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  • 1
    Electronic Resource
    Electronic Resource
    Calculations of electron inelastic mean free paths (IMFPS). IV. Evaluation of calculated IMFPs and of the predictive IMFP formula TPP-2 for electron energies between 50 and 2000 eV (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 77-89 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: We have made additional evaluations of the electron inelastic mean free paths (IMFPs) and of the predictive IMFP formula TPP-2 presented in papers II and III of this series. Comparisons have been made with other formulae for the IMFPs and electron attenuation lengths (ALs). We find substantial differences between our IMFP results for 27 elements and 15 inorganic compounds and the AL formulae of Seah and Dench; these differences include different dependences on electron energy and on material parameters. We present IMFP calculations for Al2O3 and GaAs from TPP-2 in which each parameter of the formula is varied in some physically reasonable range about the true value for each compound; these results show the sensitivity of the computed IMFPs to the choices of parameter values. Finally, we give a summary of sources of uncertainty in the IMFP algorithm, in the experimental optical data from which IMFPs are calculated, and of the TPP-2 formula. We conclude that TPP-2 is robust and useful for predicting IMFPs for electron energies and material parameter values in ranges for which the formula was developed and tested.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200112
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  • 2
    Electronic Resource
    Electronic Resource
    Calculations of electron inelastic mean free paths. V. Data for 14 organic compounds over the 50-2000 eV range (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 165-176 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: We report calculations of electron inelastic mean free paths (IMFPs) of 50-2000 eV electrons for a group of 14 organic compounds: 26-n-paraffin, adenine, β-carotene, bovine plasma albumin, deoxyribonucleic acid, diphenylhexatriene, guanine, kapton, polyacetylene, poly(butene-1-sulfone), polyethylene, polymethylmethacrylate, polystyrene and poly(2-vinylpyridine). The computed IMFPs for these compounds showed greater similarities in magnitude and in the dependences on electron energy than was found in our previous calculations for groups of elements and inorganic compounds (Papers II and III in this series). Comparison of the IMFPs for the organic compounds with values obtained from our predictive IMFP formula TPP-2 showed systematic differences of ∼40%. These differences are due to the extrapolation of TPP-2 from the regime of mainly high-density elements (from which it had been developed and tested) to the low-density materials such as the organic compounds. We analyzed the IMFP data for the groups of elements and organic compounds together and derived a modified empirical expression for one of the parameters in our predictive IMFP equation. The modified equation, denoted TPP-2M, is believed to be satisfactory for estimating IMFPs in elements, inorganic compounds and organic compounds.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740210302
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  • 3
    Electronic Resource
    Electronic Resource
    Energy calibration of x-ray photoelectron spectrometers: Results of an interlaboratory comparison to evaluate a proposed calibration procedure (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 23 (1995), S. 121-132 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Results are reported of an interlaboratory comparison conducted to evaluate a proposed procedure for calibration of the binding energy (BE) scales on x-ray photoelectron spectrometers. The calibration was performed at two points on the BE scale (the Au 4f7/2 and Cu 2p3/2 lines) and checks were made of the assumption of BE-scale linearity from measurements on other lines. It is shown here that small offsets (up to ∼0.05 eV) can arise if peaks are located with assumed backgrounds of non-zero slope or if multipeak fits are made to Cu L3VV and Ag M4VV Auger spectra. The two parameters in the linear calibration equation could vary with analyzer pass energy and choice of x-ray source on a particular instrument. Check measurements of the calibrations were performed with the Ag 3d5/2 photoelectron line and the Cu L3VV and Ag M4VV Auger lines; difference between the corrected positions of these lines and the corresponding reference data were satisfactorily small in most cases. For Auger lines excited by monochromatized aluminum x-rays, however, the differences were significant and were interpreted in terms of different average x-ray energies for the monochromated and unmonochromated x-ray sources. The interlaboratory comparison was useful in testing the proposed calibration procedure and in providing guidance for some improvements.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740230302
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  • 4
    Electronic Resource
    Electronic Resource
    Standard test data for estimating peak-parameter errors in x-ray photoelectron spectroscopy. I. Peak binding energies (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 939-956 
    Details
    ISSN: 0142-2421
