bluuebunny/crossref_metadata_2025 huggingface dataset:
Anatase TiO2 Thin Films Based CO Gas Sensor
Authors: Al-Homoudi Ibrahim A. , Rimai L. , Naik R. , Baird R.J. , Auner G.W. , Newaz G.
Published: April 2011

TiO2 anatase thin films with different thickness (100 – 1200 nm) have been deposited on glass, sapphire and Si(100) substrates using pulsed DC magnetron reactive sputtering. The thin films were exposed to carbon monoxide (CO) gas at different concentrations (20–100 ppm) in a nitrogen carrier, and the resistance was measured as a function of the CO concentration for films of different thicknesses for temperatures in the range of (100 - 300°C). The films with good crystalline order showed better response than amorphous films. The response increased monotonically with CO concentration. The thicker films showed higher sensitivity. The anatase films deposited on sapphire generally had a larger response than those deposited on glass or on silicon. The films on sapphire substrate showed good response at temperatures as high as 300°C, while those deposited on glass and silicon had good responses only to 200°C. Furthermore, the addition of different concentrations of O2 and H2 affected the response as expected. The response to CO in the presence of N2 showed good reversibility which is evidence that complete regeneration on turn off the CO does not require exposure to oxygen or air. The response and the recovery times are fast.
Interferometer Type Pressure Microsensor
Authors: Heredia-J A. , Ramirez-Pichon Alonso , Mondragón J. Sánchez , Lucio A. Andrade , Pensado M. Basurto , Romero R. J. , Torres-J A.
Published: April 2011

In this work, the fabrication of waveguide and nitride silicon membrane is presented. The measurement configuration chosen to detect the variation produced in the light properties is an Interferometer configuration of the Mach Zehnder Type (MZI), because of its high sensitivity. One of its arms is positioned on a floating silicon nitride membrane that becomes deformed under small pressures on the range of MPa. According to the parameters of the membrane and the waveguide we obtain a maximum deformation of 176 nm that produces a change of phase of 180° between the two waves, producing therein a null interferometer output for the maximum pressure.

The analyses of theory suggest that this device will be able to sense a pressure value up to 13.376MPa.
Bimorph-type Magnetostrictive Actuator/Sensor Thin Films
Authors: Okazaki Teiko , Okanisi Norimasa , Miura Yuki , Michigami Munemi , Furuya Yasubumi , Takeuchi Ichiro , Wuttig Manfred
Published: April 2011

Giant magnetostrictive Fe-Pd and Fe-Ga thin films are expected as actuator/ sensor materials with high respective velocity and huge stress created by the magnetostriction. In order to develop magnetostrictive material induced by low magnetic field, we investigated bimorph-type magnetostrictive (positive magnetostriction / substrate / negative magnetostriction) thin films, that is, Fe-Pd(1, 3µm) or Fe-Ga(1, 3µm)/substlate /Ni(1, 3µm) by magnetron sputtering system. The substrate is Al(50µm) or kapton foil (125µm). Displacement of a upper part of these films was measured using an optical lever method. The displacement of the Fe70-Pd30(3µm )/ Al(50µm)/Ni(3µm)film ( length is 20 mm) was 280 μm under low DC magnetic field of 500 Oe and exhibits little hysteresis. These magnetostrictive properties are maintained under low alternating magnetic field. Moreover, the displacement of the film at the resonance frequency exhibits a peak and reached to 1.4 mm. The bimorph-type magnetostrictive thin film is useful for application in micro device as micro-pomp.
Effect of Boron Addition on Magnetostrictive and Mechanical Properties in Rolled Polycrystalline Fe-187%Ga Alloy
Authors: Na Suok-Min , Flatau Alison B.
Published: April 2011

During attempts to roll Fe-18.7%Ga alloy (atomic%), an alloy of interest because single crystal samples exhibit magnetostriction of ∼400 ppm, cracks formed along grain boundaries and subsequently samples fractured during hot rolling such that the alloy was too brittle to make thin sheets. While variations to rolling schedules (temperatures, times, roll diameters, etc.) may improve rollability, in this paper we investigate the effect of boron addition on Fe-18.7% Ga alloy magnetostrictive and mechanical properties. Thin sheets of Fe-18.7%Ga alloy plus 0.5 and 1.0 at.%B were successfully fabricated to thickness of 0.35 mm using rolling processes. It was observed that the fracture surface of the B-free alloy clearly appeared as an intergranular fracture mode and that of the B-added alloys was changed to a transgranular fracture mode with grain refinement. The annealed sheets with boron content of 0.5 and 1.0 at.% exhibit the maximum magnetostriction values of 103 and 184 ppm, respectively. In the case of Fe-18.7%Ga plus 1.0 %B, Fe2B phase presents throughout the α-iron matrix in small amount.
Hot Carrier Effects in Self-aligned and Offset-Gated Polysilicon Thin-Film Transistors
Authors: Arpatzanis N. , Hatzopoulos A. T. , Tassis D. H. , Dimitriadis Charalambos , Kamarinos G.
Published: April 2011

The effects of hot carriers on the transfer characteristics of self-aligned and offset-gated polysilicon thin-film transistors (TFTs), with channel length L = 10 μm and offset length ΔL = 2 μm, are investigated. In the self-aligned device, the on-state current is substantially reduced, whereas the subthreshold slope remains almost unaffected. In the offset gated device, the transfer characteristic is shifted first positively and then negatively, the on-state current is still substantially reduced and well-defined kinks are formed in the subthreshold region. The device degradation is found to become more pronounced in the offset gated device. A model explaining the post-stress performance of the offset-gated device is presented.
Structural Characteristics and Piezoelectric Properties of Electrospun Piezoelectric nanofibers
Authors: Shi Yong , Xu Shiyou , Kim Sang-Gook , Libera Matthew
Published: April 2011

