bluuebunny/crossref_metadata_2025 huggingface dataset:
Polarization Properties of Superlattice-Structured Bi4Ti3O12-BaBi4Ti4O15 Single Crystals and Ceramics: Comparison with Bi4Ti3O12 and BaBi4Ti4O15
Authors: Kobayashi Tomo , Noguchi Yuji , Miyayama Masaru
Published: February 2005

Superlattice-structured Bi4Ti3O12-BaBi4Ti4O15 (BiT-BBTi) ceramics and single crystals were prepared, and their crystal structure and polarization properties were compared with those of constituent BiT and BBTi. The Curie temperature (T
C) of the BiT-BBTi crystals was 540°C, which was 40°C higher than that of the BiT-BBTi ceramics with the stoichiometric composition. The BiT-BBTi ceramics had a remanent polarization (P
r) of 12 µC/cm2, while the spontaneous polarization (P
s) along the a axis of the BiT-BBTi crystals was 52 µC/cm2, which was larger than those of BiT and BBTi crystals. The large P
s observed for the BiT-BBTi crystals is suggested to originate from the ferroelectric displacements of the Bi of Bi2O2 layers as well as from the Bi substitution for Ba induced by compositional deviation.
Crystal Growth and Characterization of Pb2KNb5O15
Authors: Kimura Hideo , Maiwa Koji , Miyazaki Akimitsu , Nakamura Hiroaki , Cheng Zhenxiang , Venkadasamy Kannan Chinna
Published: February 2005

Lead potassium niobate crystals were grown by our pulling down method and tube-seed Czochralski method. Evaporation of lead and potassium was observed. Crystal growth was not so difficult despite the evaporation. Grown crystals were brownish and transparent. Cleavage was observed in the Czochralski grown crystals on the c-plane. After heat treatment, the dielectric constant along the c-axis was about 500–1000. A large dielectric constant above 10000 was observed on the a
b-plane. On the a
b-plane, almost isotropic properties were obtained on the basis of the dielectric constant and the thermal expansion coefficient.
Optical and Electrical Studies on Trivalent-Ion (Cr, Fe)-Doped Potassium Titanyl Phosphate Single Crystals
Authors: Kannan Chinna Venkadasamy , Kimura Hideo , Miyazaki Akimitsu , Ramasamy Perumalsamy
Published: February 2005

In this paper we report the effect of trivalent ion (Cr and Fe) doping on the ionic conductivity and dielectric properties of self-flux-grown Potassium Titanyl Phosphate (KTiOPO4; KTP) single crystals. Their electrical properties revealed that Cr- and Fe-ion-doped KTP single crystals exhibit a lower ionic conductivity (1–2 orders of magnitude) than that of pure crystal. However, the frequency and temperature dispersion of the ionic conductivity and dielectric constant of Cr-and Fe-ion-doped KTP crystals are almost similar to pure KTP crystals. The measured activation energy indicates the existence of superionic conduction behavior. The incorporation of trivalent ions shifts the optical absorption edge in the UV-VIS spectrum towards the long-wavelength region and increases the optical absorption coefficient of KTP crystals. Vickers microhardness results showed that trivalent ion doping decreases the mechanical strength of pure KTP crystals.
High Dielectric Constant and Large Electromechanical Coupling Factor Relaxor-Based Piezoelectric Ceramics
Authors: Yamashita Yohachi John , Hosono Yasuharu
Published: February 2005

Lead-perovskite multicomponent system ceramics Pb(Sc1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-Pb(Ni1/3Nb2/3)O3-(Pb,Sr)(Zr,Ti)O3 (PSN-PMN-PNN-PSZT) with high dielectric constant ε
33
T/ε
0=7,200 and large sliver mode electromechanical coupling factor (EMCF) k
33'=69% near the morphotropic phase boundary (MPB) were synthesized by a conventional solid-state-reaction process. To obtain high dielectric constant ε
33
T/ε
0>7,000, a large EMCF and piezoelectric constant materials, a low-molecular-mass (LMM) B-site ion model in lead perovskite is applied to realize better dielectric and piezoelectric properties. We focused on complex perovskite system ceramics PSN-PMN-PNN-PSZT, which consist of four LMM B-site elements, such as, Sc, Mg, Ni and Nb. The maximum dielectric constants, ε
33
T/ε
0=7,200 and ε
33
S/ε
0=3,200, are confirmed in the PSN-PMN-PNN-PSZT ceramics. These ceramic show an planar-mode EMCF k

p
=69%, piezoelectric constant d
33=940 pC/N and Curie temperature T
c=135°C. The dielectric and piezoelectric properties of these ceramics are studied for the ultrasonic medical array transducer application.
Piezoelectric Properties of Polar-Axis-Oriented Ferroelectric Bi4-xPrxTi3O12 Thick Films
Authors: Matsuda Hirofumi , Ito Sachiko , Iijima Takashi , Mashimo Tsubasa , Okino Hirotake , Yamamoto Takashi
Published: February 2005

The piezoelectric response of 1.2-µm-thick Bi4-x
Pr
x
Ti3O12 (BPT, x=0.3, 0.5, 0.7) ferroelectric films with polar-axis orientation is reported. Utilizing a long-range lattice-matching character, BPT films were grown by chemical solution deposition (CSD) on (101)-oriented IrO2 layers which were formed by the oxidation of Ir bottom layers during solution depositions. An effective piezoelectric coefficient d
33=36 pm/V comparable to that of Bi4Ti3O12 (BIT) single crystal was measured in BPT thick films with x=0.3. Related to the decrease in P
s, the total strain ε
total decreased with increasing x. Stripe-shaped domain structures of ∼20 nm in width were observed in some grains in BPT thick films by piezoresponse force microscopy (PFM) and transmission electron microscopy (TEM). These structures could be attributed to 90° domain walls. The reconfiguration of these domains by the elecric field may occur to contribute to the ferroelectric polarizations resulting in a large value of P
sat=50 µC/cm2 in BPT thick films with x=0.3.
Enhanced Piezoelectric Properties of Potassium Niobate Single Crystals by Domain Engineering
Authors: Wada Satoshi , Muraoka Kazuma , Kakemoto Hirofumi , Tsurumi Takaaki , Kumagai Hirohiko
Published: February 2005

