bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long Retention Performance of a MFIS Device Achieved by Introducing High-k Al2O3/Si3N4/Si Buffer Layer
Authors: Fujisaki Yoshihisa , Iseki Kunie , Ishiwara Hiroshi 
Published: April 2011

ABSTRACTWe introduced high-k Al2O3/Si3N4 buffer layer in MFIS (Metal-Ferroelectric-Insulator-Semiconductor) devices to reduce the leakage current though the buffer (I) layer. We prepared the buffer layer by nitridizing Si substrate by atomic nitrogen radicals and then deposited Al2O3 film using ALD (Atomic Layer Deposition) technique. The interface state density between the ALD-Al2O3/Radical-Si3N4 stacked insulator and a Si substrate is as low as 1011 cm-2eV-1. The current density less than 10-9 A/cm2 is realized under the 1V bias application using films with the capacitance density of 12fF/μm2. The c-axis oriented Bi3.45La0.75Ti3O12 (BLT) ferroelectric films were deposited to make MFIS structure. With this structure, we obtained the retention time as long as 1.5×106 sec (about 17 days). This excellent retention character is attributable to the high insulating property of the ALD-Al2O3/Radical-Si3N4 stacked insulator and also attributable to the perfect elimination of defects at the interfaces in the MFIS structure.
Selective Deposition of C-axis Oriented Pb5Ge3O11 on the Patterned High k Gate Oxide by MOCVD Processes
Authors: Li Tingkai , Hsu Sheng Teng , Ulrich Bruce , Evans Dave 
Published: April 2011

ABSTRACTFor the high density FeRAM applications, the integration process-induces damages such as etching damage that degrades the properties of FRAM devices and the high surface roughness of ferroelectric thin film that results in the difficulty for alignment are critical issues. In order to solve these problems, selective deposition process is developed to simplify the integration processes and improve the properties of FeRAM memory devices. Based on the differential deposition rates of ferroelectric materials on high-k oxide and silicon dioxide, we can selectively deposit a c-axis oriented PGO thin film on the patterned high-k oxide such as ZrOx (x=0–2), HfOx (x=0–2), TiO2, and their mixtures other than on SiO2. By patterning the high-k dielectric, the PGO deposition is limited to just the preferred pattern high-k area. SEM, EDX and x-ray measurements further confirm that the c-axis oriented PGO thin films are selectively deposited on the high-k gate oxide other than on the field SiO2 including alignment mark area, which will eliminate the roughness problem for the alignments. Also the etching damage is eliminated since there is no need to etch the PGO film, which improved the properties of FeRAM devices.
Smart Heterostructures Based on Solid Solution ZnCdHgTe
Authors: Khlyap Galina M. , Sydorchuk Petro G. , Polit Jacek , Oszwaldowsky Macej 
Published: April 2011

ABSTRACTCurrent – voltage (IVC) and capacitance – voltage (CVC) of heterostructures (Cd, Zn)Te/ZnCdHgTe are studied for the first time. Thin films ZnxCdyHg1-x-yTe were grown on monocrystalline (111) CdTe and ZnTe substrates by PLE technology. Deposition was carried out on substrates held at temperatures near 290 K. The thickness of investigated films was estimated to be about 5 μm. Electric characteristics of the as-grown structures were examined under T = 77–290 K in the wide range of applied bias. All investigated samples have demonstrated diode-like IVC and CVC under test signal frequency f = 1 kHz. Heterostructures CdTe/ZnCdHgTe have exhibited a room temperature photosensitivity in spectral range 0.50–0.65 μm.
Development of a Wireless MEMS Inertial System for Health Monitoring of Structures
Authors: Kok Ronald , Furlong Cosme , Pryputniewicz Ryszard J. 
Published: April 2011

ABSTRACTAdvancements in microelectromechanical technologies have lead to progressive design of small footprint, low dynamic mass and actuation power, and high-resolution MEMS inertial sensors. In this paper, development of instrumentation and methodologies for wireless health monitoring of structures using MEMS inertial sensors is presented. A dedicated experimental setup is developed to characterize specific MEMS inertial sensors and structures. Studies presented in this paper include development and characterization of a prototype wireless data acquisition system to transmit analog and digital signals. Results show that the frequency response of the prototype wireless data acquisition system is compatible with the frequency response of the MEMS inertial sensors utilized. The prototype wireless MEMS inertial system is applied to perform tilt and rotation measurements. It is shown that with the wireless MEMS system it is possible to achieve an angular resolution of 1.8 mrad.
Piezoelectric Actuators for Synthetic Jet Applications
Authors: Mossi Karla , Bryant Robert 
Published: April 2011

