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  • 1
    Electronic Resource
    Electronic Resource
    Elastic scattering and quantification in AES and XPSInvited paper presented at the Quantitative Surface Analysis Conference (QSA-5), London, 15-18 November 1988. (1989)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 14 (1989), S. 659-685 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: In the mathematical formalism of quantitative AES and XPS, the elastic electron collisions are not taken into account. However, recent calculations have shown that the neglect of the elastic collisions may result in considerable errors. Theoretical analysis of the actual electron transport in a solid requires two major problems to be considered. (i) calculation of the differential elastic scattering cross-sections for a given potential and electron energy and (ii) description of the multiple electron scattering. Both problems are extensively reviewed. The Monte Carlo method is usually used to describe the electron trajectories in a solid at energies of surface-sensitive electron spectroscopies. Such simulations have indicated that the elastic collisions of photoelectrons affect considerably the angular distribution of the measured intensity and the photoelectron escape depth. The latter parameter may be diminished by 〉 30%. Elastic collisions of Auger electrons decrease the current recorded by the typical analysers and also considerably decrease the escape depth. Thus, the actual electron transport in a solid should be considered in calculations associated with determining the inelastic mean free path using the overlayer method or overlayer thickness measurements. The usual formalism of quantitative AES and XPS can be extended easily to account for the elastic electron collisions. The values of the corresponding correcting factors are extensively compiled. To check the validity of the Monte Carlo calculations, the results of simulations of forward electron scattering and electron back-scattering are compared with the available experimental data. Excellent agreement between experimental and theoretical angular distributions of photoelectrons has been found. A very good agreement was also observed in the case of elastic electron back-scattering from surfaces.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740141102
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  • 2
    Electronic Resource
    Electronic Resource
    Calculations of the backscattering factor for L3MM Auger transitionsPaper presented at the International Conference on Quantitative Surface Analysis, held at the National Physical Laboratory, Teddington, UK, 16-17 October 1979. (1980)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 2 (1980), S. 39-45 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The single scattering Monte Carlo algorithm of Murata, Matsukawa and Shimizu and the Gryziński ionization cross-section were used in calculations of the backscattering factor r. The calculations were based on two definitions of r. Generally, the backscattering factor was defined as the ratio of the Auger electron current recorded by the analyser to the current that would be recorded in the ideal case of no backscattering and no energy loss. The usual definition, involving the energy distribution of backscattered electrons, was also used. The calculations were performed for L3MM Auger transitions of elements with atomic numbers between 23 and 32. The primary energy ranged from 3 to 10 keV. The difference in backscattering factors resulting from both definitions varied from 0.1% to 10%, decreasing with the primary energy increase. The single scattering Monte Carlo algorithm can also be used in simulation of electron scattering in binary alloys. This makes possible the calculation of the backscattering factor as a function of the solid composition. The calculations were performed for L3MM Auger transitions of Cr, Cu, Fe and Ni in Au/Ni, Cr/Fe, Cr/Pd, Cu/Ni and Ni/Pd binary alloys. It was found that the backscattering factor varies almost linearly with mass fraction. The dependence on concentration is more pronounced when the difference in atomic numbers of alloy components is larger. The relative sensitivity factors, calculated for Cu/Ni and Cr/Fe binary alloys, are practically independent of composition, but depend on the primary energy.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740020202
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  • 3
    Electronic Resource
    Electronic Resource
    Quantitative AES: Via the inelastic mean free path or the attenuation length? (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 15 (1990), S. 559-566 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The terms inelastic mean free path (IMFP) and attenuation length (AL) of electrons in solids are described by different definitions and their values may differ profoundly, by 〉30%. For this reason, it is of crucial importance to decide which term should be used in calculations for quantitative AES analysis. An attempt to answer this question is made in the present work. The Monte Carlo algorithm was developed to simulate the Auger electron transport in metal alloys. Calculations were made for Auger electrons emitted in the Al48Ni52 ordered alloy and the corresponding standards. Comparison with the usual mathematical formalism of AES shows that elastic collisions of Auger electrons can be accounted for by two correcting parameters: (1) a correction denoted by Q, which accounts for the decrease of the Auger electron current; (2) a correction denoted by K, which accounts for the decrease of the depth of analysis. It was proved that the total correcting factor comprises four groups of parameters: atomic densities, back-scattering factors, inelastic mean free paths and corrections Q. Thus, we obtain the unexpected result that the calculations for quantitative AES require knowledge of the IMFP rather than the AL. The parameter Q is usually close to unity and can be neglected. The use of attenuation lengths in calculations may result in considerable errors. However, it is possible to recalculate values for the AL to obtain the IMFP.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740150910
