bluuebunny/crossref_metadata_2025 huggingface dataset:
DENOISING AND ENHANCEMENT OF MAMMOGRAPHIC IMAGES UNDER THE ASSUMPTION OF HETEROSCEDASTIC ADDITIVE NOISE BY AN OPTIMAL SUBBAND THRESHOLDING
Authors: MENCATTINI ARIANNA , RABOTTINO GIULIA , SALMERI MARCELLO , LOJACONO ROBERTO , SCIUNZI BERARDINO
Published: September 2010

Mammographic images suffer from low contrast and signal dependent noise, and a very small size of tumoral signs is not easily detected, especially for an early diagnosis of breast cancer. In this context, many methods proposed in literature fail for lack of generality. In particular, too weak assumptions on the noise model, e.g., stationary normal additive noise, and an inaccurate choice of the wavelet family that is applied, can lead to an information loss, noise emphasizing, unacceptable enhancement results, or in turn an unwanted distortion of the original image aspect. In this paper, we consider an optimal wavelet thresholding, in the context of Discrete Dyadic Wavelet Transforms, by directly relating all the parameters involved in both denoising and contrast enhancement to signal dependent noise variance (estimated by a robust algorithm) and to the size of cancer signs. Moreover, by performing a reconstruction from a zero-approximation in conjunction with a Gaussian smoothing filter, we are able to extract the background and the foreground of the image separately, as to compute suitable contrast improvement indexes. The whole procedure will be tested on high resolution X-ray mammographic images and compared with other techniques. Anyway, the visual assessment of the results by an expert radiologist will be also considered as a subjective evaluation.
APPLICATION OF ADAPTIVE WAVELET NETWORKS FOR VIBRATION CONTROL OF BASE ISOLATED STRUCTURES
Authors: KARIMI HAMID REZA , ZAPATEIRO MAURICIO , LUO NINGSU
Published: September 2010

This paper presents an application of wavelet networks (WNs) in identification and control design for a class of structures equipped with a type of semiactive actuators, which are called magnetorheological (MR) dampers. The nonlinear model is identified based on a WN framework. Based on the technique of feedback linearization, supervisory control and H∞ control, an adaptive control strategy is developed to compensate for the nonlinearity in the structure so as to enhance the response of the system to earthquake type inputs. Furthermore, the parameter adaptive laws of the WN are developed. In particular, it is shown that the proposed control strategy offers a reasonably effective approach to semiactive control of structures. The applicability of the proposed method is illustrated on a building structure by computer simulation.
GG DCT COEFFICIENT MODELS
Authors: NADARAJAH SARALEES
Published: September 2010

It has been known that the distribution of the discrete cosine transform (DCT) coefficients of most natural images follow a Laplace distribution. However, recent work has shown that the Laplace distribution may not be a good fit for certain types of images and that the Gaussian distribution will be a realistic model in such cases. A model that contains both Laplace and Gaussian distributions as particular cases is the generalized Gaussian (GG) distribution. Assuming this generalized model, we derive a comprehensive collection of formulas for the distribution of the actual DCT coefficients. The corresponding estimation procedures are derived by the method of moments and the method of maximum likelihood. Finally, the superior performance of the derived distributions over the standard Gaussian and Laplace models is illustrated. It is expected that this work could serve as a useful reference and lead to improved modeling with respect to image analysis and image coding.
ADAPTIVE DECOMPOSITION OF FUNCTIONS INTO PIECES OF NON-NEGATIVE INSTANTANEOUS FREQUENCIES
Authors: QIAN TAO , HO I. T. , LEONG I. T. , WANG YANBO
Published: September 2010

We introduce the concept of adaptive decomposition of signals into basic building blocks, of which each of the non-negative analytic instantaneous frequency are called mono-components. We propose certain methods based on p-starlike functions and Fourier expansions for such decomposition. We justify the terminology mono-component used in signal analysis.
MODELING AND ANALYSIS OF BEAMS WITH DELAMINATION
Authors: MAHIEDDINE ALI , OUALI MOHAMMED
Published: September 2010

In this paper, a mathematical model for beams with partially delaminated layers is presented to investigate their behavior. In this formulation account is taken of lateral strains. The principal advantage of the element is that it allows the modeling of delamination anywhere in the structure. Numerical results of the present model are presented and its performance is evaluated for static problems.
MODELING OF HIGH-SPEED FINISH MILLING PROCESS USING SOFT COMPUTING
Authors: SUREKHA B. , VUNDAVILLI PANDU R. , PARAPPAGOUDAR M. B. , PRASAD K. SHYAM
Published: September 2010

In the present study, forward modeling of high-speed finish milling process has been solved using soft computing. Two different approaches, namely neural network (NN) and fuzzy logic (FL), have been developed to solve the said problem. The performance of NN and FL systems depends on the structure (i.e. number of neurons in the hidden layer, transfer functions, connection weights, etc.) and knowledge base (i.e. rule base and data base), respectively. Here, an approach is proposed to optimize the above-mentioned parameters of NN and FL systems. A binary coded genetic algorithm (GA) has been used for the said purpose. Once optimized, the NN and FL-based models will be able to provide optimal machining parameters online. The developed approaches are found to solve the above problem effectively, and the performances of the developed approaches have been compared among themselves and with that of the results of existing literature.
SIMULINK MODEL AND FPGA-BASED OFDM COMMUNICATION SYSTEM: A SIMULATION AND HARDWARE INTEGRATED PLATFORM
Authors: DANG LE KHOA , NGUYEN HUU PHUONG , BINH LE NGUYEN , NGUYEN DUC NHAN
Published: September 2010