This paper reports the development and characterization of PZT nanofibers with average diameters ranged from 50 to 150 nm for various sensing and actuation applications. PZT nano fibers have been developed by sol-gel electrospinning process. Both randomly distributed and uniaxially aligned PZT fibers were obtained from the sol-gel solution with viscosity modified by polyvinyl pyrrolidone (PVP). The diameters of the nano fibers can be further reduced or controlled for different applications. The morphology and structure of the nanofibers were examined with SEM, TEM and XRD. We used two-step process to anneal the electrospun fibers and XRD confirmed that pure perovskite phase was formed after the as-spun fibers being annealed at about 650°C. TEM results showed that the grain size of the fibers was about 10 nm. Microelectromechanical (MEMS) based micro-fabrication technologies were used to assist the development of the nano-fibers in designing the test samples, depositing and patterning the electrodes, and also testing the performance of the nano fibers. Different approaches have been explored to fabricate the uniaxially aligned nano fibers. SEM results showed that partial aligned PZT nano-fibers were obtained on the pre-patterned substrats. Interdigitated Electrodes were evaporated on the partial aligned fibers by using shadow mask. Hysteresis curve of the nano piezoelectric fibers was also obtained, however further tests are still needed to get accurate measurement. The obtained PZT nanofibers have promising application potentials in designing and enabling micro and nano devices.
Evolving Thin Polymer Film Driven by Electrostatic Field
Authors: Kim Dongchoul , Lu Wei
Published: April 2011

Experiments have shown that a thin polymer film subjected to an electrostatic field may lose stability at the polymer-air interface, leading to uniform self-organized pillars emerging out of the film surface. This paper presents a three dimensional dynamic model that accounts for the behavior. Attention is focused on the interplay of the thermodynamic forces and the kinetic processes. The coupled diffusion, viscous flow, and dielectric effect are incorporated into a phase field framework. The semi-implicit Fourier spectral method and the preconditioned biconjugate-gradient method are applied in the simulations for high efficiency and numerical stability. Numerical simulations reveal rich dynamics of the pattern formation process.
Pressure Effect on the Superconductivity of AnTGa5 Systems and Americium Metal (An=Np, Pu, Am - T=Co, Rh, Ir)
Authors: Griveau Jean-Christophe , Rebizant Jean , Wastin Franck , Colineau Eric , Jutier Frédéric , Lander Gerard H.
Published: April 2011

We report pressure studies on the magnetic and superconducting properties of PuTGa5 (T=Co, Rh) and Americium metal down to 0.4K. Recent discovery of superconductivity in the Plutonium based compounds PuTGa5 (T=Co, Rh) has shed a new light on the study of Actinides compounds. The fact that these systems present lots of similarities with the CeTIn5 (T=Co, Rh, Ir) must not hide some fascinating features of these materials: they display superconducting characteristics one order of magnitude higher than their Cerium counterparts or all 5f Superconducting Heavy. Moreover they present at ambient pressure a Non Fermi Liquid described by a T4/3 law which seems to maintain up to the highest pressure achieved (∼20 GPa) for the 2 Plutonium superconductors. Finally we report superconducting pressure diagram of americium metal under pressure up to 27 GPa and down to 0.4K. The complex superconducting diagram Tc(p) related to the several phases transition led us to examine the localization delocalization aspect of the 5f electrons in this metal through the Mott transition.
Localized and Itinerant States in Pu Materials
Authors: Joyce John , Wills J.M. , Durakiewicz T. , Butterfield M.T. , Guziewicz E. , Graham K.S. , Sarrao J.L. , Arko A.J. , Bauer E.D. , Moore D.P. , Morales L.A. , Eriksson O.
Published: April 2011

The electronic structure of Pu materials is examined using photoelectron spectroscopy. For delta-phase Pu metal as well as PuCoGa5 and PuIn3, the 5f electrons appear to be at the threshold between localized and itinerant character. A mixed level model computational scheme is used which results in non-magnetic solutions for the electronic structure and agrees well with the photoemission measurements. Several other computational schemes are assessed against photoemission results for delta Pu. Additional insight is provided by O2 and H2 dosing of the delta Pu samples and consideration of surface effects. The experimental and computational results are consistent with the 5f electrons in Pu materials exhibiting a dual nature with some fraction of the 5f levels localized and not participating in the bonding while the other fraction of 5f character is involved in bonding and hybridization with the conduction electrons.
Studying Actinide Correlations in Solution using High-Energy X-ray Scattering
Authors: Skanthakumar S. , Soderholm L.
Published: April 2011

High energy x-ray scattering (HEXS) is becoming a valuable tool for quantifying actinide coordination environments in solution. The technique is described with and exemplified by a study on Th speciation. A comparison of data from two samples with pHs of 0 and 3.4 show differences in the Th structural environment that can be attributed to Th colloid formation at the higher pH. A further comparison of the HEXS data from the colloidal sample with Th L3-edge EXAFS data on the same sample clearly demonstrates the advantage of the scattering data when looking for correlations at second-near neighbor or longer distances.
Geochemical Approaches to Understanding a Shallow Groundwater Flow in the Kanamaru Uranium Mineralization Area (Japan)
Authors: Bros Regis , Seki Yoji , Kamei Atsushi , Kanai Yutaka , Okuzawa Koichi , Watanabe Yoshio
Published: April 2011

