how the intentionally created debond areas of the bonded wafers are changed after the subsequent thinning processes. To date, benzocyclobutene (BCB), FlareTM, and methylsilsesquioxane (MSSQ) and Parylene-N have been considered as bonding adhesives. Among these polymer materials, BCB and FlareTM are selected as initial adhesive materials after a screening process through optical inspection. Wafer pairs bonded using FlareTM have higher bond strength than those using BCB. However, the bond strength of wafer pairs bonded using BCB is still higher than that at the interface between Cu and porous low-k inter-level dielectrics (ILD) (a back end interconnect structure), indicating almost 100% of bonded area reproducibly. In the light of such evaluation results, BCB has been eventually selected as a baseline adhesive material for the wafer bonding prcess for vertical system integration.
Doping Effects from Neutral B2H6 Gas Phase on Plasma Pretreated Si Substrates as a Possible Process in Plasma Doping
Authors: Tsutsui Kazuo , Higaki Ryota , Sasaki Yuichiro , Sato Takahisa , Tamura Hideki , Okashita Katsumi , Mizuno Bunji , Iwai Hiroshi
Published: July 2005

In a low-energy plasma doping process, the contribution of not only ionized species but also neutral species to the doping process should be considered. To investigate such a contribution, experiments involving gas phase doping combined with Ar plasma pretreatment were carried out. As a result, a significant increase in boron dose from a neutral gas phase was observed when the substrate surface was subjected to Ar plasma pretreatment prior to exposure to neutral B2H6/He gas. Through a comprehensive study of the effects of plasma pretreatment and gas exposure conditions on the boron dose from the neutral gas phase, the substrate temperature at which the surface was exposed to the neutral B2H6/He gas after the plasma pretreatment was observed to significantly increase the boron dose.
Fabrication of Anodic Oxidation Films on 4H–SiC at Room Temperature Using HNO3-Based Electrolytes
Authors: Mikami Hidenori , Hatayama Tomoaki , Yano Hiroshi , Uraoka Yukiharu , Fuyuki Takashi
Published: July 2005

Oxidation of 4H–SiC substrates by anodic methods using HNO3 and HF+HNO3 electrolytes was carried out at room temperature. Oxide layers with a thickness of 1 µm were formed in 5 min, which is 100 times faster than by a conventional dry thermal oxidation method. The consumed SiC layer is 1/3 of the oxide thickness. The oxide layer was found to be SiO2 including carbon by XPS analysis. The carbon atomic concentration in the oxide layers could be reduced by thermal annealing in a gas mixture of H2/Ar=1:9.
Behavior of Transconductance and Drive Current of Decoupled Plasma Nitridation Oxynitrides
Authors: Lim Sang Woo , Luo Tien-Ying
Published: July 2005

A thinner base oxide prior to decoupled plasma nitridation produced an improved high field transconductance normalized by oxide electrical thickness as compared to a thicker base oxide. Normalized peak transconductance at a lower electrical field is improved with a lower nitrogen concentration, but normalized transconductance at a higher electrical field is improved as the nitrogen concentration increases. Although there is a trend that drive current and gate leakage current are mainly determined by base oxide thickness, drive current shows a complicated dependency on a nitrogen concentration. The findings from transistor drive current characteristics are consistent with the behavior of transconductance.
Thermal Decomposition of Ti(O–iPr)2(dpm)2 in the Gas Phase
Authors: Heo Jung Shik , Cho Yong Seok , Kim Jeong Chan , Moon Sang Heup
Published: July 2005

