Switching Behavior in Rare-Earth Films Fabricated in Full Room Temperature

In this paper, we investigated the forming-free resistive-switching (RS) behavior in the Ru/REO_x/TaN ( RE = Ce, Pr, Sm, and Eu) memory device using CeO_x, PrO_x, SmO_x, and EuO_x thin films fabricated in a full-room-temperature process. The dominant conduction mechanism of Ru/REO_x/TaN memory devices in the low-resistance state is ohmic behavior, whereas the high-resistance state is space-charge-limited conduction. The Ru/CeO_x/TaN devices show a high resistance ratio of >;10⁴, reliable data retention for 10⁵ s, and stable endurance characteristics for up to 1000 cycles. This result suggests the high concentration of the cerium ions and the low density of chemical defects (oxygen vacancies) in the CeO_x film. The Ru/CeO_x/TaN structure memory is a very promising candidate for future nonvolatile RS memory applications.