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  • 1
    ISSN: 1432-0630
    Keywords: PACS: 68.65.+g; 68.60.Dv; 68.55.Jk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  Thermal stability of Co/C multilayers prepared by a dual-facing-target sputtering system was studied. A picture of the thermally induced changes in the microstructure was obtained using complementary measurement techniques including low-angle and high-angle X-ray diffraction, transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. It was found that the period expansion, reflectivity change and compound formation, that were observed after annealing are caused by structural changes both in the sublayers and at the interfaces. Below 400 °C, the period expansion is mainly caused by the graphitization of the amorphous carbon layers, and a significant increase in the reflectivity at grazing incidence was observed. By 500 °C, the crystallization and agglomeration of Co layers induce an enormous period expansion and a serious decrease in reflectivity. A small amount of carbide is found to form at this temperature. Our results imply that new multilayer structures, e.g., compound multilayers will have to be developed for use at high temperatures or under high X-ray incident flux.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5440-5442 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: α″-Fe16N2 single crystal films can be prepared successfully by facing targets sputtering directly onto NaCl(100) substrates in a mixture of argon and nitrogen gases. Both x-ray diffractometer and transmission electron microscope are employed to characterize the crystal structure of the films. The perfect electron diffraction patterns of α″-Fe16N2 single crystal in [1¯11], [011], and [001] directions can be distinctly observed by double tilting. These patterns confirm that the crystal structure of the films corresponds to a body-centered tetragonal (bct) lattice with the parameters of a=b=5.72 A(ring) and c=6.29 A(ring) . The x-ray diffraction patterns show that α″-Fe16N2 epitaxially grows on the NaCl(100) substrate with an orientation relationship α″-Fe16N2(001)(parallel)NaCl(001) and α″-Fe16N2[100](parallel)NaCl[100]. The saturation magnetization of the Fe16N2 films is around 2100−2300 emu/cc, which agrees well with the value reported by Sugita et al.. © 1996 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2596-2600 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fe-N gradient films were prepared with a facing targets sputtering system. During deposition, the nitrogen pressure increased linearly up to a value, which is called the "ultimate pressure.'' Composition profiles, microstructure, magnetic properties, and corrosion resistance of the films were investigated by various methods. The experimental results indicate that the Fe-N films possess some composition and structural gradients. The Fe concentration decreases from the substrate to the film surface from 100 to 66 at. %. The phases α‘-Fe16N2, γ'-Fe4N, ε-FexN(2〈x≤3) and ζ-Fe2N are present in the gradient films at different depths. Ms under the ultimate nitrogen pressure of 0.05 Pa has a value of 1803 emu/cc which is higher than that of bulk iron, this is attributed to the presence of Fe16N2. Increasing further the ultimate nitrogen pressure, Ms decreases monotonically. The corrosion resistance of the gradient film with higher nitrogen concentration near the surface is good enough for magnetic recording heads. © 1995 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4488-4490 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of Co addition on the structure and the saturation magnetization of Fe16N2 were investigated. Enhancement of the formation of Fe16N2 phase by Co addition was observed. Films with 5–25 at % Co contents deposited at proper conditions exhibit a high saturation magnetization up to the range of 2.5–2.7 T. The saturation magnetization of (Fe, Co)16N2 alloys phase is expected to be 2.8–2.9 T, which is as large as that of Fe16N2. This demonstrates that proper Co addition does not induce notable changes in the high saturation magnetization of the Fe16N2. © 1999 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 184-189 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of aging on Co/C multilayer x-ray mirrors is presented. One significant result is the enhancement of the reflectivity at grazing incidence with time for the Co/C multilayers with C-on-top stored in air or argon and Co-on-top stored in argon. This can be interpreted in terms of a Co–C phase-separation at Co–C interfaces due to the positive enthalpy of Co–C mixing. Results also show that oxidation of the surface of Co-on-top Co/C multilayers plays an important role in the decrease of reflectivity. The oxidation can be prevented by storing the multilayers in an oxygen-free atmosphere or by depositing amorphous carbon as the top layer. The reflectivity of tarnished multilayers can be restored by removing the oxides by wet chemical methods. © 1997 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1428-1436 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structures