bluuebunny/crossref_metadata_2025 huggingface dataset:
The Significance of Percolation on the Dynamics of Polymer Chains Bound to Carbon Black
Authors: Nakatani Alan I. , Ivkov Robert , Papanek Peter , Jackson Catheryn L. , Yang Henry , Nikiel Leszek , Gerspacher Michel
Published: April 2011

A critical need in the fundamental understanding of reinforcement in filled polymers is the characterization of the polymer-filler interface and the dynamics of the polymer in this interfacial regime. In carbon black filled polymers, one of the central themes in the mechanism of reinforcement is that of “bound” polymer. Understanding the dynamics of this bound polymer may be key to arriving at an understanding of reinforcement mechanisms in filled polymers. The interactions between polymers and filler surfaces are also key in the development of more advanced nanocomposite materials.

We have previously utilized inelastic neutron scattering methods to examine the variation of bound polymer dynamics as a function of carbon black type for a single, initial carbon black concentration. An apparent change in the distribution in backbone motions was observed in the bound polymer compared with the pure polymer. In this study, we extend our prior work to examine the bound polymer dynamics as a function of the type of carbon black and the initial concentration of carbon black. The results suggest that two types of dynamic behavior are observed as a function of the initial carbon black concentration. This critical cutoff concentration may be related to the percolation threshold of the carbon black and suggests that quantifying the amount of bound polymer is insufficient for understanding the relationship between mechanical behavior and bound polymer content.
New Technique for Determining Mechanical Property of Polymer/Metal Interface
Authors: Du T. , Liu M. , Seghi S. , Hsia K. J. , Economy J. , Shang J. K.
Published: April 2011

A new experimental technique for determining mechanical properties of the polymer-metal interface was developed by replacing conventional mechanical testing machine with a piezoelectric actuator. Using this technique, fatigue crack growth behavior of epoxy/aluminum interface was studied as a function of electric field, crack length and cyclic frequency. The crack growth rate was found to depend on the magnitude of the applied electric field and decrease with testing frequency.
Carbon Metamorphoses in a Medium with Varying Ionic Concentration
Authors: Bouda V. , Chladek J.
Published: April 2011

Carbon black in a polymer melt was used to model self-organized processes. A gradual growth of ionic concentration in the polymer melt induced a complex behavior, including a rapid increase in AC conductivity after a time delay. Colloid theory can provide an effective interpretation. The metamorphoses of the carbon black assembly include soft axial order generation, soft lateral order generation, axial condensation, and lateral condensation of carbon black particles, respectively. Similar processes are expected to be effective in generating complex carbonaceous organic structures in natural water.
Order To Disorder Transition at The Polymer-Air Interface for Hydrophobic Octadecyl Side Chain Copolymers
Authors: Gautam Keshav S. , Dhinojwala Ali
Published: April 2011

Molecular orientation of octadecyl alkyl side chains at the poly (vinyl octadecyl carbamates-co-vinyl acetate) polymer-air interface has been studied using surface sensitive sum frequency generation (SFG) spectroscopy. At 280C, below the side chain crystalline transition temperature, the SFG spectra show strong methyl vibrations indicating ordered alkyl side chains at the polymer-air interface. In the liquid state (980C), the SFG spectra show higher contributions from the methylene vibrations indicating higher gauche defects at the interface. This surface order to disorder transition is gradual and spans over a broad temperature range (50-900C), where the bulk is in the smectic liquid crystalline state.
Structure of Carbon Blacks
Authors: Zerda T. W. , Qian J. , Pantea C. , Ungar T.
Published: April 2011

X-ray diffraction, Raman spectroscopy, and neutron scattering were used to characterize structure of carbon blacks. Different grades, N990, N774, N299, N134, and N110, untreated, after heat treatment and compressed at 2.5 GPa have been investigated. The average sizes of the crystallites obtained by X-ray diffraction agree with those estimated from Raman spectra. The distribution functions of crystallite sizes were evaluated from X-ray diffraction using the recently developed method. Heat treatment results in increased vertical and lateral sizes of graphitic crystallites. Postproduction pressure treatment has little effect on the average sizes of the crystallites, however, it affects the crystallite size distribution function. The magnitude of strain within the crystallites is affected by applied pressure. The relative concentration of amorphous carbon blacks estimated from Raman spectra decreases with increasing temperature but not with increased pressure. It is suggested that the initial growth is associated with alignment of the existing graphitic planes and later by incorporating aromatic carbon into the crystallites.
High Thermal Conductivity Shape-Stabilized Phase Change Materials
Authors: Xiao Min , Sun Luyi , Huang Chengya , Zhang Yonghua , Gong Kecheng
Published: April 2011

In this paper, shape-stabilized phase change materials (PCMs) based on paraffin and thermoplastic elastomer poly(styrene-butadiene-styrene) are prepared. The shape-stabilized PCMs can keep the same shape in a solid state even when their temperature is above the melting point of the paraffin. They exhibit same phase transition characteristics as paraffin and up to 80% of the latent heat of paraffin. Thermal conductivity of the shape-stabilized PCMs is increased significantly by the introduction of expanded graphite (EG). The time for complete solidification and complete melting of the composite P(80)/S(20)/EG(3) is two ninths and two fifths of paraffin, respectively.
The Synthesis of Silicon-containing Polyester Directly from SiO2 and Characterization of Its Structure
Authors: Song Jianhua , Sun Luyi , Liu Anhua , Gong Kecheng
Published: April 2011

