bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Of New Oxide Ceramic Materials And Nanocomposites With Mixed Conductivity By Using Mechanical Activation Route.
Authors: Zyryanov Vladimir V. , Uvarov Nikolai F. , Kostrovskii Vitalii G. , Sadykov Vladislav A. , Kuznetsova Tatiana G. , Rogov V. A. , Zaikovskii V. I. , Frolova Y.V. , Alikina G. M. , Litvak G. S. , Burgina E. B. , Moroz E. M. , Neophytides S.
Published: April 2011

Some perovskite –like Fe (Co) -containing and fluorite-like Bi –containing solid solutions considered as promising materials for high oxygen flux membranes application have been synthesized by the mechanochemical activation route. Structural/microstructural features of those systems characterized by TEM, XRD, IR, and Raman spectroscopy are compared with the data on their mixed conductivity and oxygen mobility. Some properties of nanocomposites comprised of those materials and such oxides as Fe2O3, BaTiO3, BaBiO3 etc are elucidated as well. Densification of those powdered samples by sintering in the 700–1400 K temperature range is accompanied by annealing of metastable phases generating “core-shell” nanocomposites with oxygen transport properties different from those of traditional materials.
Hydrothermal Synthesis of a Microporous Organic-Inorganic Hybrid Framework [Fe0.28V0.72OH0.8(NH4)0.2(C8H4O4)] · 0.53(C8H6O4)
Authors: Whitfield Tabatha R. , Wang Xiqu , Jacobson Allan J.
Published: April 2011

Single crystals of a novel organic-inorganic framework [Fe0.28V0.72OH0.8(NH4)0.2(C8H4O4)] · 0.53(C8H6O4), 1, have been prepared by hydrothermal synthesis in the presence of an oxidizing agent. The structure was solved by single crystal X-ray diffraction: space group Pnma, a = 17.6956 (19) Å, b = 6.8745 (7) Å, c = 11.9303(12) Å. The three dimensional framework is constructed from Fe/V-O chains that are cross-linked by 1,4-benzene dicarboxylate (BDC) anions forming large one-dimensional channels. As synthesized, the compound contains additional dicarboxylate groups occupying disordered positions in the channels that can be removed by heating. The chemical reactivity of 1 and its magnetic properties are reported. The new phase is closely related to analogous Cr (III) and V(III) phases recently reported by Férey and co-workers.
Structural and Physical Property Trends of the Hyperstoichiometric Series, La2Ni(1-x)CoxO4+δ
Authors: Amow G. , Whitfield P. S. , Davidson J. , Hammond R. P. , Munnings C. , Skinner S.
Published: April 2011

Members of the Ruddlesden-Popper system, La2Ni(1-x)CoxO4+δ (0.00 ≤ × ≤ 1.00), were synthesized and studied for their potential use as cathodes for solid-oxide fuel cells. An unusual structural trend has been noted across the series, which appears to correlate with the oxygen-hyperstoichiometry observed. Details of the structural variance by x-ray and neutron diffraction, as well as selected physical properties for this system will be presented.
Bond valence analysis of ion transport in reverse Monte Carlo models of mixed alkali glasses
Authors: Adams Stefan , Swenson Jan
Published: April 2011

An analysis of RMC structure models of ion conducting glasses in terms of our bond softness sensitive bond-valence method enables us to identify the conduction pathways for a mobile ion as regions of sufficiently low valence mismatch. The strong correlation between the volume fraction F of the “infinite pathway cluster” and the transport properties yields a prediction of both the absolute value and activation energy of the dc ionic conductivities directly from the structural models. Separate correlations for various types of mobile cations can be unified by employing the square root of the cation mass as a scaling factor. From the application of this procedure to RMC models of mixed alkali glasses, the mixed alkali effect, i.e. the extreme drop of the ionic conductivity when a fraction of the mobile ions is substituted by another type of mobile ions may be attributed mainly to the blocking of conduction pathways by unlike cations. The high efficiency of the blocking can be explained by the reduced fractal dimension of the pathways on the length scale of individual ion transport steps.
Influence of doping on the electrochemical properties of anatase
Authors: Koudriachova Marina V. , de Leeuw Simon W.
Published: April 2011

The effect of substitution on the intercalation properties of anatase-structured titania has been investigated in first principles calculations. Ti4+-ions were substituted by Zr4+, Al3+ and Sc3+ respectively and O2- -ions by N3-. For each compound the open circuit voltage profile (OCV) was calculated and compared to anatase. Lithium intercalation proceeds as in pure anatase through a phase separation into a Li-rich and a Li-poor phase in all cases examined here. The Li-content of the phases depends on the nature of the dopant and its concentration. Substitution by N3--ions does not lead to lower potentials, whereas doping with trivalent Sc3+- and Al3+- ions decreases the intercalation voltage. Substitution by tetravalent Zr4+-ions within the range of solubility does not significantly affect the OCV of anatase. A correlation is observed between the predicted equilibrium voltage and the participation of the Ti4+-ions in accommodating the donated electron density upon lithiation.
Li mobility in (Li,Na)yLa0.66-y/3TiO3 perovskites (0.09<y≤0.5). A model system for the percolation theory.
Authors: Sanz J. , Rivera A. , León C. , Santamaría J. , Várez A. , V'yunov O. , Belous A. G.
Published: April 2011

