bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical Properties of Thin Nitrogen-Doped Ultrananocrystalline Diamond Films
Authors: Polyakov V.I. , Rukovishnikov A.I. , Pimenov S.M. , Carlisle J.A. , Gruen D.M. 
Published: April 2011

ABSTRACTThe electrical properties of ultrananocrystalline diamond (UNCD) films of approximately 1μm thickness were studied. UNCD films were deposited on p-type Si substrates from CH4/Ar/N2 gas mixtures using microwave plasma CVD techniques. It was found that the UNCD films with higher nitrogen concentration and higher electron conductivity have substantially higher concentration of shallow levels with activation energy of about 0.05 eV. The change of concentration, activation energy and capture cross-section of nitrogen-induced levels for UNCD films synthesized using different nitrogen concentration in the plasma was studied by charge– based deep level transient spectroscopy.
Direct Synthesis of Silicon Nanowires using Silane and Molten Gallium
Authors: Sharma Shashank , Sunkara Mahendra K. , Dickey Elizabeth C. 
Published: April 2011

ABSTRACTWe report for the first time, bulk synthesis of single crystalline silicon nanowires using molten gallium pools and an activated vapor phase containing silane. The resulting silicon nanowires were single crystalline with <100> growth direction. Nanowires contained an unexpectedly thin, non-uniform oxide sheath determined using high-resolution Transmission Electron Microscopy (TEM). Nanowires were tens of nanometers in diameter and tens to hundreds of microns long. The use of activated gas phase chemistry containing solute of interest over molten metal pools of low-solubility eutectics such as gallium offer a viable route to generate nanowire systems containing abrupt compositional hetero-interfaces.
Microstructure of the Silicon Film Prepared Near the Phase Transition Regime from Amorphous To Nanocrystalline
Authors: Zhang Shibin , Liao Xianbo , Xu Yanyue , Hu Zhihua , Zeng Xiangbo , Diao Hongwei , Luo Muchang , Kong Guanglin 
Published: April 2011

ABSTRACTA kind of hydrogenated diphasic silicon films has been prepared by a new regime of plasma enhanced chemical vapor deposition (PECVD) near the phase transition regime from amorphous to nanocrystalline. The microstructural properties of the films have been investigated by the micro-Raman and Fourier transformed Infrared (FT-IR) spectra and atom force microscopy (AFM). The obtained Raman spectra show not only the existence of nano-scaled crystallites, but also a notable improvement in the medium-range order of the diphasic films. For the FT-IR spectra of this kind of films, it notes that there is a blueshift in the Si-H stretching mode and a redshift in the Si-H wagging mode in respect to that of typical amorphous silicon film. We discussed the reasons responsible for these phenomena by means of the phase transition, which lead to the formation of a diatomic hydrogen complex, H2* and their congeries.
Determination of the Charge Attached to Micro-scale Devices Used in Fluidic Self-Assembly Processes
Authors: Tkaczyk Eric , Handa Vandna , Lee Sangwoo , McNally Helen , Gui Lichuan , Wereley Steve , Bashir Rashid 
Published: April 2011

ABSTRACTSelf-assembly of micron sized and smaller particles has previously been demonstrated using biologically inspired events such as DNA hybridization and interactions of ligands and receptors. In order to implement these techniques to create practical electronic devices, a quantitative measure of the amount of substance attached to the device surface just prior to the final assembly is essential. In the present investigation, this crucial quantity was investigated from the electrophoretic mobility of particles, which was ascertained by examining their motion under applied electric fields ranging from 0 to 1 V/mm. Sequential CCD camera images processed with custom software enabled calculation of particle velocities during their viscous motion in an inexpensive electrophoresis chamber filled with a low-conductivity buffer solution. A linear fit through the velocity vs. electric field data points yielded the electrophoretic mobility, which was utilized in the Stokes equation to calculate the net amount of charge present on each device. For 5.44 micron carboxyl-coated polystyrene beads, this method indicated a charge of 2.69e-15 C per particle. The manufacturer of the beads, Spherotech corporation, quoted 6.37e-11 C as the expected charge. The more than three orders of magnitude discrepancy is at least partially attributable to the electrophoretic retardation and relaxation effects of small electrolyte ions in the buffer solution. The method was also applied to silicon islands in the shape of a cone frustum with similar dimensions to the beads. A mercapto-ethane-sulfonate monolayer, attached via thiol bonds to the gold-coated surface of the islands, provided the charge. The amount of charge on an island was calculated to average 2.48e-15 C, corresponding to a density of 3.82e10 mercapto-ethane-sulfonate groups per square centimeter of Au surface.
Nanowire and Nanotube Materials Prepared from Polymer Fiber Templates
Authors: Dong Hong , Nyame Verrad , Jones Wayne E. 
Published: April 2011