The thermal decomposition of gaseous Ti(O–iPr)2(dpm)2 [O–iPr = isopropoxide, dpm = bis(2,2,6,6-tetramethyl-3,5-heptadionate)], diluted with either argon or air, was investigated using infrared (IR) and mass spectrometry. The activation energies associated with the dissociation of individual bonds constituting the compound were estimated based on IR data obtained when the compound was heated at different rates. Ti(O–iPr)2(dpm)2 was decomposed even during vaporization, which occurred at temperatures near 180°C. In an argon environment, the Ti–O bond connecting the central Ti atom with the O–iPr ligand and the C–C(CH3)3 bond of the dpm ligand were dissociated at low temperatures, and the C–O bond of the dpm ligand was dissociated at higher temperatures. At temperatures below 300°C, the skeleton of the dpm ligand was preserved, even though the latter had lost the C(CH3)3 group and was bound to Ti only by one end. The dpm skeleton was decomposed at temperatures higher than 300°C due to the dissociation of C–O and C–C bonds. When the compound was decomposed in air, the sequence for the dissociation was similar to that observed in argon, except that the C–C bond of the dpm ligand was dissociated at lower temperatures than in argon and, accordingly, the dpm skeleton was decomposed at temperatures as low as 250°C. In either case of the two environments, the Ti–O bond connecting Ti to the dpm skeleton was the most stable and its dissociation eventually contributed to the formation of TiO2.
Antiferromagnetic Layer Structure Effects on Exchange Coupling Strength in Ion-Beam Deposited Ni80Fe20/Cobalt Oxide Bilayers
Authors: Lin Ko-Wei , Lin Fu-Tai , Tzeng Yi-Min
Published: July 2005

A series of Ni80Fe20/Cobalt oxide bilayers were prepared by a dual ion-beam deposition technique that produced a layer composition that varied from rock-salt CoO (a=4.27 Å) to spinel Co3O4 (a=8.21 Å) with increasing O2 content in the assist beam. Each polycrystalline layer (∼20 nm) exhibited a columnar structure perpendicular to the film surface. A strong temperature dependence of coercivity H
c and exchange bias field H
ex was found in these Ni80Fe20/cobalt oxide bilayers. At T=10 K, films prepared with 34% O2 in the assist beam exhibited an exchange shift H
ex∼-200 Oe that persisted at temperatures higher than 30 K. The variations in H
c and H
ex as a function of %O2 are related to the interfacial roughness and magnetic state of CoO or Co3O4. The transition temperature of Co3O4 has increased above the bulk value via exchange coupling with the permalloy.
Tuning Microstructural and Magnetic Properties of Ion-Beam-Deposited Ni80Fe20/NixFe1-xO Composite Films
Authors: Lin Ko-Wei , Gambino Richard J. , Lewis Laura H.
Published: July 2005

Composite films of Ni80Fe20/Ni
x
Fe1-x
O were prepared by dual ion-beam deposition. The structural and magnetic properties of these composite films were studied. The as-deposited Ni80Fe20 films (a=3.55 Å) consist of f.c.c. nanocrystallites while films prepared with 55% O2 in the assist beam consist of a rock-salt structure Ni
x
Fe1-x
O (a=4.21 Å) solid solution. The rock-salt phase undergoes an unusual dissociation reaction from Ni
x
Fe1-x
O into Ni (a=3.52 Å), NiO (a=4.19 Å), and NiFe2O4 (a=8.33 Å) upon annealing. The differences (Δ) in magnetic moment at 10 K between zero-field-cooled (ZFC) and field-cooled (FC) curves are closely related to the interphase exchange interaction in these composite films. Suppression of the Curie temperature (T
C) was observed in both pure Permalloy and Ni80Fe20/Ni
x
Fe1-x
O composite films, and the T
C depression was reduced by annealing.
Application of Microholes in Sustain Electrode to Improving UV Efficiency in Macroscopic Plasma Display Panel Cells
Authors: Park Ki Wan , Lee Tae Il , Park Hae Il , Baik Hong Koo , Lee Se-Jong
Published: July 2005

A front-panel structure with microholes in its sustain electrode for use as a macroscopic plasma display panel to achieve high UV radiation efficiency through the micro-hollow effect is proposed. When the Xe/Ne/Ar (4/76/20) pressure is 50 Torr and the driving frequency is AC 20 kH, compared with a conventional structure, the electrode with a microholes produces a high IR intensity and low a electron energy. The excitation energy measured by optical emission spectroscope is 1.4 eV. The IR intensity of the structure with microholes is about 20% higher than that of conventional plasma display panel cells.
Output Characteristics of a Dual-Wavelength Semiconductor Laser Beam in Master-Oscillator Power-Amplifier Configuration
Authors: Jung Euo Chang , Park Seong Hee , Lim Gwon , Cha Byung Heon , Song Kyuseok
Published: July 2005

