bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laser Thin Film Processing of Biopolymers: Mussel Adhesive Protein Analog
Authors: Doraiswamy Anand , Narayan R J , Dinu C Z , Cristescu R , Messersmith P B , Stafslien S , Chrisey D B 
Published: April 2011

AbstractMussel adhesive protein analogs are biologically-derived materials that possess unique adhesion properties. We have demonstrated thin film growth of DOPA modified- PEG block copolymer mussel adhesive protein analogs using a novel laser processing technique known as matrix assisted pulsed laser evaporation (MAPLE). The main functional groups of the mussel adhesive protein analog are present in the MAPLE-transferred film. These novel polymer thin films have numerous medical, electronic, and marine applications.
Dielectric and Optical Properties of Polymer Confined in Random Porous Matrices
Authors: Aliev Fouad 
Published: April 2011

AbstractWe report the results of the investigations of the influence of confinement on the glass transition and dynamics of the a-relaxation processes in poly(octylmethacrylate) (POMA) by dielectric spectroscopy. The polymer was synthesized directly in pores of the porous glass matrix with interconnected and randomly oriented pores with an average pore size of 100 nm by free radical polymerization of the monomer. We found that confinement is resulted in the reduction of the glass transition temperature Tg of the polymer. This change in Tg was mainly due to the existence of a developed pore wall-polymer interface and difference in the dynamic behavior of polymer in the surface layers compared to that in the bulk. Complementary light scattering experiments show that in 100 nm matrices containing the polymer an anomalous change in light scattering, which switches the composite from the opaque state to the transparent, in a narrow temperature range around T = 60 °C. These changes could be explained by assuming that at low temperatures (opaque state) the orientational order of the relatively long linear aliphatic side groups is induced by the inner pore surface. The assumption of the formation of the orientationally ordered regions at the pore wall in confined POMA is in agreement with the molecular structures of the polymer and the surface of silica.
Effect of Zinc Oxide Nanocrystals in Media Containing E. coli and C. xerosis Bacteria
Authors: Merced Triana , Santos Stephanie , Rivera Omayra , Villalba Nicole , Baez Yahira , Gaudier José , Avalos Javier , Perales Oscar , Tomar M. S. , Parra-Palomino A. , Avalos Javier 
Published: April 2011

ABSTRACTThe present investigation is centered on the study of the growth curves of E. coli and C. xerosis bacteria in the presence of nanosize particles of Zinc Oxide. Previous works demonstrated the sensitivity of the bacteria, when these were reproduced in media that contain nanoparticles of luminescent silicon and Cobalt Ferrite. Doped ZnO nanocrystals were synthesized by conventional precipitation in ethanol solutions as reported by Spanhel and Anderson for bare ZnO. In our case, the syntheses were carried out under room-temperature conditions.The experimental results of E. coli bacteria in contact with a stable suspension of nanoparticles of Zinc Oxide, shows a growth curve without adaptation period. Moreover a short and slowly logarithmic stage has been observed, reaching the stationary stage after approximately four hours compared with one in absence of the nanoparticles (standard curve). During the observations, a change in the lifetime of the bacteria (metabolism) with particulate was noticed,as well as the beginning of the mortality stage. However, different results were recorded for silicon and ferrite. For the case of the bacteria C. xerosis, the curve with particles is above its standard curve, for all times with none of the oscillations which occured in the nanometer silicon. For these bacteria the beginning of the mortality stage is observed when they have particles. For both bacteria with Zinc Oxide nanoparticles this occurs approximately after nine hours.
Tin-Doped Hematite Nanoparticles for Gas-Sensing Applications
Authors: Sorescu Monica , Diamandescu Lucian , Tarabasanu-Mihaila Doina 
Published: April 2011

