Interpretation of Electron Rutherford Backscattering Spectrometry for Hydrogen Quantification

In the last few years several papers have appeared showing the capabilities of Electron Rutherford Backscattering Spectrometry (eRBS) to quantify the H content at surfaces. The basis of the H detection in this technique relies on the difference in recoil energy of the incident electrons depending on the mass of the atoms located at the surface that act as scatter centers. In this paper we address the interpretation of eRBS spectra of Hydrogen containing surfaces. The aim is to compare the naïve single elastic scattering approximation with a more realistic description of eRBS spectra including multiple elastic scattering using the HQeRBS (Hydrogen Quantification eRBS) software based on a Monte Carlo algorithm. It is concluded that multiple elastic scattering is a significant contribution to experimentally measured eRBS spectra of a polyethylene surface. It induces significant broadening of the distribution of the maximum elastic scattering angle along the electron trajectories contributing to the measured spectra. However, it has weak effect in the energy distribution of the collected electrons (about 10% overestimation of the H content in the particular case of a polyethylene surface with respect to the corresponding ratio of elastic scattering cross sections).