We reported on a Ti/HfO ₂ /TiO _x /Pt memristor with self-compliance, deep-RESET characteristics and excellent switching performance, including ultrafast program/erase speed (10 ns), a large memory window (10 ³ ) and good pulse endurance (10 ⁷ cycles). The self-compliance and deep-RESET characteristics are beneficial for protecting the device from permanent breakdown in both SET and RESET processes especially under the pulse operation mode. In addition to bistable state switching, we also achieved multiple or even continuous conductance state switching under a DC sweep and a pulse-train operation mode in the Ti/HfO ₂ /TiO _x /Pt memristor, which can be seen as a substitution of a biological synapse. The capability of continuous modulation conductance (synaptic weight) in the Ti/HfO ₂ /TiO _x /Pt memristor was investigated and the potentiation and depression characteristics of the synaptic weight could be precisely tuned by the number or amplitude of the input pulse-train. Moreover, clear experimental evidence of short-term plasticity (STP) and long-term plasticity (LTP) in a single memristor was also demonstrated. Increasing the pulse amplitude or width, or decreasing the interval of two adjacent pulses of the input pulse-train resulted in the memristor behavior transitioning from STP to LTP. The realization of those important synaptic functions in the Ti/HfO ₂ /TiO _x /Pt memristor may be suitable for applications in artificial neural systems.

We reported an Al ₂ O ₃ /HfO ₂ /Al ₂ O ₃ sandwich structure resistive switching device with significant improvement of multilevel cell (MLC) operation capability, which exhibited that four stable and distinct resistance states (one low resistance state and three high resistance states) can be achieved by controlling the Reset stop voltages ( V _Reset-stop ) during the Reset operation. The improved MLC operation capability can be attributed to the R _HRS / R _LRS ratio enhancement resulting from increasing of the series resistance and decreasing of leakage current by inserting two Al ₂ O ₃ layers. For the high-speed switching applications, we studied the initial switching dynamics by using the measurements of the pulse width and amplitude dependence of Set and Reset switching characteristics. The results showed that under the same pulse amplitude conditions, the initial Set progress is faster than the initial Reset progress, which can be explained by thermal-assisted electric field induced rupture model in the oxygen vacancies conductive filament. Thus, proper combination of varying pulse amplitude and width can help us to optimize the device operation parameters. Moreover, the device demonstrated ultrafast program/erase speed (10 ns) and good pulse switching endurance (10 ⁵ cycles) characteristics, which are suitable for high-density and fast-speed nonvolatile memory applications.

Based on the constructed W/Cs ₃ Bi ₂ Br ₉ /ITO memristor, the synaptic plasticity aspects, such as STP and LTP, are successfully simulated, making it suitable for artificial neural systems.

Recently, the lead-free double perovskite Cs₂AgBiBr₆ has been considered as a promising candidate for next-generation nonvolatile memory and artificial synapse devices due to its high stability and low toxicity compared to its lead-based counterparts. In this work, we developed a simple and effective method to produce high-quality lead-free double perovskite Cs₂AgBiBr₆ thin films without pinholes and particles by applying a low-pressure assisted method under ambient condition with a relative humidity (RH) of about 45%. The formation of pinholes and Ag precipitation in the perovskite Cs₂AgBiBr6 films is effectively suppressed by the proper ratio of N,N-dimenthylformamide (DMF) mixed in dimethyl sulfoxide (DMSO) solvents. Furthermore, the grain size of the Cs₂AgBiBr₆ films can be significantly increased by increasing the post-annealing temperature. Finally, a sandwiched structure memristor with an ITO/Cs₂AgBiBr₆/Ta configuration was successfully demonstrated, featuring ultralow operation voltage (V _Set ∼ 57 ± 23 mV, V _Reset ∼ −692 ± 68 mV) and satisfactory memory window (the ratio of R _HRS/R _LRS ∼ 10 times), which makes it suitable for low-power consumption information storage devices.

Lead-free perovskites, particularly the Cs2AgBiBr6 double perovskite, have emerged as promising candidates for eco-friendly nonvolatile memory and neuromorphic computing, with halogen doping being an effective strategy to tailor its electronic properties for memristive applications. In this work, high-quality Cl-doped Cs2AgBiBr6-xClx double perovskite films were fabricated via a one-step spin-coating method followed by low-pressure assisted treatment for high-performance memristors. Systematic investigation reveals that moderate Cl doping (x = 0.5) can optimize the resistive switching performance by enlarging the memory window (RHRS/RLRS ratio). Furthermore, a critical switching failure mechanism is identified to be caused by the electrochemical reaction between the Ag electrode and halide ions (Br/Cl), which consumes the electrode and limits endurance to ~100 cycles. By introducing a thin polyvinyl pyrrolidone (PVP) interlayer, this interfacial reaction is successfully suppressed, and the cycling stability can be significantly enhanced to over 1200 cycles. The optimized Ag/PVP/Cs2AgBiBr5.5Cl0.5/ITO memristor effectively emulates essential synaptic functions, including short-term and long-term plasticity, as well as bidirectional conductance modulation. Leveraging this, a fully connected neural network based on these devices achieved a recognition accuracy of 92.3% on the MNIST handwritten digit dataset. This work provides a co-design strategy combining halogen doping and interface engineering for developing reliable lead-free perovskite memristors, offering a viable pathway toward sustainable neuromorphic electronics.