bluuebunny/crossref_metadata_2025 huggingface dataset:
Broadband Supercontinuum Spectrum Generated Highly Nonlinear Photonic Crystal Fiber Applicable to Medical and Optical Communication Systems
Authors: Begum Feroza , Namihira Yoshinori , Kaijage Shubi F. , Kinjo Tatsuya
Published: September 2011

Optical-fiber-based supercontinuum (SC) light sources have attracted much research attention in recent years. High-quality nonlinear optical fibers allow us to readily implement stable and practical SC sources. In this work, we present a highly nonlinear photonic crystal fiber (HN-PCF) in optical coherence tomography (OCT) and telecommunication windows that can generate SC spectra. The finite difference method with an anisotropic perfectly matched layer boundary condition is used to calculate different properties of the proposed HN-PCF. From numerical simulation results, it is found that the HN-PCF nonlinear coefficients are more than 108.0, 74.0, and 53.0 (W·km)-1 at 1.06, 1.31, and 1.55 µm, respectively. The flattened chromatic dispersion is 0 to -4.0 ps/(nm·km) in the wavelength range of 1.06 to 1.7 µm (640 nm bandwidth), and the confinement loss is lower than 10-2 dB/km in the entire wavelength range. The generated supercontinuum bandwidths are 295.0, 408.0, and 590.0 nm at 1.06, 1.31, and 1.55 µm, respectively. The calculated longitudinal resolutions for biomedical imaging are 1.2, 1.2, and 1.1 µm at 1.06, 1.31, and 1.55 µm, respectively.
Volume Bragg Grating-Based 70 nm Tunable and Narrow Output Spectra from a Ti:sapphire Laser
Authors: Chung Te-Yuan , Chiang Cheng-Yeh , Liang Chao-Wen
Published: September 2011

In this study, a simple V-shaped cavity Ti:sapphire laser setup is developed using a volume Bragg grating (VBG) as the folding mirror. The laser can reach single longitudinal mode operation with an output power of up to 30 mW and a tunability exceeding 70 nm. The unexpected asymmetric reduction observed in the VBG reflectivity is discussed.
Suppression of Precipitates in the La2-xSrxCuO4 Films Grown on LaSrAlO4 Substrates by Introducing Homoepitaxial Layer
Authors: Li Bing-Sheng , Sawa Akihito , Okamoto Hiroshi
Published: September 2011

We have investigated impacts of a LaSrAlO4 (LSAO) homoepitaxial layer (HL) on the quality of La2-x
Sr
x
CuO4 (LSCO) films grown on single crystal LSAO (001) substrates by pulsed laser deposition. Introduction of the LSAO HL significantly suppressed the segregation of impurity phases in the LSCO films especially in a higher Sr-doping range (x > 0.20), leading to the improvement of the surface morphology. The suppression of impurity phases also enables us to obtain the desired stoichiometry of the LSCO films, which show the superconducting dome in the x-temperature phase diagram very similar to that of bulk samples.
Effect of Heating and Cooling of Photogenerated Electron–Hole Plasma in Optically Pumped Graphene on Population Inversion
Authors: Ryzhii Victor , Ryzhii Maxim , Mitin Vladimir , Satou Akira , Otsuji Taiichi
Published: September 2011

We study the characteristics of photogenerated electron–hole plasma in optically pumped graphene layers at elevated (room) temperatures when the interband and intraband processes of emission and absorption of optical phonons play a crucial role. The electron–hole plasma heating and cooling as well as the effect of nonequilibrium optical phonons are taken into account. The dependences of the quasi-Fermi energy and effective temperature of optically pumped graphene layers on the intensity of pumping radiation are calculated. The variation of the frequency dependences dynamic conductivity with increasing pumping intensity as well as the conditions when this conductivity becomes negative in a certain range of frequencies are considered. The effects under consideration can markedly influence the achievement of the negative dynamic conductivity in optically pumped graphene layers associated with the population inversion and, hence, lead to the in-depth understanding of the experimental results and the realization graphene-based terahertz and infrared lasers operating at room temperatures.
Experimental Study on Electron Mobility in Accumulation-Mode Silicon-on-Insulator Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Kadotani Naotoshi , Ohashi Teruyuki , Takahashi Tsunaki , Oda Shunri , Uchida Ken
Published: September 2011

Junctionless, or accumulation-mode, metal–oxide–semiconductor field-effect transistors (MOSFETs), where the channel and source/drain doping types are the same, have attracted growing interests because of their simpler fabrication processes. However, carrier transport properties, in particular, mobility characteristics, in the junctionless silicon-on-insulator (SOI) MOSFETs have been less studied. Although higher mobility in accumulation-mode SOI MOSFETs has been reported, the physical mechanisms of the higher mobility have not yet been clarified. In this work, the physical mechanisms of higher mobility in accumulation-mode MOSFETs have been investigated. We fabricated junctionless SOI MOSFETs with a channel doping concentration of 1×1017 cm-3 and an SOI body thickness of 48 nm whose mobility is greater than the bulk universal mobility in spite of the high doping concentration in the channel. The drain current consists of two components: one in the accumulation layer and the other in the SOI body. The mobility of each component is evaluated separately. As a result, it is revealed that the total mobility is the weighted mean of the two mobility components, where carrier concentration is the weight.
A Physics-Based Effective Mobility Model for Polycrystalline Silicon Thin Film Transistor Considering Discontinuous Energy Band at Grain Boundaries
Authors: Yan Bing-Hui , Li Bin , Yao Ruo-He , Wu Wei-Jing
Published: September 2011

