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  • 1
    Electronic Resource
    Electronic Resource
    Structural and magnetic properties of R(Fe1−yCoy)12−xNbx compounds (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2165-2171 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of RFe12−xNbx and R(Fe1−yCoy)11.3Nb0.7 compounds with R=Y, Tb, and Dy have been investigated in the concentration region defined by 0.6〈x〈0.8 and y≤0.3, where the compounds are single phase with the ThMn12-type of structure. The Curie temperature TC of the RFe12−xNbx compounds is almost independent of the Nb content whereas the saturation magnetization Ms decreases with increasing Nb content. The spin-reorientation temperature Tsr of the TbFe12−xNbx and DyFe12−xNbx compounds decreases monotonically with increasing x. Substitution of Co for Fe in RFe11.3Nb0.7 leads to a remarkable increase of TC and the appearance of a maximum in the Co-concentration dependence of Ms. In contrast, Tsr decreases monotonically with increasing Co content for both R=Tb and Dy. The modification of T- and R-sublattice anisotropy originating from a change of the Nb content and from substitution of Co for Fe was analyzed by combining crystalline electric field theory and the individual-site model. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1425441
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  • 2
    Electronic Resource
    Electronic Resource
    Composition, residual stress, and structural properties of thin tungsten nitride films deposited by reactive magnetron sputtering (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1380-1388 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin tungsten nitride (WNx) films were produced by reactive dc magnetron sputtering of tungsten in an Ar–N2 gas mixture. The effects of the variation of nitrogen partial pressure on the composition, residual stress, and structural properties of these films as well as the influence of postdeposition annealing have been studied. The films were analyzed in situ by a cantilever beam technique, and ex situ by x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, x-ray diffraction, and transmission electron microscopy (TEM). It was found that at N concentrations below 8 at. %, the films (typical 150 nm in thickness) were essentially bcc α-W. An amorphous phase was observed in the range of about 12–28 at. % N. When N concentrations reached ∼32 at. % or above, a single-phase structure of W2N was formed. Annealing of the as-deposited films resulted in crystallization of the amorphous or an improved crystallinity of the W2N structure, which was related to the N concentration. Stresses of all W and WNx films were compressive. As the N concentration was increased, the stress decreased and reached its lowest value for amorphous samples near 20 at. % N. Past this point, the compression of films rose again. These results can be ascribed to structural changes induced by the pressure-dependent variation in the average energy of particles bombarding the film during deposition. Cross-sectional TEM studies showed that all crystalline WNx films had columnar microstructures. The average column width near stoichiometry of W2N was ∼20±5 nm near the film surface. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373827
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  • 3
    Electronic Resource
    Electronic Resource
    Large change of the giant magnetoresistance behavior after changing the spacer from Cu to CuMn alloy in Co/spacer/Co structures (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5030-5032 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The giant magnetoresistance (GMR) effects in sandwiched Co/Cu/Co and Co/CuMn/Co structures have been investigated. The GMR oscillates with the spacer thickness for both cases, but is nearly antiphased. With diluted Mn atoms in the Cu spacer, the GMR curve as a function of the magnetic field changes a lot, and the saturation/switching field for GMR can be reduced greatly compared with that in Co/Cu/Co systems. This may indicate one way to obtain a highly sensitive GMR. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370081
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  • 4
    Electronic Resource
    Electronic Resource
    On the prediction of electromigration voiding using stress-based modeling (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4039-4041 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In modeling electromigration failure, it is common to employ the concept of a critical stress at which interconnect failure occurs. In this report, we illustrate that the atomic flux divergence, obtained directly from the one-dimensional stress-based modeling, is more appropriate in characterizing the formation of void in electromigration. A numerical analysis was carried out, to model the evolution of stress, atomic flux, and flux divergence in an aluminum line containing a fast-diffusion segment. The maximum flux divergence, not the maximum tensile stress, predicts the voiding location which is consistent with microscopic observations in the experiments of Joo et al. [Acta. Mater. 46, 1969 (1998); J. Appl. Phys. 85, 2108 (1999)] utilizing nanoindented single-crystal aluminum lines. This is because the flux divergence directly reflects the extent of matter depletion, and thus the propensity of voiding. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372452
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  • 5
    Electronic Resource
    Electronic Resource
    Residual stress, microstructure, and structure of tungsten thin films deposited by magnetron sputtering (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 177-187 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The residual stress and structural properties of tungsten thin films prepared by magnetron sputtering as a function of sputtering-gas pressure are reported. The films were analyzed in situ by a cantilever beam technique, and ex situ by x-ray diffraction, cross-sectional transmission electron microscopy (TEM), x-ray photoelectron spectroscopy, electron energy-loss spectrometry, and energy-filtered electron diffraction. It is found that the residual stress, microstructure, and surface morphology are clearly correlated. The film stresses, determined in real time during the film formation, depend strongly on the argon pressure and change from highly compressive to highly tensile in a relatively narrow pressure range of 12–26 mTorr. For pressures exceeding ∼60 mTorr, the stress in the film is nearly zero. It is also found that the nonequilibrium A15 W structure is responsible for the observed tensile stress, whereas the stable bcc W or a mixture of bcc W and A15 W are in compression. Cross-sectional TEM evidence indicates that the compressively stressed films contain a dense microstructure without any columns, while the films having tensile stress have a very columnar microstructure. High sputtering-gas pressure conditions yield dendritic-like film growth, resulting in complete relaxation of the residual tensile stresses. Structural details of the A15 W and amorphous W phases were also investigated at the atomic level using energy-filtered electron diffraction with reduced radial distribution function G(r) analysis. By comparing the experimental and simulated G(r) distributions, the A15 W structure is determined to be composed of ordered and stacking faulted W3W structures and the amorphous W has a disordered structure of W3O. The effect of oxygen in stabilizing the A15 phase found is explained on the basis of structural and thermodynamic stability. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371841
