Nanostructured resistive memory cells based on 8-nm-thin TiO2 films deposited by atomic layer deposition

Nanostructured Pt/ TiO2 /Ti/Pt crosspoint junctions with lateral dimensions as small as 100×100 nm2 were prepared on silicon substrates by the use of nanoimprint lithography and reactive ion etching to structure the metal electrodes combined with atomic layer deposition of the resistive switching TiO2 layer. A thickness of the amorphous TiO 2 films of only 8 nm already led to functioning nanocrosspoint structures with respect to resistance switching behavior. As-prepared structures exhibited very high-resistance states with diodelike I-V characteristics. After a negative-current-driven electroforming step, the devices could be repeatably switched between two stable states. The switching characteristics were found to depend strongly on the resistance state after the electroforming procedure. Low resistance values around 1 k led to high current switching, and resistances of about 10 k led to low current switching. Furthermore, multilevel switching was demonstrated by the use of 10 and 50 ns set voltage pulses.