Backscattering factor for KLL Auger yield from film-substrate systems

Abstract

Backscattering factor (R) between primary energies of 2-40 keV for film-substrate KLL Auger backscattering yield (RFS) is calculated via Monte Carlo simulation for C and Al films. Substrates ranging from Be (Z = 4.0) to Au (Z = 79.0) are used in the study. Results via a normalized RFS (RN) function show that substrate effects are indeed present. This is especially so at higher primary energies and lower film atomic number. Electron range results also show that an important and meaningful quantity to describe the backscattering Anger yield with respect to film thickness is the mean backscattered energy penetration depth. This is found to be essentially different from the half-maximum electron range as proposed earlier. A power law can be used to describe the half-value range (i.e. the thickness for which RN = 0.5) with respect to primary energy. For Al film, however, a discontinuity in the power law is found for energies 4 keV. At lower energies meao values are used instead. Besides the fitted parameters from our results, known bulk R expressions for film and substrate are also required for the practical use of the model.