Electronic sputtering of thin SiO 2 films by MeV heavy ions

Abstract

The rate of removal of material from SiO 2 as a result of heavy ion irradiation, with energies in which energy loss via excitation and ionization of the solid predominates, depends strongly on the stopping power and angle of incidence of the incoming ions. There appears to be a threshold stopping power for SiO 2 of 500 eV/(10 15 at/cm 2) (or 3.5 keV/nm). This electronic sputter yield has been found to reach values as large as 10 4 atoms/incoming ion for 66 MeV Ag ions at an angle of incidence of 7° with the plane of the surface. Strikingly, the electronic sputter yield is very small for thin SiO 2 layers of a thickness ⩽1 nm when grown on c-Si, but it is appreciable for such layers deposited on the insulator silicon nitride. The data are discussed in the light of existing models for electronic sputtering invoking also models for potential sputtering of SiO 2 by low-energy, highly charged ions.