The engineered domain configuration was induced into potassium niobate (KNbO3) crystals, and the piezoelectric properties were investigated as a function of domain size. First, single-domain treatment was investigated, and a combination of chemical etching and 2-step electric poling treatment was effective. Using the single-domain crystals, all piezoelectric related constants were determined. On the basis of these piezoelectric constants, the d

31
and d

32
surfaces were calculated. The piezoelectric properties of [001]
c
oriented KNbO3 single-domain crystals were measured and were completely consistent with the calculated properties. Finally, the engineered domain configurations were induced into KNbO3 crystals by the control of the temperature and the electric-field along the [001]
c
direction. The piezoelectric properties of these KNbO3 crystals with the engineered domain configurations showed much higher values than those of the single-domain crystal. Moreover, the piezoelectric properties increased with decreasing the domain sizes of the engineered domain configuration.
Evaluation of Material Constants and Temperature Properties in Lanthanum Calcium Oxoborate LaCa4O(BO3)3 Single Crystals
Authors: Shimizu Hiroyuki , Kodama Kaoru , Takeda Hiroaki , Nishida Takashi , Shikida Takashi , Okamura Soichiro , Shiosaki Tadashi
Published: February 2005

Lanthanum calcium oxoborate LaCa4O(BO3)3 (LaCOB) single crystals were successfully grown by the Czochralski technique. It was found that LaCOB crystals belong to the monoclinic system (point group m) and the total number of independent material constants that should be determined is 27. Twenty-four of the 27 material constants at room temperature were determined by the resonance-antiresonance method. The normalized first-order temperature coefficients of some constants e.g., ε
11

T
, ε
22

T
, ε
33

T
and ε
13

T
determined at 10 kHz were 56.30, -273.6, 135.8 and -258.4 and d
11 and d
12 were -408.3 and 83.60 ppm/°C, respectively. Additionally, the thermal expansion coefficients e.g., α11, α22 and α33 determined on a single crystal cut along the X, Y and Z rectangular directions by the thermodilatometry measurement were 7.36×10-6, 8.17×10-6 and 11.4×10-6/°C, respectively. As a result of the evaluation, most of the material constants and temperature properties necessary for investigating the properties of piezoelectric devices typified by SAW were obtained.
A Novel Generation Method of Dielectric Barrier Discharge and Ozone Production Using a Piezoelectric Transformer
Authors: Teranishi Kenji , Suzuki Susumu , Itoh Haruo
Published: February 2005

A novel generation method of a dielectric barrier discharge (DBD) using a piezoelectric transformer (PT) is proposed. Spatio-temporal variations of microdischarges were investigated and discussed on the basis of the observations using a charge-coupled device (CCD) camera. As an example of a practical application of the DBD to a plasma reactor, an ozonizer using the PT was developed and ozone productions were performed in air and oxygen. Maximum ozone concentrations of 3.38 and 20.3 g/Nm3 were obtained in air and oxygen, respectively. The ozonizer can be designed in a compact configuration and driven with low applied voltages because the PT serves as both a high-voltage generator and a discharge electrode.
High Dielectric Tunability of (Ba, Sr)TiO3 Thin Films and Their Coplanar Waveguide Phase Shifter Applications
Authors: Lee Su-Jae , Moon Seung Eun , Kwak Min-Hwan , Ryu Han-Cheol , Kim Young-Tae , Kang Kwang-Yong
Published: February 2005

In the present work, we report the epitaxial growth and dielectric properties of barium strontium titanate (BST) thin film which can be used to make frequency and phase agile tunable microwave (MW) components with a high performance, such as tunable filters, tunable oscillators, and phase shifters for application in phased array antennas. Epitaxial BST thin films were deposited on a MgO substrate by the insertion of a thin BaTiO3 (BT) seed layer between the BST films and the MgO substrate using pulsed laser ablation. The crystalline structure, dielectric tunability and microwave properties of the epitaxial BST thin films depended strongly on the thickness of the BT seed layer. The dielectric tunability and microwave phase tuning increased with increasing thickness of the BT seed layer. An interdigitated (IDT) capacitor based on the epitaxial BST/BT(12 nm) film on the MgO substrate exhibited a large capacitance tunability of 78% at a frequency of 100 kHz and an applied electric field of 133 kV/cm. Also, a coplanar waveguide (CPW)-type phase shifter fabricated on the BST/BT(12 nm) film showed a phase shift of 153° at 10 GHz and 40 V. These results indicate that the thin BT layer with an intermediate lattice constant between those of the BST film and MgO substrate can be used as an excellent seed layer for improving the crystallization and dielectric properties of BST films, and the high microwave performance of ferroelectric MW devices.
Dielectric Characteristics of Ferroelectric Materials in Submillimeter-Wave Regions
Authors: Fujii Takashi , Ando Akira , Sakabe Yukio
Published: February 2005

We analyzed ferroelectric and paraelectric materials with a high dielectric constant, such as BaTiO3 (BT) ceramic, Ba1-x
Sr
x
TiO3 (BST) ceramic, SrTiO3 (ST) crystal and congruent LiTaO3 (CLT) crystal by THz time-domain spectroscopy (THz-TDS). We obtained the complex dielectric constants of BT ceramic, ST crystal, Ba0.20Sr0.80TiO3 ceramic and CLT crystal. The real and imaginary parts of the complex dielectric constant of the CLT crystal and ST crystal were in agreement with those previously reported. Furthermore, the real and imaginary parts of the complex dielectric constant of the paraelectric Ba0.20Sr0.80TiO3 ceramic were also obtained, and their values were similar to those of ST. As for the BT and BST ceramics, which are ferroelectric materials, we could characterize the real and imaginary parts of BT in the millimeter-wave region but not those of BSTs. We observed dielectric relaxation in BT at around 20 GHz in this measurement.
Director Orientation Measurement of Nematic Liquid Crystal Using Velocity Change of Shear Horizontal Wave
Authors: Moritake Hiroshi , Kim Jaeki , Yoshino Katsumi , Toda Kohji
Published: February 2005

