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  • Chemistry  (33)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 2 (1980), S. 183-186 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The principle of the technique of crater edge profiling is described as an alternative method to conventional sputter profiling. The predictions for the lateral composition profile assuming a Gaussian intensity distribution of the primary ion beam are tested for a multilayer sandwich structure of Ni/Cr layers of 11.5 nm single layer thicknesses after Ar+ ion sputtering through 20 layers and scanning Auger microscopy with a 10 µm diameter electron beam. Due to the small angle of 44.3″ of the slope of the crater formed by ion sputtering, a magnification factor (lateral variation/depth variation) of 5 × 103 is obtained.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 6 (1984), S. 75-77 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The use of non destructive depth profiling by emission angle dependent XPS analysis is demonstrated for a thin contamination layer consisting of carbon, hydrogen and hydride-bonded oxygen on top of an anodic oxide of Nb2O5 on Nb. Using a double-pass CMA with an angle resolved aperture and measured intensity ratios of O 1s (hydroxide)/O 1s (oxide) and O 1s (hydroxide-/C 1s) as a function of the emission angle, the thickness (d = 3.3 nm) and composition are determined.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 5 (1983), S. 210-216 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Thin films of anodically formed Ta2O5 and Nb2O5 on polycristalline Ta and Nb, respectively, are analysed with AES during sputtering with Ar+ ions at energies between 0.5 keV and 5 keV. A sputtering induced depletion of oxygen at the surface is observed in both oxides. The kinetics of this depletion and the steady-state composition at the surface of the samples are studied as a function of the primary ion energy. The results are interpreted using a modification of the model of Ho et al. (1976) for the preferential sputtering of alloys. The thickness of the transient layer increases non-linearly from 1.6 to 3.4 nm with increasing ion energy. Below 2 keV, the surface depletion of oxygen increases with decreasing ion energy and is constant above 2 keV up to 5 keV. The results are similar for both oxides. At 2 keV, the minimum measured width of the oxide/metal interface is 2 nm for Ta2O5/Ta and is about two times larger for Nb2O5/Nb. In both cases it increases with the square root of the ion energy and it is independent on the oxide layer thickness between 10 nm and 150 nm.
    Additional Material: 6 Ill.
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  • 4
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Equations to extract the depth resolution from measured sputtering profiles of multilayer structures are presented. The range of application and the errors involved are discussed with respect to the ratio between depth resolution and layer thickness.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The primary stages of the oxidation of NiCr23 and of NiCr21Fe12 and the final oxide layers were studied at room temperature and oxygen pressures between 10-6 Pa and 10-4 Pa using AES and XPS. The composition of the surface during oxygen exposure was monitored by continuous recording of the Auger transitions M23 VV and L3M23V of the metallic components and the KL23L23 transition of oxygen. The low energy M23VV transitions are especially indicative of the present chemical state which is additionally characterized by the 2p photoelectron spectra. After different oxygen exposures, the thickness of the oxide layers was determined by angle resolved AES, XPS results, and by sputter depth profiling which also gives the elemental in depth distribution. It is concluded that the initial preferential oxidation of Cr is followed by a surface enrichment and oxidation of the remaining elements with lower affinity to oxygen, i.e. Ni in NiCr and both Ni and Fe in NiCrFe.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Low energy valence band Auger transitions are advantageous for the study of the initial stages of metal and alloy oxidation owing to their high surface sensitivity and to their chemical bonding features. However, the latter property leads to difficulties in quantification of the spectra, particularly by using peak-to-peak heights in the derivative mode. Therefore, two other methods are applied for a quantitative evaluation of the different elemental bonding states: (a) superposition of standard spectra according to the least mean squares fitting method and (b) factor analysis. The reliability of both methods is compared for the quantitative determination of the kinetics of oxygen reaction with pure Ni and with a NiCr21Fe12 alloy at oxygen pressures between 10-6 Pa and 10-4 Pa. Although both methods give comparable results, only method (b) allows the determination of the chemisorbed oxygen bonding state on Ni using the low energy Ni M23 VV transition. For the NiCrFe alloy, only method (a) gives a clear distinction between nickel and iron oxides.