Two single-frequency laser beams at 852 nm were injected into a semiconductor tapered amplifier to generate a dual-wavelength laser beam. When the frequency difference δ between the two injection beams was less than ∼2 GHz, several sidebands appeared in the output due to the beating of the two injection frequencies. The efficiency of sideband generation was measured as a function of injection power. The total output power was measured as a function of δ. We showed that the loss of the total output power, which is always accompanied by sideband generation, is one of the noteworthy characteristics of the dual-wavelength beam in a master-oscillator power-amplifier configuration.
Automatic Pulse Duration Control of Picosecond Laser using Two-Photon Absorption Detector
Authors: Hashimoto Mamoru , Asada Takahiro , Araki Tsutomu , Inouye Yasushi , Kawata Satoshi
Published: July 2005

We have proposed and developed a new feedback control system to automatically minimize the pulse duration of an ultrafast laser using a two-photon absorption detector that has a Gires–Tournois interferometer (GTI) for compensating the positive group delay dispersion of the laser cavity. The signal of the two-photon detector is inversely proportional to the pulse duration when the average power, repetition rate, and pulse shape are maintained. The minimization of the pulse duration is accomplished by adjusting the voltage applied to the GTI to maximize the two-photon signal. We demonstrated the control of pulse duration minimization with the developed system.
Amplification of Optical Traveling Waves in Thin Slab Structure
Authors: Mizushima Yoshihiko
Published: July 2005

A novel theory of optical amplification on a traveling plasma wave along a thin semiconductor slab is proposed. Under common boundary conditions and constraints, drifting electronic space-charge waves and plasmons are phase-matched to couple with each other. The waves are hybridized to yield a traveling instability. With a perpendicular magnetic field, the Voigt dispersion anomaly strengthens the interaction. The amplification occurs in a wide wavelength range, from submillimeters (Terahertz) to near infrared (IR). Various applications of optical devices, including lasers, are suggested. On a concept of motional and spatial constraints, the effects of magnetization and waveguide are compared.
Compensation of Photoelastic Birefringence of Polymers by Anisotropic Molecules and Analysis of Compensation Mechanism
Authors: Ohkita Hisanori , Ishibashi Kayoko , Tanaka Ryo , Tagaya Akihiro , Koike Yasuhiro
Published: July 2005

We report the anisotropic molecule dopant method for compensating the photoelastic birefringence of polymers. In this method, a rodlike molecule that has a polarizability anisotropy was chosen and doped in a polymer. We demonstrated this method by compensating the negative photoelastic birefringence of poly(methyl methacrylate) and poly(2,2,2-trifluoroethyl methacrylate) at a wavelength of 633 nm. trans-Stilbene and fluorene were selected as the anisotropic molecules. Homogeneous doping with the molecules almost eliminated the photoelastic birefringence of the polymers. We found that the photoelastic birefringence of poly(methyl methacrylate) was compensated by the elastic motion of trans-stilbene in the polymer as determined by the analysis of the infrared absorption spectrum. Furthermore, the orientation distribution function of trans-stilbene in a uniaxially strained PMMA film in a solid glass state was estimated by the investigation of infrared dichroic ratios.
Application of Photoalignment Technology to Liquid-Crystal-on-Silicon Microdisplays
Authors: Zhang Baolong , Li KuenKuen , Chigrinov Vladimir G. , Kwok Hoi-Sing , Huang Ho-Chi
Published: July 2005

We applied photoalignment technology to liquid-crystal-on-silicon microdisplays and characterized their performance. A three-step photoexposure method was developed to solve problems with alignment disturbances on reflective silicon panels. The azimuthal and polar anchoring energies of photoalignment layers produced by this method were high and comparable with that of rubbed polyimide layers. We assembled both the rubbed and photoaligned microdisplays on a MTN 90° configuration for characterization and comparison. These two kinds of silicon microdisplays had good and comparable characteristics in terms of contrast, response time, voltage holding ratio and residual DC charge. The rubbed microdisplays were more uniform, which we attributed to a more mature fabrication technology, while the photoaligned microdisplays had far fewer defects due to the noncontact nature of the photoalignment technology.
Novel Way for Full Characterisation of Splayed Retarders using Wentzel–Kramers–Brillouin Method
Authors: Jung Carl Christoph , Stumpe Joachim , Peeters Emiel , Zande Bianca Maria Irma van der
Published: July 2005