The nematic liquid crystal director orientation in the vicinity of a glass substrate is evaluated in relation to the acoustic phase delay change of the shear horizontal (SH) wave propagation in a cell structure. The evaluated director angle of a nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) as a function of applied voltage is independent of temperature in the nematic phase. The evaluated director angle is less than 75 deg under sufficient applied voltage and depends on the modes whose dependence is related to the penetration depth of the SH wave in the liquid crystal layer. The time response of the director motion is observable by the SH wave propagation. The present method using SH wave propagation in a liquid crystal cell is promising for evaluating the director angle in the vicinity of the substrate surface.
Cooling-Rate-Dependent Domain Structures of Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals Observed by Contact Resonance Piezoresponse Force Microscopy
Authors: Okino Hirotake , Sakamoto Junichi , Yamamoto Takashi
Published: February 2005

The domain structures of (001) plates of (1–x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) single crystals were observed at room temperature after 240°C thermal treatment at various cooling rates. The starting composition of the PMN-PT single crystals was x=0.32; the dielectric constant of the single crystals exhibited a maximum at 153°C. Contact resonance piezoresponse force microscopy (CR-PFM) was utilized for domain imaging, because microdomain images could be obtained without domain structure degeneration. The average size of domains strongly depended on the cooling rate. The obtained domain images were approximately fingerprint patterned on a micron scale, but were fragmented by circular domains on a submicron scale. These finer circular domain structures were probably microdomains that existed in the relaxor phase and were subsequently quenched during the relaxor-to-ferroelectric phase transition.
Domain Wall Structure in Pb(Zn1/3Nb2/3)O3-PbTiO3-Mixed Crystals by Atomic Force Microscopy
Authors: Iwata Makoto , Katsuraya Kohei , Tachizaki Shinichi , Hlinka Jiri , Suzuki Ikuo , Maeda Masaki , Yasuda Naohiko , Ishibashi Yoshihiro
Published: February 2005

Domain wall structures on the etched surfaces of the solid solutions of Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-xPT; x=8%, 20%) were investigated by atomic force microscopy (AFM). Ferroelectric and ferroelastic domain wall structures were observed. In the rhombohedral phase, a zigzag domain wall structure was found. We showed that all of the ferroelastic domain wall structures observed in the tetragonal and rhombohedral phases can be explained by the Sapriel theory, and concluded that no ferroelectric charged domain wall exists in the PZN-PT crystal without an external field. The symmetry of PZN-8%PT at room temperature is rhombohedral.
Relaxor-Like Properties and Anomalous Phase Boundaries in Mixed Crystals Rb1-x(NH4)xH2PO4
Authors: Matsushita Eiko , Shinkai Yuuto
Published: February 2005

In order to search for relaxor ferroelectrics or relaxor antiferroelectrics in Pb-free substances, a theoretical approach is presented for hydrogen-bonded mixed crystals under conditions similar to those for relaxor perovskite oxides. On the basis of the theory for local resonance techniques proposed by one of the present authors, both boundary regions between ferroelectric (FE) and glassy (G) phases, and between antiferroelectric (AFE) and glassy (G) phases are investigated in FE-AFE mixed crystals of Rb1-x
(NH4)
x
H2PO4 (abbreviated as RDP-ADP). Relaxor-like behavior as a large dispersion in dielectric constants is found in the AFE-G phase boundary region where a broad spectrum of quadrupole perturbed nuclear magnetic resonance (NMR-NQR) appears in quite different form to that of the FE-G phase boundary region. From this theoretical viewpoint, the conditions for inducing relaxor behavior are discussed by comparing with the results of X-ray diffraction analysis.
High Field Conduction in a-Se75In21Pb4 Thin Films: Applicability of Meyer-Neldel Rule*
Authors: Kumar Deepak , Kumar Santosh
Published: February 2005

In general, in case of semiconductors, conductivity (σ) varies exponentially with temperature (T), i.e., σ=σ0exp
[-ΔE/k
T] where ΔE is the activation energy and σ0 is called the pre-exponential factor. In most of the semiconducting materials, σ0 does not depend on ΔE. However, in many organic and amorphous semiconductors, σ0 is found to increase exponentially with ΔE. This is called Meyer-Neldel rule. In such experiments, the activation energy is changed by changing composition of the glassy sample. In the present work we have changed ΔE by applying high electric fields. It is shown that Meyer–Neldel rule is obeyed in this case also where composition of the material is not changed. This indicates that this rule is more general in chalcogenide glasses and is not due to changes in certain parameters on changing composition. The implications of these results have also been discussed in the present paper.
Desorption of Hydrogen from SmH3-δFilms: Effect of Palladium Overlayer Thickness
Authors: Kumar Pushpendra , Malhotra Lalit
Published: February 2005

Desorption of hydrogen from palladium-capped SmH3-δfilms of 55 nm thickness has been studied using optical measurements. Result show that the thickness of the palladium cap layer affects the deloading of hydrogen from the hydrided films. The direct band gap of the SmHxfilms, calculated from the (αhν)2vs hν plots, has been found to decrease with increasing thickness of the palladium overlayer, a fact attributed to the enhanced deloading of hydrogen. The removal of hydrogen from these films also leads to the formation of localized states, whose signature is clearly visible in these plots.
A Novel Method of Removing Impurities from Multilevel Interconnect Materials
Authors: Fukuda Takuya , Yanazawa Hiroshi
Published: February 2005