ABSTRACTThe preparation of well-defined nanomaterials using template methods is well established in the materials literature including porous ceramics, open-framework layered structures and porous membranes. In an effort to prepare thermally and electrically conductive nanowire and nanotube materials, we have recently prepared carbon tubes using polymer fibers produced from an electrostatic, non-mechanical “electrospinning” process as templates. Poly(methyl methacrylate) (PMMA) fibers with average diameter of 150–200 nm were initially fabricated as core materials. The fibers were subsequently coated with a thin layer (20∼50 nm) of conductive polypyrrole (PPy) by in-situ polymerization. Upon high temperature (1000 °C) treatment under inert atmosphere, the PMMA core fibers decomposed completely, followed by carbonization of the PPy wall. The structure of the carbon tubes subsequently produced was demonstrated by SEM and TEM. The carbon tubes were analyzed by infrared, elemental analysis and electron diffraction. The results show that the tubes are largely carbon with a small amount of nitrogen and a relatively low crystallinity.
Characterization Of SnO2 Nanoparticles Deposited Via Layer-by-Layer Self Assembly And Investigation Of Their Sensing Properties
Authors: Ghan R. C. , Lvov Y. , Besser R. S. 
Published: April 2011

ABSTRACTA technique of Layer-by-Layer (LbL) self-assembly is used to deposit SnO2 nanoparticles on Quartz Crystal Microbalance (QCM) resonators, and on glass substrates which the authors believe has not been previously reported. Characterization of self-assembled SnO2 layers has been performed using QCM, Scanning Electron Microscopy (SEM), and Zeta Potential analysis.We have successfully deposited SnO2 nanoparticles on QCM resonator using self-assembly technique. LbL self-assembly is a method of organization of ultra-thin films by interlayer electrostatic attraction. The thickness and mass of the self-assembled layers can be characterized by the frequency shift obtained using the QCM and empirical equations relating change in frequency with mass and thickness of deposited layers. The deposition of SnO2 nanolayers exhibited a linear reproducibility and the process of self-assembly was independent of the residence time of QCM resonator in the SnO2 nanoparticle colloidal solution. High resolution SEM analysis reveals that the SnO2 nanoparticle layers are uniformly deposited across the entire substrate. Electrical characterization was performed on SnO2 nanoparticle layers self-assembled on glass substrates which were patterned for two point (current-voltage) IV characteristic measurements. Two classes of samples were used. One sample was self-assembled glass substrate patterned with electrical contacts and calcined (baked at 350°C for one hour) to eliminate interlayered polyions and the other sample was not calcined. Results revealed that the calcined samples demonstrated linear ohmic behavior but the uncalcined showed some spurious points which we believe are due to the polyion layers.Characterization of the self-assembled SnO2 nanoparticles is being carried out with the intention of fabricating a high-selectivity μ-gas sensor. A test chamber has been fabricated and results of resistance behavior of the sensor with variation in temperature have been presented.The sensor can find applications in high selectivity sensing of chemical, industrial, domestic, and hazardous environments. After further research and development, this μ-gas sensors could be made generic to sense a variety of gases and employed for integrated on-chip product analysis in multiple chemical microsystem applications.
Fracture Mechanical Evaluation of GaAs Wafers
Authors: Schaper M. , Jurisch M. , Bergner F. , Hammer R. 
Published: April 2011

ABSTRACTStrength and fracture toughness of (100) oriented GaAs wafers are analyzed by fracture and indentation testing. Using finite element method (FEM) critical fracture stresses are calculated from the fracture loads of wafers tested under biaxial bending, whereas atomic force (AFM), scanning electron microscopy (SEM) and acoustic C-scan microscopy of deformation and cracking patterns around micro- and nano-indentations provided information on yielding, crack initiation and crack growth resistance. Through fracture mechanical evaluation of these results critical defect sizes are derived, which are tolerable without strength degradation. It is shown, that a fracture strength of at least 800MPa can be achieved by careful fabrication even of 6' wafers. This figure is much higher then the prescribed minimum strength level estimated to avoid premature failures during wafer handling and processing routes.
High-Resolution Study of Light and Heat Patterns in Infrared Emitting Devices
Authors: Malyutenko V.K. 
Published: April 2011