The viewing angle dependency of transmissive liquid crystal (LC) displays can be reduced by use of compensation foils (retarders) exhibiting specific optical properties such as splays or tilt gradients. Thin films with tilt gradients can be characterised using the prism coupling method. This method comprises the excitation of waveguide modes in the investigated film using the evanescent field at the base of a prism in total reflection without the requirement of an immersion liquid. The resulting reflectivity curves are simulated with the help of the Berreman method. The simulations provide insights into simpler ways to evaluate the data for thin films exhibiting a tilt gradient along the layer normal. The Wentzel–Kramers–Brillouin (WKB) method for inhomogeneous films can be applied to the full characterisation of the tilt gradient without prior knowledge of thickness and refractive indices of the film. A polymerised liquid crystal sample example was investigated and a linear gradient was found for this example.
Gain-Clamped Erbium-Doped Waveguide Amplifier Module with Fiber Bragg Grating Using Optical Feedback
Authors: Lai Kuo-Hsiang , Chi Sien
Published: July 2005

A gain-clamped C-band EDWA module using forward optical feedback with a fiber Bragg grating (FBG) over the operating range of 1530 to 1560 nm has been experimentally investigated and demonstrated. A 0.3 dB minimum gain variation is observed at 1550 nm over a 10 dBm variation of the input signal power. In addition, the gain clamping behaviors have also been experimentally investigated under different operating conditions.
Operation of Saturable-Absorber-Based Autotracking Filter for a Stabilized Single-Frequency Erbium Fiber Laser
Authors: Yeh Chien-Hung , Fan Kuo-Pao , Chi Sien
Published: July 2005

A fiber ring laser with the wavelength tunability and single-longitudinal-mode oscillation based on a C-band erbium-doped waveguide amplifier is proposed and demonstrated. A saturable-absorber-based autotracking filter, consisting of an unpumped erbium-doped fiber and an optical reflector, is utilized to provide fine mode restriction and guarantee the single-frequency operation.
Polarized Raman Spectra and N-Related Local Vibrational Mode in GaNAs and GaInNAs Epitaxial Layers Grown on GaAs
Authors: Shirakata Sho , Kondow Masahiko , Kitatani Takeshi
Published: July 2005

Raman studies were performed on GaN0.025As0.975 and Ga0.94In0.06N0.025As0.975 epilayers grown on (100) GaAs. N alloying enhanced the forbidden TO phonon, while In alloying had a negligible effect on it. The forbidden TO phonon had an A
1 symmetry, in contrast to that of Ga0.969In0.031As having a T
2 symmetry. In GaInNAs, thermal annealing led to the splitting of a N-related local vibrational mode (LVM) into a doublet (472 and 490 cm-1), while no change was observed in GaNAs. LVM is discussed in terms of In–N bond formation.
Frequency Responses of Surface-Acoustic-Wave Filters with Two-Track Slanted Finger Interdigital Transducers
Authors: Tung Hsin-Yuan , Ro Ruyen
Published: July 2005

In this study, the scattering characteristics of a novel surface-acoustic-wave (SAW) filter with two-track slanted finger interdigital transducers (SFITs) are investigated. The novel SAW filter consists of two-track input and output SFITs, with each track configured in many subfilters in parallel connection. Because the arrival time of a SAW may differ among subfilters, passband ripples appear. However, by properly controlling the gap length between the input and output SFITs of each track, passband ripples can be eliminated evidently. Moreover, due to differences in radiation conductance among subfilters, a curve fitting technique is used to design the overlap width of each subfilter to maintain the passband responses of the SAW filter as flat as possible. A Chebyshev polynomial and a two-step weighting technique are employed to decrease sideband level. Simulation results show that by tailoring SAW SFITs and the gap difference of each track, a high-performance broadband IF filter can be obtained.
Phonon Echo Study on Lithium Ionic Diffusion in LiNbO3 Powder
Authors: Nakamura Koichi , Michihiro Yoshitaka , Katayama Fumiaki , Moriga Toshihiro , Mahbubar Rahman Md. , Nakabayashi Ichiro , Kanashiro Tatsuo
Published: July 2005

