Improvement of forming-free threshold switching reliability of CeO2-based selector device by controlling volatile filament formation behaviors

Diffusive memristor-based threshold switching devices are promising candidates for selectors in the crossbar memory architecture. However, the reliability and uniformity of the devices are primary concerns due to uncontrolled diffusion of metal ions in the solid electrolyte of diffusive memristors. In this study, CeO2-based selectors with Ag electrodes were demonstrated to have forming-free threshold switching characteristics. In particular, by inserting an amorphous SiO2 layer in a CeO2-based selector device, we have effectively controlled volatile filament formation that is essential for uniform and reliable switching operations. The inserted SiO2 layer acts as a barrier that could retard the migration of Ag ions and prevents the formation of strong filaments in the solid electrolyte. This enables the bilayer device to have improved uniformity and cyclic endurance. The proposed selector device, Ag/CeO2/SiO2/Pt, showed excellent DC I–V switching cycles (103), high selectivity of 104, good endurance (>104), and narrow distribution of switching voltages. These results would be helpful to implement CeO2-based threshold switching devices as selectors for high-density storage crossbar memory architectures.