ABSTRACTWe report on light and heat distributions in the active area of infrared lasers and light-emitting diodes operating at 300 K in the 0, 8–4,7 μm spectral range. To separate light and heat produced by these devices, we developed a high-resolution multi-spectral infrared (<1 m, 3–5 m and 8–12 m ranges) “vision” facility capable of providing <20 m spatial resolution and 10 s temporal resolution. We show how current crowding and Joule heating combined drastically decrease integral power emitted by light-emitting diodes and provoke remarkable non-uniformity in light and heat maps. As concerning stripe lasers, we comment on heat spreading and heat bottlenecks inside the laser dome and quality of heat sink.
A Study on Impact of Process Parameters to Metal Organic Chemical Vapor Deposition Grown (002) Zinc Oxide Thin Films, at 320°C
Authors: Chang Yuneng , Lu Hengchuan , Hung Yumeng , Lee Chunsung , Chen Jianming , Jian Yichang 
Published: April 2011

ABSTRACTThis paper reports preparation of highly oriented (002) ZnO films by atmospheric pressure CVD at 320°C, which is far below previous reported values. In this study, a cold wall horizontal system was used to thermally decompose sublimed zinc acetylacetonate (Zn(acac)2, Zn(C5H702)2) vapor, and reacted with water vapor to produce ZnO films at temperatures above 320°C. Through experimental data, we discovered that low deposition temperature, using water vapor as co-reactant and substrates with ZnO buffer layer pre-coated by PVD are the key factors to prepare (002) ZnO films. By using Si(100) pre-coated with sputtered ZnO amorphous buffer layer as substrates, the ZnO growth rate is highest. While using copper oxide pre-coated Si substrates gave the lowest growth rate, and deposited ZnO film is amorphous. Considering influence of CVD co-reactant, using Zn(acac)2 and water vapor gives higher growth rate and better crystallinity than CVD using Zn(acac)2 and oxygen. Water vapor may supply hydrogen to react with released acetylacetonyl ligand (C5H7O2), and help the formation of stable acetylaceton (C5H8O2) molecule. DPA shows that film contain 46% O and 54% Zn. XPS of Zn Auger identified the valence of Zn being Zn2+. It seems that excessive Zn might present as discrete Zn2+ dispersed between ZnO lattices.
The Role of Hydrogen in Laser Crystallized Polycrystalline Silicon
Authors: Nickel N. H. , Brendel K. 
Published: April 2011

ABSTRACTPolycrystalline silicon produced by laser crystallization of hydrogenated amorphous silicon contains large amounts of residual hydrogen. This reservoir of hydrogen can be used to passivate additional grain boundary defects by annealing the specimens at low temperatures in vacuum. Information on hydrogen bonding is obtained from hydrogen diffusion measurements. Laser crystallization results in a pronounced increase of the hydrogen binding energy in the resulting poly-Si samples compared to the amorphous precursor material. Fully crystallized poly-Si contains H concentrations of up to 17 at.%.
500 °C Formation of Poly-Si1-xGex (x≥ 0.5) on SiO2 by Ion-beam Stimulated Solid Phase Crystallization
Authors: Tsunoda Isao , Kanno Hiroshi , Kenjo Atsushi , Sadoh Taizoh , Miyao Masanobu 
Published: April 2011

ABSTRACTIon beam stimulated solid phase crystallization of a-Si1-xGex (0 ≤ x ≤ 1) on SiO2 has been investigated. The critical temperature to cause crystal nucleation can be successfully decreased by 150 °C for a-Si1-xGex with all Ge fractions (0 - 100 %) by using ion stimulation. As a result, crystal growth below the softening temperature (∼ 500 °C) of glass substrates was achieved for samples with Ge fractions exceeding 50 %. This method combined with Ge doping and ion stimulation will be a powerful tool to fabricate poly-SiGe TFTs on low cost glass substrates.
Exchange Bias and Training Effect in Polycrystalline Antiferromagnetic/Ferromagnetic Bilayers
Authors: Kirschner Markus , Suess Dieter , Schrefl Thomas , Fidler Josef 
Published: April 2011

