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Doi, M.; Shoji, T.; Yamada, T.; Wilson, R.
8. conference on total reflection x-ray fluorescence analysis and related methods2000
8. conference on total reflection x-ray fluorescence analysis and related methods2000
AbstractAbstract
[en] Accurate estimation of the background in a TXRF spectrum is necessary for trace analysis. The tailing of large peaks in the spectrum is the main source of the background. Sum and escape peaks are also part of the background caused from an SSD detector. Estimation and subtraction of these peaks from the spectrum have been successful with sophisticated software. Raman scattering is another possible phenomenon that will give rise to a background peak in the spectrum. This paper explores this Raman phenomenon. We used the W-Mα line for the low energy TXRF experiments. The W-Mα is effective for exciting aluminum, magnesium and sodium atoms. The energy of the W-Mα line, 1.78 keV, is above and near the absorption edges of these elements and yet below the absorption edge of silicon, 1.84 keV. To obtain a monochromatic W-Mα line, we used a monochromator consisting of a total reflection mirror of silicon and a crystal of RAP(001). The reflectivity of this monochromator is smaller than that of a monochromator consisting of synthesized multilayers but the energy resolution is superior. We measured the spectra from a blank silicon wafer and a silicon wafer covered with a titanium layer. A peak caused by the elastic scattering of the incident W-Mα line is the main peak that appeared at 1.78 keV in each spectrum. There is another peak at 1.65 keV in the spectrum from the blank wafer. The ratio of the intensity of this peak to that of the main peak increases with the glancing angle. The peak at 1.65 keV does not appear in the spectrum taken from a silicon wafer covered with a titanium layer. There are no characteristic x-rays which have this same energy. Also, Compton scattering cannot account for a peak at that energy. We calculated energies of diffracted x-rays by the silicon crystal assuming that x-rays having a continuous spectrum are included in the incident x-rays. However, there are no diffracted x-rays which have an energy in this range. The binding energy of electrons in a silicon atom are 0.15 keV and 0.10 keV for 2s and 2p electrons, respectively. If Raman scattering occurs for the incident W-Mα-line in the silicon wafer, inelastically scattered x-rays will have energies of 1.63 keV or 1.68 keV. The energy of 1.65 keV is near these values. The peak maybe caused by Raman scattering. The intensity of the peak maybe small but should be considered when making a proper fit of the background of the spectrum for low energy TXRF. (author)
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Wobrauschek, P. (ed.) (Atominstitut, Stadionallee 2, 1020 Vienna (Austria)); Atominstitut der oesterreichischen Universitaeten, Technische Universitaet Wien, Stadionallee 2, 1020 Vienna (Austria). Funding organisation: Amptek Inc. 6, De Angelo Drive, Bedford (United States); Atomika, Atomika Instruments GmbH, Bruckmannring 40, D-85764 Oberschleissheim (Germany); Brau AG (Austria); Coca-Cola Beverages Austria (Austria); Creditanstalt (Austria); Intax, Schwarzschildstrasse 10, D-1248 Ital Structures (Germany); Pfeiffer Vacuum Austria, Diefenbachgasse 35, A-1150 Wien (Austria); Philips Analytical, Lelyweg 1, 7602 EA Almelo (Netherlands); Stadt Wien, Vienna (Austria); Technos (Japan); TU Wien, Vienna (Austria); et al; 108 p; 2000; p. 85; 8. conference on total reflection x-ray fluorescence analysis and related methods; Vienna (Austria); 25-29 Sep 2000; Available in abstract form only, full text entered in this record. Also available from Atominstitut der oesterreichischen Universitaeten, Technische Universitaet Wien, Stadionallee 2, 1020 Vienna (AT). e-mail: wobi@ati.ac.at
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