The dependence of ionic transport on structure and composition of perovskites LiyLa0.66-y/3TiO3 (0.09 ≤ y ≤ 0.5) and Li0.5-xNaxLa0.5TiO3 (0 ≤ x ≤ 0.5) has been analyzed by means of Neutron Diffraction, NMR and Impedance Spectroscopy. In the first series, ion conductivity displays a non-Arrhenius behavior, decreasing activation energy at increasing temperatures. Li mobility is accompanied by a considerable increase of Li thermal factor deduced from ND data. In the second series, local lithium mobility decrease monotonously with the sodium content at room temperature; however, long-range dc conductivity decreases sharply at x = 0.2 more than six orders of magnitude. This decrease on dc conductivity is discussed in terms of a three-dimensional percolation theory of vacant Asites. In this model, the number of vacant sites is controlled by the amount of Na and La of the perovskite.
Preparation and Characterization of Anatase (Tio2) Nanoceramics
Authors: Weibel A. , Bouchet R. , Knauth P.
Published: April 2011

We have systematically investigated the influence of various parameters (pressure, temperature, time, sample size) on the hot pressing process of TiO2nanoceramics. This study is backed by thermodilatometric experiments and microscopic observations of the microstructure. Impedance spectra of TiO2nanoceramics with different porosity are also presented.
The Syntheses and Characterization of Layered LiNi1-y-zMnyCozO2 Compounds
Authors: Katana Ngala J. , Chernova Natasha A. , Matienzo Luis , Zavalij Peter Y. , Stanley Whittingham M.
Published: April 2011

The layered compounds of formula LiNi0.4Mn0.6-yCoyO2, for y=0.2, 0.3, and 0.4 and LiNi0.7-yMn0.3CoyO2 for y=0.3, and 0.1 were synthesized at 800°C. X-ray powder diffraction indicates layered structure of R 3m symmetry similar to a-NaFeO2. Rietveld refinement data shows that Mn and Ni increase the tendency of transition metal ions to migrate into the interlayer sites relative to LiCoO2. Both magnetic susceptibility and XPS data support a 2+ oxidation state for Ni and 4+ and 3+ for Mn and Co, respectively. The layered compound LiNi0.4Mn0.4Co0.2O2 shows a high initial capacity of about 200mAh/g when cycled between 2.5V and 4.3 V at 20°C.
Preparation and Oxygen Permeability of La-Sr-Co-Fe Oxide Thin Films by a Chemical Solution Deposition Process
Authors: Kakuta Hirofumi , Iijima Takashi , Takamura Hitoshi
Published: April 2011

Oxygen-ionic and electronic conductive thin films with the composition of La0.6Sr0.4Co0.5Fe0.5O3-α (LSCF) were prepared on a porous alumina substrate by a chemical solution deposition (CSD) process and their oxygen permeating flux densities were measured. Thickness of the LSCF layer on the substrate was about 0.4 μm. Oxygen flux density of the LSCF sample was found to be 0.6 μmol·cm-2·s-1, however, time-dependent degradation of oxygen flux was observed. The CeO2 barrier layer between the LSCF layer and the substrate was effective in order to improve time-dependent degradation of oxygen flux.
Oxide Ion Transport in Bismuth-Based Materials
Authors: Vannier Rose-Noëlle , Capoen Edouard , Pirovano Caroline , Steil César , Nowogrocki Guy , Mairesse Gaëtan , Chater Richard J. , Skinner Stephen J. , Kilner John A.
Published: April 2011

When used as ceramic membranes for the electrically driven separation of oxygen from air, BIMEVOX materials allow the production of high oxygen fluxes at moderate temperature, 300–600°C. However, 18O/16O Isotope Exchange Depth Profile Technique revealed low kinetics of oxygen transfer at the surface of these ceramics when studied under equilibrium. These kinetics were considerably enhanced when a current was applied. The same membranes were characterized under working conditions using X-ray synchrotron and neutron radiations. Their dynamical transformation under bias was confirmed and explained by a slight reduction of the BIMEVOX electrolyte under working conditions.
Study of the effect of hydrogen on Pt supported Nanoporous Carbon derived from Polyfurfuryl alcohol
Authors: Rajagopalan Ramakrishnan , Coronado Juan , Foley Henry C. , Vannice Albert
Published: April 2011

Platinum supported on nanoporous carbon (NPC) is promising candidate for using as electrodes in proton exchange membrane fuel cells. Performance of the anode of a fuel cell is markedly influenced by the efficiency of the splitting of hydrogen atoms by platinum and the transference of the produced protons to the carbon support (spillover process). Consequently a better understanding of these elemental processes could prompt the improvement of the materials used. With this aim, a series of Pt/NPC samples varying the metallic content were studied by electron spin resonance (ESR) under controlled gas environment. This spectroscopic tool is especially suitable for the investigation of processes that involve transference of electrons. In the present case, all materials studied, including bare carbon, showed a very narrow signal (Hpp=1.5–3 gauss) at g=2.0028±0.0002 after activation in vacuum at 500–C. In the case of the pure carbon and for the samples with lower platinum content (lower than 0.2 wt%) signals are significantly asymmetric, and their intensity is scarcely affected by the introduction of hydrogen up to 500°C. In contrast the spin concentration experiences a significant increment when the samples with platinum loading comes in contact with hydrogen at temperatures in the 300–500°C range. Although the centres originating these signals are located in the carbon matrix, the present results emphasize the importance of platinum for hydrogen activation and electron transference.
In-situ x-ray absorption experiments with a PEM fuel cell in hydrogen and methanol operation mode
Authors: Buhrmester Th. , Roth C. , Martz N. , Fuess H.
Published: April 2011