Ultra-broadband networks are currently attracting significant interests in employing wireless access and optical fiber access to the home and to the building at symbol rate reaching Gb/s. OFDM is a multicarrier modulation technique and considered to offer significant reduction of the data symbol to be carried per carrier channel, especially in ultra-high speed optical communications with bit rate reaching 100 Gb/s or even higher. This paper thus presents a novel and generic OFDM system employing both MATLAB Simulink and FPGA-based development software platform for simulation as well as hardware implementation for the generation and detection of OFDM signals for wireless and optical communications transmission media. Although the transmission medium is modeled with delay distortion filter in the baseband, this model would be valid for passband signals as the amplitude is represented by complex amplitude whose phase would be the phase of the carrier. The Simulink and hardware models presented hereunder are scalable to much higher speed allowing possible implementation in multi-Giga samples per second electronic processors. The sub-systems of the OFDM transmitter and receiver are presented to demonstrate the feasibility of such models for ultra-wideband communication systems such as wireless access and long haul optical fiber communication backbone networks.
Cr3+ Impurities and Photoluminescence in LaAlO3
Authors: Hirata Eiji , Tamagawa Kenta , Ohki Yoshimichi
Published: September 2010

Photoluminescence (PL) spectra induced in LaAlO3 by ultraviolet (UV) photons were measured for two types of samples, i.e., single-crystal plates and thin films. The films, which were amorphous when deposited, became polycrystalline after being annealed at 800 °C or higher. When the excitation photon energy exceeded the band-gap energy of LaAlO3, three PL peaks appeared at approximately 1.60 eV in the single crystals and polycrystalline films deposited and annealed on a Si single-crystal substrate. When the films were deposited and annealed on a CaF2 single-crystal substrate, the in-plane lattice parameters became smaller and the energies of the three PL peaks shifted to higher values. This indicates that the three PL peaks are susceptible to a crystal field. Furthermore, the intensities of the three PL peaks did not depend on the measurement temperature. Taking these results together with their spectral shapes into consideration, the three PL peaks are due to the R-line luminescence resulting from Cr3+ impurities in LaAlO3. The detection of Cr3+ ions by inductively coupled plasma optical emission spectrometry failed, indicating that the Cr3+ content of the present samples is below 1 ppm. The fact that the PL peaks appeared in both the single-crystal plates and thin films obtained from different raw chemicals with different processes indicates that there is a strong possibility that the Cr3+ ions are present in Al ore. Another PL peak appearing at 2.8 eV in the single crystals was assumed to originate from oxygen vacancies.
Analysis of Local Environment of Fe Ions in Hexagonal BaTiO3
Authors: Chikada Shunsuke , Hirose Kazuyuki , Yamamoto Tomoyuki
Published: September 2010

Fe-doped hexagonal-structured BaTiO3 is synthesized by the conventional solid-state reaction method. The local environment of the Fe ions doped in the synthesized hexagonal BaTiO3 is then investigated by X-ray absorption near edge structure (XANES) measurements and first-principles calculations. It is confirmed from the Fe L2,3-edge XANES spectrum that the charge state of the Fe ions in the synthesized specimen is trivalent. By analyzing the Fe K-edge XANES spectrum of the present specimen with the aid of the first-principles calculations, it is found that doped Fe ions are substituted at the Ti site in Ti2O9 groups of face-sharing octahedra in hexagonal BaTiO3.
A New Metal–Insulator–Metal Capacitor with Nickel Fully Silicided Polycrystalline Silicon Electrodes
Authors: Lee Jung-Hsiang , Tsai Zheng-Ye , Lin Yi-Chang , Zhu Yi-Yun , Chen Bo-Han
Published: September 2010

A novel low-cost metal–insulator–metal (MIM) capacitor with a high capacitance density of ∼10.2 fF/µm2has been developed by using nickel fully silicided (Ni-FUSI) polycrystalline silicon electrodes. The low resistivities of Ni3Si, Ni2Si, and NiSi electrodes have been achieved and determined to be around 106, 39, and 21 µΩ·cm without requiring noble metal materials. At room temperature, this MIM capacitor also displays a good leakage current density of 3.9×10-6A/cm2at 1 V and a quadratic voltage coefficient (α) of 2266 ppm/V2. Experiments demonstrated that Schottky emission is the dominant conduction mechanism at high temperatures and low fields under top electrode injection. The Schottky barrier heights (ΦB) at the Ni3Si/ZrO2, Ni2Si/ZrO2, and NiSi/ZrO2interfaces were extracted firstly to be 1.15, 1.05, and 0.8 eV, respectively. Material characterization further reveals this structure highly appropriate for advanced MIM capacitors.
Using Micro-Arc Oxidation and Alkali Etching to Produce a Nanoporous TiO2 Layer on Titanium Foil for Flexible Dye-Sensitized Solar Cell Application
Authors: Wu Shu-Yuan , Chen Ying-Hung , Chen Keh-Chang , He Ju-Liang
Published: September 2010

To increase the specific surface area of a TiO2 layer synthesized by micro-arc oxidation (MAO), an alkali etching process was developed to form a nanoflaky structure in place of the existing microporous morphology of the MAO-TiO2 layer for dye-sensitized solar cell (DSSC) electrode application. An annealing treatment was also carried out to enhance the crystallinity of the nanofeatured TiO2 layer for a higher photovoltaic efficiency. Experimental results show that a 6-µm-thick crystalline porous TiO2 layer was fabricated on a Ti foil by MAO treatment, which consists of major amorphous and anatase phases with a minor rutile phase. As expected, the pores in the MAO-TiO2 layer exhibited micrometer-scale dimensions. The maximum photovoltaic efficiency realized in a device assembled with the MAO-TiO2 layer was only 0.061%. After alkali etching, a nanofeatured layer was developed over the MAO-TiO2 layer surface with numerous pores and nanoflakes of 50 nm size. These nanoflakes were uniformly distributed over the entire surface of the treated layer. The device assembled with the alkali-etched TiO2 layer exhibited an improved photovoltaic efficiency of 0.329%. This fivefold increase of the photovoltaic efficiency for the MAO-TiO2 layer indicates the effectiveness of enlarging the specific surface area by alkali etching. Furthermore, after postannealing, the crystallinity and fraction of the anatase phase in the overall TiO2 layer were enhanced. As a result, the photovoltaic efficiency ultimately reached 2.194%.
Low-Temperature Synthesis of the Infinite-Layer Compound LaNiO2 by Soft-Chemical Techniques
Authors: Takamatsu Tomohisa , Kato Masatsune , Noji Takashi , Koike Yoji
Published: September 2010