A new approach to the synthesis of a novel silicon-containing polyester by noncarbothermal method directly from SiO2 was studied. At first, a high reactive pentacoordinate organic silicon compound (KSi(OCH2CH2O)2(OCH2CH2OH)) was prepared by the reaction of the fumed silica with ethylene glycol (EG) and KOH. Then, a novel double hydroxy tetracoordinate silicon monomer (OCH2CH2O)Si(OCH2CH2OH)(OCH2CH2OCH2CH2OH) was synthesized by the reaction of ClCH2CH2OH with reactive pentacoordinate silicon compound. Finally, a silicon-containing polyester was synthesized by low temperature solution condensation between tetracoordinate silicon compound and p-phthaloyl chloride in dimethyl sulfoxide (DMSO). The product was characterized by FTIR, TG, GPC, etc. The IR spectra of polyester exhibited a characteristic strong absorption band for ester carbonyl in the 1722.2cm-1. IR spectra also showed absorption at 1124.6cm-1 due to the O-Si-O group. TG analysis showed its good thermal stability. GPC analysis showed that the number average molecular weight of this siliconcontaining polyester was about ninety thousand.
Small Angle Scattering and the Structure and Dynamics of Filled and Unfilled Rubbers
Authors: Geissler Erik , Hecht Anne-Marie , Rochas Cyrille , Horkay Ferenc , Bley Françoise , Livet Frédéric , Sutton Mark
Published: April 2011

Random cross-linking in rubbers produces local variations in the elasticity of the network. These variations, whose characteristic size lies in the range 1-100 nm, are revealed when the rubber is swollen in a low molecular weight solvent, owing to the competition between the osmotic pressure of the solvent and the local elastic constraints, which affects the local polymer concentration. Such concentration fluctuations can be measured by small angle X-ray or neutron scattering (SAXS or SANS) as well as by dynamic light scattering.

In filled elastomers, the filler modifies the distribution of the polymer and of the elastic constraints. Swelling these systems in a solvent in which the deuteron/proton ratio can be varied permits the different components in the scattering function of the polymer and of the filler to be separated. Observations on silica particles in a poly(dimethyl siloxane) (PDMS) rubber yield measurements not only of the surface area of the particles but also of the fraction of the surface area occupied by the polymer. Analysis of the dynamic light scattering response of these systems gives confirmation of the validity of the procedure.

Coherent X-ray scattering measurements, combined with dynamic light scattering measurements of the filled uncross-linked polymer melts in the absence of solvent reveal that the structural relaxation process that follows an external mechanical perturbation is a diffusioncontrolled process.
Chitosan/Calcium Phosphate Scaffolds for Bone Tissue Engineering
Authors: Zhang Yong , Zhang Miqin
Published: April 2011

This research involves synthesis and characterization of biodegradable 3-dimensional polymer/calcium phosphate hybrid matrices as scaffolds for bone tissue regeneration. The scaffolds are comprised of chitosan and calcium phosphates [β-tricalcium phosphate (β-TCP), invert glass] and have combined optimum mechanical and biological properties of the two materials. Chitosan is a biocompatible and biodegradable polymer, and has rich hydroxyl groups for surface modification. Calcium phosphate crystals and invert glass are used as powder fillers to reinforce the scaffolds and increase bioactivity of the scaffolds. The scaffolds are fabricated using a thermally induced phase separation technique. The principal advantages of this technique are its low cost, low shrinkage levels, low sintering temperatures, and its ability to produce a variety of microstructures of various shapes and sizes. The osteoblast-like MG63 cells are seeded on the scaffolds to study the attachment and proliferation of the cells. The hydroxyl groups on the scaffolds are used to graft arginine-glycine-aspartate (RGD) peptides for promoting bone cell attachment and new tissue formation.
Development of Biodegradable Polymer Scaffolds Using Co-Extrusion
Authors: Washburn Newell R. , Simon Carl G. , Karim Alamgir , Amis Eric J.
Published: April 2011

A methodology for the preparation of porous scaffolds for tissue engineering using co-extrusion is presented. Poly(ε-caprolactone) is blended with poly(ethylene oxide) in a twin-screw extruder to form a two-phase material with micrometer-sized domains. Selective dissolution of the poly(ethylene oxide) with water results in a porous material. This method of polymer extrusion permits the preparation of scaffolds having continuous void space and controlled characteristic length scales without the use of potentially toxic organic solvents. A range of blend volume fractions results in co-continuous networks of polymer and void spaces. Annealing studies demonstrate that the characteristic pore size may be increased to larger than 100 μm. The mechanical properties of the scaffolds are characterized by a compressive modulus on the order of 1 MPa at low strains and approximately 10 MPa at higher strains. The results of osteoblast seeding suggest it is possible to use co-extrusion to prepare polymer scaffolds without the introduction of toxic contaminants.
Design and Characterization of New Ti-Ag and Ti-Ag-Sn Alloys for Cranio-Maxillo-Facial Prostheses Made by Three-Dimensional Printing
Authors: Hong Sang-Bum , Eliaz Noam , Leisk Gary G. , Sachs Emanuel M. , Latanision Ronald M. , Allen Samuel M.
Published: April 2011

new Ti-5Ag and Ti-5Ag-35Sn (wt.%) alloys were designed and synthesized by threedimensionalprinting (3DP). The identification of an appropriate binder, densificationtechnique, and densification parameters for fabricating cranio-maxillo-facial prostheses wasundertaken using microscopic observations, x-ray diffraction tests, microhardness testing, linearshrinkage and wettability measurements. Moreover, electrochemical tests and surface analysiswere used to evaluate the corrosion resistance and passivation behavior of the materials ofinterest. Silver nitrate was found to be an appropriate inorganic reactive binder for atomizedtitanium powder. The optimal temperature for densification of as-printed parts using sinteringwas determined for Ti-Ag alloys. In addition, the type of infiltrant material and use ofhomogenization in liquid-Sn infiltration was explored for Ti-Ag-Sn alloys. While the Ti-Agalloy exhibited superior corrosion and mechanical behavior to the Ti-Ag-Sn alloy, the lattershowed better dimensional stability.
Design, Synthesis, and Characterization of Hydroxyapatite Particulates
Authors: Chen Chun-Wei , Byrappa Kullaiah , Oakes Charles S. , Sushanek Wojciech , Riman Richard E. , Senna Mamoru , Brown Kelly , TenHuisen Kevor S. , Janas Victor F.
Published: April 2011