ABSTRACTStructural and morphological characteristics of (1-x)α-Fe2O3-xSnO2 (x=0.0-1.0) nanoparticles obtained under hydrothermal conditions have been investigated by X-ray diffraction (XRD) and Mössbauer spectroscopy. On the basis of the Rietveld structure refinements of the XRD spectra at low tin content, it was found that Sn4+ partially substitutes for Fe3+ at the octahedral sites. The mean particle dimension decreases from 70 to 6 nm as the molar fraction x increases. The estimated solubility limits in the system of tin-doped hematite nanoparticles synthesized under hydrothermal conditions are x<0.2 for Sn4+ in α-Fe2O3 and x>0.7 for Fe3+ in SnO2.
Combining Sol-Gel Chemistry and Extrusion Process Toward Generating First Vanadium Oxide Macroscopic Fibers
Authors: Biette L. , Serier H. , Carn Florent , Achard Marie-France , Steunou Nathalie , Livage Jacques , Backov R. 
Published: April 2011

ABSTRACTUpon extrusion process, first vanadium oxide macroscopic fibers have been obtained. They are associated to longitudinal Young modulus from 15 to 25 GPa and depict strong high scale textural anisotropy as observed through cross-polarized microscopy. TEM observations and SAXS experiments reveal that those macroscopic fibers are made of nanoscopic ribbons associated to preferential orientation parallel to the macroscopic fiber main axis, while XRD and NMR investigations reveal a microstructure close to the V2O5.1.8H2O xerogels. These fibers can detect down to 0.1 ppm of ethanol within 16 seconds at 40°C.
Single Stranded DNA Decorated Carbon Nanotube Transistors for Chemical Sensing
Authors: Staii Cristian , Chen Michelle , Gelperin Alan , Johnson Alan T. 
Published: April 2011

ABSTRACTWe demonstrate that single walled carbon nanotube field effect transistors (swCN-FET) decorated with single stranded DNA (ss-DNA) form a new, versatile, and highly sensitive class of nanoscale chemical sensors. These sensors are based on ss-DNA as the chemical recognition site and swCN-FET as the electronic read-out component. The ss-DNA decorated swCN-FETs are sensitive to chemical species (odors) that do not cause a detectable response in bare, as-fabricated swCN-FETs. Furthermore, odor responses ss-DNA decorated FETs differ in sign and magnitude for different odors, and the response characteristics depend on the base sequence of the ss-DNA used to decorate the swCN. The sensor surface is self-regenerating: samples maintain a constant response with no need for sensor refreshing through at least several dozens gas exposure cycles. These remarkable attributes suggest that DNA-decorated swCN-FET sensors could be created with sensitivity to a large variety of compounds, as required for “electronic-nose” and “electronic tongue” applications in medicine and homeland security.
Dielectric Property Controls Using Crystal Structure Anisotropy In Bismuth Layer-Structured Dielectrics
Authors: Suzuki Muneyasu , Takahashi Kenji , Watanabe Takayuki , Takenaka Tadashi , Funakubo Hiroshi 
Published: April 2011

AbstractTemperature dependency of the dielectric property of c-axis-oriented SrBi4Ti4O15 films was investigated in a temperature range from 80 to 400 K. c-axis-oriented epitaxial films with the film thickness of 30 and 140 nm were grown on (100)cSrRuO3//(100)SrTiO3 substrates by metal organic chemical vapor deposition (MOCVD). Increasing lattice distortions along the a- and c-axes with decreasing film thickness was ascertained by XRD reciprocal space mapping. However, capacitance change normalized by the capacitance data at 300 K for with temperature was independent of the film thickness; it increased from 80 to 230 K and contrary decreased with increasing the temperature. Especially, the temperature coefficient of capacitance from 230 to 330 K was almost the same. It indicates that dielectric characteristics of these films for the temperature are independent of the film thickness in the actual use. Moreover, the same mesurement for the 120 nm-thick fiber-textured c-axis-oriented SrBi4Ti4O15 film deposited on the (100)cLaNiO3/(111)Pt/TiO2/SiO2/(100)Si substrate was also investigated. Resultant capacitance change with the temperature was basically the same with that of the epitaxial one, even though the temperature at maximum capacitance value was slightly shifted to lower temperature of 200 K. These data suggest that of capacitance change with the temperature was almost independent of the film thickness and the in-plane orientation.
Effect of Composition on Ferroelectric Response of Bi4-xSmxTi3O12 Thin Films
Authors: Dussan Sandra , Tomar Maharaj , Melgarejo Ricardo , Katiyar Ram 
Published: April 2011