In-situ XAS studies have been carried out on PEM fuel cells in methanol and hydrogen operation. This has become possible due to a recently developed PEM fuel cell (single cell) equipped with inherent carbon fibre windows to allow x-ray studies in transmission geometry. The set-up chosen allows the in-situ monitoring of the structural changes of the Pt-Ru catalyst, utilised as electrode active material, during cell operation. The analysis of the white line intensities, edge shifts of the Pt-Lш edge and the XAFS signal, which was modelled for the first co-ordination shell around Platinum, exhibited no significant changes during operation in terms of the first neighbouring shell. Nevertheless, the white line intensity decreased comparing the ex-situ to in-situ measurements. From the latter, can be concluded that the catalyst is reduced during operation and further, the redox behaviour of the catalyst does not change the local environment of the Pt-centres in the first co-ordination shell to a measurable extend.
Simulation of Multi-component Charged Particle Systems
Authors: Retzlaff Ted , Shaw John G.
Published: April 2011

During the past several years, we developed a 3-D particle simulation software system to study particle transport problems that occur in research and design of electrophotographic or “laser” printers. Several particle systems have been simulated; they include various singlecomponent electrophotographic image formation systems, transport of charged micron-sized plastic particles through magnetically agitated granular bulk, and magnetic bead chain formation. The software has broader applications including granular hopper flow, and ion generation and tracking.

The software can simulate the motion of tens of thousands of particles through bounded volumes, handling particle-particle and particle-boundary collisions. It tracks individual particle motion in non-uniform ensembles of multiple material types under the influence of various forces: electric and magnetic fields, adhesion, cohesion, air drag, friction, etc. It is easily extended to include other force laws. Excellent agreement has been obtained between simulated and experimental data. When accurate materials characterization experiments are available, the software provides valuable insight into the behavior of particle systems.
Impulse Backscattering based Detection and Imaging of Shallow Buried Objects
Authors: Sen Surajit , Visco Donald P. , Krishna Mohan T. R.
Published: April 2011

We discuss our recent work on simulational studies of impulse propagation and backscattering for the detection and imaging of shallow buried objects in close packed granular beds.
The Introductory Materials Science and Engineering Course
Authors: Callister William D.
Published: April 2011

The introductory materials science and engineering course offered at the college/university level is, for many instructors, very difficult to design and to teach. This presentation discusses challenges for the course, as well as several problematic issues to include: course content, course organization, and course mechanics. The results of two surveys of engineering faculty are presented and discussed; these provide perspectives and lead to suggestions on how to manage these troublesome areas, and improve the quality of and student satisfaction in this course. Also discussed are commercially available software packages, and, in addition, a hybrid electronic-paper introductory materials textbook.
Organic Transistor Sensors and Memory Elements Fabricated VIA Solution Deposition
Authors: Katz H. E. , Someya T. , Gelperin A. , Mushrush M. , Facchetti A. , Marks T. J.
Published: April 2011

Thiophene-phenylene oligomer semiconductors (structures below) have many favorable attributes for electronics on flexible and rounded substrates. They are synthesized in 2–3 steps from readily available starting materials and are chemically stable. Their mobilities are typically above 0.01 cm2/Vs and their threshold voltages can be tuned by altering the thiophene-phenylene ratio. Deposition from solution is facile, and cast films with usable mobilities are repeatedly obtained on a variety of surfaces. Higher-order function such as nonvolatile memory and chemical sensitivity have been demonstrated.
Nanoscale Organic Electronic Devices Formed by Lamination With Stamps
Authors: Zaumseil Jana , Someya Takao , Bao Zhenan , Loo Yueh-Lin , Baldwin Kirk , Cirelli Raymond , Rogers John A.
Published: April 2011

Lamination of metal-coated elastomeric stamps against thin films of electroactive organics provides non-invasive, high resolution electrical contacts for investigations of charge transport in these materials. This approach uses the features of relief on the stamps to define, with nanometer resolution, the geometry and separation of electrodes that are formed by uniform evaporation of a thin metal film onto the stamp. Soft, room temperature contact of an element of this type with an organic semiconductor film on a gate dielectric and a gate yields a high performance top contact transistor with source/drain electrodes supported by the stamp. We review here our use of this approach to study the electrical properties of the organic semiconductor pentacene in thin film transistors structures. We also introduce a method for using the same techniques and structures to probe transport through organic monolayers.
Site-specific cross-sectioning of carbon nanotube-to-metal junctions for high spatial resolution chemical and structural analysis
Authors: Dovidenko K. , Abramson N. L. , Rullan J.
Published: April 2011

In this study, we have demonstrated successful site-specific cross-sectioning of carbon-nanotube - metal junctions which provided samples suitable for high resolution transmission electron microscopy and electron energy loss spectroscopy. For the cross-sectioning, we have suggested a modified technique based on combination of the Focused Ion Beam (FIB) lift-out and the conventional Ar+ ion milling techniques. Electron-transparent cross-sections of multiwall carbon nanotubes showing no significant surface amorphization or Ga contamination (typical artifacts of conventional FIB lift-out technique) were obtained. High-resolution transmission electron microscopy and electron energy loss spectroscopy of a multi-wall carbon nanotube cross-section have been carried out.
Ordered Structures in Ba(Cd1/3Ta2/3)O3 Microwave Ceramics: A Transmission Electron Microscopy Study
Authors: Sun J. , Liu S. J. , Newman N. , Smith David. J.
Published: April 2011