New hydrothermal technology for the preparation of hydroxyapatite designer particulates has been developed. Phase diagrams were constructed for the pH dependent equilibrium between monetite and HA from 50 to 200°C. Thermodynamic calculations were completed using temperature dependent functions for the relevant solution phase and solid-liquid equilibria and solute species activity coefficients. Model accuracy was evaluated through experiment at 50, 100, and 200°C and pHs between 2.2 and 8.9. The thermodynamic calculations and experimental results are in good agreement. Stoichiometric, crystalline HA has also been prepared by heterogeneous reaction of Ca(OH)2 powder and aqueous (NH4)2HPO4 at room temperature using mechanochemical-hydrothermal methods. This method appears to have very good reproducibility in terms of crystallinity and chemical composition.
Preparation and Charaterization of DAM-1 type Materials
Authors: Coutinho Decio , Ma Ying , Balkus Kenneth J.
Published: April 2011

Vitamin E TPGS was found to be an effective structure-directing agent for the preparation of both hexagonal all silica DAM-1 and the alumina analog, Al-DAM-1. These free flowing powders offer many advantages in the handling and oral delivery of the sticky vitamin E TPGS. Upon exposure to simulated gastric fluid, the Al-DAM-1 host molecular sieve is dissolved releasing the vitamin E TPGS. As much as 0.6 grams of vitamin E TPGS can be immobilized into 1 gram of Al-DAM-1. Vitamin E TPGS also templates highly ordered mesoporous DAM-1 with tunable morphologies such as hexagons (various lengths), gyroids, rods, spheres and discoids depending upon the temperature and gel composition. Characterization of these composites as well as a preliminary evaluation of Al-DAM-1 as an oral drug delivery system under physiological conditions is presented.
Sol-Gel Optical Sensors for Glutamate
Authors: Rickus Jenna L. , Lan Esther , Tobin Allan J. , Zink Jeffery I. , Dunn Bruce
Published: April 2011

The amino acid glutamate is the major excitatory neurotransmitter used in the nervous system for interneuronal communication. It is used throughout the brain by various neuronal pathways including those involved in learning and memory, locomotion, and sensory perception. Because glutamate is released from neurons on a millisecond time scale into sub-micrometer spaces, the development of a glutamate biosensor with high temporal and spatial resolution is of great interest for the study of neurological function and disease. Here, we demonstrate the feasibility of an optical glutamate sensor based on the sol-gel encapsulation of the enzyme glutamate dehydrogenase (GDH). GDH catalyses the oxidative deamination of glutamate and the reduction of NAD+ to NADH. NADH fluorescence is the basis of the sensor detection. Thermodynamic and kinetic studies show that GDH remains active in the sol-gel matrix and that the reaction rate is correlated to the glutamate concentration.
Optical Probing of Polarons and Triplet Excitons in Conjugated Polymer Devices
Authors: Dhoot Anoop S. , Greenham Neil C.
Published: April 2011

Polarons and triplet excitons in conjugated polymers exhibit sub-gap absorptions which allow them to be identified spectroscopically. We have used quasi-steady-state induced absorption techniques on working polymer light-emitting diodes to study charge carriers and triplet excitons in devices. We identify absorptions due to charges, and at low temperatures can also resolve features due to triplet excitons. From the magnitude of the absorption features, we study the charge and triplet densities as a function of applied voltage. We obtain a value for the triplet generation rate at low temperatures and an estimate of the singlet exciton formation probability. Analysis of the triplet lifetime as a function of charge density reveals the presence of triplet-polaron interactions and we obtain a rate constant for this triplet annihilation process.
Self-Assembled Growth of Highly Oriented Para- Sexiphenyl Thin Films Controlled by Elastic Strain
Authors: Andreev Andrei Yu. , Sitter Helmut , Brabec Christoph J. , Hinterdorfer Peter , Springholz Günter , Sariciftci Niyazi S. , Resel Roland , Plank Harald
Published: April 2011

We have studied the structure and growth regularities of highly ordered para-sexiphenyl (C36H26) thin films deposited by Hot Wall Epitaxy on mica. In particular, atomic force microscopy (AFM) was used to investigate the early growth stage of these films, in order to find the process controlling parameters. It was shown that the substrate temperature and the growth time are important parameters for control of the film morphology, in terms of the degree of anisotropy and long range order. X-ray diffraction pole figure technique and transmission electron microscopy were also used to characterize the crystallographic structure of the thicker films. We have shown that the highly ordered crystallites of para-sexiphenyl (showing needle-like morphology by AFM) are oriented with their (11 1 ) or (11 2 ) crystallographic planes parallel to the substrate surface. For each of these two orientations there are two opposite directions for growth of crystallites reflecting the two-fold symmetry of the mica surface.
Synthesis of 3,4-Disubstituted Poly(thiophene)s via Substitution of Poly(3-alkylthiophene)
Authors: Li Yuning , Vamvounis George , Holdcroft Steven
Published: April 2011

