bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inherently Smart Laminates of Carbon Fibers in a Polymer Matrix
Authors: Ang Xiaojun W , Chung D. D. L. 
Published: April 2011

AbstractReal-time monitoring of fatigue damage and dynamic strain in inherently smart andcontinuous unidirectional (0° and 90°) and bidirectional (0°/90°) carbon fiber epoxy-matrix composites by electrical resistance (R) measurement was achieved. Upon cyclic tension (0°) of 0° or 0°/90° composites, R (0°) decreased reversibly, while R perpendicular to the fiber layers increased reversibly, though R in both directions changed irreversibly by a small amount after the first cycle. Upon fatigue testing of the 0° composite at a maximum stress of 57–58% of the fracture stress, the peak R (0°) in a cycle irreversibly increased both in spurts and continuously, due to fiber breakage, which started at 30% of the fatigue life. For the 90° composite, R(0°) increased reversibly upon tension (0°) and decreased reversibly upon compression (0°).
Advanced Aircraft Engine Microlaminated Intermetallic Composite Turbine Technology
Authors: Rowe R. G. , Skelly D. W. , Jackson M. R. , Larsen M. , Lachapelle D. 
Published: April 2011

AbstractHigher gas path temperatures for greater aircraft engine thrust and efficiency will require both higher temperature gas turbine airfoil materials and optimization of internal cooling technology. Microlaminated composites consisting of very high temperature intermetallic compounds and ductile refractory metals offer a means of achieving higher temperature turbine airfoil capability without sacrificing low temperature fracture resistance. Physical vapor deposition, used to synthesize microlaminated composites, also offers a means of fabricating advanced turbine blade internal cooling designs. The low temperature fracture resistance of microlaminated Nb(Cr)-Cr2Nb microlaminated composites approached 20 MPa√m in fracture resistance curves, but the fine grain size of vapor deposited intermetallics indicates a need to develop creep resistant microstructures.
Analysis of Stresses and Strains In Passivated Metal Lines
Authors: Eppler I. , Schroeder H. , Burges U. , Schilling W. 
Published: April 2011

AbstractPassivated metal lines, commonly used in integrated circuits, show thermally induced stresses due to the difference of the thermal expansion coefficients of the lines and their surroundings. These stresses cause voidage and plastic flow of the lines. Aim of the analysis was to derive equations connecting experimentally measured strains or stresses by the X-ray diffraction and wafer curvature techniques with the magnitude of voidage and plastic shear deformation of the lines.Using the concepts of linear elasticity the volume averaged stresses of an array of parallel interconnects embedded in a passivation layer on a flat substrate are analysed. Equations are derived connecting the volume averaged stresses in the metal and in the passivation with the “Heigen-strains” of the metal which characterize the true (stress free) thermal strains and plastic deformation strains of the metal. The coefficients entering these equations are determined from (elastic) finite element method (FEM) calculations performed for various geometries and aspect ratios of the metal lines. Choosing the proper values of the coefficients allows the eigen- strains to be determined from the experimental data.By comparison of the evaluated eigen-strains with the purely elastic eigen-strains ΔαΔT the extent of voidage and/or plastic shear deformation of passivated metal lines caused by thermally induced stresses can be determined model independently.
Processing-Induced Stresses and Curvature in Patterned Lines on Silicon Wafers
Authors: Shen Y. -L. , Suresh S. , Blech I. A. 
Published: April 2011

AbstractThe evolution of stresses due to the patterning and thermal loading of thin lines on Si wafers, and the consequent changes in the overall curvature of the wafer are studied theoretically and experimentally. The analysis involves finite element simulations within the context of generalized plane strain models. The analysis is capable of predicting the wafer curvature in directions parallel and perpendicular to the lines. These predictions compare reasonably well with experimental measurements of curvature made on model systems. The thickness, width and spacing of the patterned lines have been varied systematically, and the associated changes in the evolution of stresses and curvature have been determined. The non-uniform stress field within the fine lines is also analyzed.
Stress Analysis of Titanium Dioxide Films by Raman Scattering and X-Ray Diffraction Methods
Authors: Meng Li-Jian , Santos M. P. dos 
Published: April 2011

AbstractTitanium dioxide films have been deposited onto glass substrates by dc reactive magnetron sputtering at different sputtering pressures (2×10−3 -- 2×10−2 mbar). The films have been characterized by measuring their Raman scattering and X-ray diffraction (XRD). The films stress have been calculated by analyzing their Raman spectra and X-ray diffraction spectra. Two methods give similar results which films prepared at low sputtering pressure have high stress values.
Effect of Thickness and Annealing on Stress in Tantalum and Tantalum Nitride Thin Film Hard Coatings
Authors: Saha Ranjana , Inturi Rama B. , Barnard John A. 
Published: April 2011

