bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Composite Technology for SOFCs
Authors: Petrovsky Vladimir , Anderson Harlan U. , Petrovsky Tatiana
Published: April 2011

Composite technology is a new approach to solid oxide fuel cell (SOFC) fabrication. It is based on the net shape processing, which uses a combination of colloidal suspension and polymer precursor techniques. Different elements of SOFC can be prepared and optimized using this approach and the flexibility of the net shape processing. The goal of this research was to develop net shape procedures for different elements of SOFC, to show the real possibility preparing all these elements of SOFC and to investigate the advantages of composite technology. A nickel-YSZ composite was prepared and investigated as the prospective anode material. High electronic conductivity and stability in REDOX cycles were shown for this material. Different cathode compositions were prepared using composite technology and tested. It was shown, that these materials ensure low overpotentials and are time stable at operation temperature up to 800°C. All three SOFC designs were tested: anode, cathode and electrolyte supported SOFCs. It was possible to achieve low resistance of SOFC structure for all designs, but electrode supported SOFCs had limitation in the current connected with the gas diffusion through thick electrode substrates. The best performance was achieved on an electrolyte supported system with 100 [.proportional]m YSZ electrolyte and composite anode and cathode: 0.75W/cm2 power density at 0.6 V at 800°C.
Directed Osteoblast Adhesion at Particle Boundaries: Promises for Nanophase Metals
Authors: Perla Venu , Ejiofor Jeremiah U. , Webster Thomas J.
Published: April 2011

In spite of under performance, metals and metal alloys are currently being used in orthopedic implantable devices. Poor osseointegration, severe stress shielding, bone cell death and eventual necrotic bone resulting from the generation of wear debris are known to be some of the reasons responsible for their under performance. In addition, metallic corrosion products may also initiate cancer. Steady growth in the use of metals in orthopedic applications inspired researchers to deal with these problems in an integrated way. When conventional Ti, Ti6Al4V, and CoCrMo surfaces were modified to the nano-range, this study showed increased percentages of osteoblast (bone forming cell) adhesion on nanophase metals. Moreover, larger amounts of osteoblast adhesion was related to quantitative increases in the total length of particle boundaries per unit area and the total number of pores between surface particles per unit area, and the surface particle boundary index (SPBI) of nanophase metals. Additionally, we have developed a novel anticarcinogenic orthopedic metalloid, selenium (Se). When micron range surface particles of Se compacts were modified to the nano-range by chemical etching, we found positive relationships between directed osteoblast adhesion and various particle boundary parameters mentioned above under in vitro conditions. These results provided the first evidence to utilize nanosurface Se as an anticarcinogenic and bio-inspiring material for future applications in orthopedic metallic devices.
Block Copolymer-Based Biomembranes Functionalized with Energy Transduction Proteins
Authors: Ho Dean , Chu Benjamin , Lee Hyeseung , Kuo Karen , Montemagno Carlo D.
Published: April 2011

Block copolymer-based membranes can be functionalized with energy transducing proteins to reveal a versatile family of nanoscale materials. Our work has demonstrated the fabrication of protein-functionalized ABA triblock copolymer nanovesicles that possess a broad applicability towards areas like biosensing and energy production. ABA triblock copolymers possess certain advantages over lipid systems. For example, they can mimic biomembrane environments necessary for membrane protein refolding in a single chain (hydrophilic(A)- hydrophobic(B)-hydrophilic(A)), enabling large-area membrane fabrication using methods like Langmuir-Blodgett (LB) deposition. Furthermore, the robustness of the polymer molecules/structure result in spontaneous and rapid protein-functionalized nano-vesicle formation that retains structure as well as protein functionality for up to several months, compared to one to two weeks for the lipid systems (e.g. POPC). The membrane protein, Bacteriorhodopsin (BR), found in Halobacterium Halobium, is a light-actuated proton pump that develops gradients towards the demonstration of coupled functionality with other membrane proteins, such as the production of electricity through Bacteriorhodopsin activity-dependent reversal of Cytochrome C Oxidase (COX), found in Rhodobacter Sphaeroides. Protein-functionalized materials have the exciting potential of serving as the core technology behind a series of fieldable devices that are driven completely by biomolecules.
Stable, Nanoscale Glycosphingolipid Films for Use in Sensing Applications
Authors: Stine Rory , Schengrund Cara-Lynne , Pishko Michael V.
Published: April 2011

We have developed a means of producing thin, oriented lipid monolayers which are stable under repeated washing and which may be useful in biosensing or surface- coating applications. Phosphotidylcholine (PC) and the glycosphingolipid (GSL) GM1 were used as representative lipids for this process. Initially, a mixed self-assembled monolayer of octanethiol and hexadecanethiol was constructed on a clean gold surface. This hydrophobic surface was then brought into contact with a thin lipid layer that had been deposited at the air/liquid interface of a solution by evaporating a mixture of lipid in hexane on top of a layer of water. The lipid layer, now deposited on the gold surface, was then heated to cause intercalation of the fatty acid and alkanethiol chains, and cooled to form a highly stable film which withstood repeated rinsing and solution exposure. Presence and stability of the film was confirmed via ellipsometry, FTIR, and QCM, with an average overall thickness of ∼3.5 nm. These films may be potentially useful in biotoxin detection or as a protein resistant layer for the prevention of biofouling.
In Vitro and In Vivo Tests Of Hydroxyapatite-Gleatin Nanocomposites For Bone Regeneration: A Preliminary Report.
Authors: Cc Ko , Y-L Wu , Wh Douglas , R Narayanan , W-S Hu
Published: April 2011

