Dielectric constant boost in amorphous sesquioxides

TL;DR

This study demonstrates that amorphous ScO3 exhibits a significantly higher dielectric constant than its crystalline form, due to disorder-induced activation of low-frequency modes and preserved atomic polarizability, promising for microelectronics.

Contribution

It reveals that amorphization enhances dielectric properties in X2O3 sesquioxides through disorder effects and atomic charge conservation, supported by first-principles simulations.

Findings

Dielectric constant increases by over 40% in amorphous ScO3.

Disorder activates low-frequency cation modes.

Effective dynamical charges are conserved in amorphous phase.

Abstract

High-kappa 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, ScO3, 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.