The electrophilic substitution of regioregular poly(3-hexylthiophene) (P3HT) at the 4- position was investigated to produce structurally well defined 3,4-disubstituted poly(thiophene)s. When P3HT was treated with N-bromosuccinimide (NBS) in chloroform at 25 to 50 °C, the 4-hydrogen atom in P3HT is completely substituted by bromine, as indicated by the 1H NMR, 13C NMR and elemental analysis. Similarly, the chlorinated product was obtained using N- chlorosuccinimide (NCS) at room temperature. However, only 85% of the 4-hydrogen atoms were replaced by chlorine and ∼15% of the α-hydrogen atoms on the hexyl side chain were chlorinated. P3HT readily reacts with fuming nitric acid in chloroform at 0 °C to generate a nitrated product with almost 100% substitution at the 4-position. Our preliminary study on the futher functionalizaton of these polymers was conducted on the brominated product. Our results showed that the bromine atom in this polymer could be further substituted with other groups.
Novel Guest-Host NLO Polyimide Based on Two-Dimensional Carbazole Chromophores
Authors: Kuo Wen-Jang , Hsiue Ging-Ho , Jeng Ru-Jong
Published: April 2011

Taking advantage of the multifunctional characteristics of carbazole along with rational molecular design, several two-dimensional carbazole chromophores were acquired. Doping the chromophores into poly(ether imide), a series of NLO-active guest-host polymers were obtained. The compatibility between chromophores and poly(ether imide) was investigated by SEM and extraction experiment. After poling, these NLO poly(ether imide)s with large second-order nonlinearities were achieved. Correlation between structure and nonlinear optical characteristics, and the chromophore size effect on the thermal and temporal stability have been probed. Large rotational cone volumes make the two-dimensional chromophores possessing excellent orientational stability at 60.
Microcavity Effects in Thiophene-Based Oligomers
Authors: Gigli G. , Anni M. , Patanè S. , Barbarella G. , Favaretto L. , Cingolani R.
Published: April 2011

We report on the realization and optical properties of a fully evaporated organic microcavity based on LiF-TeOx Distributed Bragg Reflectors and a substituted quinquethiophene as active material. The PL spectrum shows a strong line-width reduction, down to 10 nm, with respect to the bulk spectrum, which is about 110 nm broad. The emission at the mode wavelength shows an enhancement due to the light matter coupling in the optical resonator. The cavity mode shows a splitting for emission angles higher than about 30 degrees which continuously increases with angle up to 99 meV. This feature is observed both in angle resolved PL spectra and in angle resolved reflectance with unpolarized light. A study of angle resolved reflectance with polarized light allows us to attribute this splitting to a polarization effect, rather than to Rabi splitting due to strong coupling in the cavity.
Deposition And Characterization Of Metal/Polyaniline Bi-Layers
Authors: Liu Y. , O'Keefe M. J. , Beyaz A. , Singleton C. , Schuman T. P.
Published: April 2011

In this study bi-layers of metal/polyaniline (PAni) films were deposited and characterized in order to investigate the interaction of thin film metals with doped and de-doped PAni. The bilayers were fabricated by depositing PAni films on flat substrates via solution chemistry and then depositing metallic films by physical vapor deposition. The oxidation state of the PAni was varied from the doped emeraldine salt to a de-doped emeraldine base to a de-doped and fully reduced leucoemeraldine base. Aluminum and iron thin films were then magnetron sputter deposited onto the PAni films to form bi-layer structures. Characterization of the fabricated bi-layers by scanning electron microscopy, current-voltage measurements, and Auger electron spectroscopy was done to investigate the morphology, electrical properties and chemical composition of the samples. Results from the study indicate that the type of metal and the doping level of the PAni influence the interactions and properties of metal/PAni interfaces and films.
Photoconductivity of Pentacene Thin Film Transistors
Authors: Knipp D. , Murti D.K. , Krusor B. , Apte R. , Jiang L. , Lu J.P. , Ong B.S. , Street R.A.
Published: April 2011

A very large enhancement of the photoconductivity in pentacene transistors at negative gate voltages is observed. The enhancement is attributed to the separation of electron-hole pairs by the gate field and the consequent slow recombination. The ratio of photoconductivity to dark conductivity is approximately independent of mobility, for samples with a wide range of microstructure. The pentacene films were thermally deposited at different deposition rates and temperatures on silicon thermal oxide. The structure and the morphology of the films were studied by x-ray diffraction measurements and atomic force microscopy, and the influence of the deposition temperature on the morphology and structural properties is discussed. The size of the crystals is correlated with the crystalline bulk phase of the material, which increases with the deposition temperature and the film thickness. The mobility of the transistors increases with the size of the crystallites.
Analysis of Polymer Field Effect Transistor
Authors: Roichman Y. , Tessler N.
Published: April 2011

We compare two basic organic FET structures both experimentally and theoretically. By using time resolved analysis we gain insight into the mechanisms affecting the performance of these structures. Using a two dimensional numerical model we focus on the top contact structure and demonstrate the difference between the two structures.
Fabrication and properties of low temperature sintered PZT-PMN films
Authors: Stytsenko Eugene , Daglish Marc
Published: April 2011

A film of PZT-PMN composition was fabricated by the deposition of fine powder entrained in airflow on to a substrate at the temperature of 20 °C. The particle flow generated by a jet mill desintegrator circulated inside the cylindrical substrate tube producing a build up on the internal surface of the cylinder. The resulting film, 70 – 150 µm thick was mechanically removed (delaminated) from the substrate and sintered at 800 °C. Microscopic examination of the green and sintered films revealed a very dense microstructure with a grain size for the sintered film of 0.2 – 0.8 µm. The relative permittivity at 1 kHz was about 100 before sintering and 2000 after sintering (unpoled). The permittivity of the sintered film had the same value as for bulk ceramic samples fabricated from the same powder using conventional isostatic pressing technique and sintered at 1250 °C to 97 % of the theoretical density.