    Keywords: XPS ; reference data ; x-ray photoelectron spectroscopy ; peak fitting ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Standard test data (STD) are simulations of analytical instrument responses that help to determine the veracity of computer-based, data analysis procedures that are typically used with instruments. The STD were developed for determining errors in peak parameters obtained from data analysis algorithms used in x-ray photoelectron spectroscopy (XPS). The STD were mainly C 1s doublet spectra constructed from spline polynomial models of measured C 1s polymer spectra. Different spectra were created based on a replicated factorial design with three factors: peak separation; relative intensity of the component peaks; and fractional Poisson noise. These doublet spectra simulated XPS measurements made on different two-component specimens. Single-peak C 1s spectra for individual polymers were also simulated, to provide the null case for identification of the doublet spectra. Twenty analysts used a variety of data analysis programs and a variety of curve-fitting approaches to determine peak binding energies. Results indicate that data analysis of doublet spectra may be problematic, because up to 50% of the STD doublets were assigned incorrectly as singlets. For spectra that were correctly identified as doublets, bias and random error in peak binding energies depended on the amount of separation between the component peaks and on their relative intensities. Biases ranged from -0.055 eV to 0.34 eV, while random errors ranged from 0.012 eV to 0.13 eV. Use of the Gaussian-Lorentzian function fitted to spectra resulted in smaller biases than the use of a Gaussian function alone. As a guide to evaluating peak energy uncertainties in their own analyses, analysts may find it useful to analyze the STD themselves and then compare their results with those reported here. The spectra may be obtained at http://www.acg.nist.gov/std/main.html. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Activities of ISO technical committee 201 on surface chemical analysis (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 615-620 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A status report is given on activities of ISO Technical Committee 201 (ISO/TC 201) on Surface Chemical Analysis. The committee has seven subcommittees which met for the first time in 1993. Information is given on the working groups that have been established for specific purposes. We show national participation in ISO/TC 201 and its subcommittees, and we identify the chairmen and secretariats of the subcommittees and the conveners of the working groups.
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740210904
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  • 6
    Electronic Resource
    Electronic Resource
    The NIST x-ray photoelectron spectroscopy database (1992)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 19 (1992), S. 241-246 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The National Institute of Standards and Technology (NIST) has made available the second version of the NIST X-ray Photoelectron Spectroscopy Database. This paper reports on recent upgrades to the database to make the information more up-to-date and to make data searching and display more convenient and efficient for the user. Additional data are included in the database together with the capability to search using large chemical synonym lists, chemical formulae and other chemical classification schemes. A list of reference energies is given for the principal photoelectron and Auger electron lines of most of the elements and these values can be used for calculations of chemical shifts. Pull-down menus are now available to initiate searches for the identification of unknown lines more conveniently, to retrieve data on photoelectron lines, Auger electron lines and chemical shifts for a set of elements, to calculate and display chemical shifts, and to calculate and display information for Wagner plots to identify chemical state. In addition, the use can initiate searches based on specified fields of the database.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740190147
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  • 7
    Electronic Resource
    Electronic Resource
    Formation of Technical Committee 201 on Surface Chemical Analysis by the International Organization for Standardization (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 322-325 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The International Organization of Standardization (ISO) recently created a new Technical Comittee (ISO/TC 201) on Surface Chemical Analysis in response to a proposal from Japan. As of February 1993, ten national standards bodies had indicated willingness to become participating members of ISO/TC 201 (Austria, China, Germany, Italy, Japan, Russia, Sweden, Turkey, the United Kingdom and the United States of America) and fifteen national standards bodies had indicated willingness to become observer members (Australia, Belgium, Egypt, Finland, France, India, Ireland, Korea, Norway, Philippines, Poland, Romania, Singapore, South Africa and Switzerland). The following subcommittees are planned: Terminology; General Procedures; Data Management and Treatment; Depth Profiling; Auger Electron Spectroscopy; Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy. It is expected that working groups will be established for Glow Discharge Optical Spectroscopy and Total Reflection X-ray Fluorescence Spectroscopy. ISO/TC 201 will develop international standards and will consider standards and documents prepared by other groups as potential international standards. Information is given in this article on the purpose, structure and planned work of ISO/TC 201.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200410
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  • 8
    Electronic Resource
    Electronic Resource
