Invited Paper AS-TuM1
Recent Developments in Quantitative XPS and AES

Tuesday, October 19, 2010, 8:00 am, Room Cochiti

An overview will be given of some recent developments to improve quantitative XPS and AES [1]. First, guidance is now available for choosing integration limits in the measurement of XPS peak intensities [2]. A recent comparison of reported peak intensities in simulated XPS spectra with known intensities showed large deviations if the integration limits were chosen inappropriately. Second, Tanuma et al. have reported a new set of inelastic mean free paths (IMFPs) for 41 elemental solids that were calculated from experimental optical data for electron energies from 50 eV to 30 keV [3]. These IMFPs agree well with recent calculations and measurements. Third, examples will be given of the use of simple predictive formulae that are available for the effective attenuation length, mean escape depth, and information depth in AES and XPS [4]. Fourth, the effects of elastic scattering and analyzer-acceptance angle on the analysis of angle-resolved XPS data have recently been analyzed [5]. Calculations were made of photoelectron intensities at selected emission angles for films of SiO_1.6N_0.4 and HfO_1.9N_0.1 of various thicknesses on Si with the NIST SESSA Database [6]. Ratios of intensities for each line from the film for the least realistic model condition (elastic scattering “off”, small analyzer-acceptance angle) to those from the most realistic model condition (elastic scattering “on”, finite analyzer-acceptance angle) changed relatively slowly with emission angle but the corresponding intensity ratios for the Si(substrate) 2p line changed appreciably with emission angle; such changes can lead to erroneous results in the analysis of angle-resolved XPS data [5]. Fifth, examples will be given of a new NIST database to provide backscattering correction factors for AES using an advanced model that accounts for attenuation of the primary beam in the surface region of the sample and the instrumental configuration [7]. Finally, mention will be made of a set of reference energies for 59 Auger transitions in 42 elemental solids that should be useful for the determination of chemical shifts in AES and XPS [8].

[1] C. J. Powell and A. Jablonski, J. Electron Spectrosc. Relat. Phenom. 178-179, 331 (2010).

[2] C. J. Powell and J. M. Conny, Surf. Interface Anal. 41, 804 (2009).

[3] S. Tanuma, C. J. Powell, and D. R. Penn, Surf. Interface Anal. (to be published).

[4] A. Jablonski and C. J. Powell, J. Vac. Sci. Technol. A 27, 253 (2009).

[5] C. J. Powell, W. S. M. Werner, and W. Smekal (to be published).

[6] http://www.nist.gov/srd/nist100.htm .

[7] A. Jablonski and C. J. Powell (to be published).

[8] C. J. Powell, J. Electron Spectrosc. Relat. Phenom. (to be published).