A biomimetic process has been developed to fabricate hydroxyapatite-gelatin (HAP-GEL) nanocomposites for bone regeneration (Chang and Ko et al. 2003). We hypothesize that this newly developed HAP-GEL is osteoconductive and is suitable for tissue engineered scaffolds. This preliminary study is aimed to characterize cell affinity and osseous regeneration of the HAP-GEL. The HAP-GEL was synthesized according to the procedures described in the previous publication. The attachment and proliferation of human fetal osteoblasts on HAP-GEL discs were evaluated using three different gelatin contents (2g, 3g, and 4g). The cells were seeded onto each disc and incubated at 34 degrees Celsius in 5% CO2 air atmosphere. At different time points of cultivation, cells were stained with fluorescein diacetate (FDA) and ethidium bromide (EB) to determine their viability and morphology. To assess the cell proliferation, cells were detached at Days 1, 4, and 7 by trypsinzation and counted. For in vivo tests, HAP-GEL rods were implanted into the proximal femur of Sprague-Dawley rats. One month after the implantation, the femurs were harvested and the undecalcified HAP-GEL-bone sections were stained for histopathology. Four hours after attachment, most cells appeared round in all discs; cell spreading was observed after 24 hours. The highest gelatin content supported a significantly higher cell growth than the others at 7 days. Thus all compositions support satisfactory attachment, spreading and growth. In vivo results showed excellent interfacial bone regeneration. No necrotic tissues were found. In conclusion, the HAP-GEL not only mimics the biochemistry and nanostructures of bone but also supports the attachment, proliferation and differentiation (bone formation) of osteoblasts. The HAP-GEL we developed provides a suitable surface for regeneration.
In Situ Polypeptide Directed Silica Biomineralization
Authors: Glawe Diana D. , RodrÍguez Francisco , Stone Morley O. , Naik Rajesh R.
Published: April 2011

Silica-precipitating polypeptides were deposited onto an indium tin oxide (ITO) surface from bulk solution with and without the assistance of an externally applied electrostatic field. Exposure of the peptide-coated surface to an alkoxide precursor produced biosilica structures that were securely attached to the electrode surface. The silica morphologies resulting from the test cases using an externally applied electrostatic field during peptide deposition were distinct from the morphologies resulting from cases without an applied field. The silica morphologies observed on the ITO surface were different from the usual silica morphology resulting from static conditions. Peptide size was also shown to influence resulting biosilica morphology. The experimental results presented herein demonstrate the feasibility of creating biosilica nanostructures with controlled morphologies using polypeptides in vitro.
Microtubule Templated Synthesis of Inorganic Nanomaterials
Authors: Boal Andrew K. , Headley Thomas J. , Tissot Ralph G. , Bunker Bruce C.
Published: April 2011

Protein microtubules (MTs) have been used as templates for the biomimetic synthesis of metal oxide, metal sulfide, and metallic nanomaterials. These materials were coated onto MTs via three distinct synthetic pathways: metal ion hydrolysis which yielded iron oxide or zinc oxide-coated microtubules, metal ion/sulfide co-precipitation which yielded zinc sulfide coated MTs, and metal ion reduction which yielded gold-coated MTs. The growth process of metal oxide coating involves heterogeneous nucleation on the MT surface and produces even, microcrystalline films. Metal sulfide and metal coating initially involves the formation of nanoparticle arrays that decorate the MT surface and can eventually lead to either semi- or fully continuous coatings.
Cyclodextrins Stabilize TOPO-(CdSe)ZnS Quantum Dots In Water
Authors: Feng Jun , Kim Yong-Hyun , Zhang S. B. , Ding Shi-You , Tucker Melvin P. , Rumbles Garry , Himmel Michael E.
Published: April 2011

Chemical action between cyclodextrins (CDs) and TOPO-(CdSe)ZnS quantum dots (QDs) generates a water-soluble solution of CD-QDs. Hydrophobic TOPO molecules on surface of the QDs are compatible to thread through the pockets of CDs and make the hydroxyl group on end of CDs to approach the ZnS surface, and then cause the interaction between ZnS and the hydroxyls. In this paper, Photoluminescence of the γ-CD-QD solution appeared about 15 nm of red movement compared with that of the QDs in hexane; 58% replacement of the crystal coordinate bond of Zn-S with that of Zn-O in the ZnS shell was demonstrated by using first-principles density functional theory and the red shift of the photoluminescence of CD-QDs; and –0.11eV of the energy gain of the exchange model was calculated by using an effective mass (EM) model. CD-QDs will provide water-soluble QDs with conjugational group for biology and molecule-device applications.
Impact of Hydrogen Overpressure on Spent Fuel Alteration Behavior in Salt Brine During a Three-Year Long Corrosion Test
Authors: Loida Andreas , Metz Volker , Kienzler Bernhard , Geckeis Horst
Published: April 2011