The study showed that the properties of the green body produced by the powder deposition process were superior to the properties of bulk samples prepared by the conventional pressing procedure. The method provides a route for the formation of a fine grain microstructure, and a sintering temperature 450 °C lower than the accepted sintering temperature for this PZT-PMN composition.
Auto Feeding Epitaxial Growth of Oxide Thin Film without Oxidant
Authors: Shimoyama Kazuo , Kubo Kousuke , Maeda Tatsuro , Yamabe Kikuo
Published: April 2011

High-quality thin films of BaTiO3 and SrTiO3 on SrTiO3 substrate were obtained by shutting off the oxygen supply during growth. Epitaxial growths were carried out with molecular-beam epitaxy (MBE) under extremely low oxygen partial pressure (pO2 < 1×10−8 Pa). Although only Ba(Sr) and Ti metals were supplied without introducing oxidant during the growth, clear reflection high-energy electron diffraction (RHEED) intensity oscillations from layer-by-layer growth were observed. The deposited films were found to have approximately stoichiometric compositions of BaTiO3 and SrTiO3. Oxygen was automatically fed from the substrate during the growths. It was found that the BaTiO3/SrTiO3 interface was abrupt without intermixing, despite a considerable amount of oxygen seems to have moved from the substrate to the film through the interface.
Characterization of the interfacial layer formed during pulsed laser deposition of oxides on Si
Authors: Craciun V. , Howard J. M. , Bassim N. D. , Singh R. K.
Published: April 2011

Medium-k dielectric Y2O3 films were directly grown on (100) Si substrates by the pulsed laser deposition (PLD) technique. X-ray photoelectron spectroscopy, variable angle spectroscopic ellipsometry, current-voltage, capacitance-voltage, and high-resolution transmission electron microscopy were used to investigate the composition, thickness, and electrical properties of the grown structures. It has been found that at the interface between the Si substrate and the grown dielectric layer, a SiOx interfacial layer, whose thickness depended on the oxygen pressure used during the PLD growth, was always formed. The main oxygen source for this interfacial layer formation is the physisorbed oxygen trapped inside the grown layer during the laser ablation-deposition process. When trying to reduce the thickness of this low-k interfacial layer by decreasing the oxygen pressure during laser ablation, a marked degradation of the electrical properties of the structures was noticed.
Growth of Epitaxial LaVO3/(Pb,La)(Zr,Ti)O3/(La,Sr)CoO3 Heterostructures
Authors: Choi Woong , Sands Tim
Published: April 2011

Epitaxial semiconductor-ferroelectric-conductor LaVO3/(Pb,La)(Zr,Ti)O3/(La,Sr)CoO3 heterostructures were grown on (001) LaAlO3 single crystal substrates by pulsed laser deposition. A high degree of c-axis orientation and strong in-plane texture revealed by x-ray diffraction indicated the epitaxial crystallographic relationships between the layers. The capacitance measurement as a function of voltage revealed the modulation of the depletion layer in the semiconducting LaVO3 as well as the non-linear response of the (Pb,La)(Zr,Ti)O3 ferroelectric layer.
Transparent Conducting Indium-Tin-Oxide Thin Film with Extremely Flatted Surface
Authors: Ohta Hiromichi , Orita Masahiro , Hirano Masahiro , Hosono Hideo
Published: April 2011

Indium-tin-oxide films were grown hetero-epitaxially on YSZ surface at a substrate temperature of 900 °C, and their surface microstructures were observed by using atomic force microscopy. ITO films grown on (111) surface of YSZ exhibited very high crystal quality; full width at half maximum of out-of-plane rocking curve was 54 second. The ITO was grown spirally, with flat terraces and steps corresponding to (222) plane spacing of 0.29 nm. Oxygen pressure during film growth is another key factor to obtain atomically flat surfaced ITO thin film.
Growth and Characterization of ZnO Film on Sapphire by the Helicon Wave Plasma Assisted Evaporation Process
Authors: Kim Kyoung-Bo , Park Tae-Hee , Kim Ki-Sung , Kim Seon-Hyo
Published: April 2011

The growth of ZnO film on (0001) sapphire substrates was studied using the high density helicon wave oxygen plasma (>1011/cm2) assisted evaporation process. The addition of Ar into oxygen plasma (Ar/O2=1/2) enhanced the production of excited atomic oxygen (O*). The effect of a grounded grid installed at the exit of the plasma source on the crystallinity and optical properties of film is discussed. The full width at half maximum (FWHM) of θ rocking curve for (0002) plane is 0.53° under grid installation while 0.63° without the grid, indicating slightly improved crystallinity when adopting a grounded grid. The AFM image for the film deposited with grid installation shows a smoother surface morphology than in the case of no grid. PL spectra for the film deposited with the aid of a grid show a strong near-band edge emission at 3.36 eV at 10K, but those without a grid show prominent deep-level emissions. The deep level emission is attributed to the impurities and native defects in the film. The optical properties were greatly improved by a grounded grid, which effectively eliminated the ionic species and selectively extracted the excited neutrals.
Characterization of Zinc Oxide Thin Films Deposited by rf Magnetron Sputtering on Mylar Substrates
Authors: Fortunato Elvira , Nunes Patrícia , Marques António , Costa Daniel , Águas Hugo , Ferreira Isabel , Costa Maria E. V. , Martins Rodrigo
Published: April 2011

