Protons’ generation by laser irradiation at 5 × 109 W/cm2 from silicon dielectric targets containing an excess of hydrogen

A study of silicon plasma generated in vacuum by 532 nm Nd:YAG laser at intensities of about 5 × 109 W/cm2 from dielectric targets containing a relatively huge quantity of hydrogen was presented. Time-of-flight technique was employed to measure the particles’ energy and the relative yield with respect to other ion species. Plasma-accelerated ions show Coulomb–Boltzmann-shifted distributions depending on their charge state. Mass quadrupole spectrometry allowed the estimation of the relative hydrogen amount inside the different samples considered: silicon (Si), silicon nitride (Si3N4) and hydrogenated annealed silicon (Si(H)) as a function of the ablation depth and irradiation time. Depth profiles of the laser craters permit to calculate the ablation yield at the used laser fluence. The plasma temperature and density was evaluated by the experimental data. A special regard is given to the protons’ generation process occurring inside the plasma, due to the possible influence of the hydrogen excess on the treated samples in comparison to the not-hydrogenated silicon ones.