bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of Sol-Gel Coatings by Electrophoretic
Deposition
Authors: Hirashima Hiroshi , Obu Yusuke , Nagai Takayuki , Imai Hiroaki 
Published: April 2011

ABSTRACTThin films of ZrO2 and lead zirconate-titanate, PZT, about 100 to
1000 nm in thickness, were prepared by electrophoretic deposition from
transparent sols obtained by hydrolysis of metal alkoxides. Stainless steel
plates and Pt-coated glass plates were used as substrates/electrodes. The
applied field was up to 20 V/cm. The refractive indices of as dried films
were higher than those of dip-coated films. High temperature oxidation of
stainless steel plates was suppressed by the ZrO2 coatings.
Uniformity of the chemical composition of the as-dried PZT films, determined
by Auger electron spectroscopy, was better than the dip-coated PZT
films.
Ionic Properties of Hydrogenated and Fluorinated Fullerenes
Authors: Hettich R.L. , Jin C. , Britt P.F. , Tuinman A.A. , Compton R.N. 
Published: April 2011

ABSTRACTThe ionization potentials (IP) and electron affinities (EA) for a number of hydrogenated and fluorinated derivatives of C60 and C70 have been determined using the charge exchange “bracketing” technique. Samples of C60Hx and C70Hy were prepared by direct solid phase hydrogenation (x=2-18, y=2-30) or platinum oxide catalytic hydrogen reduction (x=36, y=36). The IP's for C60H2-18 are between 6.75 and 7.53 eV for even x<10 and lower than 6.75 for odd x<10. The EAs for C60F44,46,48, and C70F52,54 were “bracketed” to be 4.0 ± 0.25 eV. The highly fluorinated chiral C3h molecule C60F48 was observed to directly attach two electrons in the gas phase to produce C60F482- and C60F462− + F2−. Studies of the metastable decompositions and collision-induced dissociation of C60F482− showed fluorine atom and F2 loss, but no loss of an electron. In addition, the C60F48,46,442− dianions do not charge exchange with molecules possessing high electron affinities, including the neutral parent compound, C60F482− (EA = 4.06 eV). The remarkable stability of C60F482− to the removal of an excess electron is attributed to a long-range Coulomb barrier which is built from the bound state for the two electrons near the molecule and the electron-electron Coulomb repulsion between the two at large distance.
Characterization of Pulsed Supersonic Cvd System For Diamond Growth
Authors: Ohlberg Douglas A. A. , Ren James , Williams R.Stanley 
Published: April 2011

ABSTRACTAn ultra-high vacuum chemical vapor deposition system using pulsed, supersonic jets of halogenated hydrocarbon precursors has been constructed with the intention of growing diamond thin films. Experimental results from this system should determine whether the hyperthermal activation of precursors improves the carbon incorporation efficiency of film growth. The jets, produced by commercially available pulsed valves, were characterized with a fast ionization gauge. Parameters such as valve backing pressure and the pulse width were varied to optimize material flux and avoid the formation of boundary layers above the substrate that could reduce the kinetic energy of the precursors.
Optical Characterization and Modeling of Amorphous Hydrogenated Carbon Films
Authors: McGahan William A. , Woollam John A. 
Published: April 2011

ABSTRACTAmorphous hydrogenated carbon (a-C:H) thin films are of great importance in a number of industrial applications due to their hardness, chemical stability, and optical transparency. In many applications, the thickness of the a-C:H film and/or its optical properties are critical for the performance of the complete structure, and, as a result, a means of measuring these quantities is important. In this work we review the use of spectroscopic ellipsometry and transmission measurements for the estimation of the thickness and optical constants of thin a-C:H films. Spectra are shown for films exhibiting Tauc effective bandgaps ranging from 0 - 2.3 eV. The films were prepared by magnetron sputtering and plasma CVD on both silicon and glass substrates. The general energy dependence of the a-C:H optical constants is discussed in terms of the absorption processes which occur in the film.
Structure and Electronic Properties of Diamond-Like Amorphous Carbon
Authors: Wang C. Z. , Ho K. M. 
Published: April 2011

