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

Auger electron spectroscopy (AES) depth profiles using the Ni(MVV) (61 eV), C(KLL) (272 eV) and NiLMM (848 eV) lines were recorded for a 3 x (Ni(40 nm)/C(28 nm))/Si substrate sample. It was found that the Auger intensities corresponding to pure regions of the depth profile changed with depth. The behaviour of the change was different for the different layers and different Auger lines. The changes can be attributed to the change in the backscattering factor (BF) as the thickness of the sample changes due to the sputter removal. Zommer and Jablonski developed a Monte Carlo (MC) algorithm to calculate the BF for systems with a buried layer. This algorithm was applied to the present case; the intensities of the monitored Auger lines were calculated for the sample with decreasing thickness similarly to the Auger depth profiling. The agreement between the measured and calculated AES depth profiles is excellent. The MC calculation verifies that several layers contribute to the BF and thus the expressions developed for overlayer/substrate systems cannot be used.