A physics-based effective mobility model for polycrystalline silicon (poly-Si) thin film transistor (TFT) is developed by considering the discontinuous energy band between grain and grain boundary and Gaussian energy distribution at grain boundary. Three conduction mechanisms, thermionic-emission effect, drift-diffusion effect and tunneling effect, are introduced to describe the mobility. It is found that the physical factors, such as the trapped state distribution at grain boundary, the additional potential barrier, the rate of carriers' thermal velocity to diffusion velocity and the in-grain quality, have a strong influence on the effective mobility of poly-Si TFT and would not be neglected or replaced by some fitting parameters. The proposed model provides an accurate and analytical description for the effective mobility of poly-Si TFT. The calculated results of the proposed model are verified by the experimental data.
Single Electron Fault Modeling in Basic Quantum Devices
Authors: Mahdavi Mojdeh , Mirzakuchaki Sattar , Moghaddasi Mohammad Naser , Amiri Mohammad Amin
Published: September 2011

Quantum cellular automata represents an emerging technology at the nanotechnology level. There are various faults which may occur in quantum cellular automata cells. One of these faults is the single electron fault that can happen during manufacturing or operation of quantum cellular automata circuits. The behavior of single electron fault in quantum cellular automata devices is not similar to either previously investigated faults or conventional complementary metal oxide semiconductor (CMOS) logic. A detailed simulation based logic level modeling of single electron fault for quantum cellular automata binary wire and majority gate is represented in this paper. Results show that if a single electron fault occurs in a binary wire, the logic value of that wire will be inverted and if a single electron fault occurs in a majority gate, the logic value of that gate will be changed.
Multilevel Charge Storage in a Multiple Alloy Nanodot Memory
Authors: Lee Gae-Hun , Lee Jung-Min , Song Yun Heub , Bea Ji Chel , Tanaka Tetsu , Koyanagi Mitsumasa
Published: September 2011

A multilevel charge storage in a multiple FePt alloy nanodot memory is investigated for the first time. It is demonstrated that the memory structure with multiple FePt nanodot layers effectively realizes a multilevel state by the adjustment of gate voltage. Metal oxide semiconductor (MOS) capacitors with four FePt nanodot layers as a floating gate are fabricated to evaluate the multilevel cell characteristic and reliability. Here, the effect of memory window for a nanodot diameter is also investigated, and it is found that a smaller dot size gives a larger window. From the results showing good endurance and retention characteristics for the multilevel states, it is expected that a multiple FePt nanodot memory using Fowler–Nordheim (FN) tunneling can be a candidate structure for the future multilevel NAND flash memory.
Carrier Transport in Volatile Memory Device with SnO2Quantum Dots Embedded in a Polyimide Layer
Authors: Wu Chaoxing , Li Fushan , Guo Tailiang , Kim Tae Whan
Published: September 2011

Carrier transport in a volatile memory device utilizing self-assembled tin dioxide quantum dots (SnO2QDs) embedded in a polyimide (PI) layer was investigated. Current–voltage (I–V) curves showed that the Ag/PI/SnO2QDs/PI/indium–tin-oxide (ITO) device memory device had the ability to write, read, and refresh the electric states under various bias voltages. The capacitance–voltage (C–V) curve for Ag/PI/SnO2QDs/PI/p-Si capacitor exhibited a counterclockwise hysteresis, indicative of the existence of sites occupied by carriers. The origin of the volatile memory effect was attributed to holes trapping in the shallow traps formed between QD and PI matrix, which determines the carrier transport characteristics in the hybrid memory device.
Micro-Pump–Probe Spectroscopy of an Exciton in a Single Semiconductor Quantum Dot Using a Heterodyne Technique
Authors: Mitsumori Yasuyoshi , Miyahara Yuki , Uedaira Kentaro , Kosaka Hideo , Shimomura Satoshi , Hiyamizu Satoshi , Edamatsu Keiichi
Published: September 2011

A heterodyne detection scheme was applied to micro-pump–probe spectroscopy to study the transient response of an exciton in a single semiconductor quantum dot. The elimination of the pump pulse in the frequency domain provided us a direct probing of the energy relaxation process of the quantum state excited by the pump pulse. The excitonic Rabi oscillations were also monitored by this technique, even in the presence of a strong pump pulse. This spectroscopic technique is suitable for the observation of the optical response and coherent manipulation of a semiconductor quantum dot.
Mechanism of Prism-Coupled Scanning Tunneling Microscope Light Emission
Authors: Iida Wataru , Ahamed Jamal U. , Katano Satoshi , Uehara Yoichi
Published: September 2011

We have investigated the mechanism of scanning tunneling microscope light emission (STM-LE) in a prism-coupled configuration using finite difference time domain analysis. In this configuration, the sample is a metallic thin film evaporated on the bottom surface of a hemispherical glass prism. STM light emitted into the prism (prism-side emission) through the metallic film is measured. Since both localized surface plasmons (LSP) and surface plasmon polaritons (SPP) contribute to prism-side emission, this emission is stronger than that in conventional STM-LE measured from the sample surface side, which is radiated by LSP alone. We show that the spatial resolution of prism-side emission is determined not by the propagation length of SPP, but by the lateral size of LSP, similarly to conventional (i.e., tip side) STM-LE. Thus, we conclude that, by using the prism-coupled configuration, the signal level of STM-LE improves without the loss of spatial resolution attained in tip side emission.
Crystal Structure of New Carbon–Nitride-Related Material C2N2(CH2)
Authors: Sougawa Masaya , Sumiya Takahiro , Takarabe Kenichi , Mori Yoshihisa , Okada Taku , Gotou Hirotada , Yagi Takehiko , Yamazaki Daisuke , Tomioka Naotaka , Katsura Tomoo , Kariyazaki Hiroaki , Sueoka Koji , Kunitsugu Shinsuke
Published: September 2011

