SYSTEMATIC TRENDS IN THE TRANSPORT MEAN FREE-PATH WITH ELECTRON-ENERGY AND ATOMIC-NUMBER

The inelastic mean free path, lambda(i), and the transport mean free p ath, lambda(tr), hold the key to understanding the effects of elastic scattering of electrons in electron spectroscopy techniques such as Au ger electron spectroscopy (AES) and X-ray photoelectron spectroscopy ( XPS). Systematic trends in the variation of lambda(tr) and chi = lambd a(i)/X-tr with atomic number, Z, and electron energy, E, are explored using the differential elastic scattering cross-section data of Czyzew ski et al. (J. Appl. Phys., 68 (1990) 3066). At low Z, lambda(tr) incr eases with energy in accord with the predictions of the Born approxima tion, but at higher Z, a more complex behaviour is revealed. In the fi rst and second transition metal series, chi varies little with energy over much of the kinetic energy range probed in XPS in accord with the energy scaling ideas from the semi-classical scattering theory of Til inin (Soviet Physics JETP, 67 (1992) 1570). In the third transition se ries, a pronounced minimum is found at around 200 eV, with chi for Au lower than for the corresponding transition metals. The results identi fy regions of the periodic table where elastic scattering effects are particularly pronounced. (C) 1997 Elsevier Science B.V.