AbstractAn understanding of the relationship between stress and the other properties of thin films is extremely useful in the design of hard coatings for long term performance. In our earlier study, sputtered Ta and Ta(N) films were found to exhibit promising hard coating properties. For example, nano hardness as high as 30 GPa was observed in the nitride (pN2 = 0.100 mTorr) films. In this work, we study the variation in the stress in these films with respect to film thickness and annealing. Films in six different thicknesses (50, 250, 350, 500, 750, and 1000 nm) were deposited on oxide coated Si (111) wafers. Stresses in the films in the as-deposited state and as a function of temperature (300°C) were determined using a thin film stress measuring unit.
Effect of in and Out of Plane Stresses During Indentation of Diamond Films on Metal Substrates
Authors: Bahr D. F. , Gerberich W. W. 
Published: April 2011

AbstractDiamond films grown on molybdenum substrates are indented with conical diamond indenters to depths more than 5 times the thickness of the film. This causes delamination and spalling of the film. The effects of variations in indenter angle and film thickness are demonstrated. Using a radius of the delaminated area to the residual contact radius, sharper indenters are shown to cause a 10 to 20% change in that ratio. For films greater than 5 μm thick, there is no apparent film thickness effect. Possibilities for this observation are cracking due to bending stresses or the interfacial crack kinking out of the interface due to a reduction in compressive stresses, leading to mixed mode loading. The strain energy release rate of the interface for an 800 nm diamond film on molybdenum is between 2.4 and 7 J/m2.
Phase Transitions and Local Structure of PbZrO3
Authors: Teslic S. , Egami T. 
Published: April 2011

AbstractThe local atomic structure of PbZrO3 (PZ) as a function of temperature has been examined using the atomic pair distribution function (PDF) analysis of the pulsed neutron powder-diffraction data. The local structure was found to be deviated significantly from the crystallographic average structure, and to vary less with the composition than the crystallographic average structure. Disordered oxygen octahedral rotations have been observed in the low-temperature antiferroelectric state. With heating the M-type rotation of octahedra becomes dominant and it persists through the intermediate phase into the high-temperature paraelectric state. The Pb displacements reflect these strong deviations, and locally have a large z-component. At room temperature, deviation of Pb displacements from the antiparallel [110] pattern was found. With increasing temperature disorder in the Pb displacement increases.
Angle-Resolved Photoemission Extended Fine Structure Study Of Chemisorbed c(2×2)P/Fe(100): Comparison With Self-Consistent-Field Xα Scattered Wave Calculations
Authors: Huff W.R.A. , Chen Y. , Zhang X.S. , Terminello L.J. , Tao F.M. , Pan Y.K. , Kellar S.A. , Moler E.J. , Hussain Z. , Wu H. , Zheng Y. , Zhou X. , Wittenau A.E. Schach von , Kim S. , Huang Z.Q. , Yang Z.Z. , Shirley D.A. 
Published: April 2011

AbstractAngle-resolved photoemission extended fine structure (ARPEFS) was used to determine the structure of c(2×2)P/Fe(100) for the first time. P 1s core-level photoemission data were collected normal to the (100) surface and 45° off-normal along the [011] direction at room temperature. A close analysis of the auto-regressive linear prediction based Fourier transform and multiple-scattering spherical-wave calculations indicate that the P atoms adsorb in the high-coordination four-fold hollow sites. The P atoms bond 1.02 Å above the first layer of Fe atoms and the Fe-P-Fe bond angle is 140.6°. Additionally, it was determined that there is no expansion of the Fe surface. Self-consistent-field Xα scattered wave calculations were performed for the c(2×2)P/Fe(100) and the c(2×2)S/Fe(100) systems. These independent results are in excellent agreement with this P/Fe structure and the S/Fe structure previously published, confirming the ARPEFS determination that the Fe1-Fe2 interlayer spacing is contracted from the bulk value for S/Fe but not for P/Fe.
Formation and Properties of Roughened Poly-Si Electrodes for High-Density Drams
Authors: Liu H. W. , Lin Z. J. , Yu S. Y. , Huang S. C. , Cheng H. C. 
Published: April 2011

