Calculated core-level sensitivity factors for quantitative XPS using an HP5950B spectrometer (original) (raw)
1983, Journal of Electron Spectroscopy and Related Phenomena
https://doi.org/10.1016/0368-2048(83)80010-3
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Abstract
AI
Values of core-level sensitivity factors for a Hewlett-Packard HP5950B X-ray photoelectron spectrometer have been calculated using theoretical photoionization cross-sections, asymmetry parameters, and an instrument throughput function. These sensitivity factors allow for semiquantitative elemental analysis by XPS when combined with a mean-free-path function for the sample. The results are detailed in Table 1, demonstrating how these factors facilitate analysis under specific sample conditions.
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References (13)
- J. H. Scofield, J. Electron Spectrosc. Relat. Phenom., 8 (1976) 129.
- R. F. Reilman, A. Msezane and S. T. Manson, J. Electron Spectrosc. Relat. Phenom., 8 (1976) 389.
- R. J. Baird, Ph.D. Dissertation, University of Hawaii, 1977 (Dissertation Order No. 77-23,483).
- W. B. Hermansfeldt, Electron trajectory program, SLAC Rep. 166, Natl. Tech. Inf. Serv., U.S. Department of Commerce, Springfield, VA 22151, 1973 (cited in ref. 3 above).
- H. Weaver (Hewlett-Packard), private communication with R. J. Baird (cited in ref.
- M. P. Seah and W. A. Dench, Surf. Interface Anal., 1 (1979) 2.
- C. D. Wagner, L. E. Davis and W. M. Riggs, Surf. Interface Anal., 2 (1980) 53.
- D. R. Penn, J. Electron Spectrosc. Relat. Phenom., 9 (1976) 29.
- S. M. Hall, J. D. Andrade, S. M. Ma and R. N. Ring, J. Electron Spectrosc. Relat. Phenom., 17 (1979) 181.
- P. Cadman, S. Evans, G. Gossedge and J. M. Thomas, J. Polym. Sci., Polym. Lett., 16 (1978) 461.
- D. T. Clark, H. R. Thomas and D. Shuttleworth, J. Polym. Sci., Polym. Lett., 16 (1978) 465.
- B. Hupfer, H. Schupp, J. D. Andrade and H. Ringsdorf, J. Electron Spectrosc. Relat. Phenom., 23 (1981) 103.
- D. T. Clark, Y. C. T. Fok and G. G. Roberts, J. Electron Spectrosc. Relat. Phenom., 22 (1981) 173.
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