Ordered structures of Ba(Cd1/3Ta2/3)O3 ceramics with and without boron additive were investigated systemically by electron diffraction and high resolution transmission electron microscopy. The results showed a well-ordered structure of 1:2 with hexagonal symmetry for Ba(Cd1/3Ta2/3)O3 with boron additive. No significant changes in ordered structures were observed after long-period annealing. The 1:2 ordered domain structures (average domain size ∼18 nm) and high-density domain boundaries induced by ordering were observed for Ba(Cd1/3Ta2/3)O3 without boron additive sintered at relatively high temperature. The sintering process has a profound influence on the microstructure of Ba(Cd1/3Ta2/3)O3 ceramics.
Direct-Write E-beam Submicron Domain Engineering in LiNbO3 Thin Films Grown by Liquid Phase Epitaxy
Authors: Son Ji-Won , Yuen Yin , Orlov Sergei S. , Phillips Bill , Galambos Ludwig , Shur Vladimir Ya. , Hesselink Lambertus
Published: April 2011

We demonstrate submicron ferroelectric domain engineering in liquid phase epitaxy (LPE) LiNbO3 thin films grown on LiNbO3 and LiTaO3 substrates using a direct-write electron beam poling for waveguide applications. LiNbO3 thin films of several-micron thickness were grown using a flux melt of 20 mol% LiNbO3-80 mol% LiVO3. To engineer domain structures in Z- oriented LPE LiNbO3 films, a direct-write electron beam poling was implemented. It is shown that we can engineer the domain structure of LPE LiNbO3 films by using direct e-beam poling, even though the domain orientations of the film and the substrate are opposite. We also compared e-beam poling behavior in a congruent LiNbO3 single crystal and a LPE LiNbO3 film. Using the same e-beam scan parameters, a much enhanced domain structure is obtained in LPE films. Defect structure and composition effects are also discussed.
PZT Thick Films Deposited by Improved Hydrothermal Method for Thickness Mode Ultrasonic Transducer
Authors: Ishikawa Mutsuo , Kurosawa Minoru , Katsura Naoki , Takeuchi Shinichi
Published: April 2011

The purpose of this study was to improve deposition rate of the hydrothermal method for lead zirconate titanate (PZT) thick film on titanium substrate. We developed a high-speed rotaion substrate holder at a tangential velocity of about 0.8m/s in autoclave. A titanium substrate was fixed by the holder on the surface of a stirring bar. For the film deposition, powder of TiO2 was used instead of the liquid TiCl4. The deposition rate on titanium substrate was improved up to 7μm/24h. Piezoelectric constant d31 of the hydrothermal PZT film was -2.6 × 1011 V/m. This result was lower than that of PZT ceramics. However, this hydrothermal method obtained thick film and this film was confirmed to be polycrystalline PZT analyses of XRD and SEM. In addition, performance of thickness mode vibration of hydrothermal PZT 50μm thick film was investigated by radiating in water. The phase velocity of dilatational wave of the thickness mode vibration of the hydrothermal PZT film was 1800m/s and the electromechanical coupling factor was 47%.
Frequency-Dependent Electromechanical Response in Ferroelectric Materials Measured via Piezoresponse Force Microscopy
Authors: Bdikin I. K. , Shvartsman V. V. , Kim S-H. , Herrero J. Manuel , Kholkin A. L.
Published: April 2011

Local piezoelectric signal is measured via Piezoresponse Force Microscopy (PFM) in PbZr0.3Ti0.7O3 films and PbZr1/3Nb2/3O3-0.045PbTiO3 single crystals. It is observed that the amplitude of piezoelectric response is almost independent on frequency for vertical (out of plane) signal and strongly decreases with increasing frequency in the range 10–100 kHz for lateral (in-plane) response. Moreover, the in-plane piezoelectric contrast is reversed when the measurements are done at high enough frequency (phase shift exceeds 90°). As a result, the inplane polarization direction can be misinterpreted if the driving frequency exceeds certain level. For the explanation of observed effect a simple model is proposed that takes into account a possible slip between the conductive PFM tip and moving piezoelectric surface. The implications of the observed frequency-dependent contrast for the domain imaging in ferroelectric materials are discussed.
Growth Reorientation with the Annealing Temperature of SrBi2Ta2O9 Films Deposited by PLD
Authors: Cruz Ma. P. , Portelles Jorge J. , Siqueiros Jesús M.
Published: April 2011

Films of SrBi2Ta2O9 (SBT) were grown on Pt/TiO2/SiO2/Si substrates by the pulsed laser deposition (PLD) technique. The deposits were made at temperatures between 570°C and 715°C, and post-annealed at 750°C. The films grown at 610°C show a (115) preferentially orientation with a small peaks associated to (00l) planes. At higher deposition temperatures, the (00l) peaks increase their intensity, a tendency that is intensified after the heat treatment at 750°C. However, when the films grown at 590–610°C are heat-treated at 750°C, there is a reduction of the crystallites oriented in the (00l) direction, leading to an enhancement of the polarization, reflected in the maximum value of 2Pr = 9.1 μC/cm2 and a coercive field, Ec, of 52.0 KV/cm.
Nanoelectromechanics of Piezoresponse Force Microscopy: Contact Properties, Fields Below the Surface and Polarization Switching
Authors: Kalinin S. V. , Shin Junsoo , Kachanov M. , Karapetian E. , Baddorf A. P.
Published: April 2011

To achieve quantitative interpretation of Piezoresponse Force Microscopy (PFM), including resolution limits, tip bias- and strain-induced phenomena and spectroscopy, knowledge of elastic and electrostatic field distributions below the tip is required. The exact closed form solution of the coupled electroelastic problem for piezoelectric indentation is derived and used to obtain the tip-induced electric field and strain distribution in the ferroelectric material. This establishes a complete continuum mechanics description of the PFM imaging mechanism. These solutions are reduced to the point charge/force behavior for large separations from contact, and the applicability limits and charge/force magnitude for these models are established. The implications of these results for ferroelectric polarization switching processes are analyzed.
Interface states of laser ablated BaTiO3 and Ba0.9Ca0.1TiO3 thin films in MFS structure determined by DLTS and C – V technique
Authors: Victor P. , Saha S. , Krupanidhi S. B.
Published: April 2011