Aluminium doped zinc oxide thin films (ZnO:Al) have been deposited on polyester (Mylar type D, 100 µm thickness) substrates at room temperature by r.f. magnetron sputtering. The structural, morphological, optical and electrical properties of the deposited films have been studied. The samples are polycrystalline with a hexagonal wurtzite structure and a strong crystallographic c-axis orientation (002) perpendicular to the substrate surface. The ZnO:Al thin films with 85% transmittance in the visible and infra-red region and a resistivity as low as 3.6×10−2 ωcm have been obtained, as deposited. The obtained results are comparable to those ones obtained on glass substrates, opening a new field of low cost, light weight, small volume, flexible and unbreakable large area optoelectronic devices.
Structural and Electrical Properties of Colossal Magnetoresistive LSMO Thin Films Prepared by KrF Laser Ablation Method
Authors: Mitsugi Fumiaki , Ikegami Tomoaki , Ebihara Kenji , Narayan Jagdish , Grishin Alexander M.
Published: April 2011

We prepared colossal magnetoresistive La0.8Sr0.2MnO3 thin films on the MgO, SrTiO3 and LaAlO3 single crystal substrates using KrF excimer pulsed laser ablation technique. The structural and electrical properties of the La0.8Sr0.2MnO3 thin films which were strained by the lattice mismatch are reported. The in-plane lattice mismatch between the La0.8Sr0.2MnO3 and MgO, SrTiO3 and LaAlO3 substrates are -7.8 %, -0.5 % and +2.3 %, respectively. The X-ray diffraction spectra of the films exhibited c-axis orientation. In the case of the La0.8Sr0.2MnO3 / LaAlO3 thin films with thickness over 100 nm, the divided (00l) peaks were observed. The surface morphology and transport property of the strongly stressed La0.8Sr0.2MnO3 / LaAlO3 were different from those of La0.8Sr0.2MnO3 / MgO and La0.8Sr0.2MnO3 / SrTiO3thin films.
Charge transport through localized states in sputtered amorphous silicon suboxides
Authors: van Hapert J.J. , Tomozeiu N. , van Faassen E.E. , Vredenberg A.M. , Habraken F.H.P.M.
Published: April 2011

Using an RF magnetron sputtering technique, thin layers (∼500 nm) of amorphous silicon suboxides (a-SiOx) were deposited, with oxygen/silicon ratios x ranging from 0 to 1.8. These layers contain a large density (1020−1021 cm−3) of, mostly silicon dangling bond, defect states. The level of conduction decreases several orders of magnitude with increasing x. The temperature dependence of the DC conductivity showed that the variable range hopping conduction mechanism is dominant for all x, over the temperature range 30- 330 K. In this mechanism the extent of localization and density of states around the Fermi level determine the conductance. We conclude that the decrease in conductance with increasing oxygen content must, for a large part, be due to a variation in the localization, since Electron Spin Resonance (ESR) measurements showed no decrease in defect density with increasing x. We performed DC conduction measurements at both low and high electric field strengths, showing phenomena, which are consistently desribed within the variable range hopping (VRH) model. These measurements allow the extraction of quantitative information, concerning both the localization and the density of the states involved in the hopping process.
Dielectric Properties Analysis in Paraelectric ZrTiO4 Thin Films
Authors: Kim Kyunghae , Heo Jinhee , Kim Taeseok , Park Byungwoo , Yi Junsin
Published: April 2011

The dielectric constants and dielectric losses of ZrTiO4 thin films deposited by DC magnetron reactive sputtering were investigated. The paraelectric properties were measured in the 100kHz range and compared with an equivalent circuit model. As the deposition temperature increased (up to 600°C), the dielectric losses (tanσ) decreased (down to 0.017±0.007), while the dielectric constants (ε) were in the range of 35±7. Post annealing at 800°C in oxygen for 2h reduced tanσ down to 0.005±0.001, higher than those of well-sintered bulk ZrTiO4.
Characteristics of Pt/SBT/Al2O3/Si Structures for MFIS-FET Applications
Authors: Choi Jae-Hoon , Kim Ji-Woong , Oh Tae-Sung
Published: April 2011

Pt/Sr0.85Bi2.4Ta2O9/Al2O3/Si structures were prepared for MFIS-FET applications. After depositing Al2O3 film of 10-50 nm thickness by reactive sputtering on Si(100) substrate as a buffer layer, Sr0.85Bi2.4Ta2O9 (SBT) thin film of 400 nm thickness was prepared onto it by metalorganic decomposition process. With annealing at 800°C for 1 hour in oxygen ambient, the 400 nm-thick SBT film exhibited 2Pr of 10.2 μC/cm2 and Ec of 37.5 kV/cm at ±5V. C-V characteristics of the Pt/SBT/Al2O3/Si structures exhibited hysteresis loops due to the ferroelectric switching behavior of the SBT film. When the Al2O3 buffer layer was thicker than 10 nm, the memory window and maximum capacitance of the Pt/SBT/Al2O3/Si structure increased with decreasing the thickness of the Al2O3buffer layer, and the Pt/SBT(400 nm)/Al2O3(10 nm)/Si structure exhibited a memory window of 2.2 V at ±5 V.
Growth and Characterization of Self Assembled Palladium Oxide Nanostructures
Authors: Chalamala Babu R. , Reuss Robert H. , Wei Yi , Aggarwal Sanjeev , Ramesh R.
Published: April 2011