ABSTRACTSynthetic jets have been identified and utilized widely in airflow control applications. These jets of air are usually created by the use of compressed air, or an electromechanically driven vibrating platform. All of these approaches produce desired results in airflow-control such as enhanced lift and increased maneuverability. Despite the results however, system weight, size, response time and force limit their use in aircraft applications where space is a premium. The objective of this study is to characterize the relevant properties for the design of a synthetic jet utilizing three types of piezoelectric actuators as mechanical diaphragms. The limiting parameters of the actuators for this application are shape and volumetric space. Thus, the actuators were circular with a diameter of 6.35 cm, and overall device cavity volume no larger than 147.5 cm3 on a 7 cm x 7 cm areal coverage. The actuators tested were pre-stressed curved metallic unimorphs, bimorphs, and radial field diaphragms. These piezoelectric elements were chosen because of their geometry, quasi-isostatic topography and overall free-displacement. Each actuator was affixed about its perimeter in a cavity, and relevant parameters such as clamped displacement, and jet velocity though a pre-determined dimensional slot, were measured.
Cyclic magnetic-field -induced deformation and magneto-mechanical fatigue of Ni-Mn-Ga ferromagnetic martensites
Authors: Müllner P. , Chernenko V. A. , Mukherji D. , Kostorz G. 
Published: April 2011

ABSTRACTFour Ni-Mn-Ga single crystals exhibiting modulated 10M and 14M martensites were exposed to rotating magnetic fields of 1 and 2 T. Large periodic magnetic-field-induced strains were obtained for crystals that had been subjected to a mechanical stress while the martensite formed on cooling and to deformation in a magnetic field prior to the experiments with rotating field. A reduction of the magnetic-field-induced strain and fracture occurred when the field-induced strain was close to the transformation strain whereas a constant magneto-mechanical response was detected over more than 10 million field cycles when the field-induced strain was small. The cyclic magneto-mechanical response is related to the interaction of groups of twinning dislocations and twin boundaries. If the dislocations move in large groups, they nucleate cracks at twin boundaries. If the dislocations move in small groups, no cracks are formed resulting in a long lifetime.
Development of Texture-Controlled Bulky Actuator/Sensor Materials by Combining Rapid-Solidified Fiber/Ribbon Elements and Spark Plasma Sintering/Joining(SPSJ)
Authors: Furuya Y. , Yokoyama M. , Saito C. , Okazaki T. , Omori M. 
Published: April 2011

ABSTRACTThe authors have showed that rapid-solidified (RS) melt-spun fiber/ribbon/foil type samples have very often strongly textured fine columnar grains, and those can have very high performance of the metallic actuator/sensor properties. However, as for the applications of these sample materials in smart material systems, the developed rapid-solidified samples are thought to be inevitably too small force to move the machines and structures in the engineering field. In this paper, we propose one novel material processing technique that can produce the bulk type solid-state actuator/sensor materials by combing the rapid-solidified fiber/ribbon and short time spark plasma sintering/joining (SPS) method. The produced samples, both 1) the disk-type sample from stacked layers of RS-ribbons and 2)the sintered compact from ball-milled RS-fibers of shape memory Ti50Ni40Cu10 (NITINOL) alloy, showed clear thermoelastic phase transformation by DSC evaluation as well as shape recovery. The same approach was also tried for making bulky magnetostrictive FeGa(Galfenol) alloy systems from stacked FeGa ribbons. Laminated FeGa ribbons maintained large magnetostriction of about 100–200ppm under increasing stressed condition as much as in the case of the strongly textured ribbon sample.
The Development of Active and Sensitive Structural Material Systems
Authors: Asanuma Hiroshi 
Published: April 2011

