One-dimensional π-d conjugated coordination polymers: synthesis and their improved memory performance

Multilevel resistance random access memories (RRAMs) are intensively studied due to their potential applications in high density information storage. However, the low ternary device yields and high threshold voltages based on current materials cannot meet the requirement for applications. Improvement via material innovation remains desirable and challenging. Herein, five one-dimensional conjugated coordination polymers were synthesized via the reaction between metal ions (Zn²⁺, Cu²⁺, Ni²⁺, Pt²⁺ and Pd²⁺) and 2,5-diaminobenzene-1,4-dithiol (DABDT) and fabricated into RRAM devices. The as-fabricated ternary memories have relatively low threshold voltages (V_th1: −1 to −1.4 V, V_th2: −1.8 to −2.2 V). Their ternary device yields were improved from 24% to 56%. The first and the second resistance switches are interpreted by the space charge limited current (SCLC) and grain boundary depletion limited current (GBLC) modes, respectively. The Pd-DABDT, which is of planar structure, smaller band gap and better crystallinity than others, shows the best performance among these five polymers. Our work paves a simple and efficient way to optimize the performance of ternary RRAM devices employing one-dimensional hybrid materials.