We show that electric dipole layer at Al 2 O 3 /SiO 2 interface is reproduced by classical molecular dynamics simulation with a simple two-body rigid ion model. The dipole layer was spontaneously formed by the migration of oxygen ions from Al 2 O 3 side to SiO 2 side. Built-in potential at the Al 2 O 3 / SiO 2 is estimated to about 0.35 V, which roughly compares with the experimental value of the flat band voltage shift. Contrary, no significant dipole layer appeared at Y 2 O 3 /SiO 2 interface. The simulation results are explained in terms of the difference in the magnitude of multipole moments around cations of these oxides.

Electric dipole layer formation at high-k/SiO2 interface is reproduced by classical molecular dynamics simulation based on a simple two-body rigid ion model (1). The dipole layer was spontaneously formed by the migration of oxygen ions across the high-k/SiO2 interface. In case of Al2O3/SiO2, a part of oxygen ions of Al2O3 penetrated into the SiO2 side, resulting in the formation of a built-in potential of about 0.5 V. The opposite migration of oxygen ions, from SiO2 side to high-k oxide side, is also reproduced by using different potential parameters of ionic radius and effective charge. The simulation result suggests that the dipole is not merely formed by the oxygen density difference. Rather, oxygen ions are driven by some interatomic forces at the interface. We discuss the origin of the driving force of the oxygen migration in terms of the multipole moments around cations in the oxides.