ABSTRACTThis paper describes new concepts the author has proposed and demonstrated to realize metal and polymer based sensitive and/or active structural material systems suitable for smart structures. Most of the developments have been done by simple and innovative methods without using sophisticated and expensive sensors and actuators. The following topics are mainly examined: (1) forming optical interference and loss type strain sensors in epoxy matrix simply by embedding and breaking notched optical fiber in it; (2) forming a multifunctional sensor in aluminum matrix for temperature and strain monitorings by embedding an oxidized nickel fiber; (3) fabricating multifunctional composites by using conventional structural materials -an active laminate of CFRP/aluminum of which unidirectional actuation is realized by electrical resistance heating of carbon fiber in the CFRP layer and its curvature change can be monitored using optical fiber multiply fractured in the CFRP layer; (4) fabricating active fiber-reinforced metals such as SiC/Al and SiC/Ni systems by laminating a reinforced layer with a unreinforced layer to cause thermal deformation. In the case of SiC/Al composite, actuation was performed only in the fiber direction and is useful for making a light-weight active panel. In the case of SiC/Ni composite, actuation took place up to above 1200K and is useful for making a high temperature actuator.
Fundamental Investigation of Ferromagnetic Shape Memory Alloys: A New Perspective
Authors: Sullivan Matthew R. , Ateya Daniel A. , Pirotta Steven , Shah Ashish A. , Wu G. H. , Chopra Harsh Deep 
Published: April 2011

ABSTRACTIn the present study, the evolution of micromagnetic structure and microstructure is studied in-situ both as a function of temperature and applied magnetic field, using single crystal Fe-Pd and Ni-Mn-Ga Heusler alloys. Through the development of a novel technique called ‘Magnetic Transition Spectrum’ to study temperature dependent domain dynamics, the relative sequence of micromagnetic reconfiguration with respect to the martensitic transformation has been determined for the first time. Results show that the FSMAs may be viewed as magnetic mosaics, a new perspective, which is also more amenable to modeling the physical properties of these alloys. Finally, the concept of magnetic mosaics has been used to synthesize a novel class of materials with engineered magnetic anisotropies, and is briefly discussed.
Phase Transformations of Ferromagnetic Fe-Pd-Pt-Based Shape Memory Alloys
Authors: Yang Gwon-seung , Jonasson Reid , Baek Seung-nam , Murata Kinzo , Inoue Shozo , Koterazawa Keiji , Jeong Soon-jong , Mizuuchi Kiyoshi , Inoue Kanryu 
Published: April 2011

ABSTRACTSeveral ternary Fe-Pt-Pd alloys with the compositions of Fe-(25-x) at% Pt-x at% Pd and Fe-y at% Pt-(30-y) at% Pd were investigated to study their phase transformations in order to develop ductile ferromagnetic shape memory alloys appearing around room temperature. Alloys were prepared by vacuum floating induction melting, followed by hot rolling at 1000°C and homogenization at 900° C. Homogenized alloys were heat treated at 650°C for various periods of time in vacuum for atomic ordering in encapsulated quartz tubes, and quenched into iced water. It was found that in general the transformation temperatures changes with heat treatment time. In the case of Fe-23at.%Pt-2at.%Pd, Ms temperature increased and the difference between Ms and Mf increased with increasing heat treatment time, which was different from Fe3Pt where a degree of order becomes one. As heat treatment time increased, there was a tendency in that a strong first-order transformation in the disordered state was replaced by a weak first-order transformation. The Curie temperature of the alloys rose drastically with the addition of Pd, along with the transformation temperatures. Fe-23at.%Pt-2at.%Pd showed good shape memory effect after 8 hours of heat treatment at 650°C. This alloy showed much better shape recovery than any other binary Fe-Pt and Fe-Pd shape memory alloys.
Elasticity Study in Ferromagnetic Shape Memory Alloys
Authors: Dai Liyang , Cullen James , Cui Jun , Wuttig Manfred 
Published: April 2011

ABSTRACTThe temperature dependences of the elastic constants of Ni0.50Mn0.284Ga0.216 and Fe3Pd were studied. Measurements were conducted by the ultrasonic continuous wave method. Anomalous behavior of the elastic constants temperature dependence in austenitic NiMnGa was observed, especially an abrupt 15% softening of C11 at the Curie temperature. The latter anomaly was found to be strongly influenced by the presence and orientation of applied magnetic fields. In martensitic NiMnGa, the temperature dependences of the velocities of all eleven elastic wave modes had abrupt changes at 220K, which indicate a structural phase change from the tetragonal to a second phase at lower temperature. The temperature and magnetic field effects in Fe3Pd were also studied by the elastic constants measurements.
Structural and dielectric properties of Ca1-x MgxCu3Ti4O12 thin films
Authors: Bermúdez L. A. , Guzman R. P. , Tomar M.S. , Melgarejo R.E. 
Published: April 2011

