Multiply charged ions from electron bombardment ofSiO2

We present the first systematic measurements of the emission of multiply charged substrate Si ions from ${\mathrm{SiO}}_2$ under electron bombardment. The electron energy dependences of the ion yields show structure related to the Si 2p and O 1s thresholds, but delayed in energy. The ion yields do not follow core-ionization cross sections. The energy distributions of Si ions are a few eV wide, while those of ${\mathrm{O}}^{+}$ extend to >25 eV. The results are consistent with a mechanism involving Auger decay from a core hole in the presence of additional electronic excitations.