A novel method of removing impurities from dielectric films has been developed. The removal of water and charges is accomplished by humidification and wet pretreatment followed by charge extraction with CO2 supercritical fluid (SCF). Films treated in this manner exhibit intrinsic properties, which are usually masked by moisture and impurities.
Effects of Zn Doping on the Superconducting Properties of the Melt Textured Dy–Ba–Cu–O Bulk Superconductors
Authors: Latha Balakrishnan , Ikuta Hiroshi , Mizutani Uichiro
Published: February 2005

We prepared the c-axis oriented, 16-mm-diameter, Zn-doped Dy–Ba–Cu–O (DyBCO) bulk superconductors by the cold-seeding technique and studied their position dependent superconducting properties. It was found that the superconducting transition temperature (T
c) was almost the same for all positions of the undoped superconductor. The critical current density (J
c) and the density of the Dy2BaCuO5 (Dy211) secondary phase inclusions increased with the distance from the seed crystal. T
c decreased monotonically from 91.5 to 88 K as the ZnO content increased from 0 to 0.075 wt.%. In contrast, a well pronounced peak effect with high J
c was observed for both pure and optimally Zn-doped DyBCO samples. A maximum trapped flux density (B
max) of 0.48 T was recorded for the 0.025 wt.% ZnO doped bulk superconductor. These results suggest that Zn-doping is one of the most effective methods of enhancing J
c and B
max, since nanometric defects generated by chemical doping are likely to act as effective field-induced pinning centers.
Mechanism of Nonalloyed Al Ohmic Contacts to n-Type ZnO:Al Epitaxial Layer
Authors: Kim Han-Ki , Seong Tae-Yeon , Kim Koung-Kook , Park Seoug-Ju , Yoon Young Soo , Adesida Ilesanmi
Published: February 2005

The mechanism of Al ohmic contacts to n-type zinc oxide (ZnO:Al) epitaxial layer was investigated. The formation of an Al-ZnO interfacial phase at room temperature was responsible for the low specific resistivity (8±0.3×10-4 Ωcm2). The results of Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) depth profiles, and glancing angle X-ray diffraction (GXRD) indicate that an interfacial reaction between Al and ZnO results in an increased doping concentration in the region of the ZnO surface resulting in a low specific contact resistivity without the need for a thermal annealing process.
A Single-Shot Transient-Grating Autocorrelator for the Measurement of Femtosecond Laser Pulses in the Ultraviolet
Authors: Takatoi Katsutoshi , Suda Akira , Oishi Yu , Wang Pengqian , Nagasaka Keigo , Midorikawa Katsumi
Published: February 2005

We have developed a single-shot transient-grating autocorrelator that is capable of measuring femtosecond pulses in the ultraviolet region. The single-shot transient-grating method provides a simple and reliable measurement without any of the effects caused by shot-to-shot fluctuations of the pulses. The influence of nonlinear phenomena at high intensities can be observed in pulses amplified by a KrF laser.
Positive and Negative Optical Responses in High-Electron Mobility Transistors and Their Applications to Optically Controlled Microwave Oscillators
Authors: Ishikawa Atsushi , Murata Hiroshi , Tanaka Takuo , Shiomi Hidehisa , Okamura Yasuyuki , Yamamoto Sadahiko
Published: February 2005

We investigated optical responses of high-electron mobility transistors (HEMTs) by the use of a tightly focused optical beam. Positive and negative optical responses in the HEMTs were observed according to the irradiation position of the optical beam. The positive optical response was obtained by the optical beam irradiation close to the gate electrodes of the HEMTs with appropriate DC-bias voltages. While the negative optical response was obtained by the optical beam irradiation away from the gate electrodes. The light-induced increase and decrease of the drain currents were observed over 1 mA by the irradiation of a 10 µW CW light beam. The increase and decrease by as much as 5 dB of the small signal gain of the HEMTs in the microwave frequency range were also observed. We also applied these irradiation-position-dependent positive and negative optical responses to the optical control of the microwave oscillator composed of the HEMT. Microwave oscillations at 11.7 GHz from the oscillator were switched between “ON” and “OFF” by the selective irradiation of the successive focused light pulses.
Enhanced Photovoltaic Performance in Fullerene:Phthalocyanine Codeposited Films Deposited on Heated Substrate
Authors: Suemori Kouji , Miyata Takahiro , Hiramoto Masahiro , Yokoyama Masaaki
Published: February 2005

The photovoltaic performance of codeposited films of fullerene and metal-free phthalocyanine was confirmed to be affected by their nanostructure which can be controlled by adjusting substrate temperature during codeposition. Crystalline-amorphous nanocomposites possessing individual transport routes for electrons and holes showed the largest photocurrent. A photoelectric conversion efficiency of 0.56% was observed.
Study of Pulse Laser Assisted Metalorganic Vapor Phase Epitaxy of InGaN with Large Indium Mole Fraction
Authors: Kangawa Yoshihiro , Kawaguchi Norihito , Hida Ken-nosuke , Kumagai Yoshinao , Koukitu Akinori
Published: February 2005

The indium composition of the InGaN film increases with decreasing growth temperature; however, the crystalline quality of the film is poor when it is grown at low temperatures. To form a high-quality InGaN film with a large indium mole fraction, Nd: YAG pulse laser assisted metalorganic vapor phase epitaxy (MOVPE) was carried out at low temperatures. The results suggest that film quality can be improved by pulse laser irradiation on the surface of the film.
Intrinsic Valence Band Study of Molecular-Beam-Epitaxy-Grown GaAs and GaN by High-Resolution Hard X-ray Photoemission Spectroscopy
Authors: Kobayashi Keisuke , Takata Yasutaka , Yamamoto Tetsuya , Kim Jung-Jin , Makino Hisao , Tamasaku Kenji , Yabashi Makina , Miwa Daigo , Ishikawa Tetsuya , Shin Shik , Yao Takafumi
Published: February 2005