ABSTRACTAmorphous carbon networks generated by quenching high-density liquid from hightemperature using a tight-binding molecular dynamics method are found to be dominated by tetrahedral bonding sites. The overall structural and electronic properties of these networks resemble those observed in experimental diamond-like amorphous carbon films produced by the mass-selected ion beam deposition technique. Our study shows that bonding and antibonding of π states associated with pairs and quartets of threefold “defected-atoms” embedded in the fourfold matrix yield a band gap of about 2 eV.
Structure and Performance of Carbon Aerogel Electrodes
Authors: Pekala R.W. , Mayer S.T. , Poco J.F. , Kaschmitier J.L. 
Published: April 2011

ABSTRACTThe chemistry and physics of small clusters of atoms (1-100 nm) has received considerable attention in recent years because these assemblies often have properties between the molecular and bulk solid-state limits. The different properties can be explained in terms of the large fraction of atoms that are at the surface of a cluster as compared to the interior. Although the synthesis and properties of metal and semiconductor clusters, metallocarbohedrenes, fullerenes, and nanotubes are the subject of extensive investigations, little attention has been paid to cluster-assembled porous materials. This oversight is of particular interest to us since we believe that aerogels are one of the few monolithic materials presently available where the benefits of cluster assembly can be demonstrated. In particular, the unique optical, thermal, acoustic, mechanical, and electrical properties of aerogels are directly related to their nanostructure, which is composed of interconnected particles (3-30 nrm) with small interstitial pores (< 50 nm). This structure leads to extremely high surface areas (400-1100 m2/g) with a large fraction of the atoms covering the surface of the interconnected particles. As a result of these structural features, carbon aerogels are finding applications as electrodes in supercapacitors with high energy and power densities.
Growth, Structure and Stress of DC Magnetron Sputtered TiB2 Thin Films
Authors: Deng H. , Chen J. , Inturi R. B. , Barnard J. A. 
Published: April 2011

AbstractTiB2 is a very hard refractory compound that strongly resists erosion and shows metallic luster and good electrical conductivity. It has potential applications in protective coating systems. This paper investigates the microstructure and stresses of as-deposited TiB2 thin films ranging from 2000 °A to 4000 °A thick produced by dc magnetron sputtering as a function of sputtering power and Ar pressure. Three power levels: 100, 400, 600 W, and four pressures: 3, 5, 8, and 12 mTorr were used. X-ray diffraction studies indicate that two types of crystalline structure are formed: a randomly oriented fine crystalline structure and a coarser grained (001) textured structure, depending on the sputtering power and pressure. As-deposited stresses at different powers all show a transition from compression to tension as the Ar pressure increases. The relationship between the processing parameters, microstructure and residual stresses is discussed. The effects of the deposition power and pressure on the residual stress transition of TiB2 thin films are clearly mapped out by 3-D and contour maps.
Tunability of Intrinsic Stress in Siox Dielectric Films Formed by Molecular Beam Deposition
Authors: Chand Naresh , Kola R. R. , Osenbach J. W. , Tsang W. T. 
Published: April 2011

AbstractSilicon monoxide (SiO) formed by molecular beam deposition (MBD) has many attractive optical, electrical, mechanical, and chemical properties which make it a suitable dielectric for many semiconductor device applications. It can be thermally evaporated at a much lower temperature than Si, SiO2 or Si3 N4 and it condenses on cooler surfaces in uniform and adherent stoichiometric SiO (x = 1) films when evaporated in high vacuum. At low deposition rates and at high pressures of oxygen, SiOx (1 ≤ x ≤ 2) films result. This allows variation of refractive index, stress and other properties of SiOx with x. In general, the SiO (x = l) films are under tensile stress <100 MPa which is significantly lower than that observed in other dielectric films. Slight introduction of oxygen during deposition reduces the tensile stress; at an O2 pressure of 5 × 10−7 Torr and above, the films are in compression. This allows the tunability of stress in SiOx films and deposition of films essentially free from stress. Furthermore, both Si and SiO have similar values of the linear thermal expansion coefficient (average values between 23 °C and 350°C: 3.37 × 10−6°C−1 and 2.7 × 10−6°C−1, respectively). As a result, SiOx/Si films develop little thermal stress during thermal cycling.
Stacking Fault Tetrahedra Formation During Growth of Si1-xGex Strained Layers on 〈111〉 Oriented Si Substrates: Tem Observations and Defect Modeling
Authors: Howard David J. , Bower Allan F. , Paine David C. 
Published: April 2011