AbstractBismuth titanate (Bi4Ti3O12) is an electroceramic within the Aurivillius phase material with week ferroelectric memory. However, the partial substitution of Bi ion by a trivalent rare earth resulted in improved ferroelectric polarization. We synthesized Bi4-xSmxTi3O12 by a solution chemistry route and thin films were deposited by spin coating on Pt (Pt/TiO2/SiO2/Si) substrate. X-ray diffraction studies of the films showed a stoichiometric solid solution for the composition x ≤0.85. The films showed fatigue free ferroelectric polarization (Pr = 19.8 µC/cm2) for the composition x = 0.70. The films showed low leakage current at room temperature, showing the possibility of lead free ferroelectric devices.
Structural dynamics of PZT thin films at the nanoscale
Authors: Grigoriev Alexei , Do Dal-Hyun , Kim Dong Min , Eom Chang-Beom , Adams Bernhard , Dufresne Eric M. , Evans Paul G. 
Published: April 2011

AbstractWhen an electric field is applied to a ferroelectric the crystal lattice spacing changes as a result of the converse piezoelectric effect. Although the piezoelectric effect and polarization switching have been investigated for decades there has been no direct nanosecond-scale visualization of these phenomena in solid crystalline ferroelectrics. Synchrotron x-rays allow the polarization switching and the crystal lattice distortion to be visualized in space and time on scales of hundreds of nanometers and hundreds of picoseconds using ultrafast x-ray microdiffraction. Here we report the polarization switching visualization and polarization domain wall velocities for Pb(Zr0.45Ti0.55)O3 thin film ferroelectric capacitors studied by time-resolved x-ray microdiffraction.
The Formation of Smooth, Defect-free, Stoichiometric Silicon Carbide Films from a Polymeric Precursor
Authors: Pitcher Michael , Bianconi Patricia 
Published: April 2011

AbstractSilicon carbide (SiC) materials, which are used in a variety of applications, are often produced using powder processing, sintering or bulk crystal growing techniques. The formation of silicon carbide films or shaped products, via these methods, is often extremely difficult and/or requires high temperatures. Here we report the synthesis and characterization of a polymeric precursor, Polymethylsilyne (PMSy), and it subsequent conversion to â-SiC. The polymer is simple to synthesize and is easily manipulated in air. The ceramic produced from PMSy is extremely pure, stoichiometric SiC and is produced in high yields (up to 85%). The ceramic films that can be produced from PMSy on a variety of substrates, from ceramics to metals, are again stoichiometric SiC and are smooth, continuous and defect free; possibly enabling the use of these films in electronic applications.
Novel Method for High Speed SiC Vapor Growth
Authors: Wang Xiaolin , Dang Cai , Zhang Hui , Dudley Michael 
Published: April 2011

AbstractSilicon carbide is a promising semiconductor material for electrical and optoelectronic applications in the area of high power, high temperature, high frequency and intense radiation. Many groups have worked on growing SiC bulk crystals by sublimation from SiC powder source at a temperature above 2000 oC under an argon environment. They have also worked on improving the crystal growth rate. Traditional approach is to increase furnace temperature to enhance the growth rate. However, high cost of inert crucible at high temperature and impurity caused by crucible degradation set limit on the maximum growth rate which can be achieved. Current existing crucible and other components in the furnace are no longer passive at high temperature. Also understanding of vapor transport during powder sublimation and the interplay between vapor transport and powder sublimation is important for the optimization of the sublimation growth process. A comprehensive numerical model combining heat transfer, sublimation, species transport, and powder porosity evolution of SiC sublimation growth process is developed in this paper. The mechanism of vapor transport is described, in which a driving force is introduced to explain vapor transport. A new method to increase crystal growth rate is proposed based on the model. The new method includes changing the initial powder porosity and creating a hole in the packed powder. Simulation results for the case with a central hole and without hole are presented. The results show that the powder sublimation rate increases by creating a hole, and it is also validated by experiments. The results also reveal that the mass of the as-grown crystal increases if the powder sublimation rate increases. Finally, the powder geometry is optimized using numerical simulations.
Recent Results From Epitaxial Growth on Step Free 4H-SiC Mesas
Authors: Neudeck Philip G. , Trunek Andrew J. , Spry David J. , Powell J. Anthony , Du Hui , Skowronski Marek , Bassim Nabil D. , Mastro Michael A. , Twigg Mark E. , Holm Ronald T. , Henry Richard L. , Eddy Charles R. 
Published: April 2011

