bluuebunny/crossref_metadata_2025_split huggingface dataset:
First Phase Formation Kinetics in the Reaction of Nb/Al
Authors: Coffey K. R. , Barmak K. , Rudman D. A. , Foner S. 
Published: June 2019

AbstractPhase Formation kinetics in the reaction of Nb/Al multilaycred thin films were investigated using scanning calorimetry, x-ray diffraction, and transmission electron microscopy. The first phase to form upon annealing the Nb/Al layered structure is the NbAl3 intermetallic. Its formation is clearly identified by the calorimetry to be a two stage process, which has been modeled as the nucleation and three-dimensional growth to coalescence of the product phase in the plane of the initial interface, followed by the thickening of the product layer by one-dimensional growth perpendicular to the interface plane. For the initial reaction stage the reaction front velocity is higher than can be supported by diffusional transport within the lattice adjacent to the moving interface. Thus diffusion along nonequilibrium interfaces must be the growth mechanism. The large volume fraction consumed during the initial reaction stage indicates a lower nucleation site density than expected at a Nb/Al interface at local equilibrium, suggesting that the interface transport is reducing the driving force for nucleation.
Light Scattering Study of [60] Fullerenol-Based Poly(Urethane-Ether) Star-Shaped Polymers
Authors: Wang Lee Y. , Chiang Long Y. 
Published: June 2019

ABSTRACTThe dynamic behavior of the fullerenol-based polyurethane star-shaped polymer and its analog model stars, containing three or four polymer arms, was investigated in toluene solution by dynamic light scattering measurements. In these systems, the diffusion coefficients clearly showed no angular dependence. In the case of study in dilute solution, all three star polyurethanes were found to possess higher mobility than that of the corresponding linear polyurethane with a similar molecular weight. Furthermore, the conformation of anchoring polymer chains was characterized by the hydrodynamic shrinking factor and compared with the Gaussian model. Results suggested that the polymer arms in the fullerenebased star-polymer were uniformly distributed around the central C60 cage.
Preparation and Characterization of Polycrystalline and Single Crystal Gd Doped Barium Cerium Oxide
Authors: West Dave , Haile S.M. , Feigelson R.S. 
Published: June 2019

ABSTRACTPolycrystalline samples of BaCexGd1-x03 have been prepared with 0.10 < x < 0.20. X-ray powder diffraction indicates the samples contain only one crystalline phase for doping levels < 0.15. Transmission electron microscopy analyses on the 10% doped sample revealed no glassy phases in the intergranular regions. Single crystal fibers were prepared by Laser Heated Pedestal Growth (LHPG) from the polycrystalline samples. Fiber growth was non-conservative thus the single crystal quality was limited. Preliminary conductivity measurements on the polycrystalline samples using AC impedance spectroscopy are compared with literature data.
Complex Defects In Ci Doped ZnTe And CdTe
Authors: Valdna V. 
Published: June 2019

AbstractPhotoluminescence and conductivity of doped with chlorine and copper ZnTe, Zn(SeTe) and CdTe are investigated. We suppose that interstitial tellurium and complex defects of Tei with a donor dopant Cl can significantly affect the luminescence spectra and conductivity value of ZnTe and CdTe. This assumption is confirmed experimentally. We found that copper dopant in CdTe: Cl can increase the resistivity value of p-type CdTe.
Self-Assembled Organic Monolayer Films on Underpotentially Deposited Metal Layers
Authors: Jennings G. K. , Laibinis P. E. 
Published: June 2019

ABSTRACTThis paper describes a new family of organized molecular assemblies that are produced by the spontaneous adsorption of alkanethiols onto gold surfaces that have been modified by the underpotential deposition of copper or silver. The system has the flexibility associated with the formation of self-assembled monolayers by the adsorption of thiols onto gold with the advantage of improved stability. The use of these systems as modified electrodes is also addressed.
Thin Layer Electrochemical Studies of ZnS, ZnSe, and ZnTe Formation by Electrochemical Atomic Layer Epitaxy (ECALE)
Authors: Colletti Lisa P. , Thomas Sajan , Wilmer Elvin M. , Stickney John L. 
Published: June 2019

