bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epitaxial Thin Films and Heterostrcutures of Copper-Oxide-Based Isotropic Metallic Oxides for Device Applications
Authors: Eom C. B. 
Published: April 2011

AbstractWe have grown epitaxial thin films of a new family of copper-oxide-based isotropic metallic oxides such as La6.4Sr1.6Cu8O20, La5BaCu6O13 and La6BaYCu8O20in situ by 900° off-axis sputtering. These metallic oxides are pseudo-cubic perovskites with essentially isotropic properties, which could be ideal normal metals for SNS junctions in superconducting devices. We have also grown epitaxial SNS superconducting heterostructures (c-axis YBa2Cu3O7 / La6.4Sr1.6Cu8O20 / c-axis YBa2Cu3O7) with a copper-oxide-based isotropic metallic oxide (La6.4Sr1.6Cu8O20) normal metal barrier. X-ray diffraction and cross-sectional transmission electron microscopy reveal these heterostructures to have high crystalline quality and clean interfaces. This material will facilitate fabrication of ideal SNS Josephson junctions with low boundary resistance due to its excellent chemical compatibility and lattice match with cuprate superconductors and will be useful for determining the source of interface resistance in such heterostructures.
Microstructural Study of CMR Films as a Function of Growth Temperature, As-Deposited and Annealed
Authors: Hawley M. E. , Wu X. D. , Arendt P. N. , Adams C. D. , Hundley M. F. , Heffner R. H. 
Published: April 2011

AbstractThe properties encompassed by the family of complex metal oxides span the spectrum from superconductors to insulating ferroelectrics. Included in this family are the new colossal magnetoresistive perovskites with potential applications in advanced high density magnetic data storage devices based on single or multilayer thin films units of these materials fabricated by vapor phase deposition (PVD) methods. The realization of this potential requires solving basic thin film materials problems requiring understanding and controlling the growth of these materials. Toward this end, we have grown La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3 on LaAlO3 single crystal substrates by pulsed laser and RF sputter deposition at temperatures from 500° C to 900° C and annealed at over 900° C for about 10 hours. The evolution of the microstructure of these films was studied by scanning probe microscopies and transmission electron microscopy (TEM).The results of SPM characterization showed that at the lower end of the growth temperature range, the as-grown films were polygranular with grain size increasing with temperature. The 500° C as-grown films appeared to be amorphous while the 750° C film grains were layered with terrace steps often one unit cell high. In contrast, films grown at 900° C consisted of coalesced islands with some 3-D surface crystals. After annealing, all films had coalesced into very large extended layered islands. The change in microstructure was reflected in a decreased resistivity of coalesced films over their unannealed granular precursors. Previous reported work on the growth of La0.84 Sr0.16MnO3 and La0.8Sr0 2CoO3 grown demonstrated the sensitivity of the microstructure to substrate and deposition conditions. Films grown on an “accidental” vicinal surface grew by a step flow mechanism.
Epitaxial Growth and Characterization of NbxTi1−xO2 Rutile Films by Oxygen-Plasma-Assisted Molecular Beam Epitaxy
Authors: Gao Y. , Chambers S. A. 
Published: April 2011

AbstractEpitaxial films of NbxTi1−xO2 rutile were grown on TiO2 (110) and (100) at 600 °C by oxygen-plasma-assisted molecular beam epitaxy using elemental Ti and Nb sources. The epitaxial films were characterized by means of reflection high-energy and low-energy electron diffraction (RHEED/LEED), x-ray photoelectron spectroscopy and diffraction (XPS/XPD), ultraviolet photoemission spectroscopy (UPS) and atomic force microscopy (AFM). The epitaxial films grow in a layer-by-layer fashion and have excellent short- and long-range structure order at x≤0.3 on TiO2(110) and at x≤0.15 on TiO2(100). However, the epitaxial films become rough and disorder at higher doping levels. Nb substitutionally incorporates at cation lattice sites, leading to NbxTi1−xO2 solid solutions. In addition, the oxidation state of Nb in the NbxTi1−xO2 films has been determined to be +4.
A Novel Technique for Determining Local Dielectric Function During Ferroelectric to Paraelectric Phase Transformation in Barium Titanate with a Transmission Eels
Authors: Katti Kalpana S , Qian Maoxu , Sarikaya Mehmet 
Published: April 2011