There is great interest in forming nanoscale structures through thermodynamically driven self-assembly processes. Self-assembled processes hold the promise of enabling the creation of complex, next-generation device architectures that rely on the intrinsic ability of the system to organize itself into ordered patterns. This is in contrast to the artificially ordered schemes, such as those currently used in integrated circuits. Many inorganic systems display microstructural evolution that resemble self-assembled processes, for example spinodal decomposition in alloys, dendrite formation in melts, and martensitic twins in metallic and ceramic alloys, where the assembly process is driven by thermodynamic and kinetic considerations. In this paper, we report on the self-assembly of nanometer-scale hillocks of conducting palladium oxide. We report the formation of periodic arrays of self-assembled hillocks upon oxidation of Pd films. The PdO2 hillocks are referred to as “tips” due to their significantly large height (∼ 1νm) and conical shape. The tips are spaced ∼2.5μm apart and tip height is dependent on the film thickness, granularity and annealing conditions. The height and size of the PdO2 tips increased and their distribution became narrow with increasing film thickness. We show that these structures can be fabricated on a number of substrates including silicon, glass, and various ceramic substrates.
Oxide Electrodes for Buried-Channel Field Effect Transistors
Authors: Schrott A.G. , Misewich J.A. , Abraham D.W. , Ramesh R. , Nagarajan V.
Published: April 2011

In this paper we describe the fabrication of oxide based electrodes that allow epitaxial growth of multilayer structures used to fabricate buried oxide-channel field effect transistors. The distinct characteristic of our buried electrodes is that they provide an etch stop layer which allow the opening of vias through the gate oxide using chemical etching. They can be patterned to define 1μm channel lengths and exhibit low contact resistance with channel materials such as YxPr1−xBa2Cu3O7-σ (YPBCO) or YBa2Cu3O7σ (YBCO).
Nano-scale Interfacial Reactions of SrRuO3 Thin Film on Si (100) Substrate
Authors: Oh Sang Ho , Park Chan-Gyung
Published: April 2011

Interfacial reactions between SrRuO3 films and Si substrate were investigated by using field emission-transmission electron microscopy (FE-TEM). The compositional and structural variations across the interface were analyzed by using energy dispersive X-ray spectroscopy (EDS) and diffraction with an electron probe in 0.5 nm in diameter. Two constituent binary oxides of SrRuO3, i.e. SrO and RuO2, were found to react differently on Si surface: 1) SrO in stable contact with Si, and 2) RuO2 in unstable contact. The reduction of SrRuO3 to elemental Ru by Si is believed to be most favorable candidate for the reaction leading to the unstable contact of SrRuO3 on Si.
Substrate Influence on the Reversible and Irreversible Polarization Contributions in Ferroelectric Thin Films
Authors: Bolten Dierk , Böttger Ulrich , Rodriguez Julio , Lohse Oliver , Grossmann Michael , Schneller Theodor , Waser Rainer
Published: April 2011

In this contribution, the influence of different substrates and textures on the reversible and irreversible polarization in Pb(Zr,Ti)O3 (PZT) thin films will be presented. One possible scenario to explain the origin of the ferroelectric hysteresis is the notion that the domain walls move through a potential generated by their interaction with randomly distributed defects of the matrix. This potential then gives rise to reversible and irreversible changes in the ferroelectric polarization. The exact features of the interaction potential also depend on the stress state of the material which can be influenced by a suitable choice of the substrate.

To study the substrate influence, PZT thin films have been deposited on commercial Si wafers, MgO and SrTiO3 single crystals. Electrical characterization methods (hysteresis and small signal capacitance measurements) have been used to extract information on reversible and irreversible polarization contributions.
Self-Assembled 3-Mercaptopropyltrimethoxysilane (MPS) ON Ba0.5Sr0.5TiO3 as an Adhesion Layer for Microwave Devices
Authors: Cabrera Carlos R. , Warner Joseph D. , Mueller Carl H. , Keuls Fred Van , Miranda Félix A. , Tremont Rolando , Blasini Daniel , Morales Angel
Published: April 2011

The use of self-assembled monolayers in patterning, adhesion studies, corrosion protection, and electronic devices is a growing research field. Here we discuss the use of (3-mercaptopropyl)trimethoxysilane (MPS) as an adhesion layer in microwave components using metal-ferroelectric thin film-dielectric heterostructures. The MPS has been used as an adhesion layer between a ferroelectric thin film and gold (Au) in the development of tunable microwave components. The system studied was the metal/ferroelectric thin film/dielectric heterostructure with the MPS molecule as an adhesion layer between the metal and the ferroelectric thin film. Specifically, we have looked at the interface between the Au layer and the Ba0.5Sr0.5TiO3 (BSTO) ferroelectric thin film deposited on LaAlO3 (LAO). Typically, during metallization via e-beam evaporation, it is common to deposit a chrome or titanium adhesion layer (∼ 15 nm thick) between the Au and BSTO films. However, this underlayer may diffuse through the Au causing an increase of the RF losses of the device. Replacing the metal buffer layer interface with a self-assembled structure, such as MPS, can avoid the effect of inter- diffusion of chrome in the Au vapor deposit film. The surface modification of Ba0.5Sr0.5TiO3 (BSTO) thin film with MPS was studied by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. The effectiveness of MPS self-assembled monolayers as an adhesion layer was determined by analyzing the performance of Au/MPS/BSTO/LAO interdigital capacitors as a function of dc voltage and temperature at 1 MHz.
Near-field Scanning Optical Microscopy and Electron Microprobe Microscopy Investigations of Immiscibility Effects in Indium Gallium Phosphide Grown by Liquid Phase Epitaxy
Authors: Paulson C. A. , Ellis A. B. , Kuech T. F.
Published: April 2011

