Determining the stopping power of low energy hydrogen in self-assembled monolayers

Neutral impact collision ion scattering spectroscopy (NICISS) is used to measure the stopping power of H in self-assembled monolayers (SAMs) on Au at primary energies of 3000, 4000, and 4500 eV. The energy loss is determined by comparing NICIS spectra of bare Au surfaces with the same surfaces covered with SAMs of alkanethiolates. The thickness of the SAMs is determined with x-ray photoelectron spectroscopy (XPS). The measured H stopping power is compared with computer simulations using a Monte Carlo code for analyzing the Rutherford backscattering (TRBS code) data. It was found that the simulations agree with the experimental results within experimental uncertainty. Measurement of the stopping power of H in hydrocarbons is highly relevant for studying interfaces formed by organic substances involving Li such as specific ion effects at liquid surfaces and interfaces in batteries and organic based solar cells.