AbstractA novel structure, based upon phosphorus-implanted poly-Si films treated with phosphoric acid (H3P 4) and the standard RCA cleaning process, has been demonstrated as the bottom electrodes of DRAMs' stacked capacitors. After the H3PO4 treatment and the RCA cleaning process, micro-islands are formed on the poly-Si surface of the electrodes. For the capacitors with this novel structure, the capacitance value is 18.17 fF/μm2 and the effective oxide thickness is 18.9 Å in comparison with conventional capacitors of 5.77 fFW/μm2 and 59.5 Å. The roughened poly-Si electrode can achieve a surface enlargement of 3.15 times. The leakage current density at +1.65V and −1.65V are 7.24 × 10−8 A/cm2 and −3.31 × 10−8 A/cm2, respectively, fulfilling the requirements of 256Mb DRAMs. Weibull plots of time-zero-dielectric-breakdown (TZDB) characteristics under ramping voltage test also show tight distribution and good electrical properties. It indicates that the phosphorus-implanted poly-Si films etched by H3PO4 and then cleaned with the standard RCA process can easily and simply increase the surface area and have good electrical properties fulfilling the requirements of 256Mb DRAMs and beyond.
Phase Selection by Competitive Growth in Ti/Al Thin Film Diffusion Couples
Authors: Wöhlert S. , Michaelsen C. , Bormann R. 
Published: April 2011

AbstractThe early stages of the solid-state reaction between Ti and Al are characterized by a distinct phase selection in favor of TiAl3. In order to understand the selection mechanism which leads to the absence of phases other than TiAl3, trilayers were prepared by sputtering with a layer of α2-Ti3Al or γ-TiA1 being sandwiched between the Ti and Al layers. The growth of TiA13 in competition with α2 or γ was observed by transmission electron microscopy investigations. Upon annealing, the α2 and the γ layers were consumed by growth of TiA13.The results indicate that the absence of phases other than TiAl3 is not due to the existence of nucleation barriers for α2 and γ, but is caused by a growth selection. A kinetic model is presented which quantitatively explains the observed phase selection on the basis of different growth velocities which result from different diffusion rates in the competing phases.
SnO2:F Thin Films with High Fluorine Contents Produced by Spray Pyrolysis at Constant Substrate Temperature
Authors: Acosta D. R. , Zironi E. , Estrada W. , Montoya E. 
Published: April 2011

AbstractFluorine doped tin oxide thin films were prepared from solutions with high fluorine contents using the spray pyrolysis technique; the resulting films were studied by electron and X-ray diffraction methods; the resonant nuclear reaction (RNR) method was used to determine the final concentration of fluorine atoms in our films for different doping levels. Also, electrical and optical properties of SnO2:F films were measured and correlated with deposition and structural parameters obtained from X-Ray diffraction and electron microscopy studies.
In-Situ x-Ray Diffraction Analysis of TiSi2 Phase Formation from a Titanium-Molybdenum Bilayer
Authors: Cabral C. , Clevenger L. A. , Harper J. M. E. , Roy R. A. , Saenger K. L. , Miles G. L. , Mann R. W. 
Published: April 2011

AbstractWe demonstrate that the addition of a molybdenum interlayer between titanium and silicon enhances the formation of C54 TiSi2, without bypassing the formation of the C49 TiSi2 phase. In situ x-ray diffraction analysis during rapid thermal annealing, at a rate of 3 °C/s, was used to study the phase formation sequence of TiSi2 starting from a blanket bilayer of Ti on Mo on a polycrystalline Si substrate. It was shown, as in the case without the Mo layer, that the C49 TiSi2 phase forms first, followed by the C54 TiSi2 phase. The results were similar for undoped or arsenic, boron, and phosphorous doped polycrystalline silicon substrates. The temperature range over which the C49 phase is stable is reduced, on average, by 80 °C. The lower end of the range (appearance of C49) is increased by approximately 60 °C and the upper end of the range (disappearance of C49) is decreased by about 20 0C. The orientation of the C49 phase differs in that both the C49(131) and C49(060) orientations are observed, compared to the case without the Mo layer where only the C49(131) orientation is observed.
Phase Transformation and Microstructural Properties in Sputtered Vs. CVD WSi, Films
Authors: Dornenicucci A. , Dehm C. , Loh S. , Clevenger L. A. , Dziobkowski C. , Cabral C. , Lavole C. , Jorden-Sweet J. 
Published: April 2011

