Oxygen vacancy creation in SiO2 through ionization energy deposition

Using electron paramagnetic resonance we have measured the profiles of the integrated E′1 oxygen vacancy defect densities produced in thermal SiO2 by implantation of 70-keV protons. Comparison of the experimental and theoretical profiles clearly indicates that the defects are created by energy deposited into ionization processes and not into atomic displacement. Mechanisms of oxygen vacancy creation are discussed. We estimate the maximum (saturation) defect density created by ionization energy to be ∼3.3×1019 E1 per cm3 which is the same order as found for Ar+ implantation where displacement damage dominates. This figure is also within a factor of 2 of that predicted for intrinsic E′1 defect precursors in SiO2.