Ion-induced quantum transport in ultrathin amorphous silicon dioxide films

Heavy-ion beams impinging on electronic devices are known to produce conducting paths in oxide thin films. Here we report the results of first-principles calculations of the effect of ion-induced atomic displacements on the current-voltage characteristics of ultrathin oxides. We use density functional theory and the recently developed ``Source and Sink'' method to calculate currents in defected amorphous silicon dioxide layers sandwiched between two Al electrodes. The resulting current-voltage characteristics show significant enhancement of the electron tunneling and are found to depend on both the spatial distribution of ion-induced defects and the distribution of the defect energy levels in the oxide band gap. The quantum transport results are used to define a percolation model using Mott defect-to-defect tunneling. The calculated currents are in agreement with experimental data.