AbstractIn this work a transmission electron microscopy (TEM) technique was used in obtaining local dielectric properties calculated from optical parameters for dynamic investigation of the effect of cubic to tetragonal phase transformation in barium titanate. In order to obtain in situ local dielectric during phase transformation, Kramers-Kronig relations were applied using the transmission electron energy loss (EELS) measurements. The optical excitations in the EELS spectra were consistent with the band structure results. The Re (1/ε) (real part of the dielectric function) obtained from the energy loss data indicated a change at the phase transformation. A broadening of the valence plasmon excitation suggested an order-disorder nature to the cubic to tetragonal transformation. In situ electron energy loss near edge structure (ELNES) studies from 500–700 eV energy range near the O-K edge exhibited a pre-edge feature that is associated with the Ti-L1, edge which further indicates an order-disorder nature to the phase transformation. The significance of the results is discussed.
In-Situ Tem Studies of Recrystallization and Grain Growth in Al-Mg-Mn-Zr Alloys
Authors: Vetrano John S. , Bruemmer Steve M. , Robertson Ian M. 
Published: April 2011

AbstractRecrystallization and grain growth studies of Al-Mg-Mn-Zr alloys have been carried out in-situ in the transmission electron microscope. Nucleation sites were primarily on large (>I μm diameter) eutectic constituent particles. The sub-micron A16Mn dispersoids were observed to be effective as nuclei if present in clusters, and were effective at retarding grain boundary migration and dislocation motion. The smaller A13Zr precipitates seemed to have little effect on nucleation and growth, but were effective in pinning dislocations. These results have been analyzed in terms of precipitate size and shape in both the as-cold-worked microstructure and during recrystallization. The implications on the microstructural refinement of these alloys for improved superplastic properties will be discussed.
Electronic Irradiation Effect on Bi-Mo-O Catalysts Observed in a Hrtem Study
Authors: Avalos-Borja M. , Galvan D. H. , Ning X. G. 
Published: April 2011

AbstractWe studied by high resolution transmission electron microscopy (HRTEM) unsupported bismuth-molybdenum-oxide catalysts. The microscope utilized was a JEOL 4000 EX electron microscope with a resolution better than 0.19 nm (point to point). The image simulation were performed on a personal computer with the aid of a commercial program. With the aid of image simulation it is possible to identify γ-Bi2MoO6 and X-Mo4O11 phases, among several other possibilities that fit the interplanar spacings and angles.A very important aspect, thermal instability, was proved indirectly in the microscope, by the changes of the particles under the electron beam irradiation at 400 kV. After several minutes of irradiation, the amorphous surface layer was totally reconstructed to crystalline phases.The fact that we observe many phases in this sample, is certainly deleterious to the catalytic properties, since not all of them are active. Also the sensitivity to the beam indicates that minimum exposure microscopy has to be applied in order to prevent unecessary complications for phase identification.
In-Situ Tem Study of Crystallisation of Amorphous SbOx Films
Authors: Nayak R. , Petford-Long A. K. , Doole R. C. , Afonso C. N. 
Published: April 2011

AbstractAmorphous d.c. sputtered SbOx films (0.19< x<2.0) have been found to be fast crystallising materials sensitive to nano- and pico-second laser pulses, and have potential applications as optical data-storage media. They were crystallised in-situ in a JEOL 4000EX TEM, and the crystallisation recorded onto video tape. The crystallisation of the SbO0.37 films occurred by random nucleation followed by growth until coalescence. In contrast the crystallisation of the SbO0.533 films occurred by surface crystallisation across the whole film followed by bulk crystallisation through the film, during which contrast in the TEM increased steadily. Analysing the video frames in an image processing package enabled kinetic parameters such as transformation index and activation energy to be extracted. High resolution transmission electron microscopy showed the crystalline phase to contain nano-crystallites approximately 10 nm in size in a less-ordered matrix.
An in Situ Stm Study of Cu and Ni Electrodeposition
Authors: Moffat T. P. 
Published: April 2011

