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  • 1
    Electronic Resource
    Electronic Resource
    Concentration profiling using x-ray reflectivity: Application to Cu-Al interfaces (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 1793-1799 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Synchrotron radiation measurements were made using glancing-angle x-ray reflectivity to study Cu-Al thin-film interfaces. The reflectivity data contains information about film morphology, and its sensitivity to the concentration of an element can be improved by measuring above and below an absorption edge. An analysis routine for the reflectivity data was developed to extract a model of the concentration profile and roughness. The results are compared from Cu-Al interfaces prepared in an ultrahigh vacuum environment, with and without exposure to oxygen before Al deposition. The reactions caused by thermal annealing at temperatures ranging from 65 to 160 °C are also studied. Density profiles of the two samples after various anneals indicate that there are different levels of mixing at the interface, and the tendency to reach a similar level after high-temperature (140–160 °C) anneals. The low levels of reaction observed in this work are difficult to detect by other techniques, such as Rutherford backscattering spectroscopy. In view of the simplicity and the sensitivity of the glancing-angle x-ray reflectivity technique, it can be generalized to other thin-film systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344350
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  • 2
    Electronic Resource
    Electronic Resource
    Versatile focusing using a combination of toroidal and Kirkpatrick–Baez mirrors : Papers from the 12th National Synchrotron Radiation Instrumentation Conference (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1527-1529 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Toroidal mirrors can be used to efficiently focus synchrotron radiation for magnifications near 1. At the Pacific Northwest Consortium-Collaborative Access Team (PNC-CAT) insertion device beamline, a toroidal mirror is used to focus the entire undulator beam to a spot size of 400(H)×100(V) μm2. For large demagnifications, Kirkpatrick–Baez (KB) mirrors are a good choice. Spot sizes down to 1 μm have been achieved at PNC-CAT. However, these mirrors only collect a fraction of the undulator beam, and result in a highly divergent beam with a short working distance. To achieve an intermediate beam size with less divergence, the toroidal and KB mirrors can be combined. The toroidal mirror reduces the beam to match the entrance aperture of the KB mirrors. This combination can provide beam sizes below 100 μm while collecting the entire undulator beam and providing a convenient working distance. Thus, the beam size, working distance, and divergence can be tailored to the needs of the experiment. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1423632
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  • 3
    Electronic Resource
    Electronic Resource
    Use of the program SHADOW in designing a capillary focusing beamline : The 9th National conference on synchrotron radiation instrumentation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3379-3380 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this report we consider the use of the program SHADOW for ray tracing different configurations of the PNC-CAT mircrofocus beamline. The emphasis is on the final design, which will include crystal and grazing incidence optics focusing onto the entrance of a long tapered glass capillary whose outlet diameter is of the order of one micron or less. The ray-tracing program has been especially valuable in comparing different configurations, determining the required stability of components, and optimizing the capillary profile. It has also been useful in evaluating the results of actual measurements on the throughput of long tapered capillaries fabricated of silica glass. Suggestions for improvements to SHADOW are given. We also present results of a compact pc-based capillary ray-tracing program for comparison. It allows us to use different profiles with minimal programming effort. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147316
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  • 4
    Electronic Resource
    Electronic Resource
    Standing-wave-assisted extended x-ray absorption fine-structure study of a Ni-Ti multilayer (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 290-293 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extended x-ray absorption fine structure (EXAFS) measurements have been made while simultaneously exciting x-ray standing waves in a multilayer structure. This allows the EXAFS signal from selected regions within the multilayer unit cell to be enhanced. The technique is applied to a Ni-Ti multilayer in which it is verified that strong standing-wave fields can be excited in the presence of substantial interfacial roughness. The measurements reveal little Ni-Ti intermixing and a strong low-Z impurity signal in the Ti layers. The standing-wave analysis indicates that the low-Z impurity is distributed throughout the Ti layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342538
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  • 5
    Electronic Resource
    Electronic Resource
    Tungsten-carbon multilayer composition and the effects of annealing: A glancing angle extended x-ray absorption fine structure study (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4250-4255 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results are presented from a glancing angle extended x-ray absorption fine structure study to investigate the structure of W/C multilayers and the effects of moderate annealing. There is evidence of considerable interlayer mixing prior to any heat treatment. It is found that after annealing to 350 °C for several hours, drastic changes can occur in the structural environment of the W atoms, with minimal changes in the reflectivity of the sample. There is extensive formation of W2C depending on the W thickness and the W/C ratio. Identification of this carbide as the product of annealing is unambiguous. Above a critical thickness, W begins to grow in its bcc form within the W layer, as it is prepared. This bcc layer is unaffected by the annealing process. The presence of carbon is shown to stabilize the amorphous state of W and inhibits any formation of W2C when the W thickness and W/C ratio are small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343308
