Coordination-Strengthened Materials For Environmentally Stable Resistive Memory

With the rapid development of modern information technology,the traditional storage technologies are unable to meet the requirements of information storage.Therefore,it is urgent to develop a new storage technology with high information storage density.Resistive random access memory(RRAM)has attracted more and more attentions because of its simple structure,low cost and three-dimensional stackability.In addition,if multiple conductive states could be obtained in one cell,multilevel memory could be realized,which dramatically improves the information storage density.In the past decade,great progresses were made in RRAM technologies,and many kinds of material have been developed for RRAM devices.In addition,the memory performance could be effectively optimized by adjusting the conjugated structures and the electron-donor/acceptor groups.However,the environmental stability of memory devices is still unsatisfactory,especially in various harsh environments,including high temperature,high humidity and ionization radiation,most of the reported memory devices are unworkable.Therefore,it is necessary to develop a new kind of materials for environmentally stable RRAM devices.Complex materials have been widely used in many fields,and there are abundant ligand and central metal atoms,which provides a great space for adjusting the structures and chemical properties of complex materials.In addition,the complex materials also possess the stability of inorganic materials due to the existence of strong polar coordination bonds.Therefore,it has the potential to solve the problem of the environmental instability of RRAM devices by using coordination-bond-rich materials.This paper will use complex materials to prepare RRAM devices.Take the advantages of structural diversity of complex materials,and realize environmental stable memory performances.This work will mainly carry out from the following aspects:(1)Two 1D d-π conjugated coordination polymer chains(Ni-BTA and Ni-BPTA)were synthesized and fabricated into memory devices.The as-fabricated devices can perform stable ternary memory behavior and retain their memory states for as long as three months at room temperature or work for at least 104 s at 150℃.The ternary device yields of Ni-BTA-and Ni-BPTA-based devices are 48%and 42%.Thermogravimetric analysis indicates good thermal stability of these two materials because of their good crystallinity and strong intermolecular interaction.The long-term and high-temperature stability makes 1D conjugated coordination polymer chains a promising candidate for use as next-generation material for high density data storage via RRAM techniques.(2)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.By changing the central metal ions effectively adjust the conjugated structure,band gap and crystallinity,so as to optimize the memory performance.The as-fabricated ternary memories have relatively low threshold voltages.Their ternary device yields were improved from 24%to 56%.This work paves a simple and efficient way to optimize the performance of ternary RRAM devices employing one-dimensional hybrid materials(3)The pseudohalide-induced 2D(CH3NH3)2PbI2(SCN)2 perovskite thin film is prepared by using a one-step solution method and fabricated into memory devices.Ternary resistive memory based on hybrid perovskite is achieved with a high device yield(75%),much higher than most organic ternary resistive memories.Two resistance switches are attributable to the charge trap filling due to the effect of unscreened defect in 2D nanosheets and the formation of conductive filaments,respectively.This work paves way for stable perovskite multilevel RRAMs in ambient atmosphere.(4)In order to solve the thermo instability and the toxicity of lead-based perovskite.For the first time,lead-free double perovskite Cs2AgBiBr6 is utilized for environmentally robust memory devices,enabling highly efficient information storage.The memory performance of the typical ITO/Cs2AgBiBr6/Au sandwich-like device is retained after 1000 switching cycles,105 s of reading,and 104 times of mechanical bending.Most importantly,the memory behavior remains robust in harsh environments,including humidity up to 80%,temperatures as high as 453 K,an alcohol burnmer flame for 10 s,and 60Co y-ray irradiation for a dosage of 5 ×105 rad(SI).The resistance to radiation is better than commercial flash memory devices.The realization of an environmentally robust memory device from Cs2AgBiBr6 with a high memory performance will inspire further development of robust electronics using lead free double perovskites.