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  • 1
    Digitale Medien
    Digitale Medien
    Stability of tungsten/carbon and tungsten/silicon multilayer x-ray mirrors under thermal annealing and x-radiation exposure (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 168-174 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effect of thermal annealing and irradiation in an intense white synchrotron x-ray beam on the x-ray reflectance of tungsten/carbon and tungsten/silicon multilayers is reported. Thermal annealing at 400 °C for two hours produces larger effects than irradiation of cooled multilayers in the white beam of a 20-pole hard x-ray wiggler with 0.94-T peak field on the storage ring DORIS operating at 5.42 GeV and electron currents of 20–36 mA for 40 h. Thermal annealing caused the period and first order reflectance of a W/Si sample to decrease, in contrast to a W/C sample whose period and reflectance increased on annealing. Of five actively cooled samples irradiated, one W/C sample showed significant change in reflectance. Preannealing of this multilayer stabilized it to radiation-induced changes. Irradiation effects also depend on multilayer period and constituent materials. Implications of these results for models describing multilayer reflectance and for multilayer applications in the new generation of synchrotron radiation sources are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347739
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  • 2
    Digitale Medien
    Digitale Medien
    Thermal evolution of X/C multilayers (with X=W, Ni, or SiWSi): A systematic study (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5146-5154 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The thermal behavior of X/C multilayers (nanometer-thick layers made of tungsten, nickel, or SiWSi alternating with carbide or pure carbon) was studied. Two types of annealing were performed: the pulsed laser annealing in air and the classical thermal annealing in a vacuum furnace. Depending on the composition and the structure of the layered materials, thermal stability or diffusion mechanisms were observed and further analyzed by small-angle x-ray scattering, transmission electron microscopy, and Auger electron spectroscopy. The results show that the period expansion and the reflectivity evolution, that were observed in some cases after treatment, are caused both by structural changes into the layers and by exchange of matter between layers. These changes always induce a partial graphitization of the amorphous carbon and, in the case of W/C multilayers, the formation of a W2C compound.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.347055
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  • 3
    Digitale Medien
    Digitale Medien
    Anomalous expansion of tungsten-carbon multilayers used in x-ray optics (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2301-2303 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Using microcleavage transmission electron microscopy and x-ray diffraction, we have studied the anomalous expansion observed in tungsten-carbon multilayers. Our results show that the expansion is mostly due to an agglomeration of the tungsten and the effect is larger for samples that have a thinner tungsten layer. Implications for soft x-ray optics are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.337192
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  • 4
    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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  • 5
    Digitale Medien
    Digitale Medien
    Design and performance of graded multilayers as focusing elements for x-ray optics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3227-3232 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We have developed a design method to produce laterally graded multilayer x-ray mirrors based on sputter deposition techniques. The optimization of all relevant parameters yields an ab initio estimation of any layer gradient suitable to achieve precise x-ray focusing devices. The performance and the accuracy of this method are demonstrated. A graded W/B4C multilayer was deposited on a flat substrate that was bent to a parabola. The obtained nonlinear lateral gradient differed from the theoretical calculations by less than 1%. Focusing experiments performed at an x-ray energy of 8 keV on the ESRF optics beamline revealed an excellent performance with a focal spot size of about 7 μm. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1149897
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  • 6
    Digitale Medien
    Digitale Medien
    Optimization of multilayer reflectivity and bandpass for soft to hard x-ray applications [0.1–200 keV] : The 9th National conference on synchrotron radiation instrumentation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3356-3356 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In the last decades, the major motivation for manufacturing multilayer mirrors has been in soft x-ray applications, particularly for astronomy, microlithography, and polarimetry. The advent of high energy synchrotron storage rings has provided a new significant impetus emphasizing high energy applications and especially when flux, rather than resolution, is desired. In this paper we present the reflection properties of the most promising multilayer material combinations for the energy range from 0.1 keV up to 200 keV. Previous calculations by Rosenbluth were limited to a maximum of 2 keV and to multilayers composed of pure elements and operating under normal incidence. As alloys might be essential for a smooth growth and/or for stability under high heat load, our screening consisted of a list of up to 300 solids having a melting point above 100°C and that could be deposited in a sputtering process. A full computer search calculates 45000 multilayer combinations for each angle (or multilayer d-spacing) and energy of operation, the only necessary input variables. Other manufacture-related parameters can be specified to give a more realistic picture of the performance. As the number of layers is often limited, a nonperiodic design could minimize absorption effects. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1147462