AbstractWe report the observation of stacking fault tetrahedra (SFT) in strained Si1-xGex layers grown via rapid thermal CVD on (111) Si substrates. It is shown that these defects provide a mechanism for strain relief in films strained in compression due the presence of bounding edge-type stair rod partials whose Burgers vectors lie parallel to the strained layer interface. Cross section and plan view TEM were used to characterize this defect structure in epilayers (30 to 650nm thick) of Si1-xGex (0 < xGe < 0.27) grown on 〈111〉 oriented Si wafers. Stacking fault tetrahedra were observed only in alloys in the compositional range xGe ≥ 0.13 and only when growth proceeded on the 〈111〉 surface. A critical strain energy model that identifies conditions for the stable growth of stacking fault tetrahedra in a strained layer is presented. The model was based on conventional strain energy considerations where the energy of the stacking fault area plus the bounding dislocation network (including dislocation interactions but neglecting the free surface) was balanced against the strain energy released by the introduction of the defect. In addition, a formation mechanism consistent with these observations is described that involves the dissociation of Frank partial dislocation loops bounding stacking faults lying in the growth plane.
Misfit Strain Relief Beyond the Critical Thickness Using Curvature Measurements and in Situ Characterization of the Magneto-Optic Kerr Effect
Authors: Inglefield H. E. , Bochi G. , Ballentine C. A. , O’Handley R. C. , Thompson C. V. 
Published: April 2011

AbstractEpitaxial misfit has been characterized in Ni/Cu/Si (100) as a function of Ni film thickness using wafer curvature measurements. This strain can be related to measurements of magnetic anisotropy made in the deposition system using the magneto-optic Kerr effect. Films were deposited using molecular beam epitaxy (MBE) with varying Ni epilayer thickness between 10 and 1000Å. The change in wafer curvature due to misfit strain was measured using optical interferometry and the strain was calculated using Stoney’s equation. Transmission electron microscopy was used to characterize misfit dislocations at the Ni/Cu interface. It has been determined that misfit strain can have a very strong effect on magnetic anisotropy, particularly in the regime between the critical thickness and complete misfit accommodation, where strain has been found to decrease significantly as a function of film thickness. A critical strain has been determined at which a transition in the direction of magnetization easy axis from perpendicular to the film to in the film plane occurs. This discovery allows the use of Kerr effect measurements to characterize misfit strain in situ.
Nanoindentation of Epitaxial Films: A Study of Pop-in Events
Authors: Mann A. B. , Pethica J. B. , Nix W. D. , Tomiya S. 
Published: April 2011

AbstractDiscontinuities in nanoindentation loading curves are frequently observed in ceramic materials. These normally occur at fairly random loads and displacements, probably due to the random distance of pre-existing defects from the indent location. Here we report the observation of reproducible, sudden indent-depth changes which occur over a very narrow distribution of depths and loads, for GaAs and a range of related epitaxial layer systems. The surface preparation and material defect density have a significant influence. Different tip geometries have been used to gain insights into the deformation processes which cause these discontinuities.
Mechanical Properties and Microstructure of Cu/Cu-Ni And Cu/Ag Multilayer thin Films
Authors: Krzanowski James E. , Duggan Peter 
Published: April 2011

AbstractThe mechanical properties of thin-film Cu/Cu-Ni and Cu/Ag multilayers are examined in this study. Films were prepared by magnetron sputter deposition onto cleaved NaCl substrates. The use of a computer-controlled deposition system enabled the multilayer interface width to be varied, as well as the multilayer amplitude and bilayer thickness. The Cu/Cu-Ni multilayers had the form of (001) oriented single crystal films, but for Cu-Ag multilayers only polycrystalline films could be obtained in the (001) orientation. For Cu/Cu-15%Ni multilayers, the tensile strengths were measured and observed to increase with decreasing interface width at constant wavelength. Tensile strengths were also found to increase with increasing composition modulation amplitude. For films with constant interface width but bilayer thicknesses ranging from 10 to 60 nm, the tensile strength was relatively constant. The results are consistent with previous theoretical treatments, particularly the theory of modulus hardening.
In-Situ Electromigration Stressing in Transmission Electron Microscopy for Al-Cu Interconnects
Authors: Shih W. C. , Greer A.L. 
Published: April 2011