The corrosion of the Fe-based spent fuel containing canister produces large amounts of hydrogen, which dominate the composition of the gas phase. To quantify to what extent the hydrogen over- pressure may counteract radiolysis enhanced matrix dissolution, related experimental work has been performed. High burnup spent fuel was corroded in 5 M NaCl solution in different tests: (1) Fe ab-sence (<0.16 bar H2 overpressure), (2) Fe presence (2.8 bar H2 overpressure), (3) Fe absence, external applied H2 overpressure of 3.2 bar. In the absence of Fe, after the application of H2 overpressure the UO2 matrix dissolution rate decreased by a factor of about 10. The concentrations of U, Np, Tc in so- lution were found to be decreasing at least two orders, and ranging within the same level as in the presence of Fe powder. However, Pu and Am concentrations were less affected, due to the absence of Fe powder and the associated high sorption capacity for these radioelements.
Site Decommissioning of AECL Whiteshell Laboratories
Authors: Koroll Grant W.
Published: April 2011

AECL Whiteshell Laboratories (WL), near Winnipeg, Canada has been in operation since the early 1960s. R&D programs carried out at WL include a 60 MW organic-cooled research reactor, which operated from 1965 to 1985, reactor safety research, small reactor development, materials science, post irradiation examinations, chemistry, biophysics and radiation applications. The Canadian Nuclear Fuel Waste Management Program was conducted and continues to operate at WL and also at the nearby Underground Research Laboratory.

In the late-1990s, AECL began to consolidate research and development activities at its Chalk River Laboratories (CRL) and began preparations for decommissioning WL. Preparations for decommissioning included a staged shutdown of operations, planning documentation and licensing for decommissioning. As a prerequisite to AECL's application for a decommissioning licence, an environmental assessment (EA) was carried out according to Canadian environmental assessment legislation. The EA concluded in 2002 April when the Federal Environment Minister published his decision that WL decommissioning was not likely to cause significant adverse environmental effects and that no further assessment by a review panel or mediation would be required

In 2002 December, the Canadian Nuclear Safety Commission issued a decommissioning licence for WL, valid until December 31, 2008. The licence authorized the first planned phase of site decommissioning as well as the continuation of selected research programs. The six-year licence for Whiteshell Laboratories was the first overall decommissioning license issued for a Canadian Nuclear Research and Test Establishment and was the longest licence term ever granted for a nuclear installation of this complexity in Canada.

The first phase of decommissioning is now underway and focuses on decontamination and modifications to nuclear facilities, such as the shielded facilities, the main R&D laboratories and the associated service systems, to achieve a safe state of storage-with-surveillance. Later phases have planned waste management improvements for selected wastes already in storage, eventually followed by final decommissioning of facilities and infrastructure and removal of most wastes from the site.

This paper provides an overview of the planning, environmental assessment, licensing, and organizational processes for decommissioning and selected descriptions of decommissioning activities currently underway at AECL Whiteshell Laboratories.
In-Situ Diffusion Experiment In Sparsely Fractured Granite
Authors: Vilks Peter , Miller Neil H. , Jensen Mark
Published: April 2011

The in-situ diffusion experiment was conducted at AECL's Underground Research Laboratory (URL) to improve the understanding of diffusive solute transport in sparsely fractured or intact granitic rock (SFR). The experimental program used a comparative series of laboratory and in-situ field experiments to evaluate the ability of laboratory measurements to estimate in-situ rock properties and to explore issues surrounding the influence of stress relaxation, rock texture, porosity, pore geometry, and anisotropy on derived effective diffusion coefficients (De). In-situ experiments yielded iodide Debetween 1.4 × 10−13 and 1.1 × 10−12 m2/s. Unlike laboratory results, the in-situ De estimates did not exhibit correlation with sample depth or varied stress regime. Laboratory-derived measurements of De, porosity and permeability were found to systematically increase for samples removed from greater depths and higher stress regimes. Laboratory-derived iodide De values consistently trended higher than in-situ values by a factor of 1 to 15, except on the shallowest 240-m Level (σ1 ≍ 30 MPa) where differences were negligible. Laboratory-derived estimates of permeability were consistently higher than in-situ derived values by a factor of 2 to 100. This experimental program provides evidence that laboratory steady-state diffusion experiments are most likely to yield conservative values of De for simulation of diffusive mass transport in SFR.
Prediction of the Weathering Properties of Minerals Based on the Ion-Ion Interaction Potential
Authors: Raicevic Slavica , Wright Judith V. , Vujic Jasmina , Conca James L.
Published: April 2011

Selection of solid matrix for immobilization of nuclear waste and of geological sites for its disposal represents a complex and consuming task. Previously, we demonstrated that the ion-ion interaction potential (IIIP), representing the main term of the cohesive energy, can be used for estimation of stability of solid matrix/impurity systems. Here we demonstrated a strong correlation between the weathering properties of minerals and their IIIP. Based on these results we proposed a simple theoretical criterion which can be used for assessment of the long term stability of solid matrix for immobilization of radioactive and toxic metals. This criterion was applied in analysis of stability of autunites and some possible practical consequences of results obtained for immobilization of uranium by apatite are discussed.
Neptunium(V) Incorporation/Sorption with Uranium(VI) Alteration Products
Authors: Friese J. I. , Douglas M. , Buck E. C. , Clark S. B. , Hanson B. D.
Published: April 2011