Bulk samples of LaNiO2 with the so-called infinite-layer structure have successfully been synthesized. First, polycrystalline samples of LaNiO3 with the perovskite structure were prepared using molten KOH at a temperature of 400–450 °C. Then, they were finely ground with a double stoichiometric excess of reductant CaH2 and sealed in an evacuated Pyrex tube. The sealed ampoule was then heated at 300 °C for 24 h. Powder X-ray diffraction analysis has revealed that the product obtained after removing the residual CaH2 and the byproduct CaO is of almost single phase with tetragonal symmetry, indicating the formation of the infinite-layer compound LaNiO2.
Nanoscale Two-Bit/Cell NAND Silicon–Oxide–Nitride–Oxide–Silicon Devices Designed on Fully Depleted Silicon-on-Insulator Substrates
Authors: Kim Hyun Joo , You Joo Hyung , Kwack Kae Dal , Kim Tae Whan
Published: September 2010

Nanoscale 2-bit/cell NAND silicon–oxide–nitride–oxide–silicon (SONOS) memory devices with two separated control gates utilizing a fully depleted silicon-on-insulator (SOI) structure were designed. The program and erase characteristics of the proposed unique nanoscale 2-bit/cell NAND SONOS memory devices were simulated using technology computer-aided design tools. Simulation results showed that the leakage current in the subthreshold region and the subthreshold swing for the nanoscale 2-bit/cell NAND SONOS memory devices were decreased by utilizing a SOI structure. The initial threshold voltage of the nanoscale 2-bit/cell NAND SONOS memory devices with a SOI structure was larger than that of conventional SONOS devices without a SOI structure, indicative of a decrease in leakage current. Simulation results showed that the short-channel effects in the nanoscale 2-bit/cell NAND SONOS memory devices decreased in magnitude owing to a larger effective channel length.
Phase Linear, Flat Wide Band, Low-Loss Filters Using New Configuration of Unidirectional Up- and Down-Chirp Dispersive Inter Digital Transducers
Authors: Satoh Yusuke , Yamanouchi Kazuhiko
Published: September 2010

Dispersive transducers have sharp cut-off and flat wideband frequency characteristics. Also, phase linear and very low-loss characteristics are obtained by combining down- and up-chirp unidirectional dispersive transducers (DUDIST and UUDIDT). We proposed wide band filters combining DUDIDT and UUDIDT using the conventional UDT with the grating thin films. In this case, we could not obtain the low loss results. In this paper, the theoretical results of phase linear, flat wide band and low loss filters using a combinations of the new DUDIDT and UUDIDT are described. DUDIDT and UUDIDT are obtained by using the new configuration of Dispersive IDT. The large unidirectionalities of the DUDIDT and UUDIDT are obtained by changing of the electrode width and thickness, and using the open and short-circuit electrodes as the reflectors.
Finite-Difference Time-Domain Analysis of Scanning Tunneling Microscope Light Emission Spectra
Authors: Iida Wataru , Katano Satoshi , Uehara Yoichi
Published: September 2010

The finite-difference time-domain (FDTD) method has been applied to the spectral analysis of scanning tunneling microscope (STM) light emission. We found that FDTD analysis provides predictions that are consistent with those of the dielectric theory of STM light emission if the radius of curvature of the tip front is less than 50 nm. In the radius range above 50 nm, discrepancies between these theories were considerbale in predictions of the efficiency of STM light emission but moderate in those of its spectral shapes. STM light emission spectra of rods and disks embedded in substrates, to which the dielectric theory of STM light emission is not applicable, were calculated by the FDTD method, and we deduced that the spectral features specific to the rod material become distinct when the lateral size of the rod is comparable to or larger than that of localized surface plasmons determined by the dielectric theory of STM light emission; a thickness of 3–5 nm is additionally required for the disk.
Transmission of Voltage Pulses through the Cu Single-Atom Contact
Authors: Mizukami Yu-suke , Kurokawa Shu , Sakai Akira
Published: September 2010

We have conducted a pulse transmission experiment on the single-atom contact of Cu in air at room temperature. Employing a thin coaxial cable as a sample of the mechanically controllable break junction (MCBJ) method, we can produce stable Cu single-atom contacts and transmit through them pulses of 50–500 ns width. Analysis of the detected signal waveform indicates that a Cu single-atom contact behaves as a pure resistance, which is consistent with the theoretical admittance of quantum point contacts.
Thermoelectric Effects of Molecular Quantum Dot Junctions with Strong Electron Phonon Interactions
Authors: Kuo David M.-T.
Published: September 2010