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  • 6
    Electronic Resource
    Electronic Resource
    Extended x-ray-absorption fine-structure study of the position of Zr within the unit cell of Sm2Co17 : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5568-5570 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extended x-ray-absorption fine-structure spectroscopy (EXAFS) has been used to determine the position of Zr within the unit cell of Sm2Co17. Induction-melted Sm2Co17:Zr ternary alloys, aged at 1180 °C, then quenched, consisted of intimately mixed H2:17 and R2:17 having Zr in solid solution as well some regions of R2:17 that were poor in Zr. EXAFS spectroscopy of these specimens indicates that the most probable position for Zr is a site having 2 Sm near-neighbor atoms and 11 Co atoms distributed over three different interatomic distances. This is consistent with a direct substitution of Zr for Co in the Co site in the mixed planes (12j in P63/mmc or 18f in R3m).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347952
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  • 7
    Electronic Resource
    Electronic Resource
    Density and defects in thin metal films using x-ray reflectivity and variable-energy positrons (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4669-4673 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray reflectivity has been used to determine the absolute metal density for both metals in bilayers of Al on top of Co, Cr, Cu, Mn, Ni, and Pd. A large variation in density is found with an observed range of 0.87–1.0 of bulk values. The results can be correlated with changes in the defect character as determined by variable-energy positron measurements. The size of the open volume defects systematically increases as the metal density decreases. A distinct densification of the Co layer was observed after annealing, and was accompanied by a corresponding reduction in the average size of the defects. There seems to be at least a partial correlation of the density with the melting point of the metals, although other factors such as the crystal structure are likely important. These results also demonstrate the application of x-ray reflectivity and variable-energy positrons to studies of thin metal films, and a discussion of their potential utility is included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352071
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  • 8
    Electronic Resource
    Electronic Resource
    Interfacial reactions between nickel–chromium alloys and aluminum (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3766-3772 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the interface structure and reactions of Ni–Cr alloy and Al thin film bilayers using glancing-angle x-ray reflectivity and extended x-ray-absorption fine structure techniques. The Al/Ni–Cr bilayers were prepared by evaporation in ultrahigh vacuum with a clean interface (Clean) or an interface exposed to 600 Langmuir oxygen (O-exposed). No interfacial reaction is observed at room temperature in either the Clean or the O-exposed samples. Upon annealing for 10 minutes, initial reaction occurs at about 250 °C in the Clean sample and 310 °C in the O-exposed sample. The oxygen impurity at the interface retards the initial reaction and also modifies the diffusion behavior. In both Clean and O-exposed systems, the reaction starts between Ni and Al forming NiAl3. The reaction results in a Cr-rich region near the interface which transforms to the bcc structure. Only at higher temperatures do Cr and Al react to form CrAl7. The role of various diffusion channels and oxygen impurity at the interface in relationship to the reaction pattern will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350887
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  • 9
    Electronic Resource
    Electronic Resource
    EXAFS at grazing incidence: Data collection and analysis : Proceedings of the 4th international conference on synchrotron radiation instrumentation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 873-878 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Extended x-ray absorption fine structure (EXAFS) at grazing incidence can be applied to a large variety of surface and interface problems. This paper discusses in detail the collection and analysis of such data using interface EXAFS from metal/Al bilayers as an example. A comparison of the fluorescence and reflectivity detection channels is given, along with a discussion of the methods for correction of anomalous dispersion distortions. In addition, data from a Ni-Ti multilayer is used to demonstrate the potential of enhancing the sensitivity of the EXAFS signal to selected regions using standing wave effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142632
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  • 10
    Electronic Resource
    Electronic Resource
    Operation of a dynamically bent sagittally focusing double crystal monochromator for XAFS studies : Proceedings of the 4th international conference on synchrotron radiation instrumentation (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 880-884 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The X-11A beamline at the NSLS has been upgraded to include a dynamic sagittally focusing second crystal in the monochromator, currently operating in the range 5.5–11 keV. The monochromator maintains a constant focus at the sample by adjustment of the bent crystal radius during the XAFS scan. The monochromator accepts 3.3 mrad of horizontal radiation and a spot size of ∼1.5 mm2 is achieved at the sample. The sagittally focusing mechanism in the monochromator is described and the results are presented of intensity profiles, spatial stability, and energy resolution between the energy ranges 6 and 10 keV, where the system performs most favorably. Intensity gains over unfocused operation are substantial and XAFS studies of dilute fluorescence samples reveal the expected S/N improvements, without any introduction of additional noise from the bending process. The mechanism operates with close to 100% efficiency between the energy ranges 6 and 8 keV. Bending errors hinder the performance at higher energies and also preclude effective harmonic rejection, by piezocrystal detuning, over the entire energy range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142634
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