bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and Charaterization of DAM-1 type Materials
Authors: Coutinho Decio , Ma Ying , Balkus Kenneth J. 
Published: April 2011

AbstractVitamin 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

AbstractThe 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

ABSTRACTPolarons 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

ABSTRACTWe 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

ABSTRACTThe 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

ABSTRACTTaking 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

ABSTRACTWe 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

ABSTRACTIn 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

ABSTRACTA 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.
Fabrication and properties of low temperature sintered PZT-PMN films
Authors: Stytsenko Eugene , Daglish Marc 
Published: April 2011

ABSTRACTA 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

ABSTRACTHigh-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

ABSTRACTMedium-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

ABSTRACTEpitaxial 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

ABSTRACTIndium-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

ABSTRACTThe 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

ABSTRACTAluminium 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

ABSTRACTWe 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

ABSTRACTUsing 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

ABSTRACTThe 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

ABSTRACTPt/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

ABSTRACTThere 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

ABSTRACTIn 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).