AbstractUnpassivated 2.1 μm wide Al-4wt%Cu interconnects with near-bamboo grain structure, are electromigration-tested to failure in-situ in transmission electron microscopy. Early stress-induced voids stop growing and are not fatal. Hillocking is associated with precipitates, fatal voiding with copper depletion. Electromigration-induced voids form at the upstream end of inclined grain boundaries. Healing events are analysed and it is shown that open-circuit failure can occur when the proximity of grain boundaries impairs the stress-driven healing.
A Method for Analyzing the Critical Adhesion Energy of Thin Film Coatings
Authors: McGarry Frederick J. , Shaffer Edward O. 
Published: April 2011

AbstractThe edge delamination test (EDT) measures the energy required to cause a thin film, under biaxial tensile stress, to debond from a rigid substrate. Circular holes are etched through the films and if the stress is large enough, stable debond rings grow radially around the holes. A finite element analysis is used to find the applied strain-energy release rate as a function of debond crack length, hole radius and side-wall angle. However, the analysis may not be widely available, so, we present tables of reduced debond energy val ues, Gr, to facilitate the use of the EDT. With observed EDT results, Gr is extrapolated from the tables and then the critical debond energy is calculated by multiplying Gr by the maximum strain energy. Also, we have fit Gr with a semi-empirical equation, which is in good agreement over a broad range of geometries.
In-Situ Fluorescence Strain Sensing of the Stress in Interconnects
Authors: Wen Q. , Ma Q. , Clarke D. R. 
Published: April 2011

AbstractAn optical fluorescence method is introduced for determining the localized stresses in passivated aluminum lines on sapphire substrates containing a thin epitaxial ruby film at the AI/AI2O3 interface. The method is based on the piezo-spectroscopic properties of the ruby film, which acts as an in situ sensor. By focusing a laser beam through the sapphire substrate and onto the bottom of an aluminum line, the fluorescence from the ruby sensor can be excited and collected through an optical microscope. The frequency shift of the fluorescence lines is proportional to the stress in the aluminum line. To illustrate our observations two sets of measurements are presented: the spatial variation perpendicular to an interconnect line; and the temperature dependence on heating upto the deposition temperature of the SiN used to passivate the interconnects.
Time Dependent Indentation Testing At Non-Ambient Temperatures Utilizing the High Temperature Mechanical Properties Microprobe
Authors: Lucas B. N. , Oliver W. C. 
Published: April 2011

AbstractTime dependent indentation data for pure indium from -100 °C to 75 °C is presented. The properties reported include hardness, indentation strain rate, stress exponent and apparent activation energy for creep. These properties were measured using a depth-sensing indentation system capable of performing experiments between -100 °C and 300 °C in ultra-high vacuum. In addition, by employing laser interferometric techniques, this system can obtain displacement data with time constants as low as 50 ns. This allows the investigation of the material response to very fast stress changes over an extremely wide range of strain rates. The adverse and beneficial dynamic effects of step-loading the indenter into the surface of the material will be discussed. Initial results obtained from this type of experiment show that it is possible to obtain energy dissipation or damping information from the material being studied.
Nanomechanical Response of Materials and Thin Film Systems: Finite Element Simulation
Authors: Syed Asif S.A. , Derby B. , Roberts S.G. 
Published: April 2011

AbstractFinite element simulation of the nanoindentation process has been carried out to investigate the nanomechanical response of materials and thin film systems. The influence of the geometry of the indenter, friction between the indenter and the surface, and pre-stress in the film, on the nanomechanical response have all been investigated. The effect of pile-up on the contact area calculation and the problems which occur with the commonly used methods in calculating the contact area have been studied. Results shows considerable error in calculating the contact area which depends on the indentation conditions used for the simulation. Simulation results suggest, that the influence of residual stress on hardness response is material sensitive.
Ion Beam Mixing of Titanium Overlayers with Hydroxyapatite Substrates
Authors: Levine Timothy E. , Nastasi Michael , Alford T. L. , Suchicital Carlos , Russell Stephen , Luptak Karen , Pizziconi Vincent , Mayer James W. 
Published: April 2011