We theoretically study the electrical conductance, thermal power, electron thermal conductance and figure of merit of a single molecular quantum dot junction using the Anderson model with a strong coupling of electron–phonon interactions (EPIs). The figure of merit (Z
T) decreases with increasing strength of EPIs. The suppression of Z
T is mainly attributed to a considerable enhancement of electron thermal conductance. We have demonstrated that the resolution of thermal power for resolving multiple phonon-assisted tunneling processes is higher than that of electrical conductance. Because the Kelvin relation is satisfied, the Peltier coefficient can also be determined by using measuring the thermal power.
Mechanism of Aluminum Induced Lateral Crystallization of Amorphous Silicon
Authors: Huang Shih-Yang , Wang Chuan-Chi , Lin Chih-Lung , Tsai Yu-Lin , Chao Cheun-Guang , Liu Tzeng-Feng
Published: September 2010

The aluminium-induced lateral crystallization (AILC) of amorphous silicon (a-Si) on a glass substrate has been investigated. By means of a photoresist-based process, Al islands (100 nm) were thermally evaporated using 15 V, 3.5 A, and 25 V, 5.6 A on the a-Si layer (100 nm), which was deposited on a glass substrate. SEM examinations indicated that the Al islands exhibited smooth and crystalline-grain morphology. Annealing processes were carried out at 748 and 823 K for various times. After annealing, AILC could be clearly observed in the crystalline-grain sample, but not in the smooth sample. TEM analyses showed that the mechanism of AILC resulted from two layer exchange processes. First, the Al islands exchanged with the underlying a-Si layer vertically during AIC, and then the generation of Al particles accompanying AIC caused a lateral layer exchange with the remaining a-Si layer with further annealing.
Raman Spectra Study of K0.5Na0.5NbO3 Ferroelectric Thin Films
Authors: Ahn Chang Won , Hwang Hak-In , Lee Kwang Sei , Jin Byung Moon , Park Sungmin , Park Gwangseo , Yoon Doohee , Cheong Hyeonsik , Lee Hai Joon , Kim Ill Won
Published: September 2010

We have fabricated K0.5Na0.5NbO3 (KNN) thin films on Pt substrates by a chemical solution deposition method and investigated the effect of K and Na excess (0–30 mol %) for KNN thin film. The KNN film with 20 mol % excess K and Na was an optimized KNN perovskite phase. From the Raman spectra, a change in the scattering mode was observed due to the chemical composition fluctuations of the excess K and Na. The peak of the (v
1 + v
5) internal vibrational mode in the NbO6 octahedra was split into two vibration modes which were shifted toward lower or higher wavenumbers depending on the K and Na cation deficiencies or redundancies.
Optical Properties of Amorphous AlN Thin Films on Glass and Silicon Substrates Grown by Single Ion Beam Sputtering
Authors: Hajakbari Fatemeh , Larijani Majid Mojtahedzadeh , Ghoranneviss Mahmood , Aslaninejad Morteza , Hojabri Alireza
Published: September 2010

The structural and optical properties of aluminum nitride (AlN) films deposited on glass and silicon substrates by single ion beam sputtering technique have been investigated. The X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) study revealed the formation of the amorphous phase of AlN. The optical characteristics of films, such as refractive index, extinction coefficient, and average thickness, were calculated by Swanepoel's method using transmittance measurements. The refractive index and average roughness values of the films increased with film thickness. Moreover, it was found that thickness augmentation leads to a decrease in optical band gap energy calculated using Tauc's relation.
Dynamic Characteristics of Laser-Assisted Discharge Plasmas for Extreme Ultraviolet Light Sources
Authors: Lu Peng , Katsuki Sunao , Tomimaru Nobufumi , Ueno Takahisa , Akiyama Hidenori
Published: September 2010

This paper reports the dynamics of laser-assisted discharge plasmas for extreme ultraviolet (EUV) sources. A pulsed laser was focused on the tin cathode surface to form vapor jet across 5 mm long anode–cathode gap where pulsed power was applied later on. Comparison of time-resolved pinhole EUV imaging and high speed visible photography reveals that intensive EUV is emitted only from the neck of the hot plasma, which starts showing up near the laser spot on the cathode and moves away from the cathode. This movement of the neck plasma results in the enlargement of the EUV emissive region acting as its source.
Current Excitation Model for Cerenkov Lasers with a Planar Waveguide
Authors: Fares Hesham , Yamada Minoru , Kuwamura Yuji
Published: September 2010

A unified theoretical analysis of the spontaneous and stimulated emissions in Cerenkov free-electron lasers (CFELs) with a planar dielectric waveguide is shown. The excitation of the electromagnetic (EM) wave is formulated with current sources of the electron beam. A relativistic classical analysis is applied to this model, where the electron is represented as a spatially localized point particle. The spontaneous emission is evaluated through spatially varying field components associated with the motion of an electron. The stimulated emission is derived on the basis of the modulations of electron velocity and density by the EM field. Interaction regimes induced by the stimulated emission are classified into transition and steady states with the time variation. The effect of electron relaxation is introduced to explain the operation in the steady state. The compatibility of this analysis with already known analyses is also confirmed.
Tungsten Contact and Line Resistance Reduction with Advanced Pulsed Nucleation Layer and Low Resistivity Tungsten Treatment
Authors: Chandrashekar Anand , Chen Feng , Lin Jasmine , Humayun Raashina , Wongsenakhum Panya , Chang Sean , Danek Michal , Itou Takamasa , Nakayama Tomoo , Kariya Atsushi , Kawaguchi Masazumi , Hizume Shunichi
Published: September 2010