AbstractThis paper updates recent progress made in growth, characterization, and understanding of high quality homoepitaxial and heteroepitaxial films grown on step-free 4H-SiC mesas. First, we report initial achievement of step-free 4H-SiC surfaces with carbon-face surface polarity. Next, we will describe further observations of how step-free 4H-SiC thin lateral cantilever evolution is significantly impacted by crystal faceting behavior that imposes non-uniform film thickness on cantilever undersides. Finally, recent investigations of in-plane lattice constant mismatch strain relief mechanisms observed for heteroepitaxial growth of 3C-SiC as well as 2H-AlN/GaN heterofilms on step-free 4H-SiC mesas will be reviewed. In both cases, the complete elimination of atomic heterointerface steps on the mesa structure enables uniquely well-ordered misfit dislocation arrays to form near the heterointerfaces with remarkable lack of dislocations threading vertically into the heteroepilayers. In the case of 3C-SiC heterofilms, it has been proposed that dislocation half-loops nucleate at mesa edges and glide laterally along the step-free 3C/4H interfaces. In contrast, 3C-SiC and 2H-AlN/GaN heterofilms grown on 4H-SiC mesas with steps exhibit highly disordered interface misfit dislocation structure coupled with 100X greater density of dislocations threading through the thickness of the heteroepilayers. These results indicate that the presence of steps at the heteroepitaxial interface (i.e., on the initial heteroepitaxial nucleation surface) plays a highly important role in the defect structure, quality, and relaxation mechanisms of single-crystal heteroepitaxial films.
Epitaxial Growth and Characterization of SiC on Different Orientations
Authors: Rowland Larry B. , Li Canhua , Dunne Greg T. , Fronheiser Jody A. 
Published: April 2011

AbstractBackground doping as well as intentional doping using nitrogen and trimethylaluminum have been investigated for 4H-SiC epitaxy on offcut Si face, C face, and a-axis substrates over a wide range of C:Si ratio. Smooth morphology can be obtained at a C:Si ratio of 2.0 on a-axis substrates but not on Si or C face material. Background doping levels of <1 × 1015 cm-3 were achieved on a-axis and Si face material. Nitrogen incorporated much more efficiently on C face and a-axis as compared to Si face. Aluminum incorporated most efficiently on Si face and least efficiently on C face. Both of the above dopant incorporation trends were most pronounced at high C:Si ratios and were small or virtually absent at low C:Si ratios.
Comparison of Parameter Extraction Techniques for SiC Schottky Diodes
Authors: Weng Ming Hung , Horsfall Alton B. , Wright Nick G. , Vassilevski Konstantin V. , Nikitina Irina P. 
Published: April 2011

AbstractSchottky barrier diodes fabricated on Silicon carbide have been demonstrated as gas sensors for deployment in extreme environments. It has been shown that the interfacial layer formed at the Metal – Semiconductor junction, determines both the sensitivity and the reliability of the device. Hence, accurate knowledge of the thickness and interfacial trap density of this layer is required to make predictions of the behaviour of the sensor in the environment under investigation and to predict its variation with time. Diode parameters, such as the ideality factor, barrier height and series resistance have been extracted from experimental measurements on Palladium Schottky Barrier diodes on 4H SiC, over a range of temperatures. The comparison of the parameters extracted from modified Norde function, Cheung's method and Thermonic Emission model has been performed. The variation in the barrier height obtained is quite marked between the different techniques. The reverse I-V characteristics have been used to extract thickness of the interfacial layer, by fitting to the experimental data using the TEBIL model to extract the value of Dit from ä and the ideality factor, assuming the interfacial layer is stoichiometric SiO2 . This allows a comparison between the effective interfacial layer behaviour for the different parameter extraction techniques and demonstrates that knowledge of this interfacial layer is influenced by the technique selected.
Ink-Jet Printing of Encapsulated Bacteria
Authors: Coldren Faith Marie , McGuirt John B. , Levi Nicole , Palavecino Elizabeth , Carroll David L. 
Published: April 2011