of the carbon sublayers in the annealed Co/C soft x-ray multilayers fabricated using a dual-facing-target sputtering system have been characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy (RS). The results suggest that the structural variations in the carbon layers can be roughly divided into three stages, i.e. ordering, crystalline and grain growth stages. In the ordering stage with annealing temperatures below 400 °C, the upward shift of D and G lines in Raman spectra indicates that the amorphous carbon layers are changing from ones with bond-angle disorder and fourfold-bonding only to ones containing threefold-bonding. In the crystalline stage, the amorphous carbon layers in the as-deposited multilayers crystallize to graphite crystallites in the annealing temperature range of 500–600 °C. The rapid increase in the intensity ratio of D line to G line and dramatic decrease in linewidth further confirm this substantial structural change. In the grain growth stage, the specimens are annealed at temperatures higher than 700 °C. The decrease in the intensity ratio implies a growth in the graphite crystallite dimensions, which is consistent with the XRD and TEM results. © 1996 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 2270-2276 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Period expansion of Co/C and CoN/CN soft x-ray multilayers has been investigated by x-ray diffraction and Raman spectroscopy. Below the anneal temperature of 400 °C, the period expansion (〈 12%) of Co/C multilayers is mainly caused by the graphitization of the amorphous carbon layers. By 500 °C, the crystallization and agglomeration of Co layers induce an enormous period expansion (∼40%). The period expansion of CoN/CN multilayers is only 4% at 400 °C, which is much smaller than that of Co/C multilayers. The interface patterns of the CoN/CN multilayers still exist even if they were annealed at 700 °C. The Raman spectroscopy analyses indicate that the formation of the sp3 bonding can be suppressed effectively by doping N atoms, and thus the period expansion is decreased considerably at annealing temperatures below 600 °C. The significant suppression of grain growth above 600 °C is believed to be attributed to the coexistence of hcp and fcc Co structures induced by interstitial N atoms, which cause the high-temperature period expansion decrease. The results also imply that the structural stability of Co/C soft x-ray multilayers can be significantly improved through doping N atoms.© 1997 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4116-4118 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: (Fe,Ti)–N thin films with titanium concentrations 3–35 at. % were prepared at room temperature by facing targets sputtering. X-ray diffraction and transmission electron microscopic studies were employed to characterize various phases observed prior to and during in situ annealing of (Fe,Ti)–N films. The films with 3–10 at. % Ti contained an α-(Fe,Ti) phase and an α′-martensite phase and the films with 20–35 at. % Ti comprised α-Fe(N), α′-martensite, and TiN phases in the as-deposited samples. The annealing temperature (TA) was increased from RT to 800 °C in increments of 50 °C. Annealing of the samples with 8 at. % Ti showed no structural changes between RT and 300 °C, but when the sample was heated to 400 °C, α′′ and TiN phases appeared in the microstructure. The samples with 25 at. % Ti also showed no structural changes when heated to 400 °C. When TA=500 °C, α′′ phase formed in the microstructure. The phases formed at 400 or 500 °C in the two samples were stable when the samples were heated up to 800 °C and followed by cooling down to RT. © 1997 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7301-7305 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructural and magnetic properties of amorphous Co/Ti multilayer films and their variation with temperature are investigated by transmission electron microscopy (TEM) analysis and thermomagnetic measurements. Thermomagnetic curves showed two peaks at about 400 and 520 °C. The evolution of the structure monitored in the hot stage of the TEM was found to be consistent with the magnetic changes. The first peak of the saturation magnetization Ms at 400 °C was associated with the transformation from amorphous ferromagnetism to paramagnetism due to the amorphous Co existing in the film. Ms began to increase corresponding to the crystallization point of the ferromagnetic Co phase, which decreased with increasing amounts of Co in the film. Ms reached its maximum at 520 °C and then decreased because the phase transition occurred at a temperature greater than 520 °C and approached completion at 650 °C. The amorphous phase and crystalline phase formation and phase transition during annealing were observed in Co/Ti multilayer thin films and successfully explained the thermomagnetic properties of the film. © 1997 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Magnetism and Magnetic Materials 67 (1987), S. 246-248 
    ISSN: 0304-8853
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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