A new carbon–nitride-related C2N2(CH2) nanoplatelet was synthesized by subjecting a precursor C3N4H
x
O
y
nanoparticle in a laser-heating diamond anvil cell to the pressure of 40 GPa and temperature of 1200–2000 K. The C and N composition of the quenched sample was determined to be C3N2 by using an energy dispersive X-ray spectroscope attached to a transmission electron microscope. The crystal structure and atomic positions of this C3N2 were obtained through Rietveld analysis of the X-ray diffraction pattern measured using synchrotron radiation. The hydrogen composition was difficult to determine experimentally because of the several-hundred-nanometer dimensions of the sample. First-principles calculation was alternatively used to discover the hydrogen composition. The synthesized C2N2(CH2) was accordingly found to be an orthorhombic unit cell of the space group C
m
c21 with lattice constants a = 7.625 Å, b = 4.490 Å, and c = 4.047 Å. If the CH2 atomic unit is replaced with the CN2 atomic unit and the bonding rearranged, the C2N2(CH2) becomes the expected superhard C3N4.
The Effect of Carrier Injection Stress on Boron-Doped Amorphous Silicon Suboxide Layers Investigated by X-ray Photoelectron Spectroscopy
Authors: Lee Sunhwa , Park Seungman , Park Jinjoo , Kim Youngkuk , Yoon Kichan , Shin Chonghoon , Baek Seungsin , Kim Joondong , Lee Youn-Jung , Yi Junsin
Published: September 2011

In amorphous silicon solar cells, reducing degradation is one of the key issues in improving cell performance. The degradation of the p-layer can play an important role since it is directly related to the open circuit voltage (V
oc) and fill factor (FF) in the cells. In this study, we investigated the changes in boron-doped p-type silicon suboxide (SiO
x
) layers after carrier injection stress. The boron doping level was varied by controlling B2H6 gas flow rate. When these layers were degraded, the dark conductivity decay decreased from 53% to less than 5%, and the increase in activation energy decreased from 11 to 0.5% depending on the B2H6 gas flow rate increase. Our improvements are explained in conjunction with the three- and four-fold coordinated boron atoms by the shift of the B 1s X-ray photoelectron spectrum. In this paper we present how to improve the stability of hydrogenated amorphous silicon (a-Si:H) thin-film solar cells.
Discharge Luminescence Characteristics of Ultrahigh-Resolution Plasma Display Panels with a 0.3-mm Pixel Pitch
Authors: Ishii Keiji , Hirano Yoshikuni , Murakami Yukio , Kikuchi Naoya , Sumita Isao
Published: September 2011

We experimentally investigated the effect of increased generation efficiency of excited Xe atoms on ultrahigh-resolution plasma display panels (PDPs). At a horizontal cell pitch of 0.1 mm, the sustain voltage increased; however, the generation efficiency was equal to or higher than that obtained at the conventional 0.22-mm cell pitch. We investigated the luminous efficiency of fine-pitch discharge cells, which are fabricated with fine-grain colour phosphors. The absolute luminous efficiency of the experimental fine pitch panel is estimated to be 0.68 lm/W.
Modified Reset Waveform for High Speed Address under High Ambient Temperature in AC Plasma Display Panel
Authors: Jang Soo-Kwan , Park Hyung Dal , Tae Heung-Sik , Shin Bhum Jae , Seo Jeong Hyun
Published: September 2011

Achieving a stable and fast address discharge under a high ambient temperature depends strongly on how constant the wall voltage formed through the reset discharge remains throughout the address period. It was observed that the wall voltage after the reset period varied considerably under a high ambient temperature, thereby aggravating a stable address discharge, mainly due to an increase in the formative discharge delay. Thus, based on the fact that the wall voltage variation during an address period is directly related to the emission of exo-electrons from the MgO surface, it was anticipated that forcing the emission of the exo-electrons prior to the address period would minimize the wall voltage variation during the address period. As a result, the proposed reset waveform with the ramp-up holding part optimized according to the subfield conditions was able to minimize the wall voltage variation during the address period, achieving a fast and stable address discharge under a high ambient temperature of +65 °C in a 50-in. AC plasma display panel (PDP) with full high-definition (HD) resolution.
Improvement of the Size-Selective Separation of Microbeads in a Curved Microchannel Using Particle Focusing
Authors: Kwon Bong Hyun , Kim Hyung Hoon , Cha Jemyung , Ahn Cheol Hee , Arakawa Takahiro , Shoji Shuich , Go Jeung Sang
Published: September 2011

The size-selective microfluidic separation of glass beads in a curved rectangular microchannel was fabricated in our previous work. In this study, we improve its separation performance and attempt an experimental visualization to examine the separation resolution. In the previous work, we found by visualization that the trajectory of 20 µm glass beads was influenced by their travelling path along a straight inlet channel. Using a forced sheath flow, a consistent bead trajectory along the middle of the straight inlet channel was obtained, and the sheath angle to minimize the focusing width of the flowing distributed beads was determined to be 45°. The physical explanation for the dynamic behavior of microbeads was elaborated. When the ratio of Stokes force to centrifugal force mainly acting on a glass bead fell under unity, the glass bead moved out to the wall in spite of the fact that its size was less than the height of the zero velocity position. To examine the separation resolution, the newly designed size-selective separation microchannel with the sheath was fabricated and its separation performance was visualized. The movement of the glass beads showed a good agreement with the separation mechanism explained by the force ratio. The resolution of the separation was visualized to be 10 µm for the size of glass beads used in the experiment. The size-selective separation performance was explained in terms of physical forces and was improved by solving the previous problems. A cascade device for the continuous separation of microbeads of various sizes can improve the separation resolution.
Numerical Analysis of the Microwave Heating of Compacted Copper Powders in Single-Mode Cavity
Authors: Maxim Ignatenko , Tanaka Motohiko
Published: September 2011

