Data Storage and Neuromorphic Synaptic Properties of Asymmetric (SrTiO₃)₄/(LiNbO₃)₁/(LaAlO₃)₄ Superlattice Ferroelectric Tunnel Junctions

Lithium niobate (LiNbO3) crystals have attracted significant attention for their exceptional electro-optic and piezoelectric properties. Fabricating LiNbO3-based ferroelectric tunnel junctions requires a nanoscale LiNbO3 thin film with superior ferroelectric characteristics. Here, we present (SrTiO3)4/(LiNbO3)1/(LaAlO3)4 superlattices, which exhibit stable polarization switching and enhanced polarization compared to LiNbO3 thin films. The asymmetric superlattice shows an ON/OFF ratio of ∼103, with excellent repeatability and multilevel storage capabilities. More interestingly, it simulates various synaptic plastic behaviors, including excitatory postsynaptic current, paired-pulse facilitation, paired-pulse depression, and spike number-dependent plasticity. These findings highlight the great potential of LiNbO3-based superlattices for memristor devices.