ABSTRACTThin-layer electrochemical studies of the underpotential deposition (UPD) of Zn, Te, Se, and S on polycrystalline Au substrates have been performed. These studies were initiated to investigate the electrodeposition of ZnTe, ZnSe, and ZnS by electrochemical ALE (ECALE). Zn UPD on Au begins at -0.5 V and results in a coverage of 0.47 monolayer (ML). Te and Se atomic layers were formed using a two step process where bulk chalcogenide was removed by reduction, leaving the atomic layer. The reduction of the last atomic layer of Te or Se was not observed, regardless of how negative the potential was scanned. Sulfur atomic layers were spontaneously deposited below -0.6 V from a sulfide solution. Thermodynamic effects are clearly evident during the first monolayer of deposition. Zinc deposition onto Te, Se, and S coated electrodes occurs at progressively more positive potentials as the stability of the zinc compounds increase.This initial information was used to develop ECALE cycles for the compounds, and thin-films were formed by repeated application of the cycles. The dependence of the deposit coverage on the deposition potentials was examined and found to display the characteristic “S” curve of a surface limited process. In addition, the dependence of the coverage on the number of ECALE cycles performed was found to be near the ideal 0.5 ML per cycle for ZnSe and ZnS. The ZnTe coverage per cycle was less than expected indicating that further optimization of deposition conditions is needed.
UHV Model Experiments of Electrochemical Etching of GaAs BY H2O/Br2
Authors: Henrion O. , Klein A. , Ettenkofer C. , Jaegermann W. 
Published: June 2019

ABSTRACTTo investigate the initial steps of GaAs etching Br2 and H2O were (co)adsorbed onto the (110) cleavage plane at 100 K and the interaction investigated by SXPS and LEED. H2O is dissociatively adsorbed at low temperatures and leads to Fermi level pinning close to midgap. Br2 leads, depending on coverage, to the formation of bromides of different stoichiometries. During annealing to 290 K the bromides mostly evaporate from the surface (etching). Br2 and H2O coadsorption leads to Ga-oxide remaining on the surface. For the reactive interfaces band bending is not observed. The results of the adsorption experiments are compared to electrochemically prepared surfaces.
Scanning Probe Investigations of Cleaved Heterostructure Layers
Authors: Ebel J. L. , Schlesinger T. E. , Reed M. L. 
Published: June 2019

ABSTRACTWe present differential oxidation rate effects in cleaved heterostructures containing GaAs, AlGaAs, InGaP and InGaAs measured by atomic force microscopy (AFM). AFM images of the cleaved structures are presented, along with step height measurements at the different material interfaces. These height differences are the result of differences in oxidation rates of the heterostructure layers. The method used to extract the small step-height information from the images is also presented. Typical step heights range from about one to twenty angstroms for the structures measured. We have also observed steps which mimic the oxidation steps, but which are not related to the epitaxially grown material structure. However, in these cases images of both sides of the cleaved pieces show inverse (rather than similar) topographies. We also present results of digital etching techniques used to enhance the step heights based on the same differential oxidation mechanism.
Microelectrochemical Characterization and Modification of Semiconductor Surfaces with Polycrystalline Ti/TiO2 as an Example
Authors: Michaelis A. , Kudelka S. , Schultze J. W. 
Published: June 2019

ABSTRACTDifferent new micro-methods such as anisotropy micro-ellipsometry (AME), photoresist micro-electrochemistry, micro-photocurrent spectroscopy, and UV-laser scanning were performed simultaneously to characterize and modify heterogeneous semiconducter surfaces. All measurements were carried out on single grains with the Ti/TiO2 system as an example. The crystallographic orientations of the substrate grains were determined in-situ by AME. It is shown that both the electronic and the optical properties of the semiconducting TiO2 films sensitively depend on the substrate texture. Film properties such as layer thickness and defect state concentration vary with the substrate orientation in a systematic manner.The TiO2 films were modified at high local resolution by means of focused UV-laser illumination. Both a thickening (writing) or thinning (erasing) of the films could be realized depending on the potential applied during the illumination. Therefore, the anodic potential could be used to control the layer thickness and to generate semiconducting structures with thickness gradients.
Kinetic Model for Layer - by - Layer Homoepitaxial Growth
Authors: Trofimov V. I. , Mokerov V. G. , Shumyankov A. G. 
Published: June 2019

