Optimal dielectric thickness for ferroelectric tunnel junctions with a composite barrier

Abstract

Theoretical investigations on ferroelectric tunnel junctions (FTJs) with a fixed-thickness composite layer (Pt/MgO/BaTiO3/Pt and Pt/SrTiO3/BaTiO3/Pt) were conducted. It showed that there is an optimal dielectric thickness that can bring the largest tunneling electroresistance (TER) ratio provided that the ferroelectricity does not change with the dielectric thickness. The optimal dielectric thickness is insensitive to ferroelectric polarization in ferroelectric layer and increases linearly with the composite barrier thickness. Considering the size effect of ferroelectricity, the optimal dielectric thickness (unit cells) changes little if the polarization increases slowly with the ferroelectric thickness. Such studies may help to fabricate FTJs with larger TER ratio and put them into practical application.