Bipolar ${rm Ni}/{rm TiO}_{2}/{rm HfO}_{2}/{rm Ni}$ RRAM With Multilevel States and Self-Rectifying Characteristics

摘要

To be compatible with 3-D vertical crossbar arrays, a ${rm TiO}_{2}/{rm HfO}_{2}$ bilayer resistive-switching memory (RRAM) cell sandwiched between Ni electrodes is developed. The proposed device has numerous highly desired features for the implementation of 3-D vertical RRAM, including: 1) stable bipolar resistive switching; 2) forming free; 3) self-compliance; 4) self-rectification; 5) multiple resistance states; and 6) room-temperature process. The resistive switching and current rectification are attributed to oxygen vacancy migration in ${rm HfO}_{2}$ and potential barrier modulation of the asymmetric ${rm TiO}_{2}/{rm HfO}_{2}$ tunnel barrier. The rectification ratio up to $10^{3}$ is capable of realizing a single-crossbar array up to 16 Mb for future high-density storage class memory applications.