Electronic stopping of hydrogen ions deduced from TOF-LEIS spectra

Protons and deuterons with energies 0.33-10 keV were used to obtain time-of-flight low energy ion scattering (TOF-LEIS) spectra for thin layers of Au evaporated onto a B/Si substrate. The thickness (2.4 nm) and the root-mean-square roughness (0.5 nm) of the Au layer were determined by Rutherford Backscattering Spectrometry (RBS) and Atomic Force Microscopy (AFM), respectively. To deduce the electronic stopping power, TRBS simulations were performed with dE/dx as an input parameter that was optimized to fit the experimental spectra. At energies above 3 keV, the low energy edge in the experimental spectra was widened due to the film roughness. Therefore, the simulations were carried out for the Au layer composed by two different thicknesses in order to yield optimum agreement. The resulting stopping values compare favourably to literature data. No proton/deuteron isotope effect in stopping of hydrogen ions was observed.