ABSTRACTA new kinetic model for homoepitaxial growth on a singular surface is presented. The model combines the familiar rate equations approach and the concept of a feeding zone that allows connection between the growth processes occuring in neighbouring monolayers. The model involves the irreversible 2D nucleation, growth and coalescence of islands in each growing monolayer and consists of an infinite set of coupled rate equations for the adatom and island densities and coverage in successive monolayers. The temporal evolution of the surface morphology (rms roughness and RHEED intensity) is studied with this model. It is shown that the growth mode is fully determined by a single dimensionless parameter μ = D/J where D and J are the normalized surface diffusion coefficient and deposition flux, respectively. There exist five regions of μ corresponding the different growth regimes varying from smooth 2D layer-by-layer growth at sufficiently high values of μ (>108) to very rough Poisson-like random deposition growth at μ <10−4. The extension of the model to the case of heteroepitaxy is also discussed.
In Situ Investigation of Working Battery Electrodes Using Synchrotron X-Ray Diffraction
Authors: Jisrawi N. M. , Thurston T. R. , Yang X. Q. , Mukerjee S. , McBreen J. , Daroux M. L. , Xing X. K. 
Published: June 2019

ABSTRACTThe results of an in situ investigation of the structural changes that occur during the operation of working battery electrodes using synchrotron radiation are presented. Two types of electrodes were investigated: an AB2-type Laves phase alloy anode with the composition ZrxTi1-xM2 and a proprietary cell based on a LixMn2O4 spinel compound cathode made by Gould electronics. For the Laves phase alloy compositions with x=0.25 and 0.5 and M=V0.5N1.1Mn0.2Fe0.2 were examined. Cells made from two different batches of LixMn2O4 material were investigated. The relationships between battery performance and structural changes will be discussed. In the later case, we also discuss the role of over-discharging on the LixMn2O4 structure and on battery operation.
Electroless Deposition of La1−xSrxMnO3Perovskite Film on Yttria Stabilized Zirconia Substrate
Authors: Sasaki T. , Matsumoto Y. 
Published: June 2019

ABSTRACTA LaMnO3precursor was electrolessly deposited on a YSZ substrate in a solution containing Mn2+, La3+, an oxidizing agent and some additives. Peroxydisulfate was used as the oxidizing agent. The LaMnO3precursor was an amorphous and hydrous MnO2which contained La3+ions. The incorporation of La3+ions into the precursor oxide film was based on the ion-exchange reaction, where La3+ions in the solution were exchanged for H+ions on the deposited amorphous and hydrous MnO2. A La1-xSrxMnO3precursor was also prepared from the LaMnO3precursor by the ion-exchange reaction of some of the La3+ions in the LaMnO3precursor for Sr2+ions in the solution. (La0.5Sr0.5)0.75MnO3perovskite film was obtained from the precursor films on Pt substrate by heat-treatment at 800 °C.
Electrodeposition for Hi-MEMS with Special Reference to Fabrication of a Magnetic Mini-Motor
Authors: O'Sullivan E. J. , Cooper E. I. , Romankiw L. T. , Horkans J. , Kwietniak K. T. 
Published: June 2019

ABSTRACTElectrodeposition through photoresist masks is a critical, enabling technology for fabrication of the thick structures (of up to several hundred microns) involved in HI-MEMS. Process integration is an important issue in HI-MEMS. The electrodeposited structure is influenced by the choice of optical or X-ray lithography. Thickness uniformity of the deposit on the wafer scale can be optimized by the use of an auxiliary cathode. On the device or feature scales, thickness uniformity can be improved by the thoughtful design of the pattern to be plated.A variable reluctance, planar, integrated mini-motor with a 6 mm diameter rotor has been fabricated using lithography, electrodeposition and dielectric planarization processes. The rotors were fabricated separately, released from the substrate, and slipped on the shaft, which was plated up as part of the stator fabrication.
Atomic Force Microscopy Study of Surface Evolution During Electrocrystallization of Zinc-Dion Alloys
Authors: Czerwinski F. , Kondo K. , Szpunar J. A. 
Published: June 2019

ABSTRACTZn-Fe alloys, composed of η (h.c.p.) phase, were electrolytically deposited on cold rolled steel substrates from sulfate electrolytes. Deposits, which initially exhibited a morphology of approximately 20 nm thick platelets inclined 10–20 deg to the substrate surface, subsequently evolved either into triangular pyramids or hexagonal columnar crystals depending on the deposition conditions. A combination of X-ray texture measurements and AFM topographical analysis was used to characterize the growth surface of Zn-Fe alloys. For the morphology of hexagonal columnar crystals, the (00·1) basal planes were aligned perpendicular to the growth direction. For the morphology of the triangular pyramids, the (10·0) and (00·1) planes of η phase were tilted to the growth direction and surrounded the growth surface. For both morphologies the micro- and nanosize steps of growth were identified.
Corrosion of Electronic and Magnetic Devices and Materials
Authors: Frankel Gerald S. 
Published: June 2019

