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Memristor characteristics have been reported to be enhanced by inserting graphene oxide quantum dots (GOQDs) in oxide layers. However, it has not been studied how the density of GOQDs affects the resistive switching behavior of memristor devices. In this work, memristor devices in the structure of Ag/Zr0.5Hf0.5O2 (ZHO)/GOQDs/ZHO/Pt are fabricated and tested. The device measurement results show that as the applied voltage is scanned, if the density of GOQDs increases, the resistance adjustment of fabricated memristor devices shifts from abruptly to gradually. Moreover, the resistance of a high-GOQD-density device is modulated by controlling the amplitude, width, polarity, and number of applied voltage pulses. Furthermore, the fabricated memristor device demonstrates basic synaptic behavior, including tunable conductance, short-term plasticity, long-term plasticity, spike-timing-dependent facilitation, and paired-pulse facilitation. These phenomena are attributed to the high density of GOQDs, which prevents Ag+ from migrating through the switching layers, and hence, the formation of Ag conductive filaments is slower. This study reveals that the proposed memristor device with an appropriate density of GOQDs has great potential in artificial electronic synaptic applications. [ABSTRACT FROM AUTHOR]

Abstract: Memristors as electronic artificial synapses have attracted increasing attention in neuromorphic computing. Emulation of both “learning” and “forgetting” processes requires a bidirectional progressive adjustment of memristor conductance, which is a challenge for cutting‐edge artificial intelligence. In this work, a memristor device with a structure of Ag/Zr0.5Hf0.5O2:graphene oxide quantum dots/Ag is presented with the feature of bidirectional progressive conductance tuning. The conductance of proposed memristor is adjusted through voltage pulse number, amplitude, and width. A series of voltage pulses with an amplitude of 0.6 V and a width of 30 ns is enough to modulate conductance. The impacts of pulses with different parameters on conductance modulation are investigated, and the potential relationship between pulse amplitude and energy is revealed. Furthermore, it is proved that the pulse with low energy can realize the almost linear conductance regulation, which is beneficial to improve the accuracy of pattern recognition. The bidirectional progressive conduction modulation mimics various plastic synapses, such as spike‐timing‐dependent plasticity and paired‐pulse facilitation. This progressive conduction tuning mechanism might be attributed to the coexistence of tunneling effect and extrinsic electrochemical metallization effect. This work provides one way for memristor to attain attractive features such as bidirectional tuning, low‐power consumption, and fast speed switching that is in urgent demand for further evolution of neuromorphic chips. [ABSTRACT FROM AUTHOR]