AbstractCVD WSi, films produced by dichlorosilane reduction at 570°C and WSi, films sputter deposited at 50°C were characterized by in situ x-ray diffraction (IS-XRD), in situ resistivity (ISRes), in situ stress (IS-stress), ex situ/in situ transmission electron microscopy (EX/IS-TEM) and ex situ Auger electron spectrometry (EX-AES) over the temperature range 25–1100°C. The CVD films were crystalline after deposition, with columnar grains in the hexagonal phase and a Si:W atomic ratio of 2.6:1. The CVD films exhibited a sharp hexagonal to tetragonal phase transformation near 750°C. The final grain size was greater than the film thickness, with no evidence of voiding. Avrami analyses gave traditional curves with n values of 2 for the phase transition in the CVD films. In comparison, the sputtered films were amorphous as deposited (Si:W atomic ratio of 2.8:1 ) and crystallized to a different hexagonal phase microstructure than did the CVD films. The sputtered films showed a broad hexagonal to tetragonal phase transformation near 800°C, and a final grain size that was less than the fihn thickness with much voiding. A low Avrami exponent of 0.2 to 0.4 was obtained for the transformation of the sputtered films.
Native Oxide and the Residual Stress of Thin Mo and Ta Films
Authors: Parfitt L. J. , Rek Z. U. , Yalisove S. M. , Bilello J. C. 
Published: April 2011

AbstractResidual stress changed substantially between 2.5 and 80 nm film thickness in very thin Mo and Ta coatings sputtered onto Si substrates with native oxide. For both Mo and Ta, the thinnest films had a high compressive stress on the order of 2 to 3 GPa, and the stress relaxed, or became slightly tensile, with increasing film thickness. The coatings were examined using a variety of advanced characterization techniques including Auger Electron Spectroscopy (AES), Grazing Incidence X-ray Scattering (GIXS), and High Resolution Transmission Electron Microscopy (HRTEM). AES showed the presence of 0 and C contamination at the interface between the substrate and the film; these impurities originated from the adsorbed species and the native oxide on the surface of the wafers. GIXS analysis of the Mo films showed that the lattice of the thinnest layers was considerably expanded compared to the interplanar spacing of bulk, pure Mo. This expansion was caused by incorporation of impurities from the substrate into interstitial sites, which caused the very high compressive stress. HRTEM showed that the sputter deposition process did not alter the thickness of the native oxide layer, suggesting that the Mo and Ta films interacted with only the adsorbed impurities and the top one or two layers of the SiO2. Mo films deposited onto clean W layers were tensile, which supported the hypothesis that impurities caused the high compressive stresses in the films deposited onto SiO2. Grain growth and phase transformations contributed to the relaxation in stress observed in the thicker films.
Real-time Characterization of the Optical Properties of an ultra-thin Surface Reaction Layer during Growth
Authors: Dietz N. , Sukidib N. , Harrisb C. , Bachmann K. J. 
Published: April 2011

AbstractThe average optical properties of an ultra-thin surface reaction layer (SRL) during growth by pulsed chemical beam epitaxy (PCBE) can be quantitatively accessed by p-polarized reflectance spectroscopy (PRS), as demonstrated on the example of heteroepitaxial GaP growth. Under PCBE growth conditions, the surface of the substrate is exposed to pulsed ballistic beams of tertiarybutyl phosphine [TBP, (C4H9)PH2] and triethylgallium [TEG, Ga(C2H5)3]. The pulsed precursor supply causes a period in composition and thickness modulated SRL, monitored as a fine structure that is superimposed on interference oscillations, resulting from back reflection at the substratelayer interface with increasing layer thickness. The amplitude of this fine structure undergoes a period amplitude modulation and exhibits turning points at which the response to the first precursor pulse changes sign. The turning points can be characterized by the expression R4(Φmax)=R4(Φmin), which describes the maximal and minimal values of the temporally modulated phase factor in the SRL, using a four layer stack description. The positions of these turning points are not affected by the thickness of the SRL, which allows the computation of the average complex dielectric function of the SRL independent of its thickness. In the next step, the average thickness of the SRL can be extracted from the amplitude of the observed fine structure.
Stress-Driven Wrinkling oF α-Alumina Films Grown oN Fe-Cr-Al by Thermal Oxidation
Authors: Tolpygo Vladimir K. , Clarke David R. 
Published: April 2011