This paper describes electrical testing results of new tungsten chemical vapor deposition (CVD-W) process concepts that were developed to address the W contact and bitline scaling issues on 55 nm node devices. Contact resistance (R
c) measurements in complementary metal oxide semiconductor (CMOS) devices indicate that the new CVD-W process for sub-32 nm and beyond – consisting of an advanced pulsed nucleation layer (PNL) combined with low resistivity tungsten (LRW) initiation – produces a 20–30% drop in R
c for diffused NiSi contacts. From cross-sectional bright field and dark field transmission electron microscopy (TEM) analysis, such R
c improvement can be attributed to improved plugfill and larger in-feature W grain size with the advanced PNL+LRW process. More experiments that measured contact resistance for different feature sizes point to favorable Rc scaling with the advanced PNL+LRW process. Finally, 40% improvement in line resistance was observed with this process as tested on 55 nm embedded dynamic random access memory (DRAM) devices, confirming that the advanced PNL+LRW process can be an effective metallization solution for sub-32 nm devices.
Investigation of Aluminum Metallized Source/Drain Thin Film Transistors Using a Self-Aligned Fabrication Process
Authors: Duy Nguyen Van , Lee Wonbaek , Jung Sungwook , Nga Nguyen Thanh , Son Dang Ngoc , Kim Kwangryul , Choi Byoungdeog , Yi Junsin
Published: September 2010

For a better thin film transistor performance, metal silicide has been studied in order to enhance the conductivity of the source and drain electrodes. Although aluminum does not form a metal silicide with silicon, the two materials interpenetrate in an induced crystallization process. In such a structure, aluminum can act as a p-type dopant in the silicon lattice. In this work, aluminum metallized source/drain thin film transistors with excimer laser-annealed polycrystalline silicon were fabricated using a simple self-aligned process. The source/drain regions were patterned with a lift-off process. The n-channel characteristics of the as-deposited aluminum source/drain were explored and an improvement in the performance was observed after a heat treatment at 250 °C for 1 h. The devices treated at 350 °C for 10 h exhibited p-channel characteristics. The device characteristics were compared with another fabricated p-type doped source/drain structure. A remarkable enhancement in the performance of the aluminum metallized source/drain devices was observed. These structures yielded a peak field effect mobility of about 105 cm2·V-1·s-1. The simple fabrication process and resulting enhancement in device performance makes this type of structure ideal for use in thin film transistors on glass.
Relationship between Line Edge Roughness and Fluctuation of Acid Concentration in Chemically Amplified Resist
Authors: Kozawa Takahiro , Yamamoto Hiroki , Tagawa Seiichi
Published: September 2010

Line edge roughness (LER) is a critical issue in the development of chemically amplified resists used for extreme ultraviolet (EUV) lithography. The main cause of LER in state-of-the-art resists is the chemical inhomogeneity intrinsic to chemical reactions. However, the fluctuation of the initial acid concentration possibly caused by the inhomogeneous distribution of resist components such as acid generators becomes a concern with the reduction of feature sizes. In this study, the effect of the fluctuation of the initial acid concentration on LER was theoretically investigated on the basis of the reaction mechanisms of chemically amplified EUV resists. The fluctuation of line edge originating from the fluctuation of the initial acid concentration was compared with LER originating from the fluctuation of chemical reactions. Even at 16 nm half pitch, the fluctuation in the initial distribution was significantly reduced through catalytic chain reaction. The smoothing effect of acid diffusion is essential to meet the requirement for fine patterning with high sensitivity.
A New Micro-rate Sensor Based on Shear Horizontal Surface Acoustic Wave Gyroscopic Effect
Authors: Wang Wen , Xu Fangqian , He Shitang , Li Shunzhou , Lee Keekeun
Published: September 2010

In this paper, we present a new micro-rate sensor based on the shear horizontal surface acoustic wave (SH-SAW) gyroscopic effect. The new SH-SAW propagating along the ST-90°X quartz substrate with heavy metallization exhibits excellent temperature stability, large acoustic velocity, high electromechanical coupling factors, and very small propagation attenuation. The response mechanism of such an SH-SAW micro-rate sensor was established using partial-wave analysis methods. The angular detection sensitivity in the propagation path of SH-SAW was evaluated and the effect of the metal interdigital transducer (IDT) electrode thickness on the sensor performance was also studied, resulting in the realization of the optimized design parameters prior to fabrication. Two SH-SAW delay lines with a reverse direction and an operation of 80 MHz on the same chip are fabricated as the feedback of SAW oscillators. The single-phase unidirectional transducer (SPUDT) was used to structure the delay lines to decrease the insertion loss. The Coriolis force from the external rotation acts on the particles along the SAW propagation path, then a pseudo SAW was induced, and couples with the initial SH-SAW; thus, the SAW velocity was deviated. Meanwhile, the differential oscillation frequency was changed linearly and used to characterize the input angular rate. Then, using the precise rate table, the performance of the fabricated SH-SAW rate sensor was evaluated experimentally. A sensitivity of 1.268 Hz deg-1 s-1 at angular rates of up to 2000 deg s-1, good linearity, and excellent temperature stability are observed.
Simple Microfluidic Continuous Concentration of Microparticles with Different Dielectric Constants Using Dielectrophoretic Force in a V-Shaped Electrode Array
Authors: Hayashi Masahito , Yasuda Kenji
Published: September 2010

We show here that the viscous drag and dielectrophoretic force generated in a V-shaped ladder electrode array in a microfluidic channel cause both attracted and repelled microparticles to move to the electrodes at the centre of the channel. Both Bacillus spores and 1-µm polystyrene spheres in a flow concentrated at the edges of V-shaped electrodes to which a 20 Vpp 1 MHz AC voltage was applied. The results indicated the advantages of this simple setup for concentrating microparticles regardless of their dielectric constants, which is essential for highly precise cell separation and analysis.
Separation Technique for Raisins and Stems Utilizing Characteristics of Polarization
Authors: Kurosawa Takashi , Hosotani Akira , Ohmiya Tadashi , Horikoshi Minoru , Kanazawa Masao , Katto Masahito , Kaku Masanori , Kubodera Shoichi
Published: September 2010

