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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 249-254 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Period expansion after annealing in tungsten/carbon (W/C) multilayer films has been observed by several authors. Although most results have emphasized that the carbon layers play the important role in such thermal evolution, it is important to clarify the structure of the carbon atoms in those multilayers both before and after annealing in order to explain such period expansion more clearly. In this paper, Raman scattering is carried out on the W/C multilayers fabricated by various methods, all of which showed different period expansion values ranging from 0% to 20%. We show that the initial carbon in those multilayers becomes graphitized differently depending on the fabrication methods. The carbon fabricated by rf sputtering under a reactive gas has the highest amount of graphite component as compared with those prepared under a pure argon gas atmosphere. After annealing at 1000 °C, graphitization can be observed, but there are no obvious structural differences for the carbon in all the annealed W/C multilayer films. Such graphitization of the carbon layer causes a decrease in its density, and thus an increase in its thickness. Due to the different initial states of the carbon in the multilayers produced by the different methods and to the identical final state after annealing, the different carbon layer thickness expansions are expected and do agree with the small angle x-ray diffraction measurements.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 931-937 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of W/C multilayers has been fabricated using a magnetron sputtering device. In order to establish comparison with other multilayers produced by several laboratories, their atomic structure and thermal evolution has been studied by small- and wide-angle x-ray scattering, respectively, and Raman spectroscopy. By plotting the nominal thickness determined by the sputtering speed versus the thickness obtained by simulation of small-angle x-ray scattering spectra the existence has been confirmed of a WC interface compound of about 0.7 nm formed during the multilayer deposition. The multilayers fabricated by the magnetron sputtering device showed higher thermal stability and less period expansion than those produced by different apparatus [Dupuis et al., J. Appl. Phys. 68, 5146 (1990), Jiang et al., J. Appl. Phys. 65, 196 (1989)]. Raman spectra indicated that the carbon in the W/C multilayers is more graphitized than in the previous W/C multilayer. The carbon is further graphitized after annealing at 1000 °C. The graphitization of carbon induced its density to decrease, that is, thickness to increase. Consequently, in the multilayers a smaller expansion of carbon is expected after annealing at 1000 °C since there is more graphitized carbon in the initial as-deposited state than in the previous W/C multilayer. This conclusion agrees very well with the thickness variation measured by x-ray diffraction.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3348-3355 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayers consisting of alternating thin bilayers of W and Si (period: 1.5〈d〈9 nm) have been analyzed by x-ray scattering (absolute reflectivity, period, mosaicity, interface roughness, crystallinity, and density) and by cross-sectional transmission electron microscopy observations (periodicity, crystalline phase, and damaged area). Our purpose was to determine the thermal properties of the multilayers with respect to the period value under pulsed laser heating (with a nanosecond Nd-YAG laser at different energy densities up to 1 J/cm2 and at a wavelength λ=0.53 μm) and by furnace annealing (250〈T〈1000 °C under 10−7 Torr pressure). We propose that two distinct diffusion mechanisms are involved in annealings: first, interdiffusion in the amorphous phase and then crystallization into WSi2, the latter related to a period contraction of about 5–10%. The diffusion coefficients and the crystallization temperature depend drastically on the period value. Simulations of small-angle x-ray scattering curves take well into account this thermal evolution. Extinctions and modulations of the intensities of the Bragg peaks are well fitted by thickness and roughness variations.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5146-5154 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1145-1150 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: With the development of x-ray sources, high reflectivity and selectivity multilayers for optics are becoming a field of interest for the spectral region of 13–40 nm. In this article, it is shown from theoretical computations that multilayers made of two light materials such as B/Si can be used for these applications. Such multilayers were deposited by electron evaporation. Their physical properties were studied by x-ray reflectometry analyses at two wavelengths: 0.154 and 12.6 nm. The results show that the multilayers are made of dense and pure materials and that the interfacial layer thickness ranges from 0.3 to 0.7 nm. © 2001 American Institute of Physics.
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a study of magnetic dot arrays fabricated in Ru(5 nm)/Co/Ru(32 nm) films with cobalt thickness varying from 10 to 500 nm. Large array areas up to 5×5 mm2 have been obtained with lateral dot size and spacing of 0.5 μm. The magnetization curves are characteristic of a perpendicular magnetized multidomain structure. Lateral size reduction does not drasti- cally change the domain structure but has immediate consequences on the nucleation and saturation fields. A magnetic force microscopy study confirms the perpendicular multidomain struc- ture and provides intrinsic magnetic characteristics. © 1996 American Institute of Physics.
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using x-ray lithography we have patterned dot arrays in Au/Co/Au(111) sandwiches based on ultrathin Co layers with perpendicular anisotropy. Large area arrays of dots with diameters of 1 and 2 μm have been obtained, keeping mostly undamaged the ultrathin Co layer. Hysteresis loops of the arrays depend drastically on the dot diameter. Magneto-optical domain visualization experiments confirm a magnetization reversal mechanism based on a large distribution of nucleation fields in the film, with complete reversal of the magnetization of one dot through the domain wall propagation after a local nucleation process. This could give information on the magnetization reversal processes in Au/Co/Au(111) continuous films. © 1996 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6780-6783 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the anisotropic etching of submicrometer features (0.2–1 μm) on tungsten at substrate temperatures varying from −45 to +15 °C in a newly developed magnetoplasma reactor operated with SF6. In contrast to earlier reports, we have achieved such ultrafine pattern etching without external biasing, hence with low-energy ions, thus reducing possible damage to the substrate. We have observed highly anisotropic microscopically uniform etching at pressures lower than a threshold value which depends on the substrate temperature; above this threshold, the anisotropy decreases and the microscopic nonuniformity depends on linewidth and space pattern. © 1995 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2200-2202 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the biaxial Young's modulus of amorphous SiC thin films which have been produced by using laser ablation, triode sputtering, and plasma enhanced chemical vapor deposition techniques. It is observed that the biaxial Young's modulus increases with the Si—C bond density in the films.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 3154-3154 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the effect of structural disorder on the valence of cerium in different families of amorphous alloys prepared by coevaporation on to cryogenic substrates. The Ce electronic configuration was characterized by LIII x-ray absorption spectroscopy and bulk magnetization measurements. Special attention was paid to the amorphous analogs of prototypic Kondo and strongly mixed valent compounds in the crystalline state, such as Ce Si2 (TK(approximately-equal-to)200 K), CemNin, CemCon. The cerium was found to be purely trivalent in amorphous CexSi1−x (0≤x≤0.75) alloys over both the metallic and nonmetallic concentration ranges, so that the weakly mixed valent state in crystalline CeSi2 is believed to rely on details of the crystalline symmetry and band structure. In contrast, the cerium was found to remain mixed valent in amorphous CexCo1−x (0.15≤x≤0.75) and CexNi1−x (0.30≤x≤0.60) alloys, without any significant effect of the structural disorder. The concentration dependence of the Ce valence anomaly was found to be different in the Ce Ni and Ce Co alloys. This different behavior is discussed in terms of electronic band structure.
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