BaTiO3 and Ba0.9Ca0.1TiO3 thin films were deposited on the p – type Si substrate by pulsed excimer laser ablation technique. The Capacitance – Voltage (C-V) measurement measured at 1 MHz exhibited a clockwise rotating hysteresis loop with a wide memory window for the Metal – Ferroelectric – Semiconductor (MFS) capacitor confirming the ferroelectric nature. The low frequency C – V measurements exhibited the response of the minority carriers in the inversion region while at 1 MHz the C – V is of a high frequency type with minimum capacitance in the inversion region. The interface states of both the MFS structures were calculated from the Castagne – Vaipaille method (High – low frequency C – V curve). Deep Level Transient Spectroscopy (DLTS) was used to analyze the interface traps and capture cross section present in the MFS capacitor. There were distinct peaks present in the DLTS spectrum and these peaks were attributed to the presence of the discrete interface states present at the semiconductor – ferroelectric interface. The distribution of calculated interface states were mapped with the silicon energy band gap for both the undoped and Ca doped BaTiO3 thin films using both the C – V and DLTS method. The interface states of the Ca doped BaTiO3 thin films were found to be higher than the pure BaTiO3 thin films.
Raman Spectra of Srm-3Bi4TimO3m+3 Thin Films
Authors: Wang Jia , Cheng Guangxu , Zhang Shantao , Cheng Hongwei , Chen Yanfeng
Published: April 2011

A series of bismuth layer-structured ferroelectrics thin films Srm-3Bi4TimO3m+3(m=3, 4, 5, and 6) were deposited by pulsed laser deposition (PLD) on (001) LaAlO3 single crystal substrate. XRD and Raman studies have been performed. The more sensitive Raman spectra lead to a different understanding on the layer structure of Sr3Bi4Ti6O21 from XRD. This can be attributed to the lager c-axis constant of Sr3Bi4Ti6O21 due to more layers. More layers lead to increasing disorder in the local scale of the average grain.
A Novel Iridium Precursor for MOCVD
Authors: Kawano Kazuhisa , Takamori Mayumi , Yamakawa Tetsu , Watari Soichi , Fujisawa Hironori , Shimizu Masaru , Niu Hirohiko , Oshima Noriaki
Published: April 2011

A novel liquid iridium precursor (1,3-cyclohexadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(CHD), was synthesized and its physical properties were examined. Ir(EtCp)(CHD) exhibited enough vapor pressure (0.1 Torr/75°C), excellent volatility and adequate decomposition temperature. Characteristics of the Ir films deposited using Ir(EtCp)(CHD) and the conventional Ir precursor (1,5-cyclooctadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(COD), by metal-organic chemical vapor deposition (MOCVD) method were compared. Ir films grown using Ir(EtCp)(CHD) showed shorter incubation time and higher nucleation density than those of films using Ir(EtCp)(COD).
TEM and Electrical Analysis of Sputtered Barium Strontium Titanate (BST) Thin Films on Flexible Copper Substrates
Authors: Laughlin Brian , Ihlefeld Jon , Maria Jon-Paul
Published: April 2011

Ba0.6Sr0.4TiO3 (BST) films were deposited on copper foils by radio frequency magnetron sputtering. These films will be an integral part of flexible capacitor sheets intended for space borne re-configurable antenna arrays. By the use of controlled pO2 high temperature anneals, the films were fully crystallized in the absence of substrate oxidation. X-ray diffraction and transmission electron microscopy (TEM) showed no existence of copper oxidation (i.e. Cu2O or CuO phases). The deposited BST films exhibit a high permittivity (625) and a low tan δ (0.020) at zero bias and room temperature. A pronounced electrical tunability ratio of 3.5:1 is observed on these devices. Devices show loss tangents as low as 0.003 in fields approaching 400 kV/cm. Electrical field calculations are based on cross-sectional atomic force microscopy (AFM) images that reveal a film thickness of 800 nm. Temperature dependent measurements show a Tmax ∼ 230 K with a diffuse dielectric anomaly. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses indicate a conformal film with a mixed grain morphology and an abrupt Cu/BST interface.
Enhanced Dielectric Properties Of Compositionally Modified BST Based Thin Films For Voltage Tunable Microwave Devices
Authors: Cole M. W. , Nothwang W. D. , Hubbard C. , Ngo E. , Ervin M.
Published: April 2011

In this work, material compositional design and optimized film processing methods, were employed to simultaneously lower the dielectric loss and enhance the dielectric tunability of Ba0.6Sr0.4TiO3 (BST) based thin films without compromising the device impedance matching (εr<500) and device control voltage (<10 V) requirements. The films compositional design was achieved by Mg doping BST from 3 to 10 mol % via the metalorganic solution deposition (MOSD) technique and post-deposition annealing in an oxygen ambience. The films dielectric loss at these doping levels was identical, tanδ ∼0.007 and the permittivity values ranged from 339 to 220. Device quality values of tunability, 40 and 32 %, for the 3 and 7 mol% doped BST films, respectively, were achieved by elevating the applied bias to 474 kV/cm. This device quality tuning is compatible with voltage requirements of current semiconductor based systems. The results suggest that the low level acceptor doping from 3 to 7 mol%, optimized precursor solution concentration (0.43 M), and oxygenated post-deposition thermal processing were found to work in concert to lower dielectric loss, limit defect density concentration, optimize film microstructure, and eliminate undesirable film/electrode interfacial phases. The enhanced dielectric and insulating properties of the 3–7 mol% Mg doped BST thin films make them excellent candidates for integration into tunable devices.
Polarization Reversal Anti-parallel to the Applied Electric Field Observed Using a Scanning Nonlinear Dielectric Microscopy
Authors: Morita Takeshi , Cho Yasuo
Published: April 2011

