Determination of He electronic energy loss in crystalline Si by Monte-Carlo simulation of Rutherford backscattering–channeling spectra

Abstract

Spectra of He ions backscattered from thin ( 0 0 1 ) Si membranes and bulk Si/SiO 2 wafers are analyzed with the aid of simulation based on the binary collision approximation. Due to precise control of experimental parameters and detailed fitting of random spectra in thin specimens, the curve of random electronic energy loss per unit length in the energy interval 1.5–3 MeV can be given with an estimated accuracy better than 2%. The electronic energy loss in 〈0 0 1〉 alignment is determined through the fit of channeling spectra measured in bulk Si/SiO 2 samples. This is performed by the adjustment of the parameters of the semi-empirical model used in the calculation to describe the dependence of He electronic energy loss on the impact parameter of nuclear collisions. The model reproduces data reported in the literature for the 〈0 0 1〉 direction, but overestimates 〈0 1 1〉 electronic energy loss at energies below 1.5 MeV. The different ability to simulate energy loss in the two orientations is attributed to the limitations of the model to account for the non-uniform distribution of valence electrons in the Si lattice.