AbstractAn STM study has been initiated to investigate the various processes associated with electrodeposition of Cu-Ni multilayers on Cu (100). The substrates were prepared by electropolishing in phosphoric acid followed by immersion in 10 mmol/l HCl. A (√2×√) R°45 adlattice of oxidatively adsorbed chlorine is formed under these conditions. The adlayer stabilizes the surface steps in the 〈100〉 direction which corresponds to the close packed direction of the chloride adlattice. In dilute mmo1/1 solutions of cuprous ion, reduction occurs under mass transport control with the electrocrystallization reaction proceeding by step flow in the 〈100〉 direction. At more negative potentials chloride is reductively desorbed. Coincident with desorption the highly kinked metal steps become frizzy and move towards adopting the close packed 〈110〉 orientation of the metal lattice. Preliminary experiments on heteroepitaxial nickel deposition reveal regions where electrocrystallization on Cu(100) occurs via step flow in the 〈110〉 direction.
In Situ Observation of an Electrochemical Etching Reaction in Silicon
Authors: Ross Frances M. , Searson Peter C. 
Published: April 2011

AbstractWe describe a TEM specimen holder which has been designed and constructed in order to observe the process of electrochemical pore formation in silicon. The holder incorporates electrical feedthroughs and a sealed reservoir for the electrolyte and it accepts lithographically patterned silicon specimens. We present ex situ observations of progressive pore propagation and show dynamic, in situ observations of electrolyte movement within the pores.
Strain Measurement in Two-Dimensional Nanoscale Si Gratings by High Resolution X-Ray Diffraction
Authors: Tanaka So , Umbach Christopher C. , Shen Qun , Blakely Jack M. 
Published: April 2011

AbstractThe strain induced by thermal oxidation in a cylindrical silicon (Si) structure has been studied by high resolution synchrotron x-ray diffraction. The strain in the structure studied is expected to display some of the features that exist in three-dimensional non-planar surfaces in electronic devices. The sample consisted of a 2-dimensional array, with period of 300nm, of approximately cylindrical pillars covered with a thin thermal oxide (thickness ∼6nm). These showed a tensile strain of 3.7×10-4 at room temperature. This strain can be relaxed elastically by chemical removal of the oxide. Process simulation indicates the importance of both the contribution due to interface stress during the oxide growth and stress due to differential thermal contraction during the cooldown. Significant differences exist between the strain in such cylindrical pillars and in a flat wafer.
Formation of Intensive Photoluminescence in Porous Silicon
Authors: Makara V. A. , Boltovets M. S. , Vakulenko O. V. , Datsenko O. I. , Rudenko O. V. 
Published: April 2011

AbstractPhotoluminescence (PL) spectra of porous silicon (PS) samples are studied. Effect of mechanical stresses in substrate on PL intensity is shown. The quantum yield (QY) of PS luminescence is estimated by comparing PL spectra of PS and rhodamine 6G.
Restoration of Porous Silicon Luminescence in Water Vapour
Authors: Brodin M. S. , Bykov V. N. , Dan'ko D. B. , Fedorovich R. D. , Kipen' A. A. , Kiyayev O. E. , Naumovets G. A. , Yanushevskii N. I. 
Published: April 2011

AbstractInfluence of different adsorbates on recovery of porous Si luminescence was in situ investigated for samples preheated under ultra-high vacuum conditions. Exposure to simple adsorbates (O2, H2, N2 up to a pressure of 10-3 to 10-1 Torr), long exposure to air at the atmosphere pressure, or immersion into distilled water fail to recover the red luminescence. On the other hand, we found that the red luminescence can be recovered by adsorption of water vapour onto the sample surface.The red luminescence of as-prepared porous Si can be caused by water molecules (together with possible impurities) adsorbed in the pores. The immense surface of the pores provides a large number of emitting sites. The porous Si layer can filter for the emitted light, cutting off the wave region shorter than yellow. The combination of these two factors (emission and filtering) can result in the visible red-orange luminescence of porous Si.
On the Origin of Visible Luminescence from SIO2 Films Containing Ge Nanocrystals
Authors: Min K. S. , Shcheglov K. V. , Yang C. M. , Camata R. P. , Atwater Harry A. , Brongersma M. L. , Polman A. 
Published: April 2011