It is well known that spontaneous polarization of ferroelectric material is an intrinsic property applied for nonvolatile memory devices. Poling direction can be reversed in a nanometer size area using the conductive cantilever of a scanning probe microscope. In order to detect nanodots patterns, scanning nonlinear dielectric microscope (SNDM) is superior to piezore-sponse microscope in terms of resolution. In this paper, a real-time measuring method of a poling direction is proposed. Using this method, the domain reversal process was observed and an unexpected phenomenon was found, namely, that the poling directions were aligned antiparallel to the poling electric field. This antiparallel poling reversal took place when the film thickness was more than 350 nm in the case of lithium tantalate. At present, the reason and mechanism of the antiparallel poling reversal are uncertain, although it might be related to the concentrated electric field near the cantilever tip.
Effective Orientation Control of Pb(Zr0.4Ti0.6)O3 Thin Films Using A New Ti/Pb(Zr0.4Ti0.6)O3 Seeding Layer
Authors: Moon B. K. , Arisumi O. , Hornik K. , Bruchhaus R. , Itokawa H. , Hilliger A. , Zhuang H. , Egger U. , Nakazawa K. , Yamazaki S. , Ozaki T. , Nagel N. , Kunishima I. , Yamakawa K. , Beitel G.
Published: April 2011

The effect of thin Ti/PbZr0.4Ti0.6O3 seed layers on the properties of PbZr0.4Ti0.6O3 (PZT) capacitors has been investigated. The seed layer is based on a bi-layer of thin Ti and thin PZT with a total thickness ranging from 10 to 25 nm, which was deposited on Ir/Pt or Ir/IrO2/Pt by sputtering. After crystallization of the seed layers the main 130-nm-thick PZT film was deposited and crystallized. As a result, a highly preferred (111)-orientation of the PZT was obtained on a 10-nm-thick seed layer, where the peak intensity ratios of (111)/{100} and (111)/{110} are about 100 and 20, respectively. The 10-nm-thick seed forms a pyrochlore phase with a very smooth surface, where the formation of the pyrochlore phase is attributed to Pb diffusion, resulting in a Pb deficient stoichiometry. The seed layer transformed to the perovskite phase during the main PZT crystallization. It is shown that an IrO2 layer beneath the Pt can prevent Pt layer degradation related to the volume expansion due to the oxidation of Ir during the main PZT crystallization. Capacitors with the 10-nm-thick seed layer fabricated on the Ir/Pt and Ir/IrO2/Pt substrates showed typical 2 Pr values of 44.0 μC/cm2 and 41.2 μC/cm2, respectively. The voltage found for 90%-polarization saturation is about 3.0 V, and the capacitors are fatigue-free at least up to 1010 switching cycles.
RF Magnetron Sputtering Process for (Ba,Sr)TiO3 Thin Films with Higher Dielectric Constant
Authors: Jimbo T. , Kimura I. , Nishioka Y. , Suu K.
Published: April 2011

(Ba,Sr)TiO3 (BST) films were deposited by RF magnetron sputtering using BST sintered ceramic targets and an approach to deposit BST films with higher permittivity by sputtering deposition was explored aiming to the application of thin film capacitor, RF tunable components and so on.

Basic sputtering conditions such as RF power, deposition temperature and so on were varied in this study. BST films and Pt/BST/Pt capacitors were investigated by electrical properties, XRD analysis and SEM observation. It became clear that deposition temperature, deposition rate, and BST film thickness were important parameters for optimization of the dielectric constant. From the non-linearly relationship between dielectric constant and BST film thickness, we could also find that the interfacial layer between BST and Pt bottom electrode was important for controlling the BST film properties. Furthermore, an approach to enhance the crystalline quality has to be explored for further improvement of BST film properties. Dielectric constant could be raised up to 10% by just changing the gas flow sequence of BST sputtering process.
Dielectric and Ferroelectric Properties of Modified BiFeO3-PbTiO3 Thin Films Derived from Sol-gel Processing
Authors: Cheng JinRong , Eric Cross L.
Published: April 2011

In this paper, thin films of La- modified (Bi,La)FeO3-PbTiO3 (BLF-PT) morphotropic phase boundary (MPB) solid solutions have been prepared by using sol-gel processing. A thin Pb(Zr,Ti)O3 (PZT) template layer was introduced to make BLF-PT thin films adhere tightly to the platinized silicon (Pt/Ti/SiO2/Si) substrate. X-ray diffraction (XRD) analysis revealed that BLF-PT thin films were of the perovskite structure without detectable pyrochlore phase annealing at 650–750°C. The cross sectional and plain view images of or our specimen were observed by using the scan electrical microscope (SEM). The room temperature dielectric constant K and tanδ were of ∼800 and 4% respectively, for BLF-PT thin films using a measurement frequency of 1 kHz. Our preliminary experiments indicated that the sol-gel derived BLF-PT thin films have good insulation resistance and measurable dielectric and ferroelectric responses.
Microstructural and Electrical Characterization of (Ba,Sr)TiO3 Thin Films Prepared by a New Carboxylate Free Chemical Solution Deposition (CSD) route
Authors: Halder Sandip , Schneller Theodor , Waser Rainer
Published: April 2011

