Anomalous flatband voltage shift of AlF_xO_y/Al₂O₃ MOS capacitors: A consideration on dipole layer formation at dielectric interfaces with different anions

We experimentally investigated the dipole layer formation at Al₂O₃/AlF_xO_y (x:y = 1:1 and 1:2.5) interfaces, which would be explicable by considering the anion density difference as the key parameter to determine the dipole direction at the dielectric interface with different anions. Molecular dynamics (MD) simulation of Al₂O₃/AlF₃ demonstrates a preferential migration of O from Al₂O₃ to AlF₃ compared with F to the opposite direction which suggests that anion migration due to the density difference could determine the direction of the dipole layer formed at this interface. In addition, charge separation due to the difference in the anion valences could have certain effect simultaneously.