Recently, microwave single-mode cavities have been used to isolate and study the effects of electric and magnetic field components on the temperature and microstructure of samples. This paper discusses the conditions affecting the heating of metal powders in this kind of experiments. In addition, it studies general trends in the interaction of microwaves with powders of different sizes and densities. As an example, it numerically analyses the microwave heating of copper powders in single-mode WR284 TE102cavity. The optical and thermal parameters of metal powders are estimated by means of Bruggeman's effective medium approximation combined with Mie theory. Analysis shows the strong influence of the device on the temperature of samples located in the electric field maximum. In addition, the study demonstrates the existence of standing waves inside samples. In this case, high temperature is attained easily when samples are placed in the magnetic field maximum.
Soft X-ray Conversion Efficiencies in Laser-Produced Xenon and Tin Plasmas in a 5–17 nm Wavelength Range
Authors: Inoue Tomoaki , Mochizuki Takayasu , Miyamoto Shuji , Amano Sho , Watanabe Takeo , Kanda Kazuhiro
Published: September 2011

Soft X-ray conversion efficiencies in a 5–17 nm wavelength range in xenon and tin plasmas produced by a 1.06 µm Q-switched neodymium-doped yttrium aluminum garnet laser were investigated. They were measured to be 25 and 20% for the xenon and tin plasmas, respectively at a laser intensity of about 2×1010 W/cm2. These results indicate that a stand-alone soft X-ray source using a laser-produced xenon or tin plasma is useful for various applications that require intense, soft X-ray photons in a wide wavelength range.
Ion Beam Bombardment Effect on Contacts in Solution-Processed Single-Walled Carbon Nanotube Thin Film Transistor
Authors: Yi Xun , Nakagawa Gou , Ozawa Hiroaki , Fujigaya Tsuyohiko , Nakashima Naotoshi , Asano Tanemasa
Published: September 2011

Effect of argon ion bombardment (AIB) on performance of solution-processed single-walled carbon nanotube (SWCNT) thin film transistor (TFT) has been investigated. AIB was applied to the source/drain contacts to reduce contact resistance. It was found that AIB enhances on-state current of TFT. Over 5 decades' on/off ratio is obtained by applying AIB. Results of transmission line method using metallic SWCNT clearly indicate that contact resistance between CNT network and Au electrode is reduced by the application of AIB.
Fabrication of Ni/Al2O3/Ni Heteroepitaxial Junction by Post-Hydrogen Reduction of NiO/Al2O3/NiO Trilayered Epitaxial Thin Film
Authors: Yamauchi Ryosuke , Kobayashi Keisuke , Hosaka Makoto , Suzuki Toshimasa , Koyama Kohji , Matsuda Akifumi , Arai Hideki , Kato Yushi , Mitsuhashi Masahiko , Kaneko Satoru , Yoshimoto Mamoru
Published: September 2011

The fabrication of a Ni/Al2O3/Ni heteroepitaxial junction was achieved by the post-hydrogen reduction of a NiO/Al2O3/NiO trilayered epitaxial thin film grown by pulsed laser deposition. The top and bottom NiO layers were selectively reduced to Ni metal layers showing epitaxial relationships, while the Al2O3 interlayer remained. The crystallographic and interfacial characteristics were confirmed by X-ray diffraction analysis, reflection high-energy electron diffraction, and transmission electron microscopy. The fabricated Ni/Al2O3/Ni heteroepitaxial junction exhibited atomically sharp interfaces with no amorphous boundary layer.
A New Tool for Real-Time Monitoring of Photon-Beam Irradiation Using Positron Production in Radiotherapy
Authors: Maruyama Koichi , Watanabe Tetsuya , Takenaka Shigeharu , Asai Hiroyuki , Oomori Kazuyoshi , Takei Hideyuki , Saito Kyoko , Saito Hidetoshi , Hayakawa Kazushige
Published: September 2011

A method for monitoring the real-time irradiation field and irradiation dose of energetic photons has been developed for use in cancer radiotherapy that uses photoproduced positrons. A new detector system consisting of a pair of collimators and a fast crystal scintillator was designed and fabricated. It was successfully operated to confirm the irradiation field by real-time measurements of counting rates, which were found to be proportional to the intensity of the photon beam. These results indicate that this method can be used to monitor the irradiation field as well as the irradiation dose.
Iterative Decoding between Two-Dimensional Soft Output Viterbi Algorithm and Error Correcting Modulation Code for Holographic Data Storage
Authors: Kim Jinyoung , Moon Yong , Lee Jaejin
Published: September 2011

We propose an iterative decoding scheme for holographic data storage that uses modulation codes with a trellis structure to obtain some coding gain. Furthermore, the iterative scheme between a channel detector and the modulation code can achieve more coding gain. In the simulation, when there are (10%, 10%) and (20%, 20%) misalignments, the proposed iterative scheme with a pseudorandom interleaver performs approximately 0.3 and 1 dB better, respectively, compared to the scheme without iteration.
High-Speed Gap Servo Control for Solid-Immersion-Lens-Based Near-Field Recording System with a Flexible Optical Disk
Authors: Hwang Hyunwoo , Kim Jung-Gon , Song Ki Wook , Park Kyoung-Su , Park No-cheol , Yang Hyunseok , Rhim Yoon-Chul , Park Young-Pil
Published: September 2011