AbstractSynthesis of Ge nanocrystals in SiO2 is carried out by precipitation from a supersaturated solid solution of Ge in SiO2 made by Ge ion implantation. The SiO2films containing Ge nanocrystals show intense visible photoluminescence at room temperature that is very similar in spectral features to that of SiO2 containing Ge nanocrystals synthesized by other methods, such as co-sputtering and hydrothermal reduction. The dependence of the measured peak luminescence energy on the nanocrystal diameter shows a poor correlation compared to the calculated sizedependent exciton energy for Ge ‘quantum dot’ states. The measured luminescence lifetimes are much shorter than those predicted by calculated radiative decay rates for the observed size range. The photoluminescence spectra show only a weak temperature dependence. In addition, very similar photoluminescence spectra have also been observed from Xe+-implanted SiO2with damage profiles similar to Ge+-implanted SiO2. Furthermore, the luminescence has been shown to be reversibly quenched by deuterium. These results indicate that the process responsible for visible photoluminescence is not the radiative recombination of excitons in Ge ‘quantum dots’ but is instead related to luminescent radiative defect centers in the matrix or at the nanocrystal/matrix interface.
Electrical Characteristics and Temperature Effects of Electroluminescing Silicon Nanocrystals
Authors: Forsythe E. W , Whittaker E. A. , Morton D. , Khan B. A. , Sywe B. S. , Lu Y. , Liangt S. , Gorla C. , Tompart G. S. 
Published: April 2011

AbstractThe white electroluminescence (EL) demonstrated from Si nanocrystals in a wider bandgap amorphous oxide matrix based structure has exciting opportunities in electroptic applications as well as novel LEDs. In this report, we review the electroluminescent properties of the devices for rapid thermally annealed samples at anneal temperatures ranging from 875°C to 1025°C. Depending upon the anneal conditions the EL spectra has shown two distinct spectral features; a strong emission peak at 380nm with a width of 50nm, and a broader features centered above 800nm,. Further, the I-V characteristics and corresponding EL spectra have been measured for sample temperatures ranging from 317K to 240K. In addition, Raman scattering estimated the mean particle sizes of the Si nanocrystals of 6.5nm and 8nm as well as provide insight to the nature of the amorphous matrix. The novel light emission from our devices demonstrates an exciting opportunity for Si nanocrystal (and nanocrystals in general) technology in a wide variety of applications.
Incorporation of Nitrogen Atoms at Si/SiO2 Interfaces of Field Effect Transistors (FETs) to Improve Device Reliability
Authors: Lucovsky G. , Lee D. R. , Jing Z. , Whitten J. L. , Parker C. , Hauser J. R. 
Published: April 2011

AbstractIncorporation of N-atoms at the Si-Si02 interface in field effect transistors, FETs, with ultrathin dielectrics (≤ 5.5 nm) improves device reliability. Four aspects of our recent research on nitrided Si-Si02 interfaces are discussed in this paper: i) the low-temperature/low-thermal budget process by which interface chemistry is controlled, and optimized; ii) the use of on-line and off-line diagnostics to determine the spatial confinement and concentration of interfacial N-atom incorporation; iii) comparisons of device properties for non-nitrided and nitrided interfaces; and iv) the proposal of an atom-scale model for the role that interfacial N-atoms play in improving device reliability.
Characterization of Mos Structures with Ultra-Thin Tunneling Oxynitride
Authors: Fujioka H. , Wann C. , Park D. , Hu C. 
Published: April 2011

AbstractCharacteristics of ultrathin silicon oxynitride (15–25Å) and its interface with Si have been investigated. Oxynitride films with thickness down to 15Å can be grown reproducibly in a conventional furnace. The leakage currents through these films can be well explained by the direct tunneling mechanism and can be fit by the same equation as that for pure oxide. This result indicates that incorporation of nitrogen atoms does not seriously affect the basic properties of the film and its interface such as the effective mass and the barrier height. A p-type poly gate MOS structure with 22Å oxynitride has also been fabricated successfully without boron penetration even using BF2+ ion implantation and a conventional furnace. Since the leakage current thorough oxynitride with this thickness is acceptable for circuit operation, thickness of the gate insulator in the dual poly-Si process can be scaled down at least to 22Å.
Study of Periodic Surface Nanostructures Using Coherent Grating X-Ray Diffraction (Cgxd)
Authors: Shen Qun 
Published: April 2011

AbstractIt is shown that an x-ray interference phenomenon, Coherent Grating X-ray Diffraction (CGXD), can be used to study lateral nanostructure arrays on crystal surfaces and interfaces. Compared to Fraunhofer grating diffraction of visible light, x-ray grating diffraction contains information not only about geometric profiles of a surface, but also about the internal crystalline structures and lattice strain distributions in grating features. Grating diffraction patterns can also be measured in a white-beam Laue method using highly collimated polychromatic synchrotron radiation. This provides a way for parallel data collection and is useful in in-situ studies of structural evolution of nanostructure arrays.
A New Technique for Depth Profiling on a Nanometer Scale
Authors: Schwenke H. , Knoth J. , Günther R. , Wiener G. , Bormann R. 
Published: April 2011