AbstractA thin α-Al2O3 film forms on Fe-20w/oCr-5w/oAl alloys when they are heated in air to about 1000°C. This thermally grown oxide exhibits a wrinkled morphology within minutes and with an amplitude and characteristic wavelength that increases with oxidation time. Measurements of the residual strain in the oxide, using Cr3+ photoluminescence piezospectroscopy, indicate that the wrinkling is associated with stress relaxation during the course of the thickening of the oxide. AFM and piezospectroscopic measurements reveal a strong time dependence of the growth stress and oxide wrinkling, as well as a marked dependence on the crystallographic orientation of the underlying Fe-Cr-Al substrate. Small additions (about 0.3 w/o) of yttrium to the metal completely suppress the wrinkling phenomenon although it is found not to lessen the growth stresses in the oxide film.
Stress and its Effect on Surface Morphology in Multi-Layer Ti-Cu Films
Authors: Zhou Ping , Buchman Saps , Gray Chris , Turneaure John , Turlo James E. 
Published: April 2011

AbstractWe have characterized the stress and its effects on surface morphology for multi-layer thin films of about 3μm total thickness, consisting of three or seven layers of Ti and Cu. These films constitute the electrostatic suspension electrodes for the gyroscope housings of the Relativity Mission Gravity Probe B. Full understanding of surface morphology is critical for meeting the complex requirements of this application.The residual stresses have been measured using a laser curvature technique, while the surface morphology was studied by scanning electron microscopy (SEM). We find that the surface morphology depends strongly on the stress, which evolves with the Ti-Cu multi-layer period. Average stress and the resulting surface roughness decrease for thinner Cu layers (increased total number of layers). Seven layer Ti-Cu films with low stress and very smooth surface have been successfully used for the electrodes of the gyroscope housings.
Slow Decay of Reflection High Energy Electron Diffraction Oscillations in Cal1-xMgxF2
Authors: Kushibe Mitsuhiro , Shusterman Yuriy V. , Yakovlev Nikolai L. , Schowalter Leo J. 
Published: April 2011

AbstractMagnesium is incorporated into the growth of Ca1-xMgxF2 to reduce the lattice constant of fluorite (CaF2) which is 0.6% larger than that of Si at room temperature. When grown epitaxially on Si(111) substrates at 300°C, the lattice constant of the alloy became smaller than that of Si by 1.5% when the Mg concentration was around 20%. At higher Mg concentrations, the lattice constant did not decrease any further. This invariability of the lattice constant was caused by a phase separation of the Ca1-xMgxF2 layer into a Mg-rich region and a Mg-deficient region. When the growth temperature was increased, the critical Mg concentration for the phase separation became smaller. When Ca1-xMgxF2 was grown on vicinal Si(111) substrates, the reflection high energy electron diffraction (RHEED) intensity oscillations reflected no change in the composition, suggesting segregation of a Mg-rich phase along the steps. Nevertheless, the oscillations in the intensity of the specular spot for Ca1-xMgxF2 lasted longer than those observed for pure CaF2, suggesting a flatter surface for the alloy. Scanning tunneling microscopy (STM) observations support this model.
Structural Studies Of Epitaxial CdF2 Layers on Si(111)
Authors: Khilko A. Yu. , Kyutt R. N. , Mosina G. N. , Sokolov N. S. , Shusterman Yu. V. , Schowalter L. J. 
Published: April 2011

AbstractEpitaxial CdF2 layers, which may be used in light-emitting devices integrated with silicon, were grown by Molecular Beam Epitaxy (MBE). Characterization of the layers by Rutherford Backscattering Spectroscopy (RBS), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) showed that optimal growth temperature lies in the range 60–80°C. The sticking coefficient of CdF2 molecules was found to decrease at temperatures above 100°C. Different modes of misfit strain relaxation were observed above and below that temperature.
Atomic Force Microscopy Study of Hard Coating Films Prepared by Pulsed Laser Deposition Method
Authors: Chan Hsieh-Li , Kumar Ashok , Sanderson L. , Weimer J. J. 
Published: April 2011

AbstractAluminum nitride (AIN), silicon nitride (Si3N4), and silicon carbide (SIC) thin films have been snthesized using pulsed laser deposition (PLD) techniques. AIN and Si3N4 films were deposited on Si (100) substrates at different temperatures (room temperature to 600°C) and partial pressures (15 mTorr N2 to 200 mTorr N2). SiC films were deposited on Si (100) substrates at different temperatures (room temperature to 400°C) in high vacuum. The atomic force microscopy (AFM) is a useful tool for studying the surface topography of these technologically interesting thin film surfaces. This paper discusses in detail AFM analysis of thin film coatings.