An initial uranium phase that has been observed to form during the corrosion of spent nuclear fuel is the uranium oxy-hydroxide metaschoepite. It has been proposed that neptunium(V) solubility can be limited by its association with this uranium phase. Metaschoepite has been synthesized in the presence of neptunium(V) over the pH range modeled in the proposed Yucca Mountain geologic repository. Uranium (VI) phases were synthesized by varying pH and neptunium concentrations. Results of neptunium association with the uranium alteration phases are presented and the relationship to dissolved neptunium concentrations discussed.
A Radiochemical Analyses of Metastudtite and Leachates from Spent Fuel
Authors: McNamara Bruce , Hanson Brady , Buck Edgar , Soderquist Chuck
Published: April 2011

We have characterized considerable amounts of the two known uranyl peroxide phases that formed under static immersion conditions on commercial spent nuclear fuel (CSNF) samples. Milligrams of corroded fuel aggregates were observed at the air-water interface in each sample. The bulk fuel and the interfacial solids were examined by SEM, EDX, and XRD and were found to contain studtite and metastudtite, respectively. The reason for the partitioning of the two phases is not clear at this time. The unique occurrence of the floating phase prompted a radiochemical analysis of these solids. The analysis indicated that 90Sr, 137Cs, 99Tc, and to a lesser extent of 238,239Pu and 237Np, had partitioned with the air-water interface aggregates. The concentration of 241Am in the interfacial solids was two orders of magnitude lower than the inventory in the fuel prior to contact with water. The radiochemical analyses of two fuel leachate samples are compared to reported leaching data of a similar fuel which did not result in the formation of studtite.
Finite Element Analysis of Elastic and Plastic Deformation during Growth of Si1−xGex/Si Heterostructures
Authors: Karoui F. Sahtout , Karoui A. , Rozgonyi G.
Published: April 2011

The elastic and plastic stress distribution in strained Si1−xGex heterostructure (x=0.2 and x=0.5), was investigated during the growth process using a nonlinear transient finite element modeling. The material plastic behavior is described by the von Mises yield criteria coupled with isotropic work hardening conditions. The calculated stress distribution during growth of the SiGe cap layer shows that the von Mises stress fluctuates strongly within the layers and at the interfaces. The surface of constant composition Si1−xGex layer is found under compressive stress in both cases. Within that layer the normal stress in the growth direction remains compressive for x=0.2, while it changes from compressive to tensile for x=0.5. In the graded layer the stress goes from tensile to compressive for x=0.5 and in the opposite way for x=0.2. High plastic deformation is observed in the layers, with the maximum von Mises plastic stress being higher for x=0.5 and localized in the SiGe graded region. The plastic strain vanishes monotonically up to 8 μ deep into the Si bulk substrate, in agreement with TEM images that revealed dislocation loops penetrating into the substrate. The time dependent analysis shows that elastic and plastic deformation appear almost instantaneously in the sublayers, while in the Si substrate it is delayed up to 300 s.
A New MSE Curriculum
Authors: Roylance David
Published: April 2011

The MSE Department at MIT has developed a new undergraduate curriculum, and has imple- mented it for Sophomores in the 2003-2004 academic year. The Junior and Senior year curricula will be implemented as the current Sophomores advance. In addition to major core topic addi- tions such as biomaterials and computational modeling, the new curriculum features a novel mixing of laboratory and lecture hours. This permits students to experience hands-on applications of materials in the laboratory immediately after covering the associated theory in lecture. The curriculum was developed in consultation with both students and our external community (Visiting Committee, ABET, alumni), and it required construction of substantial new laboratory facilities. It also required a novel approach to scheduling, in which some loss of flexibility was accepted to gain coherence and relevance of topics.
A Way to Get Students Interested in Materials Science: Research Presentations for the K-12 Group
Authors: Martínez-Miranda L. J.
Published: April 2011

The GK-12 program involves students doing a masters or a Ph.D. in science and engineering working with a science teacher to develop demonstrations and laboratories which will bring the excitement of science into the schools. They work for an entire semester with the same group in school. We expect that the teachers will be able to carry on these demonstrations after the GK-12 students have left. Another aspect we want to bring to the students is the excitement of doing research in the field, and that what they are learning may be helpful in doing this research. As part of their work, we ask the GK-12 participants to prepare a research presentation for their schools. They have to present it in language that the students will understand, and with the material that the students have learned. In doing this, the students learn how to explain their research in much better terms and the K-12 students are exposed to real research and new approaches that nonetheless are based in the lessons they are learning.
Nanotechnology Summer Undergraduate Research Intern Program: Comprehensive Introduction to Life as a Researcher
Authors: Melloch M.R. , Lax J.
Published: April 2011

We have implemented a summer undergraduate research intern (SURI) program, the purpose of which is to give the undergraduates as real a picture as possible of what it is like to be a research scientist and what will be encountered in graduate school. Our first SURI class, the summer of 2003, consisted of a diverse group of 18 students from 9 different universities. Each student joined an ongoing cross-disciplinary research project team comprised of faculty and graduate students who have been working on research projects throughout the year. Coordinated with the students' research project was a technical writing/presentation course. The SURIs also participated in professional development activities, short courses, and a molecular conduction workshop. The culmination of the students' research and the technical writing/presentation course was a one-day conference at the end of their program in which all the SURIs presented the results of their summer research.
Shape Memory Alloys for Classroom Demonstrations, Laboratories, and Student Projects
Authors: Chen Katherine C. , Crone Wendy C. , Voss Eric J.
Published: April 2011