ABSTRACTExchange bias and training effect are simulated for IrMn/NiFe bilayers. As a function of the thickness of the antiferromagnet the bias field shows a maximum for a thickness of 22 nm. For decreasing antiferromagnetic thickness the domain wall energy approaches zero. For large thicknesses the high anisotropy energy hinders switching of the antiferromagnetic grains resulting in weak bias. Starting from the field cooled state as initial configuration a bias field of about 8 mT is obtained assuming a antiferromagnetic layer thickness of 20 nm, a ferromagnetic layer thickness of 10 nm, and a grain size of 10 nm. The next hysteresis cycle shows a reduction of the bias field by about 65%. Exchange bias and training effect in fully compensated antiferromagnet/ferromagnet bilayers are explained with a simple micromagnetic model. The model assumes no defects except for grain boundaries, and coupling is due to spin flop at a perfect interface. The simulations show that a weak exchange interaction between randomly oriented antiferromagnetic grains and spin flop coupling at a perfectly compensated interface are sufficient to support exchange bias.
Mössbauer Characterization of Iron Oxide Nanoclusters Grown within Aluminosilicate Matrices
Authors: Papaefthymiou Georgia C. , Bustamante A. , Scorzelli Rosa B. 
Published: April 2011

ABSTRACTMössbauer spectroscopy uses the resonant absorption of nuclear radiation by 57Fe to probe the electronic and internal magnetic structure of iron based magnetic materials. The technique has a characteristic measuring time of 10 ns enabling investigation of spin relaxation phenomena in nanoscale particles; and determination of their magnetic properties in the absence of externally applied magnetic fields. We report on Mössbauer studies of γ-Fe2O3 nanoparticles synthesized within hexagonally packed mesoporous MCM-41 aluminosilicate matrices with cylindrical pores of 2.5 nm diameter. Data analysis allowed differentiation of particle-matrix interfacial versus particle-core interior iron sites. Interfacial iron atoms experience large electric field gradients resulting in quadrupole splitting values of ΔEq (surface) = (1.25 ± 0.05) mm/s, while core atoms exhibit smaller values of δEq (core) = (0.73± 0.05) mm/s at room temperature. Similarly, differences were observed in the values of the internal hyperfine fields at low temperatures indicating reduced strength in the exchange interactions at the particle surface, with interfacial atoms experiencing internal fields Hhf (surface) = (458 ± 1) kOe reduced relative to the core Hhf (core) = (488 ±1) kOe at 4.2 K. Particle/matrix interactions at the surface appear to perturb the electronic interactions deeper into the core than the magnetic exchange interactions.
Epitaxial Si films Grown on Lattice Matched (LaxY1-x)O3/Si (111) Structures by Molecular Beam Epitaxy
Authors: Narayanan V. , Guha S. , Bojarczuk N. A. , Copel M. 
Published: April 2011

ABSTRACTGrowth of epitaxial Si epitaxial overlayers on lattice matched (LaxY1-x)2O3/Si (LaYO/Si) structures has been investigated by high resolution transmission electron microscopy and reflection high energy electron diffraction. Results indicate that smooth two-dimensional near lattice-matched LaYO (111) films can be grown on Si (111) substrates. However, subsequent Si epitaxial growth on the LaYO/Si structures nucleates as three-dimensional islands, a consequence of the high energy of the Si overlayer/LaYO interface. We have investigated the effect of growth temperature on the microstructure of the Si overlayers. Higher temperatures resulted in the nucleation of large faceted islands and rough overlayers while lower temperatures result in smaller islands that coalesce at an early stage and produce smoother films. In addition, formation of planar defects in these films is attributed to stacking errors on the {111} facets of initial Si islands with lower temperatures resulting in a higher density of stacking faults and twins.
Role of the First Atomic Layers in Epitaxial Relationship and Interface Characteristics of SrTiO3 Films on CeO2/YSZ/Si(001)
Authors: Yamada Tomoaki , Kiguchi Takanori , Wakiya Naoki , Shinozaki Kazuo , Mizutani Nobuyasu 
Published: April 2011

ABSTRACTThe role of the first atomic layers in epitaxial relationship and interface characteristics of SrTiO3 films on CeO2/yttria-stabilized zirconia (YSZ)/Si(001) substrates was investigated. Although SrTiO3 film deposited on CeO2/YSZ/Si directly was preferentially (110)-oriented, epitaxial SrTiO3(001) films could be grown on CeO2/YSZ/Si by controlling first atomic layer of the films. In the case of SrTiO3 film starting from TiO2 layer, the neither ion drift nor charge injection occurred in the SrTiO3/CeO2 interface. On the other hand, for the film starting from SrO layer, an injection-type hysteresis was observed. This is probably due to the electron traps in the interface.
X-ray Photoelectron and UV Photoyield Spectroscopic Studies on Structural and Electronic Properties of SrxBiyTa 2O9 Films
Authors: Takahashi Mitsue , Noda Minoru , Okuyama Masanori 
Published: April 2011