    Formalism and parameters for quantitative surface analysis by Auger electron spectroscopy and x-ray photoelectron spectroscopy (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 771-786 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: It has been realized during the last 5 years that quantitative surface analyses by Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) can be greatly complicated by the effects of elastic electron scattering. These effects had previously been largely ignored. We review here the effects of elastic scattering in the formalism of quantitative surface analysis by AES and XPS and discuss the various definitions of terms (inelastic mean free path, attenuation length and escape depth) that have been used to describe inelastic scattering and the surface sensitivities of various electron spectroscopies. We show how a realistic theoretical model of electron transport that includes elastic electron scattering can be related, for some analytical situations, to the common simple formalism of AES and XPS in which elastic scattering is neglected. We consider specifically measurements of overlayer thickness, determination of surface composition for a homogeneous surface region and estimation of the average depth of analysis and we indicate which parameter describing inelastic scattering can be utilized in the simple formalism for these applications. Information is given on sources of data for the inelastic mean free path and the attenuation length. Finally, we point out that the definitions of some terms are undergoing revision as a result of recent scientific developments and to avoid inconsistencies with established usage in other fields.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200906
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  • 9
    Electronic Resource
    Electronic Resource
    Calculations of Electron Inelastic Mean Free Paths (IMFPs) VI. Analysis of the Gries Inelastic Scattering Model and Predictive IMFP Equation (1997)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 25-35 
    Details
    ISSN: 0142-2421
    Keywords: electron inelastic mean free path ; inelastic electron scattering ; calculated IMFP ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Gries has recently reported [Surf. Interface Anal. 24, 38 (1996)] an atomistic model for inelastic electron scattering relevant to Auger electron spectroscopy and x-ray photoelectron spectroscopy and has derived an equation (designated G1) for the estimation of inelastic mean free paths (IMFPs). We present an analysis of the Gries model and the G1 equation in terms of the similarities and differences of inelastic electron scattering by free atoms and by solids. We also compare the G1 equation with our TPP-2M equation for estimation of IMFPs. The former equation was developed from fits to our published IMFPs over the 200-2000 eV energy range, and is identical in its energy dependence to the Bethe equation for inelastic scattering cross-sections and to a simplification of our TPP-2M equation for the same energy range. Comparison of parameters indicates that the Gries fitting parameter k1 should be approximately 0.0016 and 0.0022 for non-transition and transition elements, respectively. We find that the G1 equation could be improved by allowing the Gries fitting parameter k2 to depend on density (as recommended for the equivalent parameter in TPP-2M). Although we believe that the Gries model is inconsistent with current theories for the electronic structure of metals, semiconductors and inorganic compounds, we find (from sum-rule considerations) that the G1 equation can provide an approximate guide to IMFP values. For some compounds, however, there were unexplained deviations (as found by Gries). In contrast to the G1 equation, the TPP-2M equation provides useful IMFP estimates for all materials over the parameter range that has been explored. Gries claims that the G1 equation can be extrapolated to energies lower than 200 eV on the basis of limited agreement with some experimental IMFPs over the 10-100 eV range for Be and the alkali metals, and has questioned the reliability of our IMFPs for energies below 200 eV. We consider this comparison to be inadequate, and we recommend that the G1 equation not be used in the 50-200 eV range. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Energy Calibration of X-ray Photoelectron Spectrometers. II. Issues in Peak Location and Comparison of Methods (1997)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 777-787 
    Details
    ISSN: 0142-2421
    Keywords: XPS ; x-ray photoelectron spectroscopy ; energy calibration ; peak location ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An analysis is presented of issues involved in peak location for the calibration of the binding energy (BE) scales of x-ray photoelectron spectrometers. These issues include the effects of peak asymmetry, the surface core-level shift, and the avoidance of a sloping background when fitting spectra for energy calibration purposes. Examples of uncertainty budgets for BE measurements are then presented in which illustrative values are shown for the repeatability standard deviation (for repeated BE measurements of the same calibration peak), the expanded uncertainty (at the 95% confidence level) for BE measurements following calibrations based on different numbers of peak measurements, and the tolerance for BE-scale drift and non-linearity for two chosen values (±0.1 and ±0.2 eV) of the total expanded uncertainty for a BE measurement (at the 95% confidence level). It is recommended that a user prepare an uncertainty budget of this type to show clearly the sources of random and systematic error in BE measurements following a calibration.The reference data published by the UK National Physical Laboratory for BE-scale calibration were obtained from fits with a quadratic function to a group of points comprising the top 5% of each peak. Most commercial x-ray photoelectron spectrometers have software available for spectrum synthesis, and we consider here the use of the commonly available Lorentzian, Gaussian, and asymmetric Gaussian functions for peak location. Illustrative fits with Cu 2p3/2 spectra (measured with unmonochromated Al x-rays) showed that comparable accuracy and precision could be obtained with Lorentzian and Gaussian functions as with the quadratic-equation method when different fractions of the peak were fitted. For this asymmetrical line, the asymmetric Gaussian function allowed better accuracy and precision to be obtained with a greater fraction of the line than was possible with the symmetrical functions. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
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