Shape memory alloys (SMAs) are unique materials that effectively capture the attention of students due to their dramatic phase transformations that result from temperature or stress. The fascinating properties and intriguing applications of SMAs can entice students to learn about the materials field, as well as relatively complicated materials concepts. SMAs have been incorporated into a range of courses under a variety of topics, such as crystal structures, phase transformations, kinetics, constitutive relations, and smart materials. The concepts can be presented at different levels of knowledge, appropriate to the learning objectives for the particular audience. Several educational activities using NiTi shape memory alloys have been developed, such as web-based videos, shape setting of new designs, classroom demonstration of actuation, visualization of stress-induced transformations, and heat treatments to change transformation temperatures.
Multiplexed Electrical Detection of Single Viruses
Authors: Zheng Gengfeng , Patolsky Fernando , Lieber Charles M.
Published: April 2011

We report direct, real-time electrical detection of single virus particles with high selectivity using nanowire field effect transistors. Measurements made with nanowire arrays modified with antibodies for influenza A showed discrete conductance changes characteristic of binding and unbinding in the presence of influenza A but not paramyxovirus or adenovirus. Moreover, simultaneous electrical and optical measurements using fluorescently-labelled influenza A demonstrate conclusively that the conductance changes correspond to binding/unbinding of single viruses at the surface of nanowire devices. In addition, studies of nanowire devices modified with antibodies specific for either influenza or adenovirus show that multiple viruses can be selectively detected in parallel. The possibility of large scale integration of these nanowire devices suggests potential for simultaneous detection of a large number of distinct viral threats at the single virus level.
Sensing Properties of CNT hybrid MOS-based Sensors
Authors: Liou Wei-Jen , Yang Tsung-Yeh , Lin Kuang-Nan , Yang Ching-Hong , Lin Hong-Ming
Published: April 2011

The carbon nanotubes provide large surface that can enhance the gas adsorption properties and increase the conductivity at a lower temperature for gas sensing. The gas sensing properties of the hybrid TiO2/CNTs material are examined in this study. The sol-gel technique is used to prepare a thin layer of nano-TiO2 coated on CNTs. The structure of TiO2/CNTs hybrid materials is identified by X-ray diffraction (XRD) and Raman spectrum. The granules and surface morphology are analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrical properties of the hybrid TiO2/CNTs indicate that the operation temperature can be lowered to ambient temperature and this will enhance the gas sensitivity for detecting CO gas. The n-type or p-type behavior of hybrid TiO2/CNTs can be controlled by the coating thickness of hybrid TiO2. According to the image results, the mechanisms of the n-type and p-type behavior of hybrid TiO2/CNTs system are proposed.
Sr(Ti, Fe)O3-δ Exhaust Gas Sensors
Authors: Schneider Thomas , Peters Christoph , Wagner Stefan , Menesklou Wolfgang , Ivers-Tiffée Ellen
Published: April 2011

Sr(Tix, Fe1-x)O3-δ solid solutions were found to change their temperature coefficient of resistance (TCR) from negative to positive as iron increasingly substitutes for titanium, with the TCR tending towards zero at × = 0.35. This composition, Sr(Ti0.65Fe0.35)O3-δ thus shows temperature independent characteristic.

For the development of a planar type sensing element for automotive applications, Sr(Ti, Fe)O3-δ has to be applied as a thick film. To confirm the sensor characteristic temperature independence (at T = 750…950 °C, p O2 = 10−5…1 bar) and fast response times (t90 = 6.5 ms at 900 °C), both key issues of Sr(Ti, Fe)O3-δ, thick film sensors have to be maintained over the entire lifetime. In this work, the structural and electrical properties of the sensor are investigated with regard to the chemical stability of the sensing element.
High Temperature Operation and Stability of Langasite Resonators
Authors: Fritze H. , Schulz M. , Seh H. , Tuller H. L.
Published: April 2011

Factors limiting potential use of langasite as a gas sensor platform at elevated temperatures include excessive conductive and viscous damping, deviations from stoichiometry and chemical instability. This paper focuses on viscous damping which can be described by an effective viscosity of the resonator material. Based on a one-dimensional description of the resonator device, the material constants of langasite are determined as a function of temperature. Theeffective viscosity of the resonator material and the bulk conductivity are found to exhibit nearly the same activation energy at temperatures from 350 to 600 °C. Based on that fact, it is most likely that the predominant conduction mechanism, i.e. oxygen ion movement, controls the viscous damping in that temperature range. Therefore, intentional doping must suppress the oxygen conductivity to minimize losses. The effect of such dopants is presently under investigation. Further, pre-annealing specimens for several hours above 1050 °C is necessary, for the given sample dimensions, to establish reproducible materials properties. Based on oxygen diffusion data, it can be concluded that the oxygen stoichiometry of langasite specimens becomes equilibrated during the pre-annealing runs.
Performance of a MIS Type Pd-Cr/AlN/Si Hydrogen Sensor
Authors: Zhang Linfeng , Al-Homoudi Ibrahim A. , Rahman H. , McCullen Erik F. , Rimai Lajos , Baird Ron J. , Naik Ratna , Newaz Golam , Auner Gregory W. , Simon Ng K. Y.
Published: April 2011