ABSTRACTCa1-xMgxCu3Ti4O12 material has been synthesized by chemical route for different compositions and thin films have been deposited by spin coating. X-ray diffraction and Raman spectroscopy were used for detailed characterization of this material for both powder and thin films. X-ray diffraction shows single phase film material for different compositions x < 0.80. The initial measurements on dielectric response indicates high dielectric constant > 10, 000 for the composition x = 0.1.
Fabrication and Characterization of TiNi/AL Smart Composites
Authors: Lee Gyu Chang , Lee Jun Hee. , Park Young Chul 
Published: April 2011

ABSTRACTAn attempt was made to fabricate composite material of an Al alloy matrix reinforced by TiNi shape memory fiber using a hot-press method and to investigate its microstructures and mechanical properties. The analysis of SEM and EDS showed that the composite material had good interface bonding. The stress-strain behavior of the composite material was evaluated at room temperature and 363 K as a function of pre-strain, and it showed that the yield stress at 363 K is higher than that at room temperature. It is also found that the yield stress of the composite material increased with increasing the amount of pre-strain and depended on the volume fraction of the fiber and heat treatment. The smartness of the composite could be given due to the shape memory effect of the TiNi fiber, which generated compressive residual stress in the matrix material when heated after being pre-strained. Microstructural observation revealed that interfacial reactions occurred between the matrix and fiber, creating two intermetallic layers.
Characterization of NiTiNOL for Smart Structural Systems using ACES Methodology
Authors: Mizar Shivananda P. , Pryputniewicz Ryszard J. 
Published: April 2011

ABSTRACTSMAs are engineering alloys that recover extensive amounts of deformation when subjected to a temperature change. The recovery of deformation is as result of a phase transformation from martensite to austenite. For example, for NiTiNOL, a very popular SMA, this transformation occurs at 60°C. Actuation is a type of shape memory process that utilizes deformation recovery that is used in smart structural systems. These systems are designed to detect and control structural deformations due to external time varying loads encountered during functional operation. In this paper, the actuating properties of NiTiNOL are characterized using an analytical, computational, and experimental solution (ACES) methodology. Analytical models are utilized to calculate the deformation under dynamic loads. Finite element method (FEM) is used for computational investigations. Optoelectronic holography (OEH) is the experimental method utilized to obtain temperature dependent behavior of NiTiNOL. As a result of the phase transformation, NiTiNOL undergoes a stiffness change indicated by a change in the modulus of elasticity from 33 GPa to 75 GPa. Deformations of NiTiNOL samples subjected to static loads at different temperatures were measured indicating recovery of 85% due to the phase transformation. In addition, amplitudes of vibration were measured as a function of excitation frequency and temperature to determine the effects of phase transformation. The results show effectiveness of NiTiNOL in development of smart structural systems
Fabrication and characterization of freestanding NiMnGa films
Authors: Rumpf Holger , Craciunescu Corneliu , Feydt Jürgen , Gilles Achim , Wuttig Manfred , Quandt Eckhard 
Published: April 2011

ABSTRACTFreestanding Ni50Mn30Ga20 films of 13 μm thickness were fabricated by DC magnetron sputtering and analyzed. Magnetic measurements revealed the influence of the post deposition rapid thermal annealing process on the ferromagnetic hysteresis. Ferromagnetic properties evolved after annealing at 400°C. Thermal annealing of at least 600°C led to polycrystalline films that transformed reversibly and martensitically as shown by structural analysis and differential scanning calorimetry. Transformation temperatures and enthalpies of transformation of the martensitic transformation were strongly influenced by the temperature of the rapid annealing process. It is proposed that the annealing data reflect the evolution of the crystalline state.
Thermo-Mechanical Characteristics of Ti-Ni-Cu Shape Memory Alloy Fabricated by Pulse-Current Pressure Sintering Method
Authors: Kyogoku Hideki , Kadomura Takeshi , Komatsu Shinichiro , Yoshida Fusahito , Sakuma Toshio 
Published: April 2011