A new type of alkoxide precursor was developed to avoid the formation of the oxo-carbonate phase as an intermediate phase during crystallization. The precursors were synthesized from Ba metal, Sr metal and aminoethanol. The new precursors were found to be quite stable and soluble in a number of organic solvents. Films were prepared by depositing the precursor solution on Pt coated Silicon wafers and crystallized between 550 and 700°C. The films were found to crystallize only above 600°C. After crystallization Pt top electrodes were deposited by sputtering and lift off processing. FT-IR studies were performed on the films to check for any oxo-carbonate phase. Microstructural studies involving XRD, SEM and AFM were performed on the films. The films were found to have a dielectric constant of around 400 with a tunability of around 37%. The frequency and temperature dependence of the dielectric constant were also studied. In addition leakage studies were performed on the films at various temperatures.
Growth and study of BaZrO3 thin films by pulsed excimer laser ablation
Authors: Rajasekarakumar V. , Victor P. , Ranjith R. , Saha S. , Rajagopalan S. , Tyagi A. K. , Krupanidhi S. B.
Published: April 2011

Thin films of BaZrO3 (BZ) were grown using a pulsed laser deposition technique on platinum coated silicon substrates. Films showed a polycrystalline perovskite structure upon different annealing procedures of in-situ and ex-situ crystallization. The composition analyses were done using Energy dispersive X-ray analysis (EDAX) and Secondary ion mass spectrometry (SIMS). The SIMS analysis revealed that the ZrO2 formation at the right interface of substrate and the film leads the degradation of the device on the electrical properties in the case of ex-situ crystallized films. But the in-situ films exhibited no interfacial formation. The dielectric properties have been studied for the different temperatures in the frequency regime of 40 Hz to 100kHz. The response of the film to external ac stimuli was studied at different temperatures, and it showed that ac conductivity values in the limiting case are correspond to oxygen vacancy motion. The electrical modulus is fitted to a stretched exponential function and the results clearly indicate the presence of the non-Debye type of dielectric relaxation in these materials.
Liquid Injection MOCVD of Rare-Earth Oxides Using New Alkoxide Precursors
Authors: Williams Paul A. , Jones Anthony C. , Aspinall Helen C. , Gaskell Jeffrey M. , Chalker Paul R. , Marshall Paul A. , Loo Yim F. , Smith Lesley M.
Published: April 2011

High purity lanthanum oxide and praseodymium oxide thin films (C< 1 at.-%) have been deposited by liquid injection MOCVD using the volatile alkoxide precursos [La(mmp)3] and [Pr(mmp)3] in toluene-solution (mmp = OCMe2CH2OMe). 1H NMR solution studies have shown that the addition of donor species, such as tetraglyme (CH3O(CH2CH2O)4CH3) or mmpH prevent molecular aggregation and help stabilise the precursors.
Vanadium Dioxide Thin Films for Thermo-Optical Switching Applications
Authors: Jiang Lijun , Carr William N.
Published: April 2011

Vanadium dioxide (VO2) thin films were fabricated by e-beam evaporation of vanadium thin films followed by thermal oxidation in oxygen ambient. The properties of the VO2 films were investigated for thermo-optical switching applications. Synthesized VO2 film displays a phase transition at 65 – 68 °C. It exhibits an abrupt change in optical reflectivity over the phase transition temperature range. Results for VO2 on a highly reflective metal layer are strongly dependent on the VO2 thickness. The optical switching has a major hysteresis of about 15 °C between the heating and cooling branches. The evolution of the surface morphology with the oxidation time was studied with a SEM. The VO2 film was patterned on microplatforms by metal lift-off technique. We conclude that the evaporation followed by oxidation is an effective method to produce active VO2 film for thermo-optical switching devices.
Mîcromagnetic Modeling of the Behavior of Magnetostrictive Films under Stress
Authors: Shu Y. C. , Yen J. H.
Published: April 2011

We study the effect of stress on the behavior of magnetostrictive films. Our approach is different from the conventional one which neglects the strain compatibility. Here, we include the kinematic constraint in our micromagnetic model and proposed to use the average to calculate the stress-induced magnetic field. The analytic formulation of magnetostrictive energy is derived which enables us to perform simulation at a large scale with few iteration steps. The simulation results show that the conventional approach is insufficient to predict magnetic domain patterns for materials with large magnetostriction, and the effect of intrinsic stress cannot be neglected.
Multiscale Computational Model of Soft Elasticity and Director Reorientation in Nematic Gels
Authors: DeSimone Antonio
Published: April 2011

A coarse-grained model of soft elasticity of nematic elastomers is presented, in which fine-scale spatial oscillations are carefully accounted for in the definition of an effective energy density, and then averaged out from the kinematics. Algorithmically, this amounts to taking a suitable convex envelope of the original free-energy of the system. The resulting finite element simulations of stretching experiments on thin sheets of nematic elastomers enable us to resolve simultaneously the macroscopic mechanical response (e.g., deformed shape, stress-strain curves) and the underlying microscopic mechanisms (e.g., evolution of domain structures, local reorientation of the nematic director).
Fabrication of Lead Zirconate Titanate Thick Film Disks for Micro Transducer Devices
Authors: Iijima Takashi , Ito Sachiko , Matsuda Hirofumi
Published: April 2011