An MIS Hydrogen sensor with a Pd0.96Cr0.04/AlN/Si structure was fabricated, exhibiting the dynamic range considerably wider than that of analogous devices with pure Pd gates. A useful response could be obtained for Hydrogen concentrations as large as 50, 000 ppm. Although the response amplitude was much reduced at the lower concentrations, satisfactory signal to noise down to 50 ppm could be obtained. The saturating magnitude of the electrical response is in the range of 0.1 to 0.5 V, which is the same as that for the pure Pd gated devices, inspite of the 3 orders of magnitude difference in the saturation hydrogen concentration. This result will be discussed in terms of the response mechanism of these devices.
Vitreous Chalcogenide Semiconductors for Gas Sensing Application
Authors: Dmitriev Serghei V. , Dementiev Igor V.
Published: April 2011

Report presents results of research aimed the investigation of possibility to use such chalcogenide materials as vitreous As2S3, As2Se3 and their solid solutions for gas sensors applications. For a long time these materials were well-known as materials mostly used for optical information registration. Developed approach allows to widening the sphere of application of given materials and create new class of gas sensitive devices.

Thin film gas sensitive elements on the base of solid solutions of (As2S3)x-(As2Se3)1−x (where x=0; 0.3; 0.5; 0.7 and 1.0) were obtained by means of the thermal evaporation under vacuum conditions 10−5 Torr. Thin films can be deposited on both hard and flexible substrate. Formed films had specific resistance on the level 1010–1014 Ohm.cm (on dependence on composition) at the thickness of 1–2 μm.

It was established that CGS thin films possess gas sensitivity S, determined as S=(Ggas-Gait)/Gair, on the level 2–3 relative units for CO and 7–8 for hydrogen at the 100 ppm concentration levels of both gases in atmosphere already at the room temperature that allows to excluding the heater from the gas sensor construction decreasing through that both manufacturing and operational cost.

It is concluded that chalcogenide semiconductor materials can be considered as perspective materials for gas sensor application, including space exploration application.
Influence of Thermal Treatments on the Chemistry and Self-Assembly of Ge Nanoparticles on SiO2 Surfaces
Authors: Stanley Scott K. , Coffee Shawn S. , Ekerdt John G.
Published: April 2011

GeH4 is thermally cracked over a hot filament depositing 0.7–15 ML Ge onto 2–7 nm SiO2/Si(100) at substrate temperatures of 300–970 K. Ge, GeHx, GeO, and GeO2 desorption is monitored through temperature programmed desorption in the temperature range 300–1000 K. Ge bonding changes are analyzed during annealing from 300–1000 K with X-ray photoelectron spectroscopy (XPS). Low temperature desorption features are attributed to GeO and GeH4. No GeO2 desorption is observed, but GeO2 decomposition to Ge through high temperature pathways is seen above 700 K. Germanium oxidization results from Ge etching of the oxide substrate, which is demonstrated through XPS. Ge nanoparticle formation on SiO2 is demonstrated using the agglomeration process. With these results, explanations for the difficulties of conventional chemical vapor deposition to produce Ge nanocrystals on SiO2 surfaces are proposed.
Device Structures and Charicterization of one Tansistor Ferroelectric Memory Devices
Authors: Li Tingkai , Hsu Sheng Teng , Ulrich Bruce , Evans Dave
Published: April 2011

One-transistor (1T) memory devices with MFIS (Metal, Ferroelectrics, Insulator, Silicon) and MFMIS (Metal, Ferroelectrics, Metal, Insulator, Silicon) structures have been widely studied. These memory devices exhibit memory working functions but very poor retention properties. Three possible mechanisms are responsible for the poor retention of 1 T ferroelectric memories: namely, charges trapping within the gate oxide and ferroelectric film, floating gate effect, and the depolarization field. In order to overcome these problems, a novel ferroelectric transistor design using a semiconductive oxide film in place of the gate dielectric has been fabricated. The device structures are Pt/PGO/InO2/Si (MFSoxS) and Pt/PGO/Ir/InO2/Si (MFMSoxS). There is no insulator in the gate stack. These device structures do not have floating gate and the depolarization field is very low. Therefore, the memory retention time can be very long. In this paper, we report the device structures, integration processes and the working properties with improved retention properties of the Pt/PGO/InO2/Si (MFSoxS) and Pt/PGO/Ir/InO2/Si (MFMSoxS) devices.
δ-Nb-doping Effect to The Interface Between IrO2 Top Electrode and Pb(Zr, Ti)O3 by Metal Organic Chemical Vapor Deposition
Authors: Matsuura Osamu , Yamawaki Hideki , Nakabayashi Masaki , Horii Yoshimasa , Sugiyama Yoshihiro
Published: April 2011

We studied the Nb doping effect on the electrical characteristics of MOCVD-PZT capacitors using uniformly Nb-doped Pb(Zr, Ti)O3 (UND-PZT) and δ-Nb-doped PZT (DND-PZT) prepared by MOCVD. The 2Pr for UND-PZT was small and the UND-PZT hysteresis shifted in a positive direction. However, the 2Pr for DND-PZT decreased by only 5.5% and the hysteresis of DND-PZT didn't shift. In addition, the leakage current of DND-PZT decreased by one order at low bias compared to non-doped PZT, because the δ-Nb-doping layer maintains the barrier height, higher than that of none-doped PZT due to defect compensation. As a result, Nb1% DND-PZT was well suited to use Nb doping which decreases leakage current at low voltage and maintains 2Pr.
Quantifying the Role of Electronic Charge Trap States on Imprint Behavior in Ferroelectric Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) Thin Films
Authors: Lew Connie , Thompson Michael O.
Published: April 2011

Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric thin films are a potentially promising material for sensors or non-volatile memories. Imprint, the time-dependent resistance to polarization reversal, is a key material property that limits applications and is poorly understood. Based on experimental time and temperature dependences, we propose and investigate the link between imprint and charge trap states. A novel fast-ramp thermally stimulated current (TSC) measurement was developed to quantify and characterize the traps in an appropriate time-frame.