Predicting the behaviour of radioactive wastes can be facilitated by comparison with the evolution of natural groundwater systems. During a study of the Kanamaru U mineralization (Japan), geochemical approaches for understanding a shallow (0-50 m) fresh groundwater flow system are being assessed. Deep granitic waters are Ca-HCO3-dominated and slightly acidic to slightly alkaline. Shallow waters within sediments display lower pH and they are more dilute. Halide concentrations suggest the existence of a non marine Br-rich and Cl-depleted deep groundwater in the basement. 234U/238U and 230Th/234U activity ratios in the mineralized sedimentary rocks indicate that U mobilization took place within the last 350,000 years. U dissolution currently continues and it is controled by lateral groundwater flow whereas vertical diffusion appears negligible. Dissolved alkaline earths concentrations and the 87Sr/86Sr ratio indicate that solutes exchanges take place through uppermost low permeable granite followed by mixing with more dilute and Cl-type shallow groundwater.
High-throughput preparation of multinary liquid, thin-film and powder library by combinatorial electrostatic atomization system
Authors: Fujimoto Kenjiro , Ito Shigeru , Inoue Satoru , Watanabe Mamoru
Published: April 2011

A newly developed high-throughput exploration system “M-ist Combi” can control mixing ration of five-component compounds. Furthermore, the M-ist Combi system can also be obtained not only thin film but also powder and liquid libraries by controlling applied voltage and used flexibly in either a normal atmosphere or controlled atmosphere. By combining the M-ist Combi system with combinatorial XRD apparatus, we successfully completed the high-throughput powder preparation and phase identification of over 150 samples in one day.
Rapid Optimization of Pentacene Buffer for Rubrene Thin Film Transistors by Using Combinatorial MBE
Authors: Haemori Masamitsu , Yamaguchi Jun , Yaginuma Seiichiro , Itaka Kenjji , Koinuma Hideomi
Published: April 2011

By means of insertion of thin pentacene buffer layer, we have succeeded in the fabrication of highly c-axis oriented rubrene (5,6,11,12-tetraphenylnaphthacene) thin films and their field effect transistors (FETs). In the case without pentacene buffers, only amorphous rubrene films were obtained and their FETs did not show operation. After optimization of pentacene buffer by using combinatorial thickness-gradient method, we obtained the crystalline rubrene thin films and their FETs showed p-type operation with a mobility of 0.05 cm2/V·s and an on-off ratio of 106.
Novel Approach for Biofouling-Release Materials with Interpenetrating Polymer Networks
Authors: Mori Kenji , Naito Masanobu , Nakai Takashi , Fujiki Michiya , Kawabe Takuma
Published: April 2011

Environmentally friendly organic-inorganic hybrid materials with repellent activity against marine fouling organisms, such as blue mussel, have been developed using interpenetrating polymer networks (IPNs), composed of a 3-dimensional siloxane matrix of tetraethoxysilane (TEOS) and poly(vinylacetate) (PVAc). Facile bioassay using blue mussels allowed screening the adequate proportions of those components. The repellent activity of IPN with PVAc/silica reached approximately 90% at a specific fraction, relative to that of tributyl tin oxide (TBTO). On the other hand, poly(methylmethacrylate)(PMMA) /silica composite did not show marked repellent activity against blue mussel, even though chemical structure of MMA is similar to that of vinylacetate.
Arrayed Nanohydrogels for Protein Array Technology
Authors: Saaem Ishtiaq , Papasotiropoulos Vasilis , Wang Tongsheng , Soteropoulos Patricia , Libera Matthew
Published: April 2011

This paper describes studies of surface-patterned nanohydrogels and their use as possible substrates for high-density and high-sensitivity protein arrays. Nanohydrogels, approximately 200 nm in diameter, were created by locally crosslinking dry amine-terminated poly(ethylene glycol) [PEG] (5000 Da) thin films using a focused electron beam. These gels then had a dry height of 50 nm and a swell ratio of about five. They were patterned into arrays with approximately 1 μm inter-gel spacing. These arrayed gels were functionalized with Zinc Finger 9 (ZNF9), a nucleic-acid binding protein. As part of ongoing research, we are interested in how the performance of the functionalized gels compares to that of current commercial substrates. We show, using an assay that binds α-GST antibody to mediate attachment of GST-tagged ZNF9, that nanohydrogels have a consistently higher combination of fluorescent signal and signal-to-noise (SNR) ratio than the comparable commercial substrates. We further show that the SNR characteristic of our assay degrades slower on the nanohydrogel array than on a comparable microarray printed on an epoxide substrate, and we speculate that the difference is in part attributable to the fact that the nanohydrogel array presents a softer and more hydrophilic surface.
The Effect of Tethering on the Chemical Kinetics of Single Bonds
Authors: Nguyen-Duong Melanie , Koch Karl-Wilhelm , Merkel Rudolf
Published: April 2011

We investigated the force induced dissociation of single specific bonds between protein A and immunoglobulin G. In these experiments both proteins were tethered to microbeads. Pi-conewton forces were applied by means of an ultrasoft spring. Upon bond formation the thermal fluctuations of this soft spring were reduced. This resulted in a sizeable contribution to the free enthalpy of bonding. Including this effect we calculated the relation between the lifetime of bonds connecting both microbeads and the lifetime of the bond between free molecules. We found that the lifetime depended on the stiffness of the force probe. Moreover, the lifetime was reduced by almost two orders of magnitude. Both predictions were verified in our experiments.
Dynamics of DNA conformations and DNA-protein interactions
Authors: Metzler Ralf , Ambjörnsson Tobias , Lomholt Michael A. , Krichevsky Oleg
Published: April 2011

