Dielectric constant boost in amorphous sesquioxides

High-κ dielectrics for insulating layers are a current key ingredient of microelectronics. X2O3 sesquioxide compounds are among the candidates. Here, we show for a typical material of this class, Sc2O3, that the relatively modest dielectric constant of its crystalline phase is enhanced in the amorphous phase by over 40% (from ∼15 to ∼22). This is due to the disorder-induced activation of low frequency cation-related modes which are inactive or inefficient in the crystal and by the conservation of effective dynamical charges (a measure of atomic polarizability). The analysis employs density-functional energy-force and perturbation-theory calculations of the dielectric response of amorphous samples generated by pair-potential molecular dynamics.