Thin films of P(VDF-TrFE) on oxidized Si substrates were characterized following controlled initialization, fatigue, polarization, and imprint. Trap states were thermally filled/emptied by temperature cycling between 20–100 °C, using heating and cooling rates between 1 and 5 °C/s. Dynamics of this fast-ramp TSC indicate the presence of not only trap states, but also reversible and non-reversible charge accumulation. The presence of electrically active traps were verified by measurements over 1–10 s imprint times. Trapped charge directly correlated with the log of the imprint time, with a rate of ∼0.12 /μC/cm2/decade.
Dielectric and fatigue properties of Pb(Zr0.53Ti0.47)O3 thin films prepared from oxide precursors method
Authors: Shibatta-Kagesawa Silvia T. , Guarany C. A. , Araújo E. B. , Oki N.
Published: April 2011

Fatigue is an important problem to be considered if a ferroelectric film is used for non-volatile memory devices. In this phenomena, the remanent polarization and coercive field properties degrades in cycles which increase in hysteresis loops. The reasons have been attributed to different mechanisms such as a large voltage applied on ferroelectric film in every reading process in Ferroelectric Random Access Memory (FeRAM) or memories for digital storage in computer, grain size effects and others. The aim of this work is to investigate the influence of the crystallization kinetics on dielectric and ferroelectric properties of the Pb(Zr0.53Ti0.47)O3 thin films prepared by an alternative chemical method. Films were crystallized in air on Pt/Ti/SiO2/Si substrates at 700°C for 1 hour, in conventional thermal annealing (CTA), and at 700°C for 1 min and 700°C 5 min, using a rapid thermal annealing (RTA) process. Final films were crack free and presented an average of 750 nm in thickness. Dielectric properties were studied in the frequency range of 100 Hz – 1 MHz. All films showed a dielectric dispersion at low frequency. Ferroelectric properties were measured from hysteresis loops at 10 kHz. The obtained remanent polarization (Pr) and coercive field (Ec) were 3.7 μC/cm2 and 71.9 kV/cm respectively for film crystallized by CTA while in films crystallized by RTA these parameters were essentially the same. In the fatigue process, the Pr value decreased to 14% from the initial value after 1.3 × 109 switching cycles, for film by CTA, while for film crystallized by RTA for 5 min, Pr decreased to 47% from initial value after 1.7 × 109 switching cycles.
Perfectly c-axis oriented epitaxial lead titanate thin film deposited by a hydrothermal method for a data storage medium
Authors: Morita Takeshi , Cho Yasuo
Published: April 2011

A hydrothermal method is a unique method to deposit ferroelectric thin films utilizing chemical reaction in solutions. In addition to the low reaction temperature below 200°C, its simple process procedure, automatically aligned polarization and a three-dimensional deposition are advantages. In this study, a lead titanate epitaxial thin film was obtained on a strontium ruthenate bottom electrode sputterd on strontium titanate (100). The highresolution X-ray diffraction mapping showed the film was perfectly c-axis oriented. The transmission electron microscope observation revealed that the film had no lattice dislocation at the interface between lead titanate and strontium ruthenate. A remanent polarization of 96.5μC/cm2 was measured with the single crystal-like DE hysteresis curve. The observation of a scanning nonlinear dielectric microscopy indicated that this film did not contain any defect such as an a-domain and a grain boundary even on the nano scale. With various pulse parameters, nano-domain dots were patterned and the minimum dot radius of inverted domain was 12 nm corresponding to data storage density of 1Tbit/inch2.
Growth Temperature and Properties of Ge4Sb3Te3 Films
Authors: Song W. D. , Shi L. P. , Miao X. S. , Hu X. , Lee H. K. , Zhao R. , Chong J. F. , Chong T. C.
Published: April 2011

The growth temperature and properties of Ge4Sb3Te3 thin films are presented in this paper. The critical growth temperature of Ge4Sb3Te3 is between 300 and 340 °C. The Ge4Sb3Te3 films can only be grown on a substrate below the critical growth temperature. The typical resistivity and carrier density are in the order of 10-4 Ωcm and 1021 cm-3 for crystalline phase. It has a rock salt crystal structure with a lattice constant of 0.602 nm. Ge4Sb3Te3 has a better thermal stability but a lower crystallization speed than Ge2Sb2Te5.
Preparation of Strontium Bismuth Tantalate Thin Film by Liquid-Delivery Metalorganic Chemical Vapor Deposition
Authors: Silinskas M. , Lisker M. , Kalkofen B. , Matichyn S. , Garke B. , Burte E.
Published: April 2011

Thin films of BiOX, SrXTaYO, and SrXBiYTaZO (SBT) were deposited by liquid-delivery metalorganic chemical vapor deposition (MOCVD). The substrate temperature and the deposition pressure were varied from 300 to 600°C and from 0.35 to 7 mbar, respectively. Triallylbismuth (Bi-1), triphenylbismuth (Bi-2) or alkyl bismuth (Bi-3) and strontium bis-pentaethoxy-methoxyethoxy tantalate (Sr-Ta) were used as Bi precursors and as Sr-Ta precursor, respectively. X-ray photoelectron spectroscopy (XPS), ellipsometry, and scanning electron microscopy (SEM) were carried out to characterize the film properties.

