(SrTiO3)2/(BaTiO3)4/(LaAlO3)2 asymmetric superlattices as an artificial synapse for plasticity simulation

High-quality lattice-matched (SrTiO3)2/(BaTiO3)4/(LaAlO3)2 superlattice with monolayer terrace structure have been grown via pulsed laser deposition. The layer-by-layer growth mode is evidenced by oscillations in reflection high-energy electron diffraction patterns. In contrast to BaTiO3 thin films, these asymmetric superlattices exhibit enhanced polarization and stable polarization switching behavior. The superlattice-based ferroelectric tunnel junction demonstrates a high ON/OFF current ratio exceeding 10 6 , accompanied by nonvolatile resistance switching characteristics. Various synaptic plasticities, including excitatory postsynaptic current, paired-pulse facilitation, paired-pulse depression, post-tetanic potentiation, post-tetanic depression, long-term potentiation, and long-term depression, have been successfully simulated using this superlattice ferroelectric tunnel junction. It was observed that repeated stimulation can induce the conversion of short-term plasticity to long-term plasticity. Additionally, the forgetting process in the superlattice ferroelectric tunnel junction was quantitatively investigated, revealing its correlation with polarization relaxation. These experimental findings and modeling analyses clearly underscore the substantial potential of artificial superlattices, which are endowed with intrinsic asymmetric ferroelectricity and enhanced polarization, in nonvolatile memory applications.