The electronic structures of molecular beam epitaxy (MBE)-grown GaAs and GaN have been studied by means of a technique using a newly developed surface-insensitive probe, namely, high-resolution hard X-ray (HX) synchrotron radiation (hν= 5.95 keV) photoemission spectroscopy (PES). The obtained valence band spectra and shallow core electronic states are compared with those calculated by the full-potential local density approximation (LDA) calculations explicitly including the Ga 3dcore state. The experimental valence band spectra show a very good match with the calculations, simulated with linear combinations of the partial density of states. The Ga 3dcore ondcore states in GaN indicates a set of fine structures which are attributed to the Ga 3d-N 2shybridization effect. The present experiments indicate that HX-PES provides an indispensable probe for investigating valence band electronic structures of materials, which has so far been impossible due to the limitations of proper surface preparation methods.
Micro-pixel Design Milliwatt Power 254 nm Emission Light Emitting Diodes
Authors: Wu Shuai , Adivarahan Vinod , Shatalov Maxim , Chitnis Ashay , Sun Wen-Hong , Khan M. Asif
Published: February 2005

We report on AlGaN based deep ultraviolet (UV) light emitting diodes (LED) with a novel micro-pixel design and emission at 254 nm. The micro-pixel design was adopted to improve the lateral current spreading and to reduce the operation voltages. For a 4 ×4 and 10 ×10 interconnected 30 µm diameter micro-pixel design, the device series resistances as low as 17 Ω and 11 Ω were measured. For an unpackaged 10 ×10 pixel design LED, pulsed output power as high as 1 mW was measured at a pump current of 1 A which translates to a peak external quantum efficiency of 0.02%.
Two-Beam-Combined 7.4 J, 50 Hz Q-switch Pulsed YAG Laser System Based on SBS Phase Conjugation Mirror for Plasma Diagnostics
Authors: Yoshida Hidetsugu , Nakatsuka Masahiro , Hatae Takaki , Kitamura Shigeru , Sakuma Takeshi , Hamano Takashi
Published: February 2005

The phase conjugation of the optically nonlinear stimulated Brillouin scattering (SBS) process using heavy-fluorocarbon materials effectively compensated thermal degradation at two amplifier lines, resulting in an output energy of 7.4 J at 50 Hz. When combining two beams, the beat wave generation caused by the temporal coherence between the two beams can be prevented because the two beams leave at intervals longer than the coherence length of the pulse. The use of different Brillouin frequencies of reflection from different SBS substances can also be effective in preventing the interference effect caused by the spatial coherence between the two beams.
Nanoscale Dots Fabrication by Volume Change Thermal Lithography
Authors: Kuwahara Masashi , Kim Jooho , Yoon Duseop , Tominaga Junji
Published: February 2005

We have developed a novel lithography technique, called the “volume-change thermal-lithography”, for fabricating minute dots in less than 100 nm diameter. The combination of the temperature distribution induced by a focused laser beam with a Gaussian distribution and a specially designed multilayer, which consists of TbFeCo and ZnS-SiO2 films, enabled us to produce minute dots. Using a laser beam with a 405 nm wavelength, we succeeded in fabricating dots whose pitch and size are far beyond the optical diffraction limit. Furthermore, we delineated letters of approximately 1 µm size by dot arrangement for showing the high potential for more complicate fabrication using the technique.
Processing Strategies for Protecting Integrated Circuit Pattern from Damage Due to a Dicing Saw Blade
Authors: Lee Seong-Min
Published: February 2005

In the present study, in order to protect the integrated circuit (IC) patterns from the impact due to a dicing saw blade, the pattern layers on the scribe regions of a semiconductor wafer are selectively removed and so, their bare silicon surfaces are exposed therein. The scribe regions (where the layers are absent) are then replaced by polyimide prior to the wafer dicing process. Since the polyimide film has a considerably larger adhesion strength with the silicon surface than other pattern layers or plastic-encapsulants have, it effectively accommodates the impact of the saw blade. According to the experimental results, the IC devices having discontinuous layers on the scribe regions exhibit excellent thermal cycling reliability, regardless of dicing process conditions.
Photoinduced Patterning of Gold Thin Film
Authors: An Ilsin , Seong Deokkyeong , Oh Hyekeun
Published: February 2005

We report a novel etching technique for gold film based on a new phenomenon that gold is soluble in chlorine-containing solutions or solvents under UV irradiation. This is a promising method for gold patterning possibly in microdevice or nanodevice fabrication. Mask patterns can be transferred to a gold surface directly without resorting to a complex photoresist process, and etch rate can be controlled from sub-nanometer to a few tens of nanometers per minute by adjusting exposure parameters. Moreover, nontoxic liquid such as NaCl solution can be used for the process.
Electronic Transport in Multiwalled Carbon Nanotubes Contacted with Patterned Electrodes
Authors: Hobara Rei , Yoshimoto Shinya , Ikuno Takashi , Katayama Mitsuhiro , Yamauchi Norihiro , Wongwiriyapan Winadda , Honda Shin-ichi , Matsuda Iwao , Hasegawa Shuji , Oura Kenjiro
Published: February 2005

The electrical conductance of 0.8∼5-µm-long multiwalled carbon nanotubes (MWCNT) was measured at room temperature in a multiprobe scanning tunneling microscope (STM)-scanning electron microscope (SEM) system and a conventional prober system, by bringing the MWCNTs into contact with patterned metal electrodes. The contact resistance between the CNTs and metal electrodes was sufficiently small. The conductance was proportional to A/L (and also to B/L, within our experimental error), where A, B, and L are the cross section, circumference, and length of CNTs. This indicates the occurrence of diffusive transport. A nonlinear current-voltage characteristic was obtained; the conductance increased steeply with current. A multiprobe STM-SEM system was very useful for measuring individual CNTs.
Al Gettering for InGaAsN in Metalorganic Chemical Vapor Deposition
Authors: Takeuchi Tetsuya , Chang Ying-Lan , Leary Michael , Mars Dan , Luan Hsin-Chiao , Roh S. David , Mantese Lucy-Marie , Song Yoon Kyu , Tandon Ashish , Twist Rosemary , Belov Sveylana , Bour David , Tan Michael
Published: February 2005