ABSTRACTCorrosion of thin film structures commonly used in electronic and magnetic devices is discussed. Typical failure modes are presented, and galvanic corrosion is discussed in some detail since it is one common problem with such devices. A graphical explanation for the determination of the ohmic potential drop during galvanic corrosion is presented. The corrosion problem of thin film disks is shown to have changed during the past ten years owing to changes in disk structure. The corrosion susceptibility of two antiferromagnetic alloys used for exchange coupling to soft magnetic layers is discussed.
Stm Study of the Influence of Adsorption on Step Dynamics
Authors: Moffat T. P. 
Published: June 2019

ABSTRACTIn situ STM has been used to examine the influence of anion adsorption and metal underpotential deposition on the structure and dynamics of steps on copper surfaces. Chloride is shown to form potential dependent adlayer structures on Cu(100) and Cu(111) which strongly affects the orientation of the surface steps. The adlayer acts as a template guiding step evolution during metal deposition and dissolution. Metal underpotential deposition (upd) exhibits similar effects on step structure. This is demonstrated for Pb upd on Cu(lll). In this instance the Pb monolayer displaces chloride from the surface and leads to a reorientation of the steps and an alteration of the step dynamics.
Structure of Momolayers of Silicotungstate Anions on Ag(111) and Au(111) Electrode Surfaces
Authors: Ge Maohui , Niece Brian K. , Wall Craig G. , Klemperer Walter G. , Gewirth Andrew A. 
Published: June 2019

ABSTRACTα-Dodecatungstosilicate (α-SiW12O404−) anions form ordered monolayers on Ag(111) and Au(111) surfaces. In-situ STM images reveal that the silicotungstate ion forms a square adlattice with an intermolecule spacing of 10.2 ± 0.5 Å on both Ag and Au surfaces. Additional structures exhibiting either row or rhombic motifs are observed on Au electrodes. The structure of the adlattices can be modeled using a simple model which maximizes the coordination of the silicotungstate ion to the electrode while maintaining van der Waals contacts between terminal oxygens of adjacent silicotungstates.
Millimeter-Submillimeter Vector Measurements in Free Space, and in Resonant Structures. Application to Dielectrics Characterization.
Authors: GOY Philippe , Gross Michel , Caroopen Sylvain , Mallat Juha , Tuovinen Jussi , Maestrini Alain , Annino Guiseppe , Fittipaldi Maria , Martinelli Massimo 
Published: June 2019

ABSTRACTUsual vector measurements need to compare the signal detected through the Device Under Test DUT, with the signal coming directly from the source. Thanks to a very simple original method developed since 1989, vector detection can also be done with a purely electronic reference. In transmission experiments, there is no need for any directional coupler, and the frequency coverage extends from 8 to 1000 GHz. Quasi-optical propagation is used in the millimeter-submillimeter frequency range. Transmission through dielectric slabs in free space will give an easy measurement of the permittivity. Its real part will be obtained from the phase rotation, and its imaginary part from the amplitude decay. With dielectric coating deposited onto metal, the reflection method is necessary for the characterization. Low-loss materials are characterized with the open cavity perturbation technique. Extremely low loss materials can constitute “whispering gallery” resonators, very easy to excite and characterize.
Millimeter Wave Solid State Devices
Authors: Rosenau Steven A. , Liang Cheng , Zhang Weikang , Deng Bihe , Li Weiying , Chang Chia-Chan , Hsu Pei-Ling , Hsia Richard P. , Jiangs Fan , Domier Calvin W. , Luhmann Neville C. 
Published: June 2019

ABSTRACTExamples of novel solid state devices are presented, together with descriptions of their applicability to the diagnosis of laboratory, processing and fusion plasmas. GaAs varactor diodes can be arranged in large monolithic grid arrays, forming millimeter wave frequency multiplier based sources and high speed switches, or embedded in transmission lines to provide a true time delay for phased antenna array beam steering. Micro-electromechanical systems (MEMS) switches are exciting new devices with numerous applications, including low loss millimeter wave switches, phase shifters and mechanically tunable structures.
Silicon Wafer Subsurface Characterization with UV/Millimeter-Wave Technique
Authors: Ogita Yoh-Ichiro , Gan-nen Yuichiro 
Published: June 2019

