| AVS 61st International Symposium & Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS+MC-MoM |
| Session: | Quantitative Surface Analysis |
| Presenter: | Cedric Powell, National Institute of Standards and Technology (NIST) |
| Authors: | A. Jablonski, Polish Academy of Sciences, Poland C.J. Powell, National Institute of Standards and Technology (NIST) S. Tanuma, National Institute for Materials Science (NIMS), Japan |
| Correspondent: | Click to Email |
HAXPES is now being used to characterize thicker overlayer films than is possible with conventional XPS using Al and Mg Kα x-ray sources. As a result, there is a need for effective attenuation lengths (EALs) to determine film thicknesses at electron energies larger than about 1.5 keV. Jablonski and Powell [1] published a simple practical EAL expression from fits to EALs calculated from solution of the kinetic Boltzmann equation within the transport approximation for electron energies between 61 eV and 2 keV and photoelectron emission angles between 0° and 50°. This approach has now been extended to electron energies up to 5 keV with account also taken of non-dipole terms in the photoionization cross section. EALs have been calculated for Si 1s, Cu 2p3/2, Ag 3d5/2, and Au 4f7/2 photoelectrons excited by Mg Kα, Al Kα, Zr Lα, and Ti Kα x rays using the inelastic mean free paths of Tanuma et al. [2] for each solid. EALs from the non-dipole approximation were up to about 2% larger than those from the dipole approximation. Good agreement has been found between the new EALs and EALs determined from Monte Carlo simulations and from the NIST SESSA database [3]; with the latter database, simulations can be made for photoelectron energies up to 20 keV. We found that the new EALs were also consistent with the previous expression [1]. Finally, the new EALs are reasonably consistent with the EALs measured by Sacchi et al. [4] for Co, Cu, and Ge but there was poorer agreement with the EALs measured by Rubio-Zuazo and Castro [5] for Au. Disagreements between the calculated and measured EALs for Au at energies less than 5 keV were attributed to non-ideal morphologies of the thinner Au films.
[1] A. Jablonski and C. J. Powell, J. Vac. Sci. Technol. A 27, 253 (2009).
[2] S. Tanuma, C. J. Powell, and D. R. Penn, Surf. Interface Anal. 43, 689 (2011).
[3] http://www.nist.gov/srd/nist100.cfm.
[4] M. Sacchi et al., Phys. Rev. B 71, 155117 (2005).
[5] J. Rubio-Zuazo and G. R. Castro, J. Electron Sprectrosc. Relat. Phenom. 184, 384 (2011).