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Effect of Auger electron elastic scattering in quantitative AES
A356 164 EFFECTS
Surface Science 188 (1987) 164-180 North-Holland, Amsterdam OF AUGER ELECTRON
IN QUANTITATIVE
ELASTIC SCATI'ERING
AES
Aleksander JABLONSKI
Department of Catalysis on Metals, Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warszawa, Poland Received 8 January 1987; accepted for publication 5 May 1987 The Monte Carlo algorithm was developed for simulating the trajectories of electrons elastically scattered in the solid. The distribution of scattering angles was determined using the partial wave expansion method. This algorithm was used to establish the influence of Auger electron elastic collisions on the results of quantitative AES analysis. The calculations were performed for the most pronounced KLL, L3MM and MsNN Auger transitions. It turned out that due to the elastic collisions the Auger electron signal is decreased by up to 10%. The corresponding decrease of the escape depth of Auger electrons reaches 30% as compared with the value derived from the inelastic mean free path. The values of the inelastic mean free path resulting from the overlayer method may be strongly affected by elastic scattering of Auger electrons.
Surface Science 188 (1987) 181-198 North-Holland, Amsterdam NOVEL ASPECTS APPLIED
181
OF MID AND FAR IR FOURIER
TO SURFACE
AND ADSORPTION
SPECTROSCOPY
STUDIES
ON SiO 2
Pedro HOFFMANN
Departamento de Fisica, Facultad de Ciencias, Uniuersidad de Los Andes, 5101 M~rida, Venezuela and Erich KNtDZINGER
*
Institut far Physikalische Chemie, Universitiit Siegen, Postfach 101240, D-5900 Siegen, Fed. Rep. of Germany Received 1 April 1987; accepted for publication 18 May 1987
Modern Fourier transform technology as well as cryogenic detectors have been applied to remeasure the IR transmission spectrum of silica including the so-called far IR spectrum, i.e. the spectral range below 400 cm -1. On the basis of thermal H20 desorption and by the aid of spectral subtraction the stretching and the torsional modes of different types of free surface OH groups could be observed. In either case the OH stretching band is extraordinarily sharp. Its FWHM ( < 6 cm-1 at room temperature) is by more than one order of magnitude smaller than that of the torsional band. This confirms the expectation that torsional modes react more sensitively to environmental influences than stretching modes. Time-resolved IR spectroscopy on a time scale of seconds contributed to a better understanding of the physisorption and chemisorption processes of H20 on silica surfaces degassed in the temperature range between 25 and llO0°C.
Surface Science 188 (1987) 164-180 North-Holland, Amsterdam OF AUGER ELECTRON
IN QUANTITATIVE
ELASTIC SCATI'ERING
AES
Aleksander JABLONSKI
Department of Catalysis on Metals, Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warszawa, Poland Received 8 January 1987; accepted for publication 5 May 1987 The Monte Carlo algorithm was developed for simulating the trajectories of electrons elastically scattered in the solid. The distribution of scattering angles was determined using the partial wave expansion method. This algorithm was used to establish the influence of Auger electron elastic collisions on the results of quantitative AES analysis. The calculations were performed for the most pronounced KLL, L3MM and MsNN Auger transitions. It turned out that due to the elastic collisions the Auger electron signal is decreased by up to 10%. The corresponding decrease of the escape depth of Auger electrons reaches 30% as compared with the value derived from the inelastic mean free path. The values of the inelastic mean free path resulting from the overlayer method may be strongly affected by elastic scattering of Auger electrons.
Surface Science 188 (1987) 181-198 North-Holland, Amsterdam NOVEL ASPECTS APPLIED
181
OF MID AND FAR IR FOURIER
TO SURFACE
AND ADSORPTION
SPECTROSCOPY
STUDIES
ON SiO 2
Pedro HOFFMANN
Departamento de Fisica, Facultad de Ciencias, Uniuersidad de Los Andes, 5101 M~rida, Venezuela and Erich KNtDZINGER
*
Institut far Physikalische Chemie, Universitiit Siegen, Postfach 101240, D-5900 Siegen, Fed. Rep. of Germany Received 1 April 1987; accepted for publication 18 May 1987
Modern Fourier transform technology as well as cryogenic detectors have been applied to remeasure the IR transmission spectrum of silica including the so-called far IR spectrum, i.e. the spectral range below 400 cm -1. On the basis of thermal H20 desorption and by the aid of spectral subtraction the stretching and the torsional modes of different types of free surface OH groups could be observed. In either case the OH stretching band is extraordinarily sharp. Its FWHM ( < 6 cm-1 at room temperature) is by more than one order of magnitude smaller than that of the torsional band. This confirms the expectation that torsional modes react more sensitively to environmental influences than stretching modes. Time-resolved IR spectroscopy on a time scale of seconds contributed to a better understanding of the physisorption and chemisorption processes of H20 on silica surfaces degassed in the temperature range between 25 and llO0°C.