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  • 4
    Electronic Resource
    Electronic Resource
    Escape depth of photoelectrons (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 758-763 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The sampling depth of electron spectroscopies, AES and XPS, is frequently directly associated with the value of the inelastic mean free path (IMFP). Owing to elastic scattering of signal electrons, a separate parameter, the escape depth (ED), should be used to describe the analysed volume. There is no simple relation between the ED and the IMFP. In the present work, extensive Monte Carlo calculations were performed to calculate the ED for photoelectrons emitted from gold (Au 4s, Au 4p3/2, Au 4d5/2 and Au 4f7/2). All XPS configurations within a plane normal to the surface were considered. It has been found that the anisotropy of photoelectron emission is strongly reflected in the angular dependences of the ED. Furthermore, the value of ED divided by the cosine of the detection angle, which is equivalent to the attenuation length (AL) described by one of the definitions, may considerably exceed the IMFP, in contrast with common expectations. This occurs at large detection angles and/or in experimental configurations with the direction of x-rays close to the direction towards the analyser. A simple and accurate parameterization was proposed in the present work, taking into account the anisotropy of photoemission, from which the ED can be predicted for photoelectrons considered and for any XPS configuration.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740211104
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  • 5
    Electronic Resource
    Electronic Resource
    Database of correction parameters for the elastic scattering effects in XPS (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 29-37 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The common formalism of quantitative XPS can be easily modified, with two additional correction factors βeff and Qx, to account for the elastic scattering effects. These corrections, for a given solid, depend on photolectron line, the radiation used and the XPS configuration. The database compiled in the present work contains parameters describing the dependence of the correction factors on experimental geometry. These dependences are listed for 496 photoelectron lines emitted by the Mg Kα and Al Kα radiations. The database makes it possible to predict the photoelectron intensity in a geometry in which the direction of x-rays, the direction towards the analyser, and the surface normal are situated in one plane. This intensity corresponds to a theoretical model taking into account the elastic photoelectron collisions. Examples of applications of the database are briefly demonstrated.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740230105
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  • 6
    Electronic Resource
    Electronic Resource
    Efficient calculation of photoelectron angular distribution (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 823-832 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Different methods of calculating efficiently the angular distribution of photoelectrons escaping from uniform amorphous and polycrystalline targets are analysed in detail. Comparison has been made between the analytical results and Monte Carlo simulation data. The analytical approach is based on the solution of the kinetic equation in the transport approximation. The Monte Carlo codes comprise the conventional forward simulation algorithm and the reverse trajectory method. The reverse trajectory method employs the reciprocity theorem and allows same statistically significant results to be obtained with less computational effort. The angular distributions of photoelectrons leaving Al, Si, Cu, Ag, Ta and Au samples have been calculated as a function of polar and azimuthal angles for electron energies relevant in quantitative XPS analysis. It has been found that both Monte Carlo methods provide equivalent results. The discrepancies between the transport approximation and the Monte Carlo data do not exceed, as a rule, 5%. The largest deviations of the analytical results from those found by Monte Carlo codes are observed in the vicinity of the emission directions, where the photoelectric differential cross-section has its minima, and are about 15%. The agreement between the results obtained by different approaches, corresponding to the magic angle geometry, is within 2% for all cases studied.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740231205
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  • 7
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    Comments on Gallon's method for determining the ionization cross-section and the backscattering factor (1981)
    Elsevier
    Details
    Publication Date: 1981-09-01
    Print ISSN: 0039-6028
    Electronic ISSN: 1879-2758
    Topics: Physics
    Published by Elsevier
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  • 8
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    Remarks on the definition of the backscattering factor in AES (2002)
    Elsevier
    Details
    Publication Date: 2002-03-01
    Print ISSN: 0039-6028
    Electronic ISSN: 1879-2758
    Topics: Physics
    Published by Elsevier
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  • 9
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    Dependence of the backscattering factor in AES on the primary electron incidence angle (1983)
    Elsevier
    Details
    Publication Date: 1983-01-01
    Print ISSN: 0167-2584
    Electronic ISSN: 1878-1047
    Topics: Physics
    Published by Elsevier
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  • 10
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    Effects of Auger electron elastic scattering in quantitative AES (1987)
    Elsevier
    Details
    Publication Date: 1987-09-01
    Print ISSN: 0039-6028
    Electronic ISSN: 1879-2758
    Topics: Physics
    Published by Elsevier
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