Production of secondary electrons and photons and energy absorption mechanisms in amorphous carbon irradiated by photons in the energy range of 0.03 to 17.4 keV

Abstract

Energy absorption mechanisms in amorphous carbon under irradiation by 0.03–17.4 keV photons is studied by Monte Carlo simulation with accounting for the cascade decays of inner-shell vacancies and tracking all secondary electrons and photons including very-low-energy ones. Energy absorption by the atoms of the sample that underwent initial ionization by incident photons is only important at energies of several tens of eV (UV and XUV range). The principal mechanism of energy absorption on the whole incident photon energy interval is through inelastic processes caused by secondary electrons. At incident photon energies above C1s ionization threshold low-energy KLL Auger electrons produced by the cascade decay of C1s vacancy transfer energy to the medium in the vicinity of the site of initial photoionization. At energies far above the C1s-threshold, high-energy photoelectrons spread the absorbed energy over larger volumes and with smaller density. A great portion of the energy brought by incident photons, about 42 %, is transferred to the medium by low-energy secondary electrons and photons that are incapable of ionizing or exciting the atoms of the sample. The number of low-energy electrons is proportional to the energy of an incident photon, and at incident photon energies of several keV, one initial photoionization produces hundreds of secondary low-energy electrons.