Optical tweezers, atomic force microscopes, patch clamping, or fluorescence techniques make it possible to study both the equilibrium conformations and dynamics of single DNA molecules as well as their interaction with binding proteins. In this paper we address the dynamics of local DNA denaturation (bubble breathing), deriving its dynamic response to external physical parameters and the DNA sequence in terms of the bubble relaxation time spectrum and the autocorrelation function of bubble breathing. The interaction with binding proteins that selectively bind to the DNA single strand exposed in a denaturation bubble are shown to involve an interesting competition of time scales, varying between kinetic blocking of protein binding up to full binding protein-induced denaturation of the DNA. We will also address the potential to use DNA physics for the design of nanosensors. Finally, we report recent findings on the search process of proteins for a specific target on the DNA.
Finite conductivity effects and apparent contact angle saturation in AC electrowetting
Authors: Kumar Abishek , Pluntke Manuela , Cross Benjamin , Baret Jean-Christophe , Mugele Frieder
Published: April 2011

We measured the electrowetting behavior of aqueous salt solutions. By varying the conductivity and the frequency of the applied AC voltage we determined the range of the validity perfect conductor assumption of the standard electrowetting theory for the case of AC voltage. We show that the contact angle reduction is dramatically reduced at high frequency and low salt concentration due to Ohmic losses with the liquid. A simple RC-equivalent circuit model explains the observations. It is demonstrated that finite conductivity effects are more pronounced for sessile droplets than for droplets confined between to parallel plates.
Radial-breathing Mode Frequencies for Single-Walled Carbon Nanotubes of Arbitrary Chirality: First-Principles Calculations
Authors: Lawler Hadley Mark , Areshkin D. , Mintmire J.W. , White C.T.
Published: April 2011

First-principles calculations are performed for the radial-breathing mode of all 105 single-walled carbon nanotubes within the rolling-geometry diameter range of 0.4 to 1.4 nm. The diameter dependence of the frequencies is analyzed in some detail, and compared with measurable parameters of bulk graphite. The frequencies are compared with those available from other first-principles work, and experimental studies.
Nanobubble Formation at the Solid-Liquid Interface Studied by Atomic Force Microscopy
Authors: Agrawal Abhinandan , McKinley Gareth H.
Published: April 2011

The formation of nanobubbles at solid-liquid interfaces has been studied using the atomic force microscopy (AFM) imaging technique. Nanobubble formation strongly depends on both the hydrophobicity of the solid surface and the polarity of the liquid subphase. While nanobubbles do not form on flat hydrophilic (silicon oxide wafer) surfaces immersed in water, they appear spontaneously at the interface of water against smooth, hydrophobic (silanized wafer) surfaces. From the experimental observations we draw the conclusion that the features observed in the AFM images are deformable, air-filled bubbles. In addition to the hydrophobicity of the solid surface, differences in solubility of air between two miscible fluids can also lead to formation of nanobubbles. We observe that nanobubbles appear at the interface of water against hydrophilic silicon oxide surfaces after in-situ mixing of ethanol and water in the fluid-cell.

The shapes of the nanobubbles are well approximated by spherical caps, with width much larger than the height of the caps. We quantify the morphological distribution of nanobubbles by evaluating several important bubble parameters including surface coverage and radii of curvature. In conjunction, with an analytical model available in the literature, we use this information to estimate that the present nanobubble morphology may give rise to slip lengths ∼1–2 µm in pressure driven flows for water flowing over the hydrophobic surface. The consistency of the calculated slip length with the experimental values reported in the literature, suggests that the apparent fluid slip observed experimentally at hydrophobic surfaces may arise from the presence of nanobubbles.
Linearized Quantum Conductivity of Atomic Clusters and Artificial Molecules
Authors: Pozhar Liudmila A.
Published: April 2011

The explicit expression for the linearized longitudinal quantum conductivity of inhomogeneous systems (such as semiconductor atomic clusters, artificial molecules, etc.) in weak electro-magnetic fields derived recently within a first principle quantum statistical mechanical approach in terms of the equilibrium two-time temperature Green functions (TTGFs) has been analyzed to develop analytical and computational means for its calculations. This has been done using a generalized continuous fraction method due to Zubarev and Tserkovnikov (ZT). The TTGFs have been related to Kubo's relaxation functions of the charge density and its gradients that can be computed using available quantum statistical mechanical algorithms and software. Thus, it becomes possible to predict the linearized quantum conductivity of any small system (in particular small semiconductor quantum dots (QDs)) as a function of external electromagnetic fields using a unified fundamental approach. This knowledge can be used to develop small semiconductor QD-based highly sensitive tunable sensors based on changes in the conductivity caused by external electromagnetic fields (in particular, radiation).
Cationic Lipid Modulates Phospholipid Adsorption on Silica
Authors: Moura Sérgio P. , Carmona-Ribeiro Ana Maria
Published: April 2011