ABSTRACTThe Ti-Ni-Cu shape memory alloy by elemental powders was fabricated by means of a pulse-current pressure sintering method that can produce high-density sintered compacts in a very short sintering time. The fabrication conditions of Ti-Ni-Cu alloy and the influence of Cu content in Ti-Ni-Cu alloy on the tensile properties and thermo-mechanical characteristics were investigated. The relative density of the as-sintered compacts was around 97% at any Cu content. The microstructure, tensile properties and thermo-mechanical characteristics of the as-sintered compacts were improved greatly by performing a solid solution heat-treatment. The yielding behavior due to the stress-induced martensite in stress-strain curves of the alloy took place after elastic deformation at any Cu content. The deformation resistance of the alloys changed with Cu content, and it was lowest around 9at% in Cu content. The tensile strength and elongation of the alloy with Cu content around 9at% were more than 400 MPa and 6%, respectively. It was found that the thermo-mechanical behavior of the alloy becomes stable by performing cyclic deformation.
Temperature-Responsive Polymers for Biological Applications
Authors: Rackaitis M. , Manias E. 
Published: April 2011

ABSTRACTWater soluble polymers with tunable lower critical solution temperature (LCST) are of increasing interest for biological applications such as cell patterning, smart drug release, DNA sequencing etc. The present study addresses control of the polymer temperature response in water by varying chemical composition of the monomer. In order to achieve this a series of polymers were designed and synthesized based on an ethyleneoxide/ethylene monomer (EO/EE). Polymers were synthesized using polycondensation reactions of difunctional m-EO and n-EE oligomers. The cloud point follows linearly the balance of hydrophobic/hydrophilic interaction and can be tailored in the range of 7 – 70°C by varying the m/n composition and polymer type. Polymer grafting onto the silicon surface exhibits similar solubility behaviour. Adhesion energy measurements show that grafted polymers have solubility cloud points at the temperatures that are close to the ones of the bulk polymer solutions.
Exploration of an Electroactive Polymer as an Actuator for Microrobotics
Authors: Bielmeier C. , Walter W. 
Published: April 2011

ABSTRACTThe development of lightweight low power consumption actuators is critical to the development of micro-robotics. Electroactive Polymers (EAP), i.e. Nafion N-117, meet these requirements. In the actuation of an EAP, the current does not remain constant over time. The development of a circuit model of current draw over time to best predict a current dynamic has been explored. While the material mimics a parallel plate capacitor, it has been found that capacitance plays no role in achieving steady state current levels. This development is critical to understanding and developing the material as an actuator.
Synthesis and VOC gas sensing properties of Polypyrrole / MoO3 Nanohybrids
Authors: Hosono Kouta , Matsubara Ichiro , Murayama Norimitsu , Woosuck Shin , Izu Noriya 
Published: April 2011

ABSTRACTWe have prepared polypyrrole (PPy) / MoO3 nanohybrid thin films and evaluated their volatile organic compound (VOC) gas sensing properties. The (PPy)xMoO3 thin films have been prepared by intercalation reactions of highly oriented MoO3 thin films. Intercalation of hydrated sodium ions successfully proceeded without loosing the crystallographic orientation. The (PPy)xMoO3 thin films was obtained by replacing the hydrated sodium ions with PPy. The (PPy)xMoO3 thin films can detect formaldehyde gas by increasing in their electrical resistance, whereas they showed no response to toluene.
Point defects in thin HfAlOx films probed by monoenergetic positron beams
Authors: Uedono Akira , Mitsuhashi Riichiro , Horiuchi Atsushi , Torii Kazuyoshi , Yamabe Kikuo , Yamada Keisaku , Suzuki Ryouichi , Ohdaira Toshiyuki , Mikado Tomohisa 
Published: April 2011

ABSTRACTThin HfAlOx films grown on SiON(0.9 nm)/Si by atomic layer deposition technique were characterized by using monoenergetic positron beams. The lifetimes of positrons in the HfAlOx film after post-deposition annealing (PDA) ranged between 412–403 ps. Since these lifetimes were longer than the lifetime of positrons trapped by point defects in metal oxides, such as LaCoO3, PbTiO3, and BaTiO3, the positrons in HfAlOx films were considered to annihilate from the trapped state by open spaces which exist intrinsically in their amorphous structure. The line-shape parameter S of the Doppler broadening spectrum corresponding to the annihilation of positrons in HfAlOx films decreased by PDA, and the S value decreased with increasing an O2-content in an atmosphere during PDA (0.004–1%). The observed behavior of the S value was attributed to the shrinkage of the open spaces due to the change in the matrix structure of HfAlOx. After P+- and B+-implantation into poly-Si films grown on the HfAlOx films, the diffusion of positrons in the Si substrates toward the HfAlOx film was suppressed. This fact was attributed to positive charges introduced near the HfAlOx films.