AVS 49th International Symposium
    Applied Surface Science Monday Sessions
       Session AS-MoA

Paper AS-MoA4
The Information Depth and the Mean Escape Depth in Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy

Monday, November 4, 2002, 3:00 pm, Room C-106

Session: Quantification & Accuracy in Surface Analysis
Presenter: A. Jablonski, Polish Academy of Sciences, Poland
Authors: A. Jablonski, Polish Academy of Sciences, Poland
C.J. Powell, National Institute of Standards and Technology
Correspondent: Click to Email
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@sub 3/2@, Cu 2s, Cu 2p@sub 3/2@, Au 4s, and Au 4f@sub 7/2@ photoelectrons excited by Mg K@alpha@ x rays. Similar calculations were made for Si L@sub 3@VV, Si KL@sub 23@L@sub 23@, Cu M@sub 3@VV, Cu L@sub 3@VV, Au N@sub 7@VV, and Au M@sub 5@N@sub 67@N@sub 67@ Auger transitions. The ID and MEDs were derived from an analytical expression for the 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 effects were negligible, R@sub ID@ and R@sub MED@, were less than unity and varied slowly with electron emission angle @alpha@ for emission angles less than 50@super o@. For larger emission angles, these ratios increased rapidly with @alpha@. For @alpha@ @<=@ 50@super o@, average values of R@sub ID@ and R@sub MED@ varied linearly with the single-scattering albedo, @omega@, a simple measure of the strength of elastic scattering effects. For @alpha@ = 70@super o@ and @alpha@ = 80@super o@, R@sub ID@ also varied linearly with @omega@ but R@sub MED@ showed a quadratic variation. As a result of elastic scattering of the signal electrons, AES and XPS measurements at @alpha@ = 80@super o@ are less surface-sensitive than would be expected if elastic scattering had been neglected. Conversely, AES and XPS measurements made for @alpha@ @<=@ 50@super o@ are more surface sensitive as a result of elastic-scattering effects.