The backscattering factor for systems with a buried layer

Abstract

The accuracy of quantitative Auger-electron spectroscopy analysis can be further improved, for example, by a proper description of the matrix effects. The backscattering effect in Auger spectrometry for a uniform medium has attracted significant interest in the literature. Studies on the Auger backscattering factor (BF) for a layered sample are unique, and the case of the BF for a buried layer in a certain material is still untouched. We develop the Monte Carlo model for the BF calculation for a layered system. We used a continuous slowing down approximation and the electron stopping power instead of the simulation of the individual inelastic scattering effects. We performed calculations of the BF for selected cases of a Au layer buried in a Ni matrix for Au M5N67N67 Auger transition and a Si buried layer in a Au matrix for Si KL23L23 Auger transition versus the buried layer depth for sorting out the layer thickness for a primary electron beam of 5 keV energy at normal incidence. The calculations reveal that the BF for a buried layer may differ from that for a uniform sample even by about 60%. This phenomenon can be explained in terms of the excitation depth distribution function. The results obtained are very useful when the variation in the BF is expected to be the most important matrix effect, as can happen for a layered system investigated by the technique known as the Auger depth profiling.

Monte Carlo calculation of backscattering factor for Ni–C multilayer system

“…In the case of such studies, the primary electron beam excites several layers and the BF is to be calculated for such a complex system. Zommer and Jablonski developed a Monte Carlo (MC) model for calculations of the BF for multilayered systems [16]. We will show that MC based calculation of the BF can describe the experimental findings.…”

“…The MC model for BF calculations for a buried layer in a multilayered system has been developed in [16] and the formula derived there enabling the calculations of BF is…”

“…It represents the number of Auger electrons created at the depth z. This formula was used to obtain the BF [16] for a layer buried in a sample for the selected case when the surroundings of the buried layer were uniform to simplify results interpretation, but the MC model presented in [16] is also valid for a layer placed in any medium composed of any number of different but uniform layers. Formula (4) is well founded when the probability of Auger escape is significant only in one layer of interest (the case studied here), otherwise it would require some modifications but it is not the case considered in this paper.…”

“…In this work we will apply the MC model [16] to simulate our AES depth profiling results of a multilayered system-Ni/C/Ni/C/Ni/C/Si. This system is a good test ground since we measured three depth profiles made by the Auger lines of Ni MVV (61 eV), C KLL (272 eV) and Ni LMM (848 eV) produced by strongly different transport parameters.…”

Contribution of elastic photoelectron scattering to the shape of the measured XPS intensity in‐depth profile

“…Zommer and coworkers developed a theoretical model including simultaneously two effects: elastic scattering of Auger electrons and backscattering of the primary beam electrons. Monte Carlo (MC) simulations of both phenomena, performed for the Ni/C multilayer deposited on Si, indicated that the shape of the in‐depth AES profile is slightly different for each layer, even if identical thicknesses of analyzed layers have been assumed.…”