Higher data storage capacities and higher data transfer rates will be required in next-generation information storage devices. However, there is a limit to the rotational speeds of conventional disk structures. Hence, conventional disks will not be able to achieve high data transfer rates of over 250 Mbps that is required for next-generation storage devices. To increase the data transfer rate of a disk, flexible optical disks have been studied with the goal of stable rotation at a high speed, using a stabilizer to reduce disk oscillations. If a flexible optical disk is implemented in a near-field recording (NFR) system, simultaneous high data transfer rates and high-density recording should be possible. In an NFR system, it is very important to maintain the gap between the solid immersion lens (SIL) and the disk at distances below tens of nanometers. In this study, to simultaneously achieve high data storage capacity and high data transfer rate, we propose an improved gap servo control system for an SIL-based NFR system with a flexible optical disk. To enable robust control at a high rotational speed, a repetitive controller was designed and applied to the NFR servo algorithm. In both simulation and experiment, the newly designed gap servo controller stably maintained the gap distance in the SIL-based NFR system using a flexible optical disk.
Application of Herringbone Pattern to a Slim-Type Optical Disk Drive for the Reduction of Warpage and Vibration of the Rotating Disk
Authors: Seo Junho , Choi Moonho , Kim Hyung-Gi , Rhim YoonChul
Published: September 2011

A herringbone pattern is applied beneath the top cover of a slim-type optical disk drive to suppress the warpage and vibration of a rotating disk since the pattern can modify the pressure generation over the disk by changing its geometric parameters. The effect of the herringbone geometries on the pressure generation is evaluated for various geometric parameters. The flow field and the pressure distribution in the cavity are calculated by using a commercial program with the k–ε model for the turbulent computation. To confirm the numerical results, the axial vibrations of the rotating disk as well as the pressure distribution of the air gap between the disk and the top cover are measured at various points. In this study, the application of the herringbone pattern reduces the disk warpage and axial vibration by 34 and 10% at most, respectively.
Angular Spacing Control for Segmented Data Pages in Angle-Multiplexed Holographic Memory
Authors: Kinoshita Nobuhiro , Muroi Tetsuhiko , Ishii Norihiko , Kamijo Koji , Kikuchi Hiroshi , Shimidzu Naoki , Ando Toshio , Masaki Kazuyoshi , Shimizu Takehiro
Published: September 2011

To improve the recording density of angle-multiplexed holographic memory, it is effective to increase the numerical aperture of the lens and to shorten the wavelength of the laser source as well as to increase the multiplexing number. The angular selectivity of a hologram, which determines the multiplexing number, is dependent on the incident angle of not only the reference beam but also the signal beam to the holographic recording medium. The actual signal beam, which is a convergent or divergent beam, is regarded as the sum of plane waves that have different propagation directions, angular selectivities, and optimal angular spacings. In this paper, focusing on the differences in the optimal angular spacing, we proposed a method to control the angular spacing for each segmented data page. We investigated the angular selectivity of a hologram and crosstalk for segmented data pages using numerical simulation. The experimental results showed a practical bit-error rate on the order of 10-3.
Design of Reference Pattern and Input Phase Mask for Coaxial Holographic Memory
Authors: Saita Yusuke , Nomura Takanori , Nitanai Eiji , Numata Takuhisa
Published: September 2011

Design methods of a reference pattern and an input phase mask for a coaxial holographic memory are described. By the proposed method, it is expected that the useless consumption of the dynamic range of a recording medium will decrease, and the light efficiency and the interference efficiency between the signal beam and the reference beam will be improved. A reference pattern and an input phase mask are designed by a simulated annealing. The performance of the proposed design method is confirmed by numerical simulations and optical experiments. Furthermore, the holographic memory system using both the designed reference pattern and the designed input phase mask is also confirmed by numerical simulations and optical experiments.
Symbol Error Characteristics of Hybrid-Modulated Holographic Data Storage by Intensity and Multi Phase Modulation
Authors: Takabayashi Masanori , Okamoto Atsushi , Tomita Akihisa , Bunsen Masatoshi
Published: September 2011

For the purpose of increasing the data density of holographic memories, we propose a novel signal modulation method named hybrid modulation method, which is a combination of multi level phase-modulated signals and intensity-modulated signals. As a first step, we show that the data density of holographic data storage is mainly determined by multiplexing numbers and by coding efficiency in input signals. In this study, we focus on increasing coding efficiency using the hybrid modulation method. From the results of recording and reading simulations based on the fast-Fourier transform beam propagation method, the hybrid modulation method achieves approximately 2 times higher data density than the conventional methods of two-level phase-only modulation and two-level intensity-only modulation.
Focusing Error Detection Method in Microholographic Data Storage System Using Polarization Characteristics
Authors: Kim Taeseob , Im Chang-Hyuk , Lee Sang-Hyuck , Kim Nakyeong , Park No-Cheol , Yang Hyunseok , Park Young-Pil , Park Kyoung-Su
Published: September 2011

We present a disk-focusing error detection method for microholographic data storage systems using polarization characteristics. In high-speed optical storage systems, disturbances exist along the vertical direction of a disk. The diffraction efficiency of a readout signal depends on the distance between the focusing point of the reference beam and the vertical center of the microholographic grating. The proposed disk focusing error detection method uses only one laser source, unlike most existing systems, which use two laser sources. By using polarization characteristics, disk-focusing and reading beams are inserted in the media without interference, and the proposed system achieves the simultaneous reading of microholograms and disk-focusing control. By evaluating the focus error signal, we verified the reliability of the optical path and tolerableS-curve (FES) balance (1.8%) for the proposed system. It is possible to achieve a diffraction efficiency of over 90% at the best focus position using the proposed disk-focusing method.
Improvement of Storage Capacity Using Confocal Scheme in Reflection-Type Holographic Memory System with Speckle Shift Multiplexing
Authors: Matoba Osamu , Yonetani Yusuke , Nitta Kouichi
Published: September 2011

