Effect of Atomic Interface on Tunnel Barrier in Ferroelectric HfO2 Tunnel Junctions

We have demonstrated the dependence of the atomic terminations on ferroelectric tunnel junctions (FTJs) based on ferroelectric HfO2 using density functional theory calculation. The atomistic structures of HfO2 FTJs with various interfaces are constructed and their device performances are calculated. We have found that the potential barrier is significantly tailored by atomic species of the terminating atom of HfO2. In particular, the atomistic effect contributes to the electric field across the tunnel barrier, which leads to asymmetric behavior. We demonstrate that the ON/OFF current ratio of FTJs can be improved by adjusting the atomic terminations, albeit without the external asymmetric structure such as dissimilar metal electrodes and additional composite layers.