A combination of the preparation techniques for the ferroelectric films and the micro machining of Si is considered to be an effective way to fabricate microelectromechanical systems (MEMS), such as piezoelectric micro-transducer devices for the electrical and medical fields. In this study, 10-μm-thick disk shape lead zirconate titanate (PZT) thick films were successfully fabricated using a chemical solution deposition (CSD) process. Pt top electrode and PZT layer were etched by reactive ion etching (RIE) process, and 100 to 500-μm-diameter PZT micro disks were fabricated on Pt/SiO2/Si substrate. The relative dielectric constant, dissipation factor, remnant polarization and coercive field were εr = 1130, tanδ = 0.02, Pr = 14 μC/cm2 and Ec = 25 kV/cm, respectively. This means that the ferroelectric and dielectric properties of the PZT micro disks were comparable with that of the bulk PZT ceramics. The PZT micro disk showed the butterfly-shaped displacement curve, related with piezoelectric response, in the case of bipolar measurement. The piezoelectric constant of the PZT disks poled at 80Vfor 10 min was estimated to be AFM d33 = 221 pm/V. A resonance frequency of the radial oscillation was evaluated to apply for micro transducer devices.
Analysis and Modeling of Electro-Mechanical Coupling in an Electroactive Polymer-Based Actuator
Authors: Bowers Thomas A. , Anquetil Patrick , Hunter Ian , Hogan Neville
Published: April 2011

A non-linear constitutive model was formulated for ionic electroactive polymers (EAP) to describe the energetic coupling between electrical and mechanical domains. The polymer was modeled as a multi-port energy storage element with inputs from the electrical and mechanical domain. Using energy conservation methods, general relationships between stress, strain, voltage, and charge were determined. A solution to the uniaxial loading boundary condition was developed fully and compared to a linear model published by Madden and an electrochemical model published by Mazzoldi et al. Experimental results from a conducting polymer actuator composed of polypyrrole were used to validate the electro-mechanical coupling model. It was found that the correlation between the model and experimental data was very good for strains up to 3% and applied voltages up to 1 Volt; these are within the typical operating range of polypyrrole. The model is sufficiently simply to allow real-time control while also exceeding the linear coupling models in its ability to predict polymer behavior in normal operating ranges.
Structural and dielectric proper ties of CaCu3Ti4O12 thin film. deposited using laser ablation.
Authors: Gupta V. , Das R.R. , Dixit A. , Bhattacharya P. , Katiyar R.S.
Published: April 2011

CaCu3Ti4O12 (CCT) thin films were deposited on Pt/TiO2/SiO2/Si substrates using pulsed laser deposition technique. During the thin films deposition, the substrate temperature was varied in the range of 700–800 °C with a constant O2 pressure of 200 mTorr. X-ray diffraction showed the polycrystalline nature of the films. The dielectric properties of the films were studied in metal insulator configuration. Films grown at higher substrate temperature exhibited highest value of dielectric permittivity (∼2200). Micro Raman spectroscopy was used to study the vibrational modes of the CCT thin films in comparison with the bulk ceramics.
Fabrication and Characterization of Fe-Pd Ferromagnetic Shape-Memory Thin Films
Authors: Sugimura Yuki , Cohen-Karni Tzahi , McCluskey Patrick , Vlassak Joost
Published: April 2011

Fe-Pd thin films with approximately 30 at.% Pd have been produced by magnetron sputtering. Various heat treatment conditions were studied in order to obtain the face-centered tetragonal (fct) martensitic phase at room temperature. X-ray diffractometry was used to identify the various phases present at room temperature and the substrate curvature technique was employed to measure film stress as a function of temperature. The shape memory effect was demonstrated in samples containing the fct martensite phase at room temperature.
Characterization of the Electronic Structure and Optical Properties of Al2O3, ZrO2 and SrTiO3 from Analysis of Reflection Electron Energy Loss Spectroscopy in the Valence Region
Authors: Tan G. L. , Denoyer L. K. , French R. H. , Ramos A. , Gautier-Soyer M. , Chiang Y. M.
Published: April 2011

Characterization of thin surficial films of oxides has become the focus of increased interest due to their applications in microelectronics. The ability to experimentally determine the electronic structure and optical properties of oxide materials permits the direct study of the interband transitions from the valence to the conduction band states. In the past years there has been much progress in the quantitative analysis of transmission electron energy loss spectroscopy (TEELS) in the electron microscope

Here we employed reflection electron energy loss function (REELS) as well as vacuum ultraviolet (VUV) spectroscopy to determine the dielectric functions of oxide materials, i.e. Al2O3, ZrO2 and SrTiO3. The two main steps in the analysis are the removal of the effects of multiple scattering from the REELS spectra followed by application of the Kramers-Kronig dispersion transforms to the single scattering energy loss function to determine the conjugate optical variable and then the complex dielectric function. The surface and bulk plasma resonance spectra for these oxide materials have been determined from VUV and REELS, along with the influence of primary electron energy on the REELS results. The relative contribution of surface and bulk plasmon oscillation in REELS has been investigated. Comparison with VUV results and existing TEELS results indicate that Kramers-Kronig analysis can also be applied to REELS spectra and the corresponding conjugate optical properties can be obtained. Quantitative studies of the electronic structure and optical properties of thin surficial films using VUV and REELS or TEELS, represent a new avenue to determine the properties of these increasingly important films.
Disorder Characterization of Oxide/Silicon Interfaces from I-V Curves
Authors: Nemzer Louis , Zypman Fredy R.
Published: April 2011

In this paper, we present results on transmission-energy curves through quantum wells with disordered interfaces. We propose a rule to process experimental data to obtain information about the degree of disorder.