We have improved the accuracy of the laser separation of stems from raisin samples on the basis of the degree of polarization of scattered light from raisins and stems. The specular reflection from wet raisins was minimized by regulating the degree of polarization of their scattered emissions. Wet and dry raisins were therefore judged as the same samples. Using these polarization characteristics, wet or dry raisins were separated from their stems in our laser inspection system. The detection error was reduced from 25 to 7% in our system.
Temperature Dependence of Dielectric Properties of Barium Titanate Ceramic Films Prepared by Aerosol Deposition Method
Authors: Suzuki Muneyasu , Akedo Jun
Published: September 2010

BaTiO3 (BTO) thick films were deposited by an aerosol deposition (AD) method and their physical and electrical properties were investigated. The films were deposited on Pt/Ti/Al2O3 and Pt/Ti/ZrO2 (YSZ) ceramic substrates at a thickness of approximately 2 µm. Two powders were selected for this investigation. The primary BTO powders have a perovskite structure with average particle diameters of 0.1 and 0.5 µm, respectively, and are commercially available as raw powders (BT01 and BT05). These powders were heat-treated for 1 h at 1000 °C in a furnace prior to deposition. The particle size was not changed by the heat treatment while a large aggregate with a size of 10–50 µm was observed in the heat-treated BT01 powder. As-deposition films showed a relative dielectric constant (ε
r) of approximately 100 regardless of the powder and the substrates used. A post-deposition heat treatment at 1000 °C for 1 h was carried out for the BTO thick films. After annealing, the ε
r was improved. The BTO thick films prepared from BT01 heat-treated powders on the Pt/Ti/YSZ ceramic substrates showed an ε
r at room temperature of 1120 which is higher than that of 910 of the films deposited on Pt/Ti/Al2O3. The BTO films fabricated from BT05 heat-treated powders on Pt/Ti/Al2O3 ceramic substrates have an ε
r of 650, larger than that for the films deposited on Pt/Ti/YSZ. Control of powder aggregation by heat treatment along with the use of AD as the method of film fabrication and appropriate substrate selection are demonstrated to be important parameters to obtain BTO ceramic films with a high ε
r.
Annealing Effects on Sensitivity of Atomic-Layer-Deposited SrTiO3-Based Oxygen Sensors
Authors: Hara Toru , Ishiguro Takashi , Shinozaki Kazuo
Published: September 2010

Semiconductive dielectric SrTiO3-based thin films are promising candidates for in situ monitoring of trace levels of oxygen in semiconductor or organic light-emitting diode (LED) display manufacturing processes. SrTiO3-based thin films, which are deposited by atomic-layer deposition (ALD), exhibit high sensitivity to oxygen at room temperature; however, the sensitivity can be affected by SrO-based surface segregation. In this study, we will show that annealing temperature and time are the key parameters for decreasing the coverage of oxygen-insensitive SrO-based surface segregation.
Crystal Structures and Electrical Properties of Epitaxial BiFeO3 Thin Films with (001), (110), and (111) Orientations
Authors: Sone Keita , Naganuma Hiroshi , Miyazaki Takamichi , Nakajima Takashi , Okamura Soichiro
Published: September 2010

BiFeO3 (BFO) films were formed on (001), (110), and (111) La-doped SrTiO3 single-crystal substrates. All the films were epitaxially grown and had mainly rhombohedral structure. The BFO film formed on the (001) substrate had only a (001) component whereas the BFO films on (110) and (111) substrates had (110) and (111) components, respectively. The (001), (110), and (111) epitaxial BFO films showed the remanent polarizations of 63, 84, and 106 µC/cm2, respectively. It seems that the (110) and (111) components were changed to (110) and (111) ones, respectively, by applying an external voltage. The (001) epitaxial BFO film showed marked asymmetry in its electrical properties. It was found that the (001) epitaxial BFO film had a thin tetragonal layer with spontaneous polarization fixed in the downward direction near the substrate. Finally, we concluded that this tetragonal layer caused the accumulation of space charges at the interface, causing a downward built-in field to be generated. The downward build-in field facilitated the switching of upward polarization and caused asymmetric relaxation.
Effect of Film Thickness and Crystal Orientation on the Constituent Phase in Epitaxial BiFeO3–BiCoO3 Films Grown on SrTiO3 Substrates
Authors: Yasui Shintaro , Yazawa Keisuke , Yamada Tomoaki , Nishida Ken , Uchida Hiroshi , Azuma Masaki , Funakubo Hiroshi
Published: September 2010

The crystal symmetries of epitaxial (1-x)BiFeO3–xBiCoO3 films (x=0–0.46) grown on (100)SrTiO3, (110)SrTiO3, and (111)SrTiO3 substrates covered with/without SrRuO3 layers were systematically investigated as a function of film thickness and the crystal orientation of the substrates. Raman analysis was an effective method of crystal symmetry research on epitaxial BiFeO3–BiCoO3 films. Crystal symmetry was changed from being rhombohedral to tetragonal through the mixture of these symmetries with increasing BiCoO3 content irrespective of film thickness and the crystal orientation. However, the constituent phase was strongly depended on film and the crystal orientation of the substrates. The perovskite single phase was observed up to a higher x for the films grown on (100)SrTiO3 substrates than for those grown on (110)SrTiO3 and (111)SrTiO3 substrates. On the other hand, the constituent phase of the films grown on (111)SrTiO3 substrates was similar to that of the strain free powders obtained by high-pressure synthesis.
Ferroelectric Properties of Bi1.1Fe1-xCoxO3 Thin Films Prepared by Chemical Solution Deposition Using Iterative Rapid Thermal Annealing in N2 and O2
Authors: Tho Nguyen Truong , Kanashima Takeshi , Sohgawa Masayuki , Ricinschi Dan , Noda Minoru , Okuyama Masanori
Published: September 2010