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  • 6
    Electronic Resource
    Electronic Resource
    Stresses, curvatures, and shape changes arising from patterned lines on silicon wafers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1388-1398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental and numerical results are presented on the evolution of stresses and the accompanying changes in the overall curvatures due to the patterning of silicon oxide lines on silicon wafers and subsequent thermal loading. The finite element analysis involves a generalized plane strain formulation, which is capable of predicting the wafer curvatures in directions parallel and perpendicular to the lines, for both the patterning and thermal cycling operations. The predictions compare reasonably well with systematic curvature measurements for several different geometrical combinations of the thickness, width and spacing of the patterned lines. The non-uniform stress fields within the fine lines and the substrate are also analyzed. It is shown both experimentally and theoretically that certain geometries of patterned lines on the substrate induce dramatic shape changes and reversals of curvature in the direction perpendicular to the lines. The mechanistic origin of this effect is identified to be the Poisson effect arising from the anisotropic strain coupling in the patterned structure. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362938
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  • 7
    Electronic Resource
    Electronic Resource
    Oxygen-induced amorphous structure of tungsten thin films (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2211-2213 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A combination of energy-filtered electron diffraction, electron energy-loss spectroscopy, transmission electron microscopy, and x-ray diffraction are used to establish that oxygen impurities incorporated in tungsten films prepared by magnetron sputtering in the early stage of the deposition play a dominant role in the formation of an amorphous phase. Energy-filtered electron diffraction data collected from a range of amorphous films were Fourier transformed to a reduced density function (RDF) and matched with an amorphous model. The results show that better agreement with the experimental RDF is achieved if the amorphous model consists of a random continuous matrix of clusters with W3O-like symmetry. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124967
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  • 8
    Electronic Resource
    Electronic Resource
    Excitation of higher harmonics in transient laser gratings by an ablative mechanism (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1640-1642 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser-induced transient gratings were excited at the surface of an aluminum film by picosecond laser pulses. The counterpropagating surface acoustic waves with a fundamental frequency of 70 MHz that were launched were monitored outside the source region by laser probe beam deflection. The second and third harmonics were observed for ablative interaction of the laser radiation with the aluminum surface. A simple model is presented that describes the effects on the basis of nonlinear photoacoustic signal generation at the source due to a nonsinusoidal driving force. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122231
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  • 9
    Electronic Resource
    Electronic Resource
    Stresses, deformation, and void nucleation in locally debonded metal interconnects (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 5525-5530 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three-dimensional analyses of stresses and deformation in metal interconnects were carried out using the finite element method within the continuum framework. Particular attention is devoted to the preexisting local debond between the metal line and dielectric, which serves as the void nucleation site. Thermal mismatch induced stresses in the aluminum line near the interface defect are considered. The local reduction of stresses as well as the stress gradient along the line are quantified for various debond sizes. It is found that, for aluminum lines with an aspect ratio of unity, the influence of local debond on the stress profile along the line direction becomes negligible in regions greater than about one line height away from the debond edge. A unique stress pattern due to the preexisting debond is identified, which forms the basis of constructing a void nucleation model in terms of crystallographic slip. This three-dimensional modeling provides quantitative information on the initial stress field useful for modeling stress and electromigration induced voiding; it also confirms the qualitative features of stress evolution obtained from a previous two-dimensional analysis. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368597
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  • 10
    Electronic Resource
    Electronic Resource
    Modeling of thermal stresses in metal interconnects: Effects of line aspect ratio (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1578-1581 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical results are presented on the evolution of thermal stresses in metal interconnects. Finite element analyses are carried out for a series of parallel aluminum lines embedded within silicon dioxide. The effects of line aspect ratio on the longitudinal and hydrostatic stresses in lines are investigated, for various spaces between lines. Comparisons with the results based on an isolated line under passivation are also made. It is shown that, contrary to what was frequently found by employing the single-line approach, maximum stresses in periodically arranged aluminum lines do not occur when the line width and the line height are approximately equal. The variation of stresses with line aspect ratio is affected by the spacing between lines. Implications of the present findings to the modeling of stresses and to the damage evolution through void formation are discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365944
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