Microscopic origin of transition from threshold switching to memory switching in oxide-electrolyte-based RRAM

In this work, both memory switching (MS) and threshold switching (TS) are demonstrated in single Ag/SiO₂/Pt planar structure device. After electroforming process with low current compliance (I_CC), a discontinuous conductive filament (CF) is formed and device shows TS characteristics. When increasing I_CC to relatively high value, a continuous CF is formed and device shows MS behavior. By controlling the I_CC during electroforming process, different CF morphologies were captured by scanning electron microscopic. I-V fitting of transition regions between HRS and LRS of TS loop confirmed that the discontinuous CF is similar to typical multi-island tunneling system. Combining with KPFM test results, we demonstrated that the TS behavior is dominated by tunneling barrier modulation of discontinuous CF.