AbstractEven though viability for printed bacteria has been demonstrated, the effect of thermal ink-jet printing on cellular ultrastructures is unknown. Retention of viability is useful when colony growth is desired. However, when bacteria are isolated from a human infection they often exhibit characteristics that can be lost when grown in standard laboratory cultures. Ideally, individual bacteria from an infection could be printed and studied without extensive culturing or processing.We have investigated the gram-positive organism Staphylococcus aureus and the extracellular polymeric ultrastructure that encapsulates the bacterial cell. The capsule is composed of cell-wall associated polysaccharides. Our goal was to use ink-jet printing to spatially control the placement of S. aureus, without affecting the extracellular ultrastructure. Observation by scanning electron microscopy comparing the integrity and uniformity of encapsulated S. aureus before and after thermal ink-jet printing suggests that the capsule is disrupted, possibly completely removed, during printing.
Dynamical Fracture Instabilities Due to Local Hyperelasticity at Crack Tips
Authors: Buehler Markus J. , Gao Huajian 
Published: April 2011

ABSTRACTWhen materials break and cracks propagate, bonds between atoms are broken generating two new material surfaces. Most existing theories of fracture assume a linear elastic stress-strain law. However, the relation between stress and strain in real solids is strongly nonlinear due to large deformation near a moving crack tip, a phenomenon referred to as hyperelasticity or nonlinear elasticity. Cracks moving at low speeds create atomically flat mirror-like surfaces, whereas cracks at higher speeds leave misty and hackly fracture surfaces. This change in fracture surface morphology is a universal phenomenon found in a wide range of different brittle materials, but the underlying physical reason has been debated over an extensive period. Using massively parallel large-scale atomistic simulations employing a new, simple atomistic material model allowing a systematic transition from linear elastic to strongly nonlinear material behaviors, we show that hyperelasticity can play a governing role in dynamical crack tip instabilities in fracture of brittle materials. We report a generalized model that treats the instability problem as a competition between different mechanisms controlled by local stress field and local energy flow near the crack tip. Our results indicate that the fracture instabilities do not only appear in defected materials, but instead are an intrinsic phenomenon of dynamical fracture. Our findings help to explain controversial experimental and computational results, including experimental observation of crack propagation at speeds beyond the shear wave speed in rubber-like materials.
Effect of MeV Si Ion Bombardment on Thermoelectric Characteristics of Sequentially Deposited SiO2/AuxSiO2(1-x) Nanolayers
Authors: Budak S. , Zheng B. , Muntele C. , Xiao Z. , Muntele I. , Chhay B. , Zimmerman R. L. , Holland R. L. , Ila D. 
Published: April 2011

ABSTRACTWe made 50 and 100 periodic nano-layers of electro-cooling system consisting of SiO2/AuxSiO2(1−x) super lattice with Au layer deposited on both side as metal contact using Ion Beam Assisted Deposition (IBAD) system. The deposited multi-layer films have a periodic structure consisting of alternating layers where each layer is between 1-10 nm thick. The ultimate objective of this research is to tailor the figure of merit of layered structures used as thermoelectric generators. The super lattices were then bombarded by 5 MeV Si ion at different four fluences to form nano-cluster structure. The film thickness and stoichiometry were monitored by Rutherford Backscattering Spectrometry (RBS) before and after MeV bombardments. We measured the thermoelectric efficiency of the fabricated device before and after MeV bombardments. To accomplish this we measured the cross plane thermal conductivity by 3rd harmonic method, measured cross plane Seebeck coefficient, and measured electric conductivity using Van Der Pauw method before and after 5 MeV Si Bombardments. As predicted the electronic energy deposited due to ionization by MeV Si beam in its track produces nano-scale structures which disrupt and confine phonon transmission therefore reducing thermal conductivity, increasing electron density of state so as to increase Seebeck coefficient, and electric conductivity, thus increasing figure of merit. We will present our findings during the meeting.* Research sponsored by the Center for Irradiation of Materials, Alabama A&M University and by the AAMURI Center for Advanced Propulsion Materials under the contract number NAG8-1933 from NASA, and by National Science Foundation under Grant No. EPS-0447675.