The growth rates of the MOCVD of BiOX and SrXTaYO were compared to the growth rate of SBT to obtain information about mutual interaction between the precursors. The growth rate of bismuth oxide thin films deposited from Bi-1 and Bi-2 was low (∼10 nm/h at 0.35 mbar). The growth rate of strontium tantalate films was higher (up to 50 nm/h) and depended strongly on the temperature. Eight times higher (∼400 nm/h) growth rates of BiOX and SBT films were observed for the Bi-3 precursor. The deposition rate of the SBT films was quite similar to the rate of the bismuth oxide. However, the deposition rate of SBT was always lower than the deposition rate of the single Bi precursors. The growth rate significantly depended on the deposition pressure. A decrease of the deposition pressure in the reactor chamber reduced the deposition rate of BiOX, SrXTaYO, and SBT, but on the other hand, it improved the uniformity of the film thickness over the entire 150 mm wafer surface.

The XPS measurements showed a deficit of bismuth in the SBT films even though the concentration of the Bi-1 or Bi-2 precursor was several times higher compared to the Sr-Ta precursor. This problem disappeared when Bi-3 source was used.
Prospect of Emerging Nonvolatile Memories
Authors: Jeong Hongsik , Kim Kinam
Published: April 2011

Conventional nonvolatile memories such as Flash and EEPROM memory have successfully evolved toward high density and low cost. Especially, the market and density of flash memories has grown rapidly which leads semiconductor technology. However, there have been concerns about whether this successful progress can be maintained in the future nano era and can satisfy the requirement of diversified future IT market. Flash memories have the advantage of high density with small cell size and by contraries the disadvantage of slow writing speed and limited endurance. This slow writing speed and limited endurance is not aligned with the trend of high speed and reliability for future semiconductor memories.

The future for these conventional nonvolatile memories forces many research groups and companies to develop alternative memories with ideal memory characteristics such as non-volatility, high density, high speed, and low power, which none of the conventional memories can satisfy at the same time.

In this article, I will evaluate the characteristics of future nonvolatile memories such as ferroelectric random access memory (FRAM), magnetoresistive random access memory (MRAM) and phase change random access memory (PRAM). These memories have been recently evaluated because of the possibility that they can overcome the challenges that conventional memories are facing. Finally we will review critical technology barriers in developing future memory and predict the promising technology to overcome the barriers in conventional and emerging new memories, which will be technology guidelines for future memory development.
Effect of the Bottom Electrode Contact (BEC) on the phase transformation of N2 doped Ge2Sb2Te 5 (N-GST) in a Phase-change Random Access Memory
Authors: Lee Suyoun , Song Y. J. , Hwang Y. N. , Lee S. H. , Park J. H. , Ryoo K. C. , Ahn S. J. , Jeong C. W. , Oh J. H. , Shin J. M. , Yeung F. , Jeong W. C. , Kim Y. T. , Park J. B. , Koh K. H. , Jeong G. T. , Jeong H. S. , Kim Kinam
Published: April 2011

With respect to the operation of a Phase-change Random Access Memory (PRAM or PcRAM), we studied the effect of the contact between the electrode metal and the chalcogenide glass, N2 doped Ge2Sb2Te5 in this report. We investigated a change of the resistance-programming current pulse (R-I) curve varying the contact size and the electrode material. Also we tested the surface oxidation of the electrode. We found that the programming current, the resistance of the programmed state (“RESET”) and the erased state (“SET”) were highly dependent on the above parameters. These results are presented and a more effective way to the high density PRAM will be proposed.
Effect of Deposition Temperature and Post-Heat-Treatment Condition on the Characteristics of (100)-Self-Orientation LaNiO3 Films Prepared by RF Magnetron Sputter Deposition
Authors: Takahashi Kenji , Suzuki Muneyasu , Oikawa Takahiro , Chen Haydn , Funakubo Hiroshi
Published: April 2011

La-Ni-O films were deposited at deposition temperature ranging from 250 to 540°C by rf magnetron sputter deposition. The effects of deposition temperature and the following heat-treatment condition on the constituent phases and characteristics of LaNiO3 films were investigated. LaNiO3 phase was obtained at the deposition temperature of 250 and 360°C, while La-rich phase of La2NiO4 was appeared above 540°C. Crystalline phases of resultant films after the following heat-treatment strongly depended on the partial pressure of oxygen gas in ambience, i.e., in case of the heat-treatment at 800°C, diffraction peaks originated from LaNiO3 phase disappeared on XRD patterns in pure nitrogen gas ambience, while impurity peaks of NiO appeared in oxygen-excess (>50%) ambience. As a result, LaNiO3 films with high crystallinity and the same lattice parameter as the bulk one were obtained in the deposition at 360°C followed by the heat-treatment at 700°C in air.