We proposed and demonstrated an Al gettering process for high-quality InGaAsN quantum wells grown by metalorganic chemical vapor deposition. Ammonia flow prior to InGaAsN growth eliminates undesirable Al incorporation in the InGaAsN continuously grown on GaAs/AlGaAs layers. The InGaAsN quantum well without Al contamination showed a smooth surface and strong photoluminescence intensity. An InGaAsN vertical cavity surface-emitting laser structure grown in a single-step process using the Al gettering process showed continuous-wave operations with 2.7 mW of 1279 nm emission at room temperature.
Air Core Thickness Dependence of Propagation Loss of Slab Hollow Waveguide
Authors: Sakurai Yasuki , Miura Toru , Koyama Fumio
Published: February 2005

We present the core thickness dependence of the propagation loss and the polarization dependence loss (PDL) of hollow waveguides of various air core thicknesses. The addition of phase-control layers to GaAs/AlAs multilayer mirrors enables us to reduce the PDL by one order of magnitude. The propagation loss and the PDL of a 5 µm air core hollow waveguide are 2.8 dB/cm and 1.7 dB/cm, respectively, which are currently limited by the reflectivity (0.998) of the GaAs/AlAs multilayer mirrors.
Vertical Junction Type Organic Photovoltaic Cells
Authors: Suemori Kouji , Miyata Takahiro , Hiramoto Masahiro , Yokoyama Masaaki
Published: February 2005

Vertical junction type organic photovoltaic cells having a pn junction formed perpendicularly to a light irradiated surface were fabricated. Short-circuit photocurrent density of 8.5 mA·cm-2 and power conversion efficiency of 0.54% were observed under simulated solar illumination. The large photocurrent density is attributed to the light collection effect via the transparent vertical layer.
Beam Combining for Three High-Power Laser-Diode Stacks with a Stripe Mirror Technique
Authors: Gao Xin , Ohashi Hiroyuki , Saitoh Masayuki , Okamoto Hiroshi , Takasaka Masaomi , Shinoda Kazunori
Published: February 2005

We describe a beam-combining technique for three high-power laser-diode stacks to effectively increase the power density. Employing this beam-combining technique using two slit-stripe mirrors, the power density increased to 722 W/cm2 from a raw power density of 291 W/cm2 by combining the beams of three high-power laser-diode stacks. We also achieved a focused power density of 250 kW/cm2 by focusing the combined beam of the three high-power laser-diode stacks with a lens of 40-mm focal length.
Optically Pumped Lasing at 353 nm Using Non-polar a-plane AlGaN Multiple Quantum Wells over r-plane Sapphire
Authors: Chen Changqing , Shatalov Maxim , Kuokstis Edmundas , Adivarahan Vinod , Gaevski Mikhail , Rai Shiva , Khan M. Asif
Published: February 2005

We report an optically-pumped alternative nitride-based laser with room-temperature emission at 353 nm. The active region comprised of non-polar a-plane Al0.04Ga0.96N/Al0.08Ga0.92N multiple quantum wells whereas the lasing cavity consisted of Al0.15Ga0.85N clad and Al0.10Ga0.85N waveguide layers and naturally cleaved facet mirrors. The layers were grown over r-plane sapphire substrates by metalorganic chemical vapor deposition technique. A room temperature lasing threshold for N2-laser photoexcitation of 110 kW/cm2 and a modal optical gain of 215 cm-1 was measured at the peak emission wavelength.
BB84 Quantum Key Distribution System Based on Silica-Based Planar Lightwave Circuits
Authors: Nambu Yoshihiro , Hatanaka Takaaki , Nakamura Kazuo
Published: February 2005

We constructed an optical interferometer for a Bennett-Brassard quantum key distribution system using integrated optics based on planar lightwave circuit technology, and tested its operation and stability. Experimental results show that this interferometer is useful in implementing a practical quantum key distribution system.
Temperature-Insensitive Eye-Opening under 10-Gb/s Modulation of 1.3-µm P-Doped Quantum-Dot Lasers without Current Adjustments
Authors: Otsubo Koji , Hatori Nobuaki , Ishida Mitsuru , Okumura Shigekazu , Akiyama Tomoyuki , Nakata Yoshiaki , Ebe Hiroji , Sugawara Mitsuru , Arakawa Yasuhiko
Published: February 2005

We demonstrate temperature-insensitive eye-opening under 10-Gb/s direct modulation of 1.3-µm p-doped quantum-dot lasers without using any current adjustments. The lasers show a 6.5-dB extinction ratio between 20°C and 70°C. An active region consisting of ten quantum-dot layers with p-type doping enabled this highly temperature-stable dynamic performance, which was much superior to conventional 1.3-µm quantum-well lasers. These results make it possible to use uncooled 1.3-µm quantum-dot lasers without any current adjustments.
Electrodeposition of Diamond-like Carbon Films on Silicon Substrates Using N,N-Dimethylformamid
Authors: Yasumori Yoshio , Okada Takumi , Kimura Hideki , Choe Il Yong , Kurosu Tateki , Iida Masamori
Published: February 2005