    Additional Material: 8 Ill.
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  • 7
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The chemical differences between passivated and oxidized layers on 17.5 at.% FeCr and 5 at.% FeTi alloys are analysed by means of soft x-ray absorption spectroscopy (XAS). The relative absorption strengths were used to obtain a quantitative estimation of the composition of the layers. In FeCr, the passivated layer shows a relative Cr enrichment of 34 at.% with respect to the oxidized surface. In addition, Cr2O3 has been identified as the main oxide formed in the passivated layer of FeCr. By contrast, in FeTi, the results are consistent with the formation of a ternary oxide. The potential of XAS in the study of oxidation and passivation is discussed.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 304-309 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Depth profiling with sample rotation has become a frequently applied method to obtain the in-depth distribution of composition in thin films with high resolution. Sample rotation strongly diminishes the effect of local variations of the ion beam intensity and of the sputtering yield, which are the main cause of increasing surface roughness during sputtering and therefore of profile broadening. Capabilities and limitations of rotational profiling are considered with respect to its dependence on various parameters, such as inhomogeneity of the ion beam instensity, ion incidence angle and rotation speed. In particular, it is shown that non-linear components and excentric movement of the sample lead to periodic features in the profile and to non-vanishing degradation of depth resolution with depth. For smooth sample surfaces, depth resolution improves with increasing ion incidence angle but is much less pronounced, as for profiling with stationary samples. For originally rough surfaces, the deterioration of depth resolution with increasing ion incidence angle is considerably reduced. The key parameter for optimized conditions in rotational profiling is the ratio of sputtering rate and rotation speed. The minimum necessary, useful rotation speed depends on this ratio and on the magnitude of other contributions to the depth resolution that are not affected by sample rotation.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The preparation of well-characterized silicide thin films for microelectronics needs a control of interfacial reactions and diffusion processes during heat treatment of metal/semiconductor systems. Two sandwich structures of Si(33 nm)/Me(50 nm)/Si(33 nm), where Me = Ni or Cr, with a total thickness of each structure of 116 nm were sputter deposited onto smooth silicon-(111) substrates. The reactions of both metals with amorphous silicon thin films were activated in a differential scanning calorimeter (DSC), at a heating rate of 40°C/min-1, between room temperature and different higher temperatures. Auguer electron spectroscopy depth profiles showed that the Si/Ni/Si sandwich structure reacted almost completely during heat treatment up to 320°C and formed reaction products with a composition close to Ni3Si2. Selected area diffraction patterns revealed that this is a mixture of Ni2Si and NiSi silicides. A much less pronounced reaction between Si and Cr was observed in the Si/Cr/Si sandwich structure, even with heating to 630°C, resulting in CrSi2 silicide and different Cr-Si solid solutions. The results of AES depth profiling studies of the thermally treated sandwich structures are discussed in terms of diffusion processes, movement of interfaces and formation of silicides. The additional information obtained with differential scanning calorimetry and transmission electron microscopy enables a detailed identification of reaction products formed in the early stage of the thermally treated Si/Me/Si structures.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 809-814 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Neural pattern recognition was used to analyse the low-energy Auger spectra of a thermally annealed Si/Ni/Si layered structure measured during the acquisition of a depth profile. The purpose was to gain information about the chemical state of the elements at the interfaces by processing the data in a way quite similar to conventional target factor analysis (TFA). The new approach, however, has some important advantages: no standards are required, it is extremely fast and it is fully automatic. In principle, there is only one arbitrary parameter, the vigilance parameter ρ, which sets a threshold for the level of similarity required for assuming two spectra as belonging to the same class of data. However, the requirement that the optimal value for ρ should correspond to the maximal correlation between the experimental data set and the recalculated spectra makes the system also robust against misconclusions based on subjective interpretation of the data set, which is not always the case in TFA.
    Additional Material: 6 Ill.
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