Two-pulse phonon echo measurements were performed from room temperature to 900 K in micro particles of polycrystalline and single crystalline LiNbO3 to investigate the relationship between lithium ionic diffusion and decay time, T
2, in a phonon echo study. Decay time was dependent on temperature, showing a rapid decrease above 800 K in the polycrystalline sample. The origin of this anomaly is interpreted in terms of a simple Debye-type relaxation due to lithium ionic diffusion. The activation energy, which was evaluated as 0.93 eV in the polycrystalline samples, was comparable with reported values from ionic conductivity and NMR studies. On the other hand, single crystalline LiNbO3 showed no signs of lithium ionic diffusion up to 900 K. The contribution to T
2 from lithium ionic diffusion would be dominant at higher temperatures than 900 K because of the much higher activation energy in a single crystalline sample. It is shown that phonon echo decay time is strongly connected with ionic diffusion in the particles.
Novel Ir–Ti Alloy Electrodes for High-Density Ferroelectric Memory Applications
Authors: Koo June-Mo , Shin Sangmin , Kim Sukpil , Lee June Key , Park Youngsoo
Published: July 2005

An Ir-based Ir–Ti alloy was improved by controlling the interface layer between Pb(Zr,Ti)O3 (PZT) and an electrode for the high-density ferroelectric memory application. Compared with the Ir electrode, the Ir–Ti alloy electrode was resistant to oxygen annealing and the surface did not roughen much. The increase in resistivity after the annealing was also sufficiently low to maintain its feasibility as an electrode. Furthermore, Ti in the Ir–Ti alloy seemed to assist the growth of (111) grains of PZT, thus resulting in a larger 2P
r. The Ir–Ti alloy layer also acted as a seed layer for PZT. This means that we can skip the deposition of the seed layer for the purpose of good quality PZT. Furthermore, the Ir–Ti alloy is still applicable to very thin films. In ultra thin films of PZT and a bottom electrode, IrTiO
x
(20 nm)/IrTi (10 nm) is a good choice as the bottom electrode to conserve 2P
r as well as protect the reliability of thin PZT. This is a very different result from IrO
x
. It is believed that these results could provide a possibility for commercializing embedded or stand-alone FeRAM in high-density ferroelectric memory applications.
Near-edge X-ray Absorption Fine Structure of PdO at O K-edge
Authors: Mogi Masato , Inoue Yasuhide , Yamamoto Tomoyuki , Tanaka Isao , Nachimuthu Ponnusamy , Perera Rupert C. C.
Published: July 2005

The first-principles band structure calculations are carried out to interpret the spectral fine structure of the near-edge X-ray absorption fine structure (NEXAFS) spectrum of PdO at the O K-edge by the full-potential augmented plane wave plus local orbitals (APW+lo) method. The observed NEXAFS fine structure of PdO is quantitatively reproduced by our calculations. Three types of PdO polymorph are examined, which show a significant difference in theoretical NEXAFS profile. They can be used as theoretical finger prints for future studies.
Blocking Impurities in Organic Light Emitting Device by Inserting Parylene Interlayer
Authors: Ke Lin , Kumar Ramadas Senthil , Burden Adrian Paul , Chua Soo-Jin
Published: July 2005

Secondary-ion mass spectrometry is used to study ion diffusion from a substrate into an organic film, which is considered as one of the reasons for organic-light-emitting-device degradation and instability. Results show that a 1 µm-thick parylene layer inserted between an indium–tin–oxide (ITO) anode and a soda-lime glass substrate effectively controls the diffusion of sodium, potassium, silicon and sulphur ions from the substrate to the device. The effect is the same as that in the case of using a plastic substrate which is sodium- and potassium-free. Also a 3 nm-thick parylene layer grown in between an ITO anode and a hole transport layer (HTL) not only shows improvement in device performance, but also is capable of blocking impurities such as sodium, potassium, silicon and sulphur ions. This study shows that the use of a parylene layer is effective for controlling contamination coming from the substrate.
Fe Gettering for High-Efficiency Solar Cell Fabrication
Authors: Terakawa Takeshi , Wang Dong , Nakashima Hiroshi
Published: July 2005