We have used Near-field Scanning Optical Microscopy (NSOM) and Electron Probe Microanalysis (EPMA) to study the topographic and microscopic optical properties of indium gallium phosphide (In1−xGaxP) samples grown by Liquid Phase Epitaxy (LPE) on gallium arsenide substrates. Photoluminescence (PL) intensity images gathered using NSOM exhibit strong, highly localized variations in the optical properties of these samples that are seen to occur roughly in registry with the surface topography. Shifts in the PL peak position (by 27 meV) occur across highly mismatched samples with high In content, whereas no shifts were seen for In1−xGaxP films with a nearly lattice matched composition. Compositional fluctuations lead to these PL peak energy shifts, measured by NSOM with a resolution of 250 nm. These composition fluctuations arise from the known solid-solid miscibility gap in the In1−xGaxP system at temperatures used for the growth of these samples.
Amorphous Nitride Alloys as Hosts for Rare-Earth Luminescent Ions.
Authors: Caldwell M. L. , Little M. E. , Spalding C. M. , Kordesch M. E. , Richardson H. H.
Published: April 2011

Amorphous alloys of aluminum-gallium nitride doped with erbium (Er) were deposited at 300 K. The compositions ranged from 19% Al to 86% Al with optical band gaps varying linearly with composition from 3.4 eV (GaN) to 6.2 eV (AlN). The films were deposited on p-doped silicon (111) by a dc/rf dual gun system in a nitrogen/argon atmosphere at a pressure of 4.8 milli-Torr. After growth the films were thermally “activated” at 1070 K for 10 minutes in a nitrogen atmosphere. The cathodoluminescence emission intensities decreased linearly with Ga composition. This dependence suggests that the higher energy transitions in the Er ion are quenched by transitions to the conduction band of the alloys.
Luminescence of nanocrystalline ZnS:Pb2+
Authors: Bol Ageeth A. , Meijerink Andries
Published: April 2011

Nanocrystalline ZnS:Pb2+ is synthesized via a precipitation method. The luminescence is studied and the influence of the size of the nanocrystals on the luminescence properties is investigated. Nanocrystalline ZnS:Pb2+ shows a white emission under UV excitation. At least two luminescence centers are involved. One center is identified as a Pb2+ ion located on a regular Zn2+ site and gives a red emission under 480 nm excitation. The luminescence properties of this emission are characteristic for transitions on Pb2+ ions. The other centers are not as well defined and give a broad green emission band under 380 nm excitation and also show luminescence properties typically observed for Pb2+. The green emission probably originates from a charge-transfer like D-band emission of Pb2+ in ZnS close to a defect (e.g. an S2− vacancy or an O2− ion on an S2− site). A relation between the temperature quenching of the emissions and the band gap is observed and indicates that photoionization occurs.
Pressure Tuning Spectroscopy of Mn2+ in Bulk and Nanocrystalline Sulfide Semiconductors
Authors: Smith Randy J. , Shen Yongrong , Bray Kevin L.
Published: April 2011

We report the results of high pressure luminescence studies of the emission of Mn2+ in bulk Zn0.55Ga0.30S up to ∼214 kbar, bulk ZnS up to ∼184 kbar, and nanocrystalline ZnS (∼8 nm particle sizes) up to ∼300 kbar. We observed a strong redshift with pressure (-30(3) cm−1/kbar) for the 4T1→6A1 emission transition of Mn2+ in all three systems. We also observed emission quenching at high pressure in all three systems and attribute the quenching to a pressure induced phase change of the ZnS host lattice to a rocksalt (NaCl) phase.
Low-temperature technology and physical processes in green thin-film phosphor Zn2GeO4-Mn
Authors: Bondar V. , Popovich S. , Felter T. , Wager J.
Published: April 2011

Thin-film Zn2GeO4:Mn phosphors with lower temperature of crystallization and potentially compatible with industrial technologies were investigated. The technology of thin films synthesis has been developed and their structure and crystal parameters have been investigated. Photoluminescence excitation spectra, photoconductivity, temperature dependencies and ESR-spectra of manganese ions were studied. A mechanism for luminescence in this phosphor has been proposed. Results are presented of cathodo- and electro-luminescence of thin film structures of Zn2GeO4:Mn.
Doping process issues for Sub-0.1 μm generation MOSFETs
Authors: Sugii Toshihiro , Pidin Sergey , Momiyama Youichi , Goto Ken- ichi , Tanaka Takuji , Yamamoto Tomonari , Futatugi Toshirou , Kase Masatak
Published: April 2011

To meet the market demands for higher performance LSIs, traditional scaling has been aggressively pursued and has enjoyed great success over the 0.1-μm generations. To maintain continued growth of CMOS performance beyond the 0.1-μm generation, key issues originating from traditional scaling are addressed from the viewpoint of the doping processes (channel engineering, high-activation, and gate- electrode structure) in this paper.

To meet the acceleration in gate-length miniaturization, short-channel effects must be suppressed at a low threshold voltage by using aggressive channel engineering. A channel-impurity profile must be optimized two-dimensionally, not uniformly or one-dimensionally. Channel engineering using tilted-channel implantation (TCI) with Indium is demonstrated.

Traditional scaling results in large variations of threshold voltage due to the statistical-impurity variation in a channel region. We studied the effect of the above channel engineering on threshold voltage fluctuation caused by a statistical- dopant variation by measurement and simulation. It is reported that the two-dimensionally optimized channel profile enhances threshold-voltage fluctuation even if the implantation process variation is negligible.

As CMOS device scales, reduction of parasitic resistance becomes very important for a high performance operation. Resistance at extension egde and contact resistance at silicide-Si interface are dominant factors.The traditional approach is to use a higher RTA temperature and a shorter RTA time. The ultimate RTA is laser annealing. We will demonstrate the laser annealing process with an ultra-low contact resistance of 4 × 10−8 Ω-cm2.

By integrating the above technologies, ultra-thin gate insulators, and reduction in gate to source/drain overlap length, we can establish front-end process for sub-0.1 μm generations.