Electronic stopping power of Al2O3 and SiO2 for H, He, and N - art. no. 012902

An experimental and theoretical study of the energy loss of hydrogen, heliu m, and nitrogen ions in alumina and silica is presented. Experimental data show that silica and alumina have a different stopping behavior. By using a model insulator dielectric function to estimate the target valence electro n contribution to the stopping power, we explain the energy loss of point c harges in the two oxides and extend the model to helium projectiles, where charge state effects have to be considered. At low velocities this theoreti cal approach shows a noticeable threshold effect related to the band gap no t observed in the experiment. The low velocity data for H, He, and N ions a re qualitatively explained using an electron gas model with an effective nu mber of electrons (different for the two oxides) and a nonlinear screening description within density-functional theory. A comparison with Firsov and Lindhard-Scharf models is included for N ions as well.