The storage capacity of a reflection-type holographic memory with three-dimensional speckle shift multiplexing embedded in a confocal scheme is presented. The confocal optical system can eliminate the interpage cross-talk noise in the speckle shift multiplexing. This leads to the increase in signal-to-noise ratio and the decrease in bit error rate. Numerical simulation results show that a maximum storage capacity can be increased up to 4.35 Tbyte/disk by using the confocal scheme. This value is derived numerically from the ideal situations of recording medium and evaluation of bit error rate in three-dimensional multiplexing.
Design of Copying System for Reflection Disk-Type Multiplex Hologram
Authors: Chen Chih-Hung , Cheng Yih-Shyang
Published: September 2011

Using the symmetric property of diffracted image rays generated from a 360° viewable disk-type multiplex hologram, we designed a stable optical system for holographic copying as a reflection hologram. The production of the master hologram and the design of a single-beam copying system for the fabrication of transfer holograms are described in this paper.
Proposal of a Design Principle of Multilayer Media
Authors: Kikukawa Takashi , Inoue Motohiro , Kosuda Atsuko , Ushida Tomoki
Published: September 2011

We propose a design principle of stacking-type super-multilayer media in this paper. By the use of an original high-transmittance and high-recording-sensitivity recording material, bismuth–germanium–oxide, the recording layers of a 10-layer super-multilayer disc can be designed using only two types of recording layer. This leads the conventional super-multilayer media structure to a much simpler structure with only two thicknesses of spacer layers while maintaining a satisfactory signal quality on the farthest layer from the incident laser beam, where signal fluctuation due to coherent crosstalk is the strongest. The above design principle will greatly contribute to the reduction of the cost of super-multilayer media.
Preparation of Textured BaTiO3 Thick Films by Screen Printing
Authors: Sakai Yuichi , Futakuchi Tomoaki , Adachi Masatoshi
Published: September 2011

The preparation of textured BaTiO3 thick films by screen printing was investigated. The addition of SiO2 and MnO2 together or MgO and MnO2 together was effective for preparing such thick films with a- and c-axis-preferred orientations. The evaluation result of pole figure measurement for the thick films showed that MgO and MnO2 addition was particularly effective for advancing the orientation. The grain growth could have been promoted using solutions of Mg ions and Mn ions for BaTiO3. The preferred orientation increased with increasing holding time for the firing of the thick films. The holding time required to obtain highly oriented thick films in the case of using a 0.5-mm-thick substrate was shorter than that in the case of using a 0.2-mm-thick substrate. The difference in orientation ease could be related to the stress of the thick films and the solution of Mg ions for BaTiO3. The remanent polarization P
r and coercive field E
c of the thick films fired for 20 h were 4.2 µC/cm2 and 2.5 kV/cm, respectively. These results show that the highly oriented BaTiO3 thick-film patterns can be prepared by a simple process.
Fabrication of Lead-Free (Na0.5K0.5)NbO3–BaZrO3–(Bi0.5Li0.5)TiO3Ferroelectric Thin Films on (111)Pt/Ti/SiO2/(100)Si Substrate by Pulsed Laser Deposition
Authors: Yamazoe Seiji , Miyoshi Yuzo , Fukada Masaki , Komaki Kazuki , Adachi Hideaki , Wada Takahiro
Published: September 2011

0.92(Na0.5K0.5)NbO3–0.06BaZrO3–0.02(Bi0.5Li0.5)TiO3(NKN–BZ–BLT) thin films were fabricated on a (111)Pt/Ti/SiO2/(100)Si substrate by pulsed laser deposition (PLD). The quality of the NKN–BZ–BLT thin films was improved by introducing an NKN–BZ–BLT buffer layer, which was deposited at a high substrate temperature of 850 °C. An X-ray diffraction pattern (XRD) showed that the 100ptpreferential-oriented NKN–BZ–BLT thin films [on the basis of a pseudotetragonal perovskite (pt) structure] were obtained without and with buffer layers. From the rocking curves, the crystallinity of the film was slightly improved by introducing the buffer layer. SEM images showed that the grain size was increased and cracks were eliminated by introducing the buffer layer. The dielectric constant of the films was comparable to that of NKN–BZ–BLT ceramics. TheP–Ehysteresis loops showed that the remanent polarization and spontaneous polarization of the films increased with the increase in the thickness of the buffer layer. The NKN–BZ–BLT film with a 0.8-µm-thick buffer layer exhibited a remanent polarization of 6.7 µC/cm2and a spontaneous polarization of 28.0 µC/cm2. This improvement of the ferroelectric properties would be due to the relaxation of the tensile stress in the presence of the buffer layer.
Solution-Based Fabrication of Perovskite Multilayers and Superlattices Using Nanosheet Process
Authors: Li Bao-Wen , Osada Minoru , Akatsuka Kosho , Ebina Yasuo , Ozawa Tadashi C. , Sasaki Takayoshi
Published: September 2011