The gettering behavior of Fe into Si at 600°C for samples with and without a p+ layer was investigated by deep-level transient spectroscopy. These samples contaminated with Fe at 930°C for 4 h at a concentration of 4.6×1013 cm-3 were annealed at 600°C to induce gettering. The concentration of Fe atoms in the bulk Si markedly decreased with annealing time at 600°C. It was found that the gettering site of Fe is not the p+ layer but the very thin surface layer.
Relationship between Surface Order and Surface Azimuthal Anchoring Strength on Polyimide with Linearly Polarized Ultraviolet Light Exposure
Authors: Mitsumoto Takashi , Oka Shinichirou , Kimura Munehiro , Akahane Tadashi
Published: July 2005

The liquid crystal (LC) molecular order near the polyimide surface with linearly polarized ultraviolet (LPUV) light exposure is re-examined by the improved torque balance method. The surface azimuthal anchoring strength measured by the improved torque balance method is larger than that measured by the conventional torque balance method and is considered to be significantly affected by the phase transition behavior. On the basis of this result, it can be argued that the correlation between the LPUV light dosage and the surface azimuthal anchoring strength should be improved in considering of the surface order mechanism. The absolute surface azimuthal anchoring strength is investigated with respect to the phase transition characteristics. Photoalignment revealed that a relatively strong surface azimuthal anchoring strength may be obtained. Furthermore, the effects of photoalignment and rubbing of different alignment processes were examined.
A Microscopic Model for Helical Twisting Power by the Optical Isomers of an Octahedral Metal Complex
Authors: Sato Hisako , Yamagishi Akihiko , Yoshida Jun , Nakano Haruyuki , Hoshino Naomi
Published: July 2005

A computational approach to the evaluation of helical twisting powers (HTP) of chiral metal complexes of [Ru(blade)2(backbone)] type is presented. The dopant contains helically attached “blade” ligands and an elongated “backbone” ligand, and some remarkably powerful examples have been reported. In this work, the observed HTP is interpreted in terms of a microscopic interaction of a dopant and host molecules with atomistic details. For this purpose, the stable structure of a triad system comprising a dopant and two host molecules was obtained by geometry optimization using Gaussian03. As a result, the host molecules interacted attractively with the dopant, being twisted in the same direction as observed experimentally. Interaction energy was assessed as a function of the dihedral angle between the two host molecules, leading to a quadratic dependence with a minimum at the equilibrium twisting angle of -32°. Based on this, the expression was derived, in which helical twisting power was given in terms of the equilibrium twisting angle of a pair of strongly interacting host molecules.
Temperature-Screening System for Determining Protein Crystallization Conditions
Authors: Adachi Hiroaki , Niino Ai , Takano Kazufumi , Matsumura Hiroyoshi , Murakami Satoshi , Inoue Tsuyoshi , Mori Yusuke , Sasaki Takatomo
Published: July 2005

A newly proposed temperature-screening system has a practical application in determining protein crystallization conditions. Using a batch method, we demonstrated multitemperature conditions on one plate in a multitemperature experimental unit, providing accurate temperature control with a linear gradient. This screening system, which we call temperature at once (TAON), enables us to easily construct a solubility phase diagram and to search for the optimum temperature for crystal growth using microscale samples.
Precise Thermal Characterization of Confined Nanocrystalline Silicon by a 3ω Method
Authors: Kihara Takashi , Harada Toshihiro , Koshida Nobuyoshi
Published: July 2005

Due to a strong quantum confinement effect, the thermal conductivity and heat capacity per unit volume of a nanocrystalline silicon (nc-Si) layer prepared by electrochemical anodization are extremely lowered in comparison to those of single crystal silicon (c-Si). Based on this high contrast between the thermal properties of nc-Si and c-Si, we have developed novel thermally induced ultrasound emitter devices. The thermal insulating properties of the nc-Si layer play a key role in this case. This paper concerns precise measurements of the thermal conductivity and heat capacity per unit volume of the nc-Si layer using a dynamic approach called the 3ω method. The measured thermal conductivity is 1.08±0.2 W/(m·K) in good agreement with that reported previously as measured by conventional techniques. The obtained heat capacity per unit volume of the nc-Si layer is, on the other hand, considerably smaller than that estimated from the porosity of the sample. These results provide useful information for designing an efficient ultrasound emitter.
Molecular Rearrangement and Optical Property Changes of p-Sexiphenyl Vacuum-Deposited Film Induced by Rubbing
Authors: Aoki Naofumi , Koshiba Yasuko , Ueda Yasukiyo
Published: July 2005

