Bipolar Ni/TiO2/HfO2/Ni RRAM With Multilevel States and Self-Rectifying Characteristics

Abstract

To be compatible with 3-D vertical crossbar arrays, a TiO2/HfO2 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 HfO2 and potential barrier modulation of the asymmetric TiO2/HfO2 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.