Diamond-like carbon (DLC) films were synthesized by an electrodeposition technique on silicon (Si) substrates using liquid N,N-dimethylformamid (DMF). The electrodeposition was performed in the temperature range from 40 to 80°C and the applied voltage range from -1 kV to -5 kV. The structures of the films were characterized by Raman spectroscopy. The films with the electrical resistivity of about 1010 Ω·cm can be deposited using the liquid DMF under the liquid temperature of 80°C and the applied voltage of -2 kV. Moreover, the current density has an important role in the deposition of the films.
Design Proposal of Light Emitting Diode in Vacuum Ultraviolet Based on Perovskite-Like Fluoride Crystals
Authors: Ouenzerfi Riadh EL , Ono Shingo , Quema Alex , Goto Masahiro , Sarukura Nobuhiko , Nishimatsu Takeshi , Terakubo Noriaki , Mizuseki Hiroshi , Kawazoe Yoshiyuki , Yoshikawa Akira , Fukuda Tsuguo
Published: February 2005

The variation of band gap energy, band structure and lattice constant of mixed LiBaF3, LiCaF3 and LiSrF3 perovskites is studied. The band structure and transition type of these fluorides is predicted by ab initio band calculation based on the local density approximation. The design principle of vacuum ultraviolet light emitting diode is proposed. The lattice-matched double-hetero structure of different perovskite-like fluorides is found to be sufficiently feasible to fabricate with direct-band-gap compounds LiBa
x
Ca
y
Sr(1-x-y)F3 on LiSrF3.
Fabrication of Porous Silica with Three-Dimensional Periodicity by Si Anodization
Authors: Asoh Hidetaka , Uehara Aya , Ono Sachiko
Published: February 2005

Ordered nanoporous silica has been fabricated using self-assembled polystyrene beads as a template for the anodization of a Si substrate in an aqueous solution. The closely packed structure of the nanospheres formed on the Si substrate could act as a template during anodization without additional fixation of beads onto the underlying substrate. The obtained porous silica with spatially ordered features up to a thickness of 5 µm, which could be produced only in the voids between the beads on the substrate, had a structure inverse to the colloidal crystal structure used as a template. The hole interval of porous silica, which was in good agreement with the diameter of the nanospheres, was slightly lower than that achieved by a conventional dry process.
Optimization of Device Design for Thin-Film Stacked Tandem Solar Modules in Terms of Outdoor Performance
Authors: Nakajima Akihiko , Ichikawa Mitsuru , Sawada Toru , Yoshimi Masashi , Yamamoto Kenji
Published: February 2005

The device current-voltage (I-V) characteristics of thin film silicon stacked tandem solar modules (HYBRID modules) consisting of a hydrogenated amorphous silicon (a-Si:H) cell and a thin-film microcrystalline silicon solar cell (µc-Si) have been investigated under various spectral irradiance distributions. The spectrometric characterization had revealed that the performance of the HYBRID module exposed to sunlight tended to be limited by the top a-Si:H cell due to the photodegradation of the top cell, and the bottom µc-Si cell of the modules was stable as before exposure. The HYBRID module limited by the top cell exhibited a more efficient performance than the bottom-limited module in natural sunlight at noon. This behavior is well explained by the contour analysis of the performance as a function of spectral irradiance ratio and module temperature.
Two-Dimensional Manipulation of Poly(3-dodecylthiophene) using Light-Driven Instant Mass Migration as a Molecular Conveyer
Authors: Zettsu Nobuyuki , Ubukata Takashi , Seki Takahiro
Published: February 2005

Microrelief structures were optically inscribed on binary polymer blend films which consist of a liquid crystalline azobenzene polymer as a host matrix and π-conjugated poly(3-dodecylthiophene) as a guest functional polymer. In this process, full migrations occurred to a level where the bare substrate surface was exposed within only 20 s. The inscribed film exhibited a high-contrast fluorescent pattern corresponding to the relief structure. We can conclude that poly(3-dodecylthiophene) is transferred together with the active migration of the azobenzene polymer. The light-driven mass migration technique which works as a molecular conveyer is useful in the two-dimensional patterning of functional materials.
Novel Electroluminescence Properties of Thin Films Using Soluble Metallophthalocyanine Salts
Authors: Ikeda Shingo , Matsuda Masaki , Ando Yoriko , Oh Ji-Won , Hanasaki Noriaki , Tajima Hiroyuki , Akiyama Hidefumi
Published: February 2005

We have prepared organic thin films of soluble dicyano(phthalocyaninato)iron salt, [(n-C7H15)4N][FeIII(Pc)(CN)2], and fabricated the electroluminescence (EL) devices having the Metal-Insulator-Metal structure. The device exhibits emission for both positive and negative bias voltages. We observed two bands in the EL spectra. One band was assigned to the Q band of the phthalocyanine molecule. The other, which shifts with changing the applied voltage, could correspond to the metal-to-ligand charge transfer (MLCT) band and/or the ligand-to-metal charge transfer (LMCT) band.
High Field-Effect Hole Mobility in Organic-Inorganic Hybrid Thin Films Prepared by Vacuum Vapor Deposition Technique
Authors: Matsushima Toshinori , Fujita Katsuhiko , Tsutsui Tetsuo
Published: February 2005

Organic-inorganic layered perovskite films, (C6H5C2H4NH3)2SnI4, were grown on 60°C substrates at a growth rate of 0.0005 nm/s by a vacuum vapor deposition technique, and field-effect transistors with a hybrid semiconductor were fabricated. From measurements of ultraviolet-visible (UV-VIS) absorption spectra and X-ray diffraction profiles, the vacuum-deposited films contained a well-developed layered perovskite structure, where inorganic sheets alternate with organic layers in the direction perpendicular to the substrate surface. In the field-effect transistors, the vacuum-deposited hybrid films acted as p-channel semiconductors and exhibited a hole mobility of 0.78 cm2/Vs in the saturation regime, a threshold voltage of -1.7 V, and a drain current on/off ratio of 4.2 ×105.
Impact of Image and Exchange-Correlation Effects on Ballistic Electron Transport in Nanoscale Double-Gate Metal–Oxide–Semiconductor Transistors
Authors: Iwata Hideyuki , Matsuda Toshihiro , Ohzone Takashi
Published: February 2005

