Ferroelectric domain wall memory with embedded selector realized in LiNbO₃ single crystals integrated on Si wafers

Interfacial ‘dead’ layers between metals and ferroelectric thin films generally induce detrimental effects in nanocapacitors, yet their peculiar properties can prove advantageous in other electronic devices. Here, we show that dead layers with low Li concentration located at the surface of LiNbO₃ ferroelectric materials can function as unipolar selectors. LiNbO₃ mesa cells were etched from a single-crystal LiNbO₃ substrate, and Pt metal contacts were deposited on their sides. Poling induced non-volatile switching of ferroelectric domains in the cell, and volatile switching in the domains in the interfacial (dead) layers, with the domain walls created within the substrate being electrically conductive. These features were also confirmed using single-crystal LiNbO₃ thin films bonded to SiO₂/Si wafers. The fabricated nanoscale mesa-structured memory cell with an embedded interfacial-layer selector shows a high on-to-off ratio (>10⁶) and high switching endurance (~10¹⁰ cycles), showing potential for the fabrication of crossbar arrays of ferroelectric domain wall memories.