At 2 % cationic lipid and 98 % phospholipid, pH 6.3, in pure water, high affinity adsorption isotherms with limiting adsorption indicative of one bilayer deposition on each silica particle were obtained whereas for the other molar proportions tested, limiting lipid adsorption was either above or below the level expected for bilayer deposition. This suggested a modulating role for cationic lipid allowing control of total amount of lipid adsorbed on silica. Silica sedimentation documented from photographs was almost absent over a range of lipid concentrations where bilayer deposition was achieved.
Platinum nanoparticle encapsulation during hydrothermal growth of mesoporous oxides: Synthesis, characterization and catalytic properties
Authors: Rioux Robert M. , Song Hyunjoon , Hoefelmeyer James D , Niesz Krisztian , Grass Michael , Yang Peidong , Somorjai Gabor A
Published: April 2011

A synthetic method for the design of heterogeneous catalysts incorporating monodisperse platinum nanoparticles into ordered mesoporous oxide frameworks has been developed. Nanoparticles were synthesized in solution in the presence of surface templating polymer and encapsulated into mesoporous oxide matrices. After polymer removal by calcination, ethylene hydrogenation rates were consistent with previously reported results, while superior activity of low coordination atoms in small crystallites during ethane hydrogenolysis was demonstrated. Changes in reaction selectivity with particle size during the hydrogenation/dehydrogenation of cyclohexene were attributed to a hydrogen coverage effect influencing the hydrogenation pathway and the apparent structure sensitivity of the dehydrogenation pathway.
Quantitative Study of Au Catalytic Nanoparticles by Stem and Hrtem
Authors: Xu Fengting , Menard Laurent , Xu Huiping , Kang Joo , Gao Shangpeng , Wang Lin-lin , Frenkel Anatoly , Nuzzo Ralph G , Johnson Duane D , Yang Judith C
Published: April 2011

The highly dispersed metal (e.g. Au) nanoparticles have exhibited exceptional catalytic activity for several reactions, including CO oxidation. Their high catalytic activity has been attributed to nanoparticles nano-structural effects (including cluster thickness, shape, chemical information, and number of atoms of the cluster). The three dimensional exact structure and chemical bonding state of these supported nanoparticles is still challenging to be quantified by conventional methods due to their limitations in understanding size distribution of supported metal nanoparticles that are usually less than 1 nm (< 100 atoms). In this paper, the structure of Au heterogeneous catalysts has been successfully characterized by High Resolution Electron Microscopy (HREM), Z-contrast Scanning Transmission Electron Microscopy (STEM). The ligand protected Au13 nanoparticles on TiO2 support have been studied by ozone and thermal treatments to remove the ligands. The ozone removal method results in the truncated cuboctahedral structure while the thermal treatment results in the cuboctahedral structure. The ozone treatment yields less Au nanoparticles sintering than thermal treatment. Their FCC structure was confirmed by quantified Z-contrast STEM, HREM and its Fourier transformation.
Study on the Synthesis of Carbon Nanotubes using the Catalyst Metal Deposited Carbon Cathode Electrode in a DC Arc Discharge Process
Authors: Kim Hyeon Hwan , Kim Hyeong Joon
Published: April 2011

Carbon nanotubes (CNTs) were grown using a dc arc discharge process and relevant process parameters were investigated. Unlike the usual process in which a carbon anode is filled with metal catalyst powder, CNTs were prepared using a carbon cathode on which the metal catalyst had been deposited using an electroplating system. Various transition metals, Ni, Co and Ti, were used as a catalyst. The results show that multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) can both be synthesized using this technique. And yield and morphology of the prepared CNTs varied depending on the experimental condition and catalyst. While MWNTs were produced in the deposit and soot sample, SWNTs with diameters near 1nm were only detected in the soot collects. When Ni film was used as a catalyst, the yield of SWNTs was higher than in case of using Co or Ti film as a catalyst. From these results, the optimized preparing condition of CNTs and the properties of a good catalyst are discussed.
Selective Heating of Multiple Nanoparticles
Authors: Wijaya Andy , Brown Katherine Alice , Alper Joshua , Hamad-Schifferli Kimberly
Published: April 2011

A method for heating multiple types of magnetic nanoparticles independently is described. This technique exploits tuning of the size and material dependent properties of magnetic field heating of nanoparticles to allow independent heating by application of the field at different frequencies. Magnetic field heating experiments as a function of field frequency show that there is potential for this technique in vitro.
The Effect of Substrate and Catalyst Properties on the Growth of Multi-Wall Carbon Nanotube Arrays
Authors: Neralla Sudheer , Yarmolenko Sergey , Sankar Jag , Shanov Vesselin , Yun Yeo Heung , Schulz Mark J.
Published: April 2011

Self-aligned arrays of long multi-walled carbon nanotubes (MWCNT) were grown by chemical vapor deposition (CVD) from a gas mixture of C2H4-H2-Ar-H2O at 750°C. A catalytically active alumina surfaces coated with a thin layer of iron and supported by a Si/SiO2 substrate were prepared using pulsed laser deposition method. Combinatorial approach has been used for optimization of catalytic properties of the multilayered system Si/SiO2/Al2O3/Fe. Sixteen different combinations of catalytic surfaces having thicknesses of Fe (0, 1, 2, and 3 nm), alumina (0, 10, 20 and 30 nm) per sample were deposited on two Si/SiO2 substrates with silica thickness 150 and 500 nm. To study the effect of alumina phase on efficiency of catalytic surfaces two substrate temperatures 200 and 700°C were used to produce amorphous and γ-alumina phases correspondingly. This approach allowed the optimal structure of catalytic surface to be determined from 64 different substrates on 4 samples in a single MWCNT growth experiment, for a given set of processing conditions. It was found that most efficient growth of MWCNT arrays on amorphous alumina occurred at Fe nanolayer thickness of 2 nm while catalyst having γ-alumina layer has tendency to be more efficient at higher thickness of Fe. Catalytic substrate containing amorphous alumina has less sensitivity to thickness of iron while γ-alumina based catalyst has significant variation in catalytic activity with change of iron content.
A New Intelligent Material Based on Long Carbon Nanotube Arrays
Authors: Shanov Vesselin , Yeo-Heung Yun , Schulz Mark , Gollapudi Ramanand , Yarmolenko Sergey , Neralla Sudhir , Sankar Jagannathan , Tu Yi , Subramaniam Srinivas
Published: April 2011