Ferroelectric Bi1.1Fe1-x
Co
x
O3 (BFCO) thin films with x = 0–0.3 have been prepared on Pt/Ti/SiO2/Si substrates by chemical solution deposition (CSD) using iterative rapid thermal annealing (RTA) in nitrogen and oxygen. The crystallization of the rhombohedral structure of BiFeO3 (BFO) is observed clearly in all thin films, and a monoclinic Bi2O3 phase is also observed and is markedly larger in Co-doped BFO thin films than in BFO thin films. An electric field of 2 MV/cm is applied to the Bi1.1Fe0.9Co0.1O3 thin film annealed in nitrogen at 520 °C without dielectric breakdown, but its polarization versus electric field (P–E) hysteresis loops are not saturated owing to its high leakage current density. The Bi1.1Fe0.8Co0.2O3 thin film prepared at 520 °C in oxygen shows a very good saturation of P–E hysteresis loops at room temperature (RT) at the low leakage current of about 8.7 ×10-3 A/cm2 under a high electric field of 1.5 MV/cm. The leakage current at a low electric field may be Ohmic emission at any temperature; however at a high electric field, it may be attributed to tunnel emission at 80 K and Schottky emission at RT.
Synthesis and Electrical Properties of KF-Doped BaTiO3 Ceramics
Authors: Akishige Yukikuni , Honda Kazuo , Tsukada Shinya
Published: September 2010

KF-doped barium titanate ceramics, Ba1-x
K
x
TiO3-x
F
x
(KF-BT/x: 0≦x≦0.15), were fabricated by spark plasma sintering (SPS) using fine particles prepared by a sol–gel method. We measured the dielectric and piezoelectric properties of the SPS ceramics after annealing in an O2 gas flow at 1273 K. The dielectric constant and the piezoelectric constant d
33 were enhanced in KF-BT/0.10, as found in the single crystals, because the composition of x=0.10 locates near the tricritical point (TCP). However, some different behaviors from those of the single crystals were found; in particular, T
C of the ceramic forms is much higher than that of the crystalline forms, and the difference becomes marked with increasing x. We consider that the evaporation of F-, which occurs during the O2 annealing process, markedly increases T
C.
Effect of Sn2+ Ion Substitution on Dielectric Properties of (Ba,Ca)TiO3 Ferroelectric Ceramics
Authors: Suzuki Shoichiro , Takeda Toshikazu , Ando Akira , Oyama Takashi , Wada Nobuyuki , Niimi Hideaki , Takagi Hiroshi
Published: September 2010

In this study, we investigated the sintering atmosphere dependence of the electric properties of Sn-doped (Ba0.82Ca0.13)TiO3 ceramics to clarify the effect of Sn2+ ions. The temperature of the dielectric constant peak for Sn-doped (Ba0.82Ca0.13)TiO3 ceramics sintered in a low P(O2) (1×10-11 MPa) atmosphere is higher than that for the sample sintered in a high P(O2) (2×10-2 MPa) atmosphere. The remanent polarization and coercive field for the Sn-doped (Ba0.82Ca0.13)TiO3 ceramics sintered at low P(O2) (1×10-11 MPa) also increased compared with those of the sample sintered at high P(O2) (2×10-2 MPa) at room temperature. The low P(O2) sintering atmosphere for Sn-doped (Ba0.82Ca0.13)TiO3 ceramics leads to a high tetragonality and the existence of Sn2+ ions. In addition, by X-ray absorption spectroscopy, it was verified that Sn2+ ions occupy Ba2+ sites in the (Ba0.82Ca0.13)TiO3 ceramics. Consequently, it is concluded that the high ferroelectric-to-paraelectric phase transition temperature and the high remanent polarization on the ceramics originate from Sn2+ ions substituted for Ba2+ sites in Sn-doped (Ba0.82Ca0.13)TiO3 ceramics.
Molecular Alignment of Ferroelectric Liquid Crystal in Wide-Gap Cell for Liquid Crystal Lens
Authors: Furue Hirokazu , Sakai Hirokuni , Tanaka Daich
Published: September 2010

The high-speed response of ferroelectric liquid crystals (FLCs) is advantageous for optical devices such as an electrically controlled lens. We have investigated the molecular alignment structure of FLC in a wide-gap cell for application to the lens. As a result, it has been found that a zigzag defect-free FLC medium can be obtained by utilizing alignment films, which possess a smooth surface and give rise to the defect-free situation in a narrow-gap cell, and by cooling from the nematic to the smectic phase at a low rate of <1 °C/min. However, the transformation of the smectic layer structure has been observed under an electric field, particularly under a very low electric field in the wide-gap cell. We have attempted to suppress this transformation, which considerably degrades the optical performance of FLC, by the polymer stabilization technique.
Piezoelectricity of Poly(L-lactic Acid) Composite Film with Stereocomplex of Poly(L-lactide) and Poly(D-lactide)
Authors: Yoshida Tetsuo , Imoto Kenji , Tahara Komei , Naka Kyohei , Uehara Yusuke , Kataoka Shingo , Date Munehiro , Fukada Eiichi , Tajitsu Yoshiro
Published: September 2010