AbstractA new technique is presented for the determination of concentration depth profiles. Surface atoms are sputtered by an ion beam and deposited on a clean silicon wafer. The wafer is rotated behind a slit in step with the sputtering progress. In this way the depth profile of the sample is transferred into a lateral distribution of the sputtered atoms on the target wafer. Subsequently the wafer is scanned by Total Reflection X-ray Fluorescence Spectrometry (TXRF) which is capable of detecting traces of metallic impurities on wafers down to 10-4 of an atomic monolayer. The sequence of ion-beam sputtering, deposition of the sputtered atoms and TXRF analysis results in an excellent depth resolution in the case of areal structures. Using an ion source of the Kaufmann type, an extrapolated perpendicular resolution better than 0.1 nm was obtained for a 1500 mm2 surface. For a surface area of 3 mm2 a depth resolution of 1 nm is expected. 1.4 nm was actually measured to be the width of a coherent Ti/Al-interface within a layered structure.
The Uniformity of Surface Passivation After (NH4)2S Treatment Studied by Near-Field Scanning Optical Microscopy
Authors: Liu Jutong , Kuech T. F. 
Published: April 2011

AbstractWe have achieved spatially resolved room temperature photoluminescence (PL) from MOVPE GaAs (001) surfaces by Near-Field Scanning Optical Microscopy (NSOM). The PL intensity variation was related to the change of surface state density. Using this technique, the uniformity of surface passivation after (NH 4)2S treatment has been studied. We have performed the topography, reflection and PL measurements by NSOM as well as the topography measurements by Atomic Force Microscopy (AFM) on the as grown, etched and sulfur passivated GaAs samples. The uniformity of GaAs with a thin Al0 65Ga0.35As cap layer has also been studied and compared with the (NH 4)2S treatment. We found the sub-micron scale variations in PL intensity which were not correlated to the topographic features. Theoretical modeling has been used to obtain semi-quantitative analysis of the experimental results.
Reduction of Lateral Dimension on InGaAs/GaAs Multilayers on Non-(111) V-Grooved GaAs(100) Substrate by Chemical Beam Epitaxy
Authors: Kim Sung-Bock , Ro Jeong-Rae , Park Seong-Ju , Lee El-Hang 
Published: April 2011

AbstractWe have found that the lateral dimension of InGaAs and GaAs multiple layers can be effectively controlled on non-( 111) V-grooved GaAs substrates by chemical beam epitaxy using triethylgallium and trimethylindium coupled with precracked arsine or unprecracked monoethylarsine. We suggest that this effect is due to the efficient migration of adatoms from (111) to non-(111) planes. This is an improved method which overcomes the difficulty that has been associated with the method of using only (111) V-grooves in which the lateral dimension is controlled by the differences in the growth rates between (111) and (100) planes. In case of InGaAs and GaAs epilayers, the anisotropy factors of growth rate were less than 0.1 at optimum growth temperature. Photoluminescence peak originated from InGaAs/GaAs quantum wire was significantly distinct from other peaks, suggesting an effective reduction of InGaAs lateral dimension.
Facet Evolution and Selective Growth of GaAs/AlGaAs Lateral Structure Grown by Growth–Interrupted Chemical Beam Epitaxy Using Unprecracked Monoethylarsine
Authors: Ro Jeong-Rae , Kim Sung-Bock , Park Seong-Ju , Lee Jihwa , Lee El-Hang 
Published: April 2011

AbstractFacet evolution and selective area epitaxy of GaAs/AIGaAs ridge and V-groove structure grown on non-planar GaAs(100) substrate by chemical beam epitaxy(CBE) have been investigated for nanostructure applications. To enhance the crystallographic selectivity and to study the new facet evolution on patterned substrate, GaAs and AlGaAs epilayer were grown by growth-interruption mode and continuous mode, respectively. High selectivity of GaAs layer was observed to depend on the various crystallographic planes even at low growth temperature. This was attributed to the efficient Ga surface migration and desorption during the growth-interruption periods. The growth-interruption method was found to be very efficient in improving the morphology of faceted surfaces. We demonstrated that the formation of (111) V-groove and (411) ridge GaAs structures which were surrounded by AlGaAs layer to show the potential implication of this method for the formation of quantum wires.