Highly aligned multi-walled carbon nanotube (MWCNT) arrays were synthesized on Si wafers. Water vapor was used to enhance the catalyst performance, which enabled continuous growth of MWCNT arrays for up to 3 hours. Various types of Fe patterning on a Si substrate with a multilayered structure were tested. MWCNT arrays up to 4 mm long were grown by Chemical Vapor Deposition (CVD). Environmental scanning electron microscopy was used to characterize the MWCNT morphology and showed that the nanotubes typically reveal a 20 nm outer diameter and 8 nm inner diameter. To investigate applications, a nanotube tower 1 mm × 1 mm × 4 mm in size was grown and peeled off the Si wafer. Each tower contains millions of individual nanotubes with 20–30 nm diameters. Electrochemical actuation of one MWCNT tower was demonstrated in a 2M NaCl solution. The MWCNT tower actuator operated up to 10 Hz without significantly decreasing strain. Only 1-2 volts was needed to obtain 0.2% strain. The aligned nanotube morphology of the tower is the reason for the high strain in the axial direction, which is an improvement compared to previously tested entangled buckypaper actuators. Cyclic voltammetry (CV) was performed to analyze the redox behavior of the nanotube tower used as an electrode. The CV response showed a sigmodal shape in a 6 mM K3(CN)6 ferrocyanide solution. This behavior provides ideal characteristics for biosensor development and application. Also, the measured electrical volume resistivity of the material was in the range of 0.1 ohm · cm. The overall improvement in the electrochemical actuation and electrical conductivity was much greater than previous nanocomposites obtained by dispersing powdered nanotubes into polymers. The demonstrated good properties suggest nanotube array towers can be considered a novel intelligent material.
Controlled Growth of Gold Nanorod Arrays from Polyethylenimine-coated Alumina Templates
Authors: Moon Jeong-Mi , Wei Alexander
Published: April 2011

Au nanorod arrays were grown by electrodeposition in Au-backed nanoporous alumina templates modified with polyethylenimine (PEI) as an adhesion layer. By varying the concentration and molecular weight of PEI, the length of nanorod arrays could be finely controlled. The local length distribution was extremely narrow with relative standard deviations on the order of 2% for rod lengths from 700 nm to 17 microns. The uniform growth rate appears to be determined by the adsorbed PEI matrix, which controls the growth kinetics of the grains comprising the nanorods. Templates coated with poly(acrylic acid) did not impart fine control in nanorod growth. The nanorods could also be thermally annealed within the template and released as monodisperse particles of uniform size.
Electric-Field-Induced Displacements in Pt/PZT/Pt/SiO2/Si System Investigated by Finite Element Method: Material-Constant Dependences
Authors: Okino Hirotake , Hayashi Masahiro , Iijima Takashi , Yokoyama Shintaro , Funakubo Hiroshi , Setter Nava , Yamamoto Takashi
Published: April 2011

Electric-field-induced displacements of PZT film capacitor Pt/PZT/Pt/SiO2/Si(100) were calculated by finite element method (FEM) with changing all piezoelectric and elastic constants of PZT so as to discuss how to evaluate intrinsic d33 of piezoelectric thin films. Two kinds of conditions, namely, “ideal conditions” and “second-best conditions” are discussed. The ideal conditions indicate that the diameter of top electrode φTE is equal to or less than PZT film thickness tPZT and continuous PZT is etched to isolate the capacitor from the continuous piezoelectric film layer. Under the ideal conditions, d33 measured by atomic force microscopy (AFM) and double beam interferometry (DBI) were the same value that was equal to intrinsic d33 of PZT and was independent of other material constants. Under the second-best conditions, i.e. 20×tPZT < φTE for DBI and 20×tPZT < φTE < 0.5×(tsub: substrate thickness) for AFM, measured d33 depended on only d31, s11, s12 and s13, and obeyed the Lefki's equation qualitatively. However, quantitative differences between FEM analysis and the Lefki's equation were not negligible.
Enhanced Electrical properties in Mn-doped Bi3.25La0.75Ti3O12 thin films
Authors: Singh Sushil Kumar , Ishiwara Hiroshi
Published: April 2011

Mn-doped Bi3.25La0.75Ti3O12 (BLT) thin films were fabricated by depositing sol-gel solutions on Pt/Ti/SiO2/Si <100> substrates. The surface morphology and ferroelectric properties of Mn-doped BLT films depend upon the orientation of the films. Small amount of Mn-doping in BLT films influences the ferroelectric properties of the films, that is, it enhances the remanent polarization and reduces the coercive field. The 1% Mn-doped BLT films show enhanced remanent polarization and reduced the coercive field by about 22%. To the contrary, Mn-doping more than 1% decreases polarization gradually. Mn-doping significantly improves the fatigue resistance of BLT films. The reduced polarization in the 3.3% Mn-doped thin film recovers during switching cycles higher than 5 × 105. Under high switching field, the probability of field-assisted unpinning of domains is expected to be high and this may be the main cause for increase in polarization after 5 × 105 in the 3.3% Mn-doped BLT film.
A new model of imprint mechanism in ferroelectric memory
Authors: Miyazawa Hiromu , Hamada Yasuaki , Higuchi Takamitsu , Natori Eiji , Kijima Takeshi , Shimoda Tatsuya , Yoshiya Masato , Oguchi Tamio
Published: April 2011