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  • 7
    Digitale Medien
    Digitale Medien
    Performance of multilayers in intense synchrotron x-ray beams : International conference on synchrotron radiation instrumentation (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 1999-2002 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The use of multilayer reflectors under intense synchroton x-ray beams requires to develop a new generation of multilayered materials that can withstand a high-power load in excess of 100 W/mm2. Multilayers with the high-Z layer consisting either of a pure element or of compounds such as carbides, nitrides, or silicides have been produced. Because the fabrication conditions are not yet optimized, thin films with satisfactory layer were not obtained leading to poor reflectivities. Such multilayers have been both thermally annealed in a furnace and exposed to a synchrotron beam with a power density of about 1 W/mm2. The resulting damage ranges from the total destruction of the layering to a reduction of the reflectivity by typically 40%–60%. In some cases an only 1%–15% loss in reflectivity has been observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1140859
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  • 8
    Digitale Medien
    Digitale Medien
    Scanning tunneling microscopy characterization of the morphology of Fe/C multilayers grown on silicon substrates (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 248-254 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Fe/C multilayers have been deposited by rf sputtering on two silicon substrates with a significant difference in surface quality. Scanning tunneling microscopy (STM) shows a roughness replication process: the smoother the substrate, the smoother the final surface. Both samples present a Gaussian height distribution. The fractal analysis of the STM data shows that, for dimensions larger than the grain size, the surface can be described as a self-affine fractal with a fractal dimension of 2.6±0.1, which agrees with the prediction of ballistic deposition models without restructuring. For dimensions lower than the grain size, the fractal dimension is close to the Euclidean value 2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.355891
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  • 9
    Digitale Medien
    Digitale Medien
    Performance of very thin silicon single-crystal foils under high x-ray power density : 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. 442-445 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In this paper x-ray diffraction tests of very thin silicon single crystals exposed to a wiggler beam that can generate a power density up to 200 W/mm2 are reported on. This beam was provided by the beamline X25 at NSLS, where 75 W total power are focused into a spot of 0.8 mm(h)×0.45 mm(v). An 11 μm "thin'' Si foil glued at its periphery onto an aluminum ring at 30 °C was applied to a box that could be pressurized with He. The whole assembly was then mounted on an optically polished and watercooled Be support. By increasing the temperature of the water and thus of the Al ring above 30 °C it was possible to apply a stretching force to the Si membrane in order to keep it flat. Rocking curves 3.3 arcsec wide were obtained with a strongly attenuated beam. The rocking curve width increased to 3.9 arcsec when the power density was increased to 15 W/mm2. The crystal was destroyed at 125 W/mm2 because of the limited thermal conductivity across the small He gap.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1142725
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  • 10
    Digitale Medien
    Digitale Medien
    Performance of beryllium crystals exposed to high x-ray power density : 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. 446-449 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: High quality beryllium single crystals are currently proposed for several applications in synchrotron radiation x-ray optics, in particular as the first element which will have to take the high power of the beam generated by insertion devices. Be has the advantage that much of this incident radiation is transmitted, especially higher energy wiggler radiation. Therefore, it is important to know how Be crystals behave under high x-ray power. For our test measurements we used the focused wiggler beam of the beam line X25 at the National Synchrotron Light Source, Brookhaven, that provides a power of 75 W at 230 mA ring current and a peak power density in excess of 200 W/mm2. A Be crystal was positioned in this white beam and its reflection properties were studied using a perfect silicon analyzer crystal. An "ideal mosaic'' type rocking curve 58 arcsec wide was obtained with a strongly attenuated beam increasing to 73 arcsec at 200 W/mm2. No deterioration of the crystal was observed. Much better performance is expected for thinner crystals. It can be concluded that presently available Be single crystals have the properties required for currently proposed applications as first optical element.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1142726
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