ABSTRACTPhotoelectron spectra by X-ray photoelectron spectroscopy (XPS) and UV-photoyield spectroscopy (UV-PYS) have been analyzed to study O2-annealing effects on band diagrams of ferroelectric SrxBiyTa2O9 (SBT) thin films deposited by pulsed laser deposition (PLD) and metalorganic dcecomposition (MOD) methods. XPS studies on the annealed PLD-SBT film has shown a rapid shift in its Bi 4f core peaks from the oxidized to the metallic ones, as the film suffer Ar+ bombardment. Surface of the annealed film has exhibited lower Fermi level than the as-deposited one in UV-PYS. The result suggests O2-annealing can suppress leakage current through PLD-SBT films. The UV-PYS studies on MOD-SBT have shown almost the intrinsic Fermi levels before and after the additional annealing. The XPS studies have shown that the additional annealing is not effective to improve stabilities of (Bi2O2)2+ layers, once the film is baked and crystallized.
An angular dependent X-ray photoemission study of Indium-tin-oxide surfaces
Authors: Fong H. H. , Song W. J. , So S. K. 
Published: April 2011

ABSTRACTThe surface properties of indium-tin-oxide (ITO) thin films treated by UV ozone or plasma were analyzed by angular dependent X-ray photoelectron spectroscopy (ADXPS) and by ultraviolet photoemission (UPS). The chemical composition, chemical states and the work function of the ITO surfaces were deduced. Our analysis indicate that ITO surface is Sn-rich. Both UV ozone and O-plasma treatments are most effective in removing surface hydrocarbon. Among all treatments, O-plasma treated surface achieved the highest work function of 4.4eV, whereas argon ion sputtered surface had the lowest work function of 3.9eV. Both O-plasma and UV ozone treatments increase the surface oxygen concentration. It is proposed that O2-ions diffuse into ITO. The diffusion length is about 50Å as deduced from ADXPS. The stoichiometry of the surface is the major factor in controlling the surface work function of ITO. A surface band bending model is proposed to account for the change of work function due to “oxidized” ITO surface after UV-ozone or oxygen plasma treatments.
Atomistic simulation study of misfit strain relaxation mechanisms in heteroepitaxial islands
Authors: Dongare Avinash M. , Zhigilei Leonid V. 
Published: April 2011

ABSTRACTThe mechanisms of the misfit strain relaxation in heteroepitaxial islands are investigated in two-dimensional molecular dynamics simulations. Stress distributions are analyzed for coherent and dislocated islands. Thermally-activated nucleation of misfit dislocations upon annealing at an elevated temperature and their motion from the edges of the islands towards the positions corresponding to the maximum strain relief is observed and related to the corresponding decrease of the total strain energy of the system. Differences between the predictions of the energy balance and force balance criteria for the appearance of misfit dislocations is discussed. Simulations of an island located at different distances form the edge of a mesa indicate that the energy of the system decreases sharply as the island position shifts toward the edge. These results suggest that there may be a region near the edge of a mesa where nucleation and growth of ordered arrays of islands is favored.
Experiments with in-situ thin film telephone cord buckling delamination propagation
Authors: Volinsky Alex A. 
Published: April 2011

ABSTRACTThere are many different stress relief mechanisms observed in thin films. One of the mechanisms involves film debonding from the substrate. In the case of tensile residual stress a network of through-thickness cracks forms in the film. In the case of compressive residual stress thin film buckling and debonding from the substrate in the form of blisters is observed. The buckling delamination blisters can be either straight, or form periodic buckling patterns commonly known as telephone cord delamination morphology.The mechanics of straight-sided blisters is well understood. Current study relies on the in-situ observation of phone cord delamination propagation in different thin film/substrate systems. Both straight and phone cord delaminations are shown to simultaneously propagate in the same film system. Straight-sided blisters propagate several times faster than the phone cords, and may be followed by thin film fracture along the line of maximum film buckling amplitude. Phone cord delaminations originally start as straight-sided blisters, but then deviate to the periodic phone cord geometry due to the fact that the compressive residual stress in the film is biaxial. Digital analysis of motion recordings shows that partial crack “healing” is present at the curved portions of the phone cords due to the “secondary” buckling pushing thin film back to the substrate. These experimental observations allow for the correct interpretation of the telephone cord delamination morphology.