AbstractThe mixing of titanium overlayers with hydroxyapatite (HA) substrates via ion irradiation has been demonstrated. Analysis via secondary ion mass spectroscopy (SIMS) indicates an interfacial broadening of titanium and calcium of the implanted sample compared to that of the unimplanted sample. Attendant to the observed ion beam mixing of titanium into the HA, the oxygen signal of the titanium overlayer increases as a result of ion irradiation. It is supposed that this change is evident of diffusion through the metal layer and possibly from titania formation at the free surface and perovskite formation at the film/substrate interface. This possibility is consistent with thermodynamic predictions. Additionally, the force required to separate the film from the substrate increased as a result of ion irradiation, validating the continued study of ion beam processing of Ti/HA systems towards the improvement of long term fixation of implant devices.
Effects of Interlayers on the Scratch Adhesion Performance of Ultra-Thin Films of Copper and Gold on Silicon Substrates
Authors: McAdams S. D. , Tsui T. Y. , Oliver W. C. , Pharr G. M. 
Published: April 2011

AbstractScratch testing has long been used to assess the adhesion of a film to its substrate. As film thicknesses have decreased, the need for greater precision and sensitivity in the scratch testing apparatus has increased. To this end, a nanoindenter was modified to make finely controlled, low-load scratches. Scratches at various loads and two orientations of a Berkovich scratching diamond were made in films of 100 nm of gold and 200 nm of copper, each on single crystal silicon. For each film type, samples with no interlayer, with an SiO2 interlayer, and with a TiW on SiO2 interlayer were tested. The scratch morphology was found to vary in a regular way with load, diamond orientation and interlayer material.
On the Use of Electrostrictive Actuators in Recovering the Optical Performance of the Hubble Space Telescope
Authors: Fanson James L. 
Published: April 2011

AbstractThis paper describes the development of a space qualified active mirror—the Articulating Fold Mirror—which forms part of the scheme for recovering the optical performance of the Hubble Space Telescope. Three Articulating Fold Mirrors are incorporated into the optical train of the Jet Propulsion Laboratory's Wide Field and Planetary Camera-2, which was installed into Hubble by astronauts in December, 1993. Each Articulating Fold Mirror utilizes six electrostrictive ceramic multilayer actuators to precisely position a mirror in tip and tilt in order to correct the spherical aberration of the Hubble Space Telescope's primary mirror. Flight qualification aspects of the electrostrictive actuators are described. Pre- and postrepair images from the Wide Field and Planetary Camera, showing the effect of the optical correction, are presented.
Optical Non-Invasive Evaluation of Ferroelectric Films/Memory Capacitors
Authors: Thakoor Sarita , Thakoor A. P. , Cross L. Eric 
Published: April 2011

AbstractNON-INVASIVE photoresponse (photocurrent/voltage, reflectance and transmittance) from ferroelectric thin films and memory capacitors, with its strong dependence not only on the remanent polarization, but also on the film microstructure, crystal orientation, and nature of the interfaces (state of formation/degradation, etc.) offers an excellent “tool” for probing the ferroelectric capacitors at virtually any stage of fabrication, including on-line quality control. In fact, simultaneous measurement of spectral photoresponse and spectral reflectance, as a distinctive signature of the device probed, is an ideal, high speed, non-invasive means of evaluation for such thin films at high spatial resolution (∼ 100 nm) using beam scanning. This paper discusses three aspects of such evaluation. First, the spectral transmittance of the film as a direct function of the microstructure, second, the use of band-gap illumination (365 nm) to condition a fatigued capacitor; and third, the optical E field interaction with the ferroelectric capacitor, yielding a high speed photoresponse which is related to the remanent polarization and the operational history (status of internal fields) of the ferroelectric capacitor. Combined, these different kinds of photoresponses provide a good signature of the device quality.