The Information Depth and the Mean Escape Depth in Auger Electron Spectroscopy and X-Ray Photoelectron Spectroscopy

Published

January 1, 2003

Author(s)

Aleksander Jablonski, Cedric J. Powell

Abstract

The information depth (ID) is a measure of the sampling depth for the detected signal in Auger-electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) while the mean escape depth (MED) is a measure of surface sensitivity. We report ID and MED calculations for Si 2s, Si 2p_3/2, Cu 2s, Cu 2p_3/2, Au 4s, and Au 4f_7/2 photoelectrons excited by Mg K α x rays. These calculations were made for various electron emission angles and for a common XPS configuration. Similar calculations were made for Si L₃VV, Si KL₂₃L₂₃, Cu M₃VV, Cu L₃VV, Au N₇VV, and Au M₅N₆₇N₆₇ Auger transitions. The ID and MEDs were derived from an analytical expression for the signal-electron depth distribution function obtained from a solution of the kinetic Boltzmann equation within the transport approximation. The ratios of the IDs and the MEDs to the corresponding values found if elastic-electron scattering were assumed to be negligible, R_ID and R_MED, were less than unity and varied slowly with electron emission angle α for emission angles less than 50^o. For larger emission angles, these ratios increased rapidly with α. For αless than or equal to} 50^o, average values of R_ID and R_MED varied linearly with the single-scattering albedo, ω, a simple function of the electron inelastic mean free path and transport mean free path. For α = 70^o and α=80^o , R_ID also varied linearly with w but R_MED showed a quadratic variation. The albedo is thus a useful measure of the magnitude of elastic-scattering effects on the ratios R_ID and R_MED. As a result of elastic scattering of the signal electrons, AES and XPS measurements at α = 80 are less surface-sensitive than would be expected if elastic scattering had been neglected. Conversely, AES and XPS measurements made for α less than or equal to} 50^o are more surface sensitive as a result of elastic-scattering effects.

Citation

Journal of Vacuum Science and Technology A

Volume

21

Issue

No. 1

Pub Type

Journals

Keywords

auger electron spectrscopy, copper, gold, information depth, mean escape depth, silicon, surface analysis, surface sensitivity, X-ray photoelectron spectroscopy

Citation

Jablonski, A. and Powell, C. (2003), The Information Depth and the Mean Escape Depth in Auger Electron Spectroscopy and X-Ray Photoelectron Spectroscopy, Journal of Vacuum Science and Technology A (Accessed April 19, 2024)