The influence of image and many-body exchange-correlation effects on electron transport has been studied for nanoscale double-gate metal–oxide–semiconductor field-effect transistors (DG MOSFETs), using the non equilibrium Green function (NEGF) method. It has been found that the inclusion of image and exchange-correlation effects increases the calculated value of the drain current. This is because the potential energy is reduced except in some region around the surfaces, mainly due to the exchange-correlation effect. In this study, the wavefunction penetration into the gate oxide and gate electrode has also been taken into account. Compared to the case without considering this penetration, the electron occupancy of each valley type markedly changes though no substantial difference in the drain current is observed.
Anomalously Directed Amplified Spontaneous Emission from a Wedge-Shaped Cell Sandwiched by Cholesteric Liquid Crystal Films
Authors: Nagata Takaaki , Ohta Takashi , Song Myoung Hoon , Takanishi Yoichi , Ishikawa Ken , Watanabe Junji , Toyooka Takehiro , Nishimura Suzushi , Takezoe Hideo
Published: February 2005

An amplified spontaneous emission (ASE) from wedge-shaped cells of dye-doped glycerol sandwiched between two cholesteric liquid crystal films has been studied. Upon laser excitation at nearly normal incidence on a slightly wedged cell with a wedge angle of 1.2°, ASE occurs along the direction oblique (about 45°) to the surface normal. This effect was interpreted by increasing the incidence angle and consequent shift of a photonic band upon successive internal reflection in the wedge cell.
Magnetic Cluster Behavior of α-LiFeO2 Related to the Cation Arrangements
Authors: Kohiki Shigemi , Hori Kyoko , Ogawa Kazuyuki , Shimooka Hirokazu , Tajiri Takayuki , Deguchi Hiroyuki , Mitome Masanori , Bando Yoshio
Published: February 2005

In transmission electron microscopy of α-LiFeO2, we found electron diffraction patterns of both cubic structure (a = 4.2 Å) and doubled unit cell structure (a = 8.3 Å) with wavy shaped diffuse scattering due to short-range ordering of Li+ and Fe3+ ions. An unusual magnetic state with coexistence of phenomena related to magnetic ordering and glassy behavior in the a
c and d
c susceptibilities was observed for α-LiFeO2. The bifurcation point was ≈90 K, and the temperature of a broad maximum in the zero-field cooled susceptibility was ≈40 K. Below ≈90 K, the field cooled susceptibility increased monotonically and the zero-field cooled susceptibility deviated below the field cooled one with lowering the temperature. The in-phase a
c susceptibility demonstrated a cusp at ≈90 K with a broad shoulder around 60 K. The third harmonic nonlinear susceptibility showed no sharp peak below 200 K. Observed magnetic behavior of α-LiFeO2 can be understood as formation of ferromagnetic clusters, with short-range ordering of Fe3+ spins within the clusters, and progressive freezing of the clusters. The unusual glassy behavior is due to the short-range ordering of cubic structure in α-LiFeO2.
Comparison of Capped Carbon Nanotube with Open-Ended One for Field Emission
Authors: Tanaka Hiroyoshi , Akita Seiji , Pan Lujun , Nakayama Yoshikazu
Published: February 2005

Field emission properties of standalone carbon nanotubes have been investigated in terms of the capped and open-ended tip shapes. The capped multiwall nanotube with a tip curvature of ∼2.5 nm is compared with the open-ended single wall nanotube with a diameter of ∼5 nm. These samples have almost the same current-voltage characteristics but show different field-emission-microscope images. The capped one shows some bright spots and in contrast the open-ended one shows twelve bright stripes with a spindle shape. The magnification of the images is larger for the capped one than for the open-ended one.
A Vibrating String-Type Multifunctional Tactile Sensor for Material Property Analysis
Authors: Chi Zhiyu , Shida Katsunori
Published: February 2005

The main objective of this study is to propose a vibrating string-type multifunctional tactile sensor with a simple structure to analyze some properties of an object imitating an animal antenna. It is characterized by a small sensing area and moving measurement method. Three sensing functions are involved in the entire multifunctional sensing, and in each sensing function, a single property of a test object is obtained. By analyzing the output of the sensor, three material properties, that is, hard or soft, smooth or rough, and flat or curved surface can be obtained. Here, we discuss the design guideline for and the structure of the sensor, with deep inquiries into three measuring methods and experimental results.
Crystallinity and Photocatalytic Activity of TiO2 Films Deposited by Reactive Sputtering Using Various Magnetic Field Strengths
Authors: Song Pung Keun , Irie Yukiko , Ohno Shingo , Sato Yasushi , Shigesato Yuzo
Published: February 2005

TiO2 films were deposited by r.f. reactive magnetron sputtering on nonalkali glass without substrate heating using a 3-inch-φ magnetron cathode with various magnetic field strengths (MFS, 150–1000 G) and shapes (balanced or unbalanced) at a total gas pressure of 1.0 or 3.0 Pa. The crystallinity and photocatalytic activity of TiO2 films showed a clear tendency to decrease with the decrease in MFS during the deposition. Decrease in plasma impedance by increasing the MFS was confirmed to be effective in the deposition of high-performance photocatalytic TiO2 films by magnetron sputtering.
Extraction of Trap Distribution in Organic Semiconductors by Transient Photocurrent
Authors: Ohno Akira , Hanna Jun-ichi , Dunlap David H. , Cabral Aaron
Published: February 2005

The mobility of photoinjected holes in smectic-B liquid crystals as measured by time of flight shows an electric field dependence at low fields. This dependence is suspect, for whether the mobility rises or falls with field depends on the method by which the photocurrent transients are analyzed. In the context of the multiple trapping model, a general formalism is developed for analyzing the transients, in which the distribution of traps may be determined under the assumption that the Einstein relation between the mobility and the diffusion constant is obeyed. For the smectic-B liquid crystal, this distribution is adequately described by a Gaussian of depth 100 meV and width 50 meV.