Structural and optical property changes of p-sexiphenyl (6P) films induced by rubbing were investigated. 6P molecules vapor-deposited on a fused silica glass adsorbed obliquely but had no in-plane orientation. After rubbing, the film surface became smooth and the electron microscopic analysis revealed that the longitudinal direction of the 6P molecules is parallel to the substrate surface and oriented uniaxially along the rubbing direction. The absorption spectrum changed corresponding to the orientation change of the 6P molecules. The 6P molecules grew homoepitaxially on the rubbed film, and the film exhibited a high anisotropic optical property (dichroic ratio: 9.6) when deposition was performed at a low substrate temperature (RT) and a high deposition rate (5 nm/min).
Ion-Beam Induced Liquid Crystal Alignment on Diamond-like Carbon and Fluorinated Diamond-like Carbon Thin Films
Authors: Ahn Han Jin , Rho Soon Joon , Kim Kyung Chan , Kim Jong Bok , Hwang Byoung Har , Park Chang Joon , Baik Hong Koo
Published: July 2005

Homogeneous and homeotropic orientations of nematic liquid crystal (NLC) are investigated on various inorganic thin films which are exposed to Ar ion-beam. It is the novel investigations which results in a completely dry processing technique for both the thin film deposition and alignment steps. In the case of homogenous alignment on diamond-like carbon (DLC) layer, optical band gap and the polar surface energy are investigated in order to elucidate the alignment mechanism by ion beam (IB) irradiation. We elucidate the role of surface polarity in DLC films with respect to the LC orientation. On the other hand, FDLC thin films are selected by homeotropic alignment layer with regard to the relationship between surface tension and LC orientation. Selected pretilt angles in the range of 71.1–89.8° can be easily obtained with ion beam irradiation. It is sensitively changed by thin films composition and the angle of ion beam irradiation.
Preparation of Low-Stress SiNx Films by Catalytic Chemical Vapor Deposition at Low Temperatures
Authors: Takano Masahiro , Niki Toshikazu , Heya Akira , Osono Tetsuo , Yonezawa Yasuto , Minamikawa Toshiharu , Muroi Susumu , Minami Shigehira , Masuda Atsushi , Umemoto Hironobu , Matsumura Hideki
Published: July 2005

Silicon nitride (SiN
x
) films were prepared by catalytic chemical vapor deposition (Cat-CVD) at low substrate temperatures below 130°C. The stress in the films was low, typically lower than 100 MPa, and could be varied from compressive to tensile by changing the deposition conditions used. The cause of the changes in stress was investigated from the relationship between film properties and deposition conditions. Stress was more compressive when the SiH4 flow rate was high, while it was more tensile when the substrate temperature and gas pressure were high. This is attributed to the shrinkage of the film accompanied by gas desorption from the growing surface. The gas desorption is enhanced by the elevation of substrate temperature and the attack of atomic hydrogen. The gas desorption also leads to low hydride densities and high mass densities. The SiN
x
films prepared by Cat-CVD can be used for passivating organic materials.
Electron Emission Properties of ZnS-Based Thin-Film Cold Cathode for Field Emission Display
Authors: Noda Daiji , Hagiwara Kei , Yamamoto Toshihiro , Okamoto Shinji
Published: July 2005

A thin-film cold cathode emitter has been produced for application in flat-panel displays. This structure is fabricated by modifying a thin-film electroluminescence device. The thin-film cold cathode employs hot electrons generated in a ZnS accelerating layer by a high electric field, with these electrons being emitted through a thin Au electrode. The thin-film cold cathode emitter exhibited emission properties over large areas with excellent uniformity. For application to field emission displays, a matrix of electrodes was fabricated using thin-film cold cathodes. Although the pixel pitch was fine, electron emission exhibited spatial uniformity. This feature makes this device attractive for flat-panel displays and other applications.
New Penning Gas (Deuterium) for the Improvement of Luminance and Luminous Efficiency in Alternative Current-Plasma Display Panels
Authors: Kwon Shi-Ok , Kim Ji-Sun , Joung Bong-Kyu , Hwang Ho-Jung
Published: July 2005

