Mechanism Exploration, Performance Manipulation, And Logic Application Of Redox-Based Resistive Random Access Memories

Redox-based resistive random access memories?RRAMs?are one promising candidate for the next-generation high-speed,high-density,and low-power nonvolatile memory.In the past decades,mechanism exploration,performance enhancement,and application expansion of redox-based RRAMs have aroused much attention from both academic and industrial communities.In this dissertation,P3HT:PCBM and PEDOT:PSS films were deposited using spin-coating,whereas SiO₂ and Ta₂O₅ films were deposited using radio-frequency magnetron sputtering.Then redox-based RRAMs with these films as storage media were developed and systematically characterized.The focuses of this dissertation are on the dynamic growth process of metal filaments and the controllable modulation of binary oxides' switching behaviors.Besides,multiple implementation methods of logic operations in RRAMs were explored.The dynamic growth process of metal filaments in redox-based RRAMs was systematically studied by selecting various electrode materials and storage media.Two growth modes of metal filaments,which differ from the conventional one of growing from inert electrode to active electrode,have been successfully obtained,i.e.,the growth modes of growing from active electrode to inert electrode in the Cu/P3HT:PCBM/ITO devices and of extending from the center of storage medium to two electrodes in the Ag/PEDOT:PSS/Pt devices.Theoretical analysis and computer simulation indicated that the growth mode of metal filaments is affected by both the migration process of cations and the nucleation process of metal filaments.The growth mode of growing from active electrode to inert electrode is dominated by the migration process of cations,whereas that of growing from inert electrode to active electrode is dominated by the nucleation process of metal filaments.When these two processes compete with each other and both play a part,metal filaments show the growth mode of extending from the center of storage medium to two electrodes.In addition,by optimizing measurement parameters to modulate the evolution process of metal filaments,conductance quantization of Ag filaments was successfully observed in the P3HT:PCBM and SiO₂ storage media.The switching characteristic of Ta₂O₅ film was modulated by selecting n-Si semiconducting electrode and by inserting untra-thin Ta nanolayers.Self-rectifying Pt/Ta₂O₅/n-Si RRAMs with high ON/OFF ratio of ¹04and high rectification ratio of⁶00 have been successfully fabricated.The observed self-rectifying effect originates from the Schottky contact between the formed oxygen vacancy filament and the n-Si semiconducting electrode,and can settle the sneak-path issue of a maximum crossbar size of 212 × 212?⁴4 kbit?.The intrinsic nonpolar switching behavior of a 10 nmTa₂O₅ film has been successfully and controllably transformed into self-compliance bipolar switching behavior and complementary switching behavior by inserting 2 nm and 4 nm Ta nanolayers,respectively.Also,the operation voltage and current values have been lowered,and the switching uniformity has been improved.In order to enhance the ability of RRAMs for logic operation,a novel type of complementary resistive switches with intrinsic switchable diode has been theoretically designed and experimentally proved.More importantly,in a Ta/Ta₂O₅/Pt/Ta₂O₅/Ta novel complementary resistive switch,both the intrinsic switchable diode and the complementary switching behavior itself have been demonstrated to be enough for performing all 16 Boolean logic functions.