We report a solution-based fabrication of perovskite multilayers and superlattices using perovskite nanosheets. Perovskite nanosheets (LaNb2O7, Ca2Nb3O10, and Sr2Nb3O10) were prepared by delaminating layered perovskites. A layer-by-layer approach using Langmuir–Blodgett deposition was effective for fabricating high-quality nanofilms of perovskite nanosheets on various substrates, such as quartz glass, Si, and SrRuO3. Structural characterizations by X-ray diffraction, transmission electron microscopy, and hard X-ray photoelectron spectroscopy revealed that these perovskite nanofilms are composed of a well-ordered lamellar structure with an atomically sharp interface. The multilayer films exhibited a stable dielectric response inherent to the perovskite nanosheet. We also found that the superlattices of (LaNb2O7/Ca2Nb3O10)5 and (Sr2Nb3O10/Ca2Nb3O10)5 possess strong interface coupling, which gives rise to enhanced dielectric constant.
Thermooptic Property of Polycrystalline BiFeO3 Film
Authors: Shima Hiromi , Tsutsumi Koichi , Suzuki Michio , Tadokoro Toshiyasu , Naganuma Hiroshi , Iijima Takashi , Nishida Ken , Yamamoto Takashi , Nakajima Takashi , Okamura Soichiro
Published: September 2011

We have fabricated a polycrystalline BiFeO3 (BFO) film with a thickness of 650 nm on a Pt/Ti/SiO2/Si substrate by a chemical solution deposition method, and its optical and thermooptic properties were evaluated by spectroscopic ellipsometry. The optical band gap energy of the BFO film was 2.95 eV at 50 °C and monotonically decreased with increasing temperature to 2.79 eV at 530 °C. The extinction coefficient was significantly low at a wavelength longer than 600 nm in the temperature range from 50 to 530 °C. The refractive index of the BFO film was estimated to be 2.96 at 600 nm and 2.68 at 1550 nm at 50 °C using a single Gaussian oscillator, and a thermooptic coefficient of 0.8×10-4 K-1 was obtained at a wavelength of 1550 nm. Although the refractive index decreased with increasing temperature at all wavelengths, the variation was larger at shorter wavelengths. This seems to be caused by the combination of broadening in the Gaussian oscillator vibration and thermal expansion.
Preparation of BiFe0.9Co0.1O3 Films by Pulsed Laser Deposition under Magnetic Field
Authors: Park Jung Min , Gotoda Fumiya , Nakashima Seiji , Sohgawa Masayuki , Kanashima Takeshi , Okuyama Masanori
Published: September 2011

BiFe0.9Co0.1O3 (BFCO) films have been prepared on Pt/TiO2/SiO2/Si substrates with a magnetic field of 0.4 T by pulsed laser deposition. BFCO films prepared under magnetic field show a single-phase perovskite structure with a little secondary phase, and their (010) and (020) peaks shift to lower angles than those of the film prepared without magnetic field. The BFCO film of about 1 µm thickness shows a columnar structure, although the BFCO film of about 350 nm prepared without magnetic field shows a grain like structure. The leakage current density of the BFCO film prepared under magnetic field is much lower than that of the BFCO film prepared without magnetic field. The saturated P–E hysteresis loops of both BFCO films are obtained at 80 K, and the M–H hysteresis loops of both BFCO films show a weak ferromagnetism behavior at room temperature.
Synthesis of BiFeO3–Bi0.5Na0.5TiO3 Thin Films by Chemical Solution Deposition and Their Properties
Authors: Hieno Atsushi , Sakamoto Wataru , Moriya Makoto , Yogo Toshinobu
Published: September 2011

Multiferroic BiFeO3–Bi0.5Na0.5TiO3 thin films were synthesized on Pt/TiO
x
/SiO2/Si substrates by chemical solution deposition. When the amount of Bi0.5Na0.5TiO3 exceeded 30 mol %, perovskite BiFeO3–Bi0.5Na0.5TiO3 single phase thin films were successfully fabricated in the temperature range of 550–700 °C. Also, the surface morphology of the 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 thin films was improved by optimizing the amounts of excess Bi and Na in 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 precursor solutions. However, measurements of ferroelectric polarization-electric field hysteresis loops were difficult for 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 thin films due to the large leakage current densities at room temperature. At low temperatures, the 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 thin films demonstrated improved insulating resistance and exhibited potential ferroelectric properties. Furthermore, by Mn doping of the 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 films, improved ferroelectric properties with weak ferromagnetism were achieved at room temperature. In 0.7Bi(Fe0.95Mn0.05)O3–0.3Bi0.5Na0.5TiO3 thin films, ohmic conduction was dominant in an electric field range of 0–200 kV/cm and the abrupt increase in leakage current was suppressed even at high electric fields, whereas nondoped 0.7BiFeO3–0.3Bi0.5Na0.5TiO3 films exhibited nonohmic conduction with a larger leakage current. The remanent polarization and coercive field of the 0.7Bi(Fe0.95Mn0.05)O3–0.3Bi0.5Na0.5TiO3 films at room temperature were approximately 26 µC/cm2 and 250 kV/cm, respectively.
Hierarchical Domain Structures in Relaxor 24Pb(In1/2Nb1/2)O3–46Pb(Mg1/3Nb2/3)O3–30PbTiO3 near a Morphotropic Phase Boundary Composition Grown by Bridgman Method
Authors: Yasuda Naohiko , Fuwa Tomohiro , Ohwa Hidehiro , Tachi Yoshihito , Yamashita Yohachi , Fujita Kazuhiko , Iwata Makoto , Terauchi Hikaru , Ishibashi Yoshihiro
Published: September 2011

