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  • 1
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.352071
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347952
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.350887
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1423632
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  • 5
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147316
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  • 6
    Digitale Medien
    Digitale Medien
    Transmission electron microscopy of interfaces utilizing mean inner potential differences between materials (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 4316-4318 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An electron beam propagating nearly parallel to the interface between two materials of different mean inner Coulomb potential (V0) is deflected towards the material with the largest ||V0||. It is experimentally demonstrated that this effect can be used to determine which of the two materials at an interface has the largest V0 and to image interfaces. Examples are presented from the SiO2/Si (111) interface and from a thin sandwich comprising the Al/Cu/Cr/SiO2/Si(100) interface system. Electron energy-loss spectroscopy of electrons deflected at the Si(111)/vacuum interface shows a strong surface plasmon peak, and with some instrumental improvements this may be a useful spectroscopic technique on buried interfaces.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.337475
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  • 7
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.343308
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  • 8
    Digitale Medien
    Digitale Medien
    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
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.342538
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  • 9
    Digitale Medien
    Digitale Medien
    An improved double fluorescence detector for fluorescence EXAFS measurements : INTERNATIONAL CONFERENCE ON SYNCHROTRON RADIATION INSTRUMENTATION (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 2509-2510 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In many cases the fluorescence EXAFS signal is contaminated with fluorescence from nearby elements. If this fluorescence is of lower energy than the element of interest, x-ray filters are not effective. One method for dealing with this problem is the double fluorescence method described by Wong and Rao. This paper describes an improved version of this double fluorescence scheme that greatly improves its efficiency. Data are presented for a sample of 1/2% Hf in Ni3 Al, and 1.6% CuO in NiO. When standard fluorescence is used, both signals are almost completely obscured by the (approximately-equal-to)100× larger Ni K fluorescence signal. With the double fluorescence detector the Hf L3 and Cu K-edge signals are clearly observed, and good spectra can be obtained in about an hour.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1140714
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  • 10
    Digitale Medien
    Digitale Medien
    Beamline X-11A at the NSLS: A unique facility for x-ray absorption spectroscopy : INTERNATIONAL CONFERENCE ON SYNCHROTRON RADIATION INSTRUMENTATION (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 1932-1935 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The design and operation of beamline X-11A at the NSLS is described. It employs a unique optical design using a two/four crystal monochromator and a SiC collimating mirror. In either the two- or four-crystal mode a sagittal focusing crystal allows collection of up to 5 mrad of horizontal divergence. Two techniques for rapid scanning of a sagitally focusing crystal will be described and compared. These are dynamically bending the crystal during the scan or translating a fixed radius bent crystal in a manner to maintain a fixed focus on the sample. The flexibility of this two/four crystal design allows the intensity and/or resolution of the beamline to be optimized for particular experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1140892
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