Investigation of switching mechanism in forming-free multi-level resistive memories with atomic layer deposited HfTiO_x nanolaminate

Forming-free resistive memories (RRAM) have recently attracted significant attention as the forming process requires high voltage and can lead to low yield because of current overshoot [1-2]. We have recently demonstrated forming-free switching with multi-level operation in TiN/HfTiO_x/TiN resistive memories [3]. However, a fundamental understanding of the switching mechanisms is lacking. Recently the Quantum Point Contact model (QPC) has been applied to analyze switching behavior of conductive filament based resistive memories [4-5]. Investigation of multi-level switching in HfTiO_x-based resistive memories using the QPC model has not been attempted previously. In this work we have investigated the multi-level conduction mechanism of forming-free HfTiO_x RRAMs using the QPC model. We demonstrate that the model can successfully describe the entire dynamic range of multi-level switching for the HfTiO_x RRAMs.