Improved calculation of the backscattering factor for quantitative analysis by Auger electron spectroscopy

Abstract

Based on a Monte Carlo simulation method, an improved calculation of the backscattering factor in quantitative analysis by Auger electron spectroscopy has been performed by integrating several aspects of recent progresses in the related fields. The calculation used a general definition of backscattering factor, more accurate ionization cross section, up-to-date Monte Carlo model of electron inelastic scattering, and a large number of electron trajectories to ensure less statistical error. The results reveal several noticeable properties of backscattering factor, i.e., its slow variation with primary energy at higher overvoltage ratios, and dependence on the geometrical configuration of a detector. However, only for large emission angles of Auger signals a considerable angular dependence of backscattering factor is found. Specifically a calculation is carried out for detection in the solid angles of a cylindrical mirror analyzer. This backscattering factor can be less than unity for very low primary energies closing to ionization energy and/or for large incident angles. The physical cause has been detailed and analyzed.

NIST Backscattering-Correction-Factor Database for Auger Electron Spectroscopy, Version 1.1 of SRD 154

“…Finally, a number of papers have been published that show significant differences between BCFs from the advanced model and BCFs from the simplified model [9,[11][12][13][14][15][16]. BCFs from the advanced model also can differ from BFs from the Shimizu formulae [4], also based on the simplified model, due to the use of different algorithms and new data for the differential elasticscattering cross sections [17] in recent work that are believed to be more accurate than the data used earlier [18].…”

Backscattering effect in quantitative AES sputter depth profiling of multilayers

“…The reduction of both, the Si backscattering factor R Si,C for C and that for Ni, R Si,Ni , by about the same amount, ( 14% and 18%, respectively) appears to be consistent and may indicate too high a value from the Ichimura-Shimizu relations. Recent calculations of Jablonski and Powell 7 and of Ding et al 8 show a considerable difference to typical predicted values of Ichimura and Shimizu, which is supported by measurements of Goto (referred to in Ref. 8).…”

“…Obviously, r ½ 0 should always be valid. However, new and more detailed calculations by Jablonski and Powell 7 and by Ding et al 8 based on a more general definition of the backscattering factor show that R < 1, i.e. r < 0, is possible for primary energies near the excitation threshold or for glancing incidence angles.…”

The Backscattering Correction Factor in AES: A New Outlook

“…The correction for electron-backscattering effects was proposed by Bishop and Riviere [4] in one of the first papers on the formalism for quantitative AES analysis. Recent advances in the theory of electron transport in solids have led to the conclusion that the theoretical model assumed in previous derivations of the formula for the backscattering factor is oversimplified [5][6][7][8][9][10][11]. As a result, BFs calculated from this simplified model are unreliable for low primary energies and/or more-grazing incidence angles.…”

“…Recent work has shown that BCFs from the advanced model are a function of the Auger-electron emission angle in addition to other parameters [6][7][8][9][10][11]. As shown above, the BCF also generally depends on the size of the analyzer-acceptance angle.…”