We have studied imprint mechanism of ferroelectric memory based on the oxygen-vacancy screening model. Interface charge density and offset bias for PZT resulted from the imprint were estimated as a function of effective depth for diffusion of oxygen vacancy based on this model. In order to understand microscopic dynamics during the imprint that might affect the interface charge density, molecular dynamics simulation (MD) was carried out. Diffusion length during the real imprint test for PZT was estimated based on the diffusion constant obtained from the MD simulation. By using the diffusion length, interface charge density and, in turn, offset bias was quantitatively estimated. Based on the quantitative analysis, it is found that the oxygen-vacancy screening model with microscopic dynamics obtained from the simulation explains well the imprint mechanism for PZT materials family.
Spectral Characterization of Persistent Photo Conductance in SiC
Authors: Smith Steven , Evwaraye Andrew , Mitchel William
Published: April 2011

The transient photo response of 4H- and 6H-SiC specimens at various wavelengths has been studied using Optical Admittance Spectroscopy. Differences in the transient response were found for excitation and recombination for different specimens in both materials. The results indicate that optical excitation of charge carriers to the conduction band is a single transition, but recombination of free carriers from the conduction band is a process involving multiple transitions to the ground state mediated by deep centers in the material. Similarities in the persistent photoconductance after excitation from deep centers, and after excitation at above bandgap energies, suggest that carriers from the conduction band drop through deep centers on the way to the valence band.
Electrical Measurement of the Vanadium Acceptor Level in 4H- and 6H-SiC
Authors: Mitchel William C , Mitchell William D. , Smith H. E. , Zvanut M. E. , Lee Wonwoo
Published: April 2011

Temperature dependent Hall effect, Fourier transform infrared absorption, and electron paramagnetic resonance (EPR) studies have been performed on both 6H and 4H vanadium doped semi-insulating SiC samples grown by the physical vapor transport technique. Nitrogen and boron concentrations have been measured in some samples by secondary ion mass spectrometry (SIMS). Unlike undoped s.i. SiC, where several different thermal ionization energies have been observed, the ionization energies for all of the vanadium doped s.i. samples studied here were found to cluster around only two values for the two polytypes, EC – 0.85 eV and EC – 1.54 eV for 6H and EC – 1.11 eV and EC – 1.57 eV for 4H. SIMS measurements indicate that the nitrogen concentration exceeds the boron concentration in samples with the shallower of two values while the opposite is true for the deeper level samples. EPR detected both V3+ and V4+ in shallower level samples while only V4+ was detected in the deeper level samples. These results indicate that the vanadium acceptor level, V3+/4+, is located at EC – 0.85 eV in 6H-SiC and EC – 1.11 eV in 4H-SiC. However, some EPR results do show a small, unexpected asymmetry in the angular dependence of the V4+ signal, most noticeably in the 4H samples. This suggests that at least some of the vanadium related levels might be complexed with another defect or be under higher local strain than expected.
Process Control During Liquid Phase Rerowth of 3C-SiC on Si Substrates
Authors: Smith Mark , Voelskow Matthias , McMahon Richard A. , Muecklich Andreas , Anwand Wolfgang , Skorupa Wolgang
Published: April 2011

Flash lamp annealing in the millisecond regime of heteroepitaxial silicon carbide on silicon structures involves melting the Si below the SiC layer, but the deep facetted nature of the solid-liquid interface leads to unacceptable surface roughness. This paper describes a method of controlling melting by implanting a high dose of carbon or germanium at a controlled depth below the Si/SiC interface, which significantly alters the melting characteristics of the silicon. Results confirm the effectiveness of these approaches for increasing surface uniformity, making liquid phase processing compatible with standard device fabrication techniques. A thermal model has also been developed to describe this process and results indicate that the theoretical work is consistent with the experimental evidence. The model is a valuable tool for predicting onset of melting, maximum temperatures and process windows for liquid phase epitaxy.
Creating catalytically active nanoparticles via block copolymer templates for carbon nanotube and silicon nanowire growth
Authors: Lu Jennifer , Chamberlin Danielle
Published: April 2011

Using solution micelles formed by a block copolymer template, a variety of highly ordered catalytically active transition metal nanoparticles, ranging from single metallic nanoparticles of Fe, Co, Ni and Au to bimetallic nanoparticles such as Ni/Fe with uniform size and periodicity, have been created. These nanoparticles are excellent catalyst systems for the synthesis of carbon nanotubes and silicon nanowires. High quality, small diameter carbon nanotubes and silicon nanowires with narrow size distribution have been successfully produced. Since this block copolymer is fully compatible with conventional top-down photolithography, spatially selective growth of carbon nanotubes and silicon nanowires on a surface or carbon nanotubes suspended across trenches have been achieved using standard semiconductor processing techniques. The ability of the block copolymer template to generate catalyst with adjustable size and composition on a variety of surfaces not only enhance the manufacturability of these 1D nanobuilding blocks but also facilitates studying the growth mechanism.
Formation of Epitaxial Ge Nanorings on Si by Self-assembled SiO2 Particles and Touchdown of Ge Through a Thin Layer of SiO2
Authors: Li Qiming , Krauss Joshua L. , Hersee Stephen , Han Sang M.
Published: April 2011