The effects of addition of deuterium (D2) to conventional gases [Ne (92%)–Xe (8%) and He (70%)–Ne (27%)–Xe (3%)] on discharge characteristics were investigated in this work, with the aim of improving luminance and luminous efficiency as well as achieving low sustain voltage. When the gas-inlet amounts of D2 added to Ne–Xe or He–Ne–Xe gas-inlet mixture were varied from 0 to 0.1%, we measured the sustain voltage, the luminance, the luminous efficiency and the wall charge corresponding to each gas-inlet. The addition of extremely small gas-inlet amounts of D2 increased the number of electrons, which improves the Xe* density [Xe*(1s4)→Xe+hν(147 nm)]. As a result, luminance and luminous efficiency increased while the sustain voltage decreased.
Imaging of Fusion Protons from a 3 kJ Deuterium Plasma Focus
Authors: Springham Stuart Victor , Moo Siew Pheng , Lee Paul , Rawat Rajdeep Singh , Patran Alin Constantin , Lee Sing
Published: July 2005

This paper reports a study of the proton emission from a 3 kJ, 14 kV plasma focus device operated with deuterium gas at 400 Pa. A filtered pinhole camera with a 1.8 mm diameter hole is placed axially downstream of the plasma focus, and images of the proton-emitting region are recorded using CR-39/PM-355 nuclear track detectors. The detector plates are scanned using an automated track measurement system and the spatial track density profile is acquired. The resulting density distribution is interpreted with the help of a simple pinhole imaging model that assumes the 2H(d, p)3H reaction protons are emitted from a conical region extending from the tip of the anode to a fixed distance downstream. Comparison of the experimental track density profile with the model calculations supports the view that the beam-target mechanism is the dominant fusion production mechanism in this small plasma focus device.
Ultrasonic Linear Motor using L1–B4 Mode and its Analysis
Authors: Park Jong-Sung , Kim Sang-Tae , Kim Jin-Woo , Lee Jung-Kun , Hong Kug Sun
Published: July 2005

This paper presents the results of a transient dynamic analyses and experiments on an ultrasonic linear motor (USLM). For a simulation of dynamics of the ultrasonic linear motor, an analytic method has been used. Numerical analysis was performed to determine the precise characteristics of the ultrasonic linear motor. The contact between slider and stator has hindered the transient dynamic finite element method (FEM) analysis of ultrasonic motors. In this study, the problem was solved using the reaction force. Transforming the applied electric field to the mechanical reaction force, transient dynamic analysis was performed in contact condition. The resonance frequency and the velocity of the linear motor were determined to be 35.6 kHz and 34 cm/s respectively from FEM analysis. And the equilibration time when the vibration and velocity of motor reach the steady states can be calculated. The validity of analysis results including eigen frequencies and a velocity of a motor, was confirmed by comparison with steady state analysis and experiments.
Reaction Processes of Germane Molecules with Catalytic Water
Authors: Ibuta Naoomi , Sagara Fumihiko , Doi Kentaro , Nakamura Koichi , Tachibana Akitomo , Ishihara Yoshio , Suzuki Katsumasa
Published: July 2005

We have carried out ab initio quantum chemical calculations for the decomposition reactions and propagation reactions of germane (GeH4). All self-decomposition reaction series are endothermic, and in contrast, Ge-chain propagation reactions are exothermic at the B3LYP/6-31G** and B3LYP/6-311G** levels. The exothermicity of Ge-chain propagation is a characteristic property of GeH4 in contrast to methane and silane, though the activation energy is estimated to be as large as about 80 kcal/mol. We have confirmed that the activation energy of the decomposition reaction is reduced due to catalytic water in the form of (H2O)2 dimer. We have also presented the mechanism of Ge-chain propagation with a low activation energy due to catalytic water leading to the explosive decomposition of GeH4 gas.