Ultra-Low Power Multilevel Switching with Enhanced Uniformity in Forming Free TiO2-x-Based RRAM with Embedded Pt Nanocrystals

Accurate control over the various resistance states is highly desired in order to attain reliable multilevel memory performance. However, due to the inherent random nature of oxygen vacancy creation, serious variability issues may arise. In this work, we demonstrate promising multilevel capability with ultra-low power consumption in the range of nW, using sub-200nA operating current in a 45nm TiO2-x-based resistive random access memory (RRAM) with embedded small (approximate to 5nm in diameter) Pt nanocrystals (NCs). As the resistance values present a strong dependence on both the oxygen vacancy density and the diameter of the conducting filament (CF), hence the degree of the variability (or uniformity) can be improved by controlling one of these two parameters. It is shown here that the presence of NCs allows for the generation of multiple and dense CFs due to the concentrated electric field around the NCs which, in turn, enhance the consecutive cycling (temporal) uniformity, even at very low operating power conditions.