Analysis of the conduction mechanisms responsible for multilevel bipolar resistive switching of SiO2/Si multilayer structures

We report on the bipolar resistive switching behavior of a SiO2/Si multilayer (ML) structure measured without current compliance for non-volatile memory applications. The SiO2/Si ML structure was thermally annealed to induce the formation of Si nanocrystals, which act as conductive nodes. It was found that the SET/RESET voltages and the ON/OFF resistance ratio (107-102) depend on the current-voltage measurement cycles. Moreover, the low resistance state from the initial cycle can be recovered by increasing the stop voltage in a subsequent cycle. The space charge limited conduction (SCLC) is the mechanism responsible for the charge transport in the high resistance state (HRS) during the first measurement cycle, while the Ohmic conduction predominates in the low resistance state (LRS). This suggest the formation of a conductive path within the SiO2/Si ML, which breaks apart and becomes reconstructed upon switching between the LRS to HRS and vice versa. Performing a sequence of switching cycles, one can observe that the SCLC becomes predominant for the both LRS and HRS, suggesting the partial formation and breakdown of several different conductive paths.