ABSTRACTIn subsurface characterization for Si wafers using a photoconductivity technique with a ultra-violet photoexcitation and millimeter wave reflection, high sensitivity technique for100 GHz was discussed experimentally and theoretically. The technique detected photoconductivity decays measured for p/p+ and n/n+ epitaxial wafers. The epilayer contaminated with Mo and Fe was characterized by the technique. Photoconductivity amplitude (PCA) intensity measured for as-polished Si wafers in commercial use after removing the subsurface by SC1 cleanings well reflected the behavior of removal of slight subsurface damage induced by mirror-polishing. The damage depth was determined to be 21 nm.
Millmeter Wave Aquametry
Authors: Meriakri Viacheslav V. 
Published: June 2019

ABSTRACTSpecific advantage of millimeter (MM) wave aquametry is discussed. MM waves ensure better spatial resolution and better sensitivity to water than microwaves. MM waves are less sensitive to conducting impurities than microwaves, and MM waves can be used for water testing in media that are opaque to optical and infrared radiation. In the paper the water content measurement methods for some liquid and solid-state materials are described. Examples of devices for water control in crude oil, alcohol, powders used in metallurgy, paper, timber are considered. Usually it is possible to measure moisture content in real time (including in flow) with uncertainty less than 0.1%.
Dynamical X-ray diffraction analysis of Solid Phase Epitaxy growth of Si1-yCy heterostructures
Authors: Rodriguez-Viejo J. , el-Felk Zakia 
Published: June 2019

AbstractThe strain and damage produced on Si substrates by high-dose ion implantation of Si and C is investigated after thermal treatments by double and triple crystal X-ray diffraction, high ressolution transmission electron microscopy (HRTEM) and Secondary Ion Mass Spectrometry (SIMS). Si implantation (180 keV, 5×1015 Si at cm−2) at liquid nitrogen temperature forms a buried amorphous layer. Annealing at temperatures close to 650°C results in epitaxial films with significant defect recovery. X-ray rocking curves show the existence of interference fringes on the left hand side of the 004 Si peak indicating the presence of tensile strained Si layers due to the generation of Si interstitials during the implantation process. C implantation, at 60 keV, 7×1015 cm−2 and 450°C, in the preamorphized Si wafers results in the growth of Si1-yCy epitaxial films with a low amount of substitutional carbon (y≍ 0.1%). Rapid thermal annealing at 750°C results in highly defective epitaxial films with a maximum carbon content close to 0.4%.The high density of defects is responsible for the partial strain relaxation observed in those layers. The amount of substitutional Si also decreases drastically with increasing temperature. Profile fitting of rocking curves using dynamical X-ray theory is used to estimate the C concentration and the strain and disorder profiles of the heterostructures.
Interaction and Energy Level Alignment at Interfaces between Pentacene and Low Work Function Metals
Authors: Koch N. , Ghijsen J. , Ruiz R. , Pflaum J. , Johnson R. L. , Pireaux J.-J. , Schwartz J. , Kahn A. 
Published: June 2019

ABSTRACTA number of low workfunction metals (samarium, alkali metals) were deposited onto vacuum sublimed thin films of pentacene. The change in the valence electronic structure of the organic material was studied by in situ ultraviolet photoemission spectroscopy (UPS). Alkali metal intercalation leads to the appearance of a new photoemission feature within the pentacene energy gap, due to a charge transfer from the alkali atoms to the lowest unoccupied molecular orbital (LUMO) of the organic material. The energy spacing between this emission feature and the relaxed highest occupied molecular orbital (HOMO) of the pristine molecule is 1 eV. From X-ray photoemission spectroscopy core level analysis, we estimate a concentration ratio of two alkali metal atoms per pentacene molecule at maximum intercalation level, leading to a complete filling of the LUMO. This is consistent with the results from UPS that the new emission is always observed below the Fermi-level. Samarium is found to exhibit a more subtle interaction with pentacene: the molecular orbitals remain almost unperturbed upon Sm deposition. The resulting energy level alignment at this interface seems to be very favorable for the injection of electrons from Sm into pentacene, as the HOMO-onset is found at 1.8 eV below the metal Fermi edge. This value is close to the 2.2 eV HOMO-LUMO gap of pentacene measured by UPS and inverse photoemission spectroscopy, thus corresponding to a small electron injection barrier.