Abstract
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•Trap concentration is important for trap-controlled RRAM with SCLC conduction.•A flexible multi-level NiPc RRAM is explored due to its high trap-concentration.•NiPc film provides numerous traps, enabling effective resistance switching.•NiPc RRAM shows the flexibility, reliability, uniformity and multi-level capability.•A fast operation speed is also primary for NiPc RRAM.
Metal phthalocyanine is considered one of the most promising candidates for the design and fabrication of flexible resistive random access memory (RRAM) devices due to its intrinsic flexibility and excellent functionality. However, performance degradation and the lack of multi-level capability, which can directly expand the storage capacity in one memory cell without sacrificing additional layout area, are the primary obstacles to the use of metal phthalocyanine RRAMs in information storage. Here, a flexible RRAM with pristine nickel phthalocyanine (NiPc) as the resistive layer is reported for multi-level data storage. Due to its high trap-concentration, the charge transport behavior of the device agrees well with classical space charge limited conduction controlled by traps, leading to an excellent performance, including a high on-off current ratio of 107, a long-term retention of 106 s, a reproducible endurance over 6000 cycles, long-term flexibility at a bending strain of 0.6 %, a write speed of 50 ns under sequential bias pulses and the capability of multi-level data storage with reliable retention and uniformity.