The piezoelectricity of a film of the eco-material poly(L-Lactic acid) (PLLA) with high transparency and flexibility has been noted for its possibility of application to new types of devices used in mobile equipment. However, for its application, there are many difficult problems to be solved, because the PLLA film has poor thermal stability. To change the high-order structure of the PLLA film, thus realizing an improvement in the temperature dependence of its piezoelectricity, a composite film with a stereocomplex crystal (SC) formed from PLLA and poly(D-lactide acid) (PDLA) molecules was fabricated. As a result, we obtained a composite film with a stable piezoelectric temperature dependence compared with a pure PLLA film. To analyze its piezoelectric temperature dependence, we first observed the high-order structure of the composite film using a polarized microscope (POM). However, we did not find any difference between the high-order structures of the composite film and the pure PLLA film. In contrast, from observation by atomic force microscopy (AFM), it was found that the grain structure in the composite film became more homogeneous than that in the pure PLLA film. These experimental results indicate that, by changing the high-order structure through a compound with SC, the external stress always has a constant effect over a wide temperature range and, as a result, the induced polarization is constant in the composite film. Thus, the composite film shows excellent thermal stability of piezoelectricity compared with the pure PLLA film.
Relationship between Nonlinear Piezoelectricity and Decrease of Mechanical Quality Factor in Pb(Mn1/3Sb2/3)O3–PbZrO3–PbTiO3 Piezoelectric Ceramics Driven at High Power
Authors: Ishii Keisuke , Tashiro Shinjiro
Published: September 2010

By changing the Pb(Mn1/3Sb2/3)O3 content and Zr/Ti ratio, Pb(Mn1/3Sb2/3)O3–PbZrO3–PbTiO3 (PMS–PZT) system piezoelectric ceramics having different nonlinear piezoelectricities were fabricated. The transient responses of the sample current and the vibration velocity at the sample end were simultaneously measured during high-power driving. Both mechanical quality factors, Q
m, which were calculated from these two kinds of transient responses, changed similarly on the driving power scale. This indicates that the change in Q
m when driven at a high power can be estimated from the transient response of the sample current. From the analysis of the experimental results of Q
m, it was found that high-power driving induces a decrease in Q
m more easily in the samples with larger nonlinear piezoelectric constants of third-higher term, ξD31.
Nonlinear Shear Responses of Lead Zirconate Titanate Piezoelectric Ceramics
Authors: Hagiwara Manabu , Hoshina Takuya , Takeda Hiroaki , Tsurumi Takaaki
Published: September 2010

The nonlinear piezoelectric and dielectric responses in the shear mode against an applied field were investigated using hard and soft Pb(Zr,Ti)O3 (PZT)-based piezoelectric ceramics. The shear strain was measured using a double-beam leaser Doppler vibrometer. The third-order harmonic components of the strain and the current of soft PZT markedly increased with the increase in the field while those of hard PZT were maintained at low values. In hard PZT, the elastic nonlinearity in the shear mode was also estimated by measuring the change in fundamental resonance frequency. This nonlinearity showed a small dependence on the strain compared with that in the length-extensional mode.
Polarization and Piezoelectric Properties of High Performance Bismuth Sodium Titanate Single Crystals Grown by High-Oxygen-Pressure Flux Method
Authors: Suzuki Muneyasu , Morishita Akifumi , Kitanaka Yuuki , Noguchi Yuji , Miyayama Masaru
Published: September 2010

(Bi0.5Na0.5)TiO3 (BNT) single crystals were grown by flux method at a high oxygen pressure (P
O2
) of 1 MPa, and their polarization and piezoelectric properties were investigated. BNT single crystals exhibited a saturated polarization hysteresis with remanent polarizations (P
r) of 31 µC/cm2 along [100]c, 44 µC/cm2 along [110]c and 54 µC/cm2 along [111]c. These results show that spontaneous polarization of BNT is approximately 55 µC/cm2 or larger. Strain measurements of rhombohedral BNT crystals suggest that the polarization reversal along [111]c is achieved by non-180° P
s rotation whereas that along [100]c is accomplished by 180° P
s switching.
Effect of Grain Size on Mechanical Properties of Full-Dense Pb(Zr,Ti)O3 Ceramics
Authors: Miyoshi Tetsu , Funakubo Hiroshi
Published: September 2010

The grain size dependence of mechanical properties was investigated in full-dense Pb(Zr,Ti)O3 (PZT) ceramics using a microindentation fracture method. Full-dense PZT ceramics with an average grain size ranging from 0.09 to 2.3 µm were successfully prepared by a novel compaction method based on aerosol deposition (AD). Vickers hardness (H
v) increased with decreasing grain size and the Hall–Petch relationship (H
v=H
v0+k
d
-1/2) was confirmed over almost the entire grain size range investigated, which indicates that grain size could be the determining factor of hardness in full-dense PZT ceramics. On the other hand, fracture toughness (K
C) decreased with decreasing grain size below the critical grain size of 1.0 µm. The critical grain size was consistent with that below which the volume fraction of the tetragonal phase (V
Tet) decreased with decreasing grain size, which indicates that ferroelastic 90° domain switching is a viable toughening mechanism in PZT ceramics. In this study, we have demonstrated that, with suitable microstructural control, the PZT ceramics with ultra-high strength for contact situations can be realized without any sacrifice in piezoelectric properties.
X-ray Spectroscopic Study on Photoluminescence Properties of Red Phosphor SrTiO3:Pr3+,Al
Authors: Nakajima Nobuo , Deguchi Masataka , Maruyama Hiroshi , Ishiji Kotaro , Tezuka Yasuhisa
Published: September 2010

The electronic structure of the practical red phosphor SrTiO3;Pr3+,Al is studied by X-ray absorption and emission spectroscopy under ultraviolet (UV) irradiation. In contrast to the invariance of the oxygen Kα emission spectra, the titanium K-edge absorption spectra show two characteristic changes depending on UV energy, one of which is proportional to the photoluminescence excitation spectrum while the other is insensitive to it. With these results, a schematic energy diagram is proposed where the titanium 4p band pulled down by oxygen valence holes overlaps Pf 4f radiative centers situated just below the conduction band. The photoluminescence properties are briefly discussed in relation to the ferroelectric phase transition from an electronic viewpoint.