Co-existed unipolar and bipolar resistive switching effect of HfOx-based RRAM
Both unipolar and bipolar resistive switching behaviors are demonstrated and investigated in the TaTiN/HfOx/Pt structured RRAM devices. A physical model based on the recombination among the electron-depleted oxygen vacancies (VO2+) and the oxygen ions (O2-) released from the TaTiN electrode is proposed to clarify the co-existed bipolar and unipolar resistive switching effect. In the proposed physical model, Joule heating controlled O2- decomposition and electric-field controlled O2- drift dominate the unipolar and bipolar resistive switching behaviors, respectively.