Lead-free perovskite MASnBr3-based memristor for quaternary information storage

Memristors are a new type of circuit element with a resistance that is tunable to discrete levels by a voltage/current and sustainable after removal of power,allowing for low-power computation and multilevel information storage.Many organic-inorganic lead perovskites are reported to demonstrate memristive behavior,but few have been considered for use as a multilevel memory;also,their potential application has been hindered by the toxicity of lead ions.In this article,lead-free perovskite MASnBr3 was utilized in memristors for quaternary information storage.Indium tin oxide(ITO)/MASnBr3/Au memristors were fabricated and showed reliable memristive switching with well-separated ON/OFF states of a maxima resistance ratio of 102 to 103.More importantly,four resistive states can be distinguished and repeatedly written/read/erased with a retention time of 104 seconds and an endurance of 104 pulses.By investigating the current-electrode area relationship,Br distribution in the ON/OFF states by in situ Raman and scanning electron microscopy,and temperaturedependent current decay,the memristive behavior was explicitly attributed to the forming/breaking of conductive filaments caused by the migration of Br−under an electric field.In addition,poly(ethylene terephthalate)-ITO/MASnBr3/Au devices were found to retain their multiresistance state behavior after being bent for 1000 times,thus demonstrating good device flexibility.Our results will inspire more lead-free perovskite work for multilevel information storage,as well as other memristor-based electronics.

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(Zn^(2+), Cu^(2+), Ni^(2+),Pt^(2+) and Pd^(2+)) 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.