The domain structures of the lead-based relaxor ferroelectric solid solution single crystal, 24Pb(In1/2Nb1/2)O3 (PIN)–46Pb(Mg1/3Nb2/3)O3 (PMN)–30PbTiO3 (PT), near a morphotropic phase boundary (MPB) composition grown by the Bridgeman method were studied by polarized light microscopy (PLM), piezoresponse force microscopy (PFM) and scanning electron microscopy (SEM). The change in domain structures with poling from rhombohedral spindlelike domains of 3–5 µm width to orthorhombic domains of ∼20 µm width with rectangular cells with a size of 3–5 µm, characterized with an antiferroelectic double hysteresis loop in the electric field-induced strain behavior, was found. Such domain structures were microscopically identified from SEM images as small circular tetragonal defects, planar monoclinic defects such as edge and screw dislocations with Burgers vector b along <110>cub and/or <100>cub directions and their agglomerate rectangular orthorhombic defects, also characterized by PFM. Hierarchical domain structures are discussed from the viewpoints of domain structures due to defects such as edge and screw dislocations originating in the chemical order region (COR) and the piezoelectric responses and dielectric properties.
Effects of Manganese Oxides/Gold Composite Electrode on Piezoelectric Properties of Lead Magnesium Niobate Titanate Single Crystal
Authors: Yamamoto Yohachi , Itsumi Kazuhiro , Hosono Yasuharu
Published: September 2011

We have confirmed a high dielectric constant after poling ε33
T/ε0 of 7700 and piezoelectric constant d
33 = 2250 pC/N, which are 40% larger than those of the initial sample, for a lead magnesium niobate–lead titanate 0.72 Pb(Mg1/3Nb2/3)O3–0.28 PbTiO3 single crystal plate with a manganese oxide/gold (Au) composite electrode. The increased ε33
T/ε0 and d
33 may be attributable to the smaller domains realized by fine patterning semiconductor manganese oxide and conductive Au composite electrodes on the single crystal plate. The use of a semiconductor/conductor composite electrode is an effective method of improving the properties of piezoelectric single-crystal transducers.
Characterization of Dielectric Nanocubes Ordered Structures Fabricated by Solution Self-Assembly Process
Authors: Mimura Ken-ichi , Dang Feng , Kato Kazumi , Imai Hiroaki , Wada Satoshi , Haneda Hajime , Kuwabara Makoto
Published: September 2011

Ordered structures of barium titanate (BT) nanocubes, strontium titanate (ST) nanocubes and BT–ST nanocube mixture were directly fabricated on Si and Pt-coated Si substrates using a colloidal solution assembly method inspired by convection self-assembly. BT/ST alternating layered structure was also fabricated by repeating the self-assembly process several times. The microstructure of the self-assembled structures was observed using field emission scanning electron microscopy (FE-SEM) and scanning probe microscopy (SPM). It was revealed that nanocubes were arranged with various degrees of ordering to develop monolayer regions at the surface of the substrates. The crystallographic phase and orientation of the assembly consisting of BT and ST nanocubes were evaluated by X-ray diffraction analysis. The (100) and (200) diffractions of BT and ST were observed and no other diffractions were observed. The BT and ST nanocubes had a 100 face and were arrayed orderly with their faces parallel to the surface of the substrates. The piezoresponse properties obtained by scanning probe microscopy (SPM) indicated that the heterointerface between BT and ST nanocubes would introduce an anomaly in piezoelectric properties.
Structural Characterization of Na0.5K0.5NbO3 Ceramic Particles Classified by Centrifugal Separator
Authors: Kakimoto Ken-ichi , Shinkai Yuya
Published: September 2011

Na0.5K0.5NbO3 (NKN)-based materials have been studied intensively as a lead-free candidate for piezoelectric application, but it has been well known that inhomogeneous microstructure often arises during the sintering process. In general, the “size effect” is well recognized in the electric property of dielectric materials. In this study, the size classification of NKN particles has been achieved by a wet-type centrifugal separation technique using one sample source fired at 1100 °C for 2 h to avoid the effect of heating conditions and to investigate the distribution of the crystallinity in the sample. The selected rotating rates successfully produced 6 kinds of the classified powders with different mean-particle sizes from 0.3 to around 40 µm (NKN-0.3 to NKN-38.9). Their crystallinity were characterized by the X-ray diffraction technique, and the refined crystal structures confirmed that a considerable change occurred in lattice parameters for the samples between NKN-0.3 and NKN-7.0, and that non linear variations in the Nb–O bond distance and the bond angle were also recognized in the samples between NKN-0.9 and NKN-2.4. The calculated P
s was maximized to 35 µC/cm2 in NKN-2.4, and markedly decreased to 25 µC/cm2 in a particle with size exceeding 7.0 µm.
Structural, Dielectric, and Piezoelectric Properties of Mn-Doped BaTiO3–Bi(Mg1/2Ti1/2)O3–BiFeO3 Ceramics
Authors: Fujii Ichiro , Mitsui Ryuta , Nakashima Kouichi , Kumada Nobuhiro , Shimada Mikio , Watanabe Takayuki , Hayashi Jumpei , Yabuta Hisato , Kubota Makoto , Fukui Tetsuro , Wada Satoshi
Published: September 2011

Mn-doped (0.9-x)BaTiO3–0.1Bi(Mg1/2Ti1/2)O3–xBiFeO3 (x = 0.6, 0.7, and 0.8) ceramics were studied as candidate lead-free piezoelectric materials. The crystal structures were a pseudo-cubic perovskite at x = 0.6, a rhombohedral perovskite at x = 0.8, and a mixture of the pseudo-cubic and rhombohedral perovskite at x = 0.7. The Curie temperature was found to be 470 °C at x = 0.6 and more than 600 °C at x = 0.7 and 0.8. A strong pinning of domain walls was observed for high-field responses at x = 0.7 and 0.8, which was relaxed by high-temperature annealing and subsequent quenching. Piezoelectric properties increased with decreasing x, and the small-field piezoelectric constants d
33 and d
31 were 94 and 31 pC/N at x = 0.6, respectively.