We demonstrate that hexagonally packed single-crystalline Ge rings can be grown around the contact region between self-assembled SiO2 spheres and 1.2-nm-thick chemical SiO2 on Si. When the oxide-covered Si substrate is pulled from a colloidal suspension of SiO2 spheres, the SiO2 spheres self-assemble into a hexagonally packed monolayer on the substrate. These SiO2 spheres provide a surface diffusion path to guide the Ge adspecies to reach the substrate. We have previously determined that the Ge adspecies readily desorb from the bulk SiO2 surface with a desorption activation energy of 42±3 kJ/mol. This low desorption activation energy gives rise to a low surface diffusion barrier, which in turn leads to a high diffusion length on the order of several micrometers, exceeding the dimension of the SiO2 spheres. With a flux of Ge impinging at 45° from the surface normal, the Ge beam cannot directly impinge on the underlying substrate through the openings between SiO2 spheres. The Ge adspecies diffuse around the SiO2 spheres and "touchdown"[Li et al., APL, 85(11), 1928 (2004)] through the chemical SiO2, forming epitaxial ring structures. The touchdown process anchors nanoscale Ge seed pads to the underlying Si substrate. The ring formation uniquely takes advantage of the SiO2 sphere self-assembly; the weak interaction between Ge adspecies and SiO2; and the touchdown where Ge densely nucleates on Si surface through the 1.2-nm-thick chemical oxide.
SiC Based Neutron Flux Monitors for Very High Temperature Nuclear Reactors
Authors: Windl Wolfgang , Khorsandi Behrooz , Luo Weiqi , Blue Thomas E.
Published: April 2011

The Gas Turbine-Modular Helium Reactor (GT-MHR) and the Very-High-Temperature Reactor (VHTR) are next-generation high-temperature reactor types that are being designed to operate under normal conditions with primary coolant outlet temperatures in the range of 850 °C and 1000 °C, respectively. A new type of silicon carbide based diode neutron detector is currently under development in order to monitor the neutron flux in this environment. An important problem, in this context, is the long-time reliability of the diodes under continuous irradiation at high temperatures. In this paper, we discuss a computational methodology to study the accumulation of radiation damage in the detectors as a function of temperature and its influence on the electrical properties.
Nanostructural Evolution of Au on Silica Surfaces Exposed to Low Energy Ions
Authors: Abidzina Volha , Tereshko I. , Elkin I. , Zimmerman R.L. , Budak S. , Zheng B. , Muntele C. , Ila D.
Published: April 2011

We studied the effects of the low energy ions to induce nucleation of nanoscale crystals on and near surface of silica nano-layer containing low concentrations of Au. Suprasil substrates were coated with thin layer of gold followed by low-energy ion irradiation in a glow discharge plasma. The formation of nanoscale crystals due to low energy ion irradiation were then studied using RBS and optical absorption spectrometry.
Study of the Effects of Various Nanopowders in the Properties of GPC
Authors: Minamisawa Renato Amaral , Chhay Bopha , Muntele Iulia , holland Lawrence , Zimmerman Robert Lee , Muntele Claudiu , Daryush Ila
Published: April 2011

We have introduced various nanopowders in the precursor of glassy polymeric carbon (GPC) and studied its electrical, thermal, and mechanical properties as well as its chemical structure. In general the GPC ware produced at AAMU is used for making crucibles, heat exchangers, and for prosthetic devices because of its biocompatibility. GPC ware at AAMU is synthesized from a phenolic resin solution from Georgia Pacific in a pyrolyser system at temperatures between 100 °C all the way to 2800 °C. The heat treatment includes several stages: gelling, curing, postcuring, precarbonization and carbonization. The fabrication of GPC is complicated because of the high production rate of gaseous products in critical temperature ranges where out-diffusion is relatively slow. Special care should be taken in temperature programming to avoid kilning faults and misshapen or porous GPC end results. In this work we have introduced SiC, CNT or Al2O3 to the precursor and studied the properties of the final product treated at 1000oC pyrolysis temperature.
Controlling Cell Growth by Nanoparticles
Authors: Zankovych Sergiy , Bossert Joerg , Thiele Ines , Jandt Klaus D. , Berzina-Cimdina Liga
Published: April 2011

We report preliminary results of using nanoparticles to control cell attachment and growth. We present the way to create titanium surfaces with different roughness in a rage between 2 nm and 117 nm by using nanoparticles as a superficial layer and varying the evaporation parameters. We examined cell proliferation on titanium substrates with increased surface roughness compared to smooth titanium surface. We used nanoparticles to create a micrometer-sized lateral layout onto substrates preliminary structured by microcontact printing. We demonstrate controlled cell growth on substrates laterally structured with nanoparticles.
Microstructured Bioactive Interfaces using Piezoelectric Ink Jet Technology
Authors: Doraiswamy Anand , Dinu Cerasela Z. , Sumerel Jan , Chrisey Douglas B. , Narayan Roger J.
Published: April 2011

We have demonstrated microscale patterning of biotin and streptaividin proteins using an athermal rapid prototyping process based on piezoelectric inkjet technology. A MEMS-based piezoelectric actuator was used to dispense picoliter quantities of fluid through micron-sized nozzles. Atomic force microscopy and Fourier infrared spectroscopy studies were performed on CAD/CAM deposited proteins that were prepared using several firing voltages. Our results indicate that piezoelectric inkjet deposition is a powerful non-contact, non-destructive process for developing high-throughput biological microarrays for use in biosensing, cell culturing, and tissue engineering.