Multilevel resistive switching memory behaviors arising from ion diffusion and photoelectron transfer in α-Fe2O3 nano-island arrays

Enhancing Efficiency and Stability of Tin Halide Perovskite Light-Emitting Diodes via Engineered Alkali/Multivalent Metal Salts

Sn-based perovskite light-emitting diodes (PeLEDs) have emerged as promising alternatives to Pb-based PeLEDs with their rapid increase in performance owing to the various research studies on inhibiting Sn oxidation. However, the absence of defect passivation strategies for Sn-based perovskite LEDs necessitates further research in this field. We performed systematic studies to investigate the design rules for defect passivation agents for Sn-based perovskites by incorporating alkali/multivalent metal salts with various cations and anions. From the computational and experimental analyses, sodium trifluoromethanesulfonate (NaTFMS) was found to be the most effective passivation agent for PEA2SnI4 films among the explored candidate agents owing to favorable reaction energetics to passivate iodide Frenkel defects. Consequently, the incorporation of NaTFMS facilitates the formation of uniform films with relatively large crystals and reduced Sn4+. The NaTFMS-containing PEA2SnI4 PeLEDs demonstrate an improved luminance of 138.9 cd/m2 and external quantum efficiency (EQE) of 0.39% with an improved half-lifetime of more than threefold. This work provides important insight into the design of defect passivation agents for Sn-based perovskites.

A Facile Hydrothermal Synthesis and Resistive Switching Behavior of α-Fe2O3 Nanowire Arrays

A facile hydrothermal process has been developed to synthesize the α-Fe₂O₃ nanowire arrays with a preferential growth orientation along the [110] direction. The W/α-Fe₂O₃/FTO memory device with the nonvolatile resistive switching behavior has been achieved. The resistance ratio (R_HRS/R_LRS) of the W/α-Fe₂O₃/FTO memory device exceeds two orders of magnitude, which can be preserved for more than 10³s without obvious decline. Furthermore, the carrier transport properties of the W/α-Fe₂O₃/FTO memory device are dominated by the Ohmic conduction mechanism in the low resistance state and trap-controlled space-charge-limited current conduction mechanism in the high resistance state, respectively. The partial formation and rupture of conducting nanofilaments modified by the intrinsic oxygen vacancies have been suggested to be responsible for the nonvolatile resistive switching behavior of the W/α-Fe₂O₃/FTO memory device. This work suggests that the as-prepared α-Fe₂O₃ nanowire-based W/α-Fe₂O₃/FTO memory device may be a potential candidate for applications in the next-generation nonvolatile memory devices.

Ternary Conductance Switching Realized by a Pillar[5]arene-Functionalized Two-Dimensional Imine Polymer Film

Nowadays, most manufacturing memory devices are based on materials with electrical bistability (i. e., "0" and "1") in response to an applied electric field. Memory devices with multilevel states are highly desired so as to produce high-density and efficient memory devices. Herein, we report the first multichannel strategy to realize a ternary-state memristor. We make use of the intrinsic sub-nanometer channel of pillar[5]arene and nanometer channel of a two-dimensional imine polymer to construct an active layer with multilevel channels for ternary memory devices. Low threshold voltage, long retention time, clearly distinguishable resistance states, high ON/OFF ratio (OFF/ON1/ON2=1 : 10 : 10³ ), and high ternary yield (75 %) were obtained. In addition, the flexible memory device based on 2DP_TPAZ+TAPB can maintain its stable ternary memory performance after being bent 500 times. The device also exhibits excellent thermal stability and can tolerate a temperature as high as 300 °C. It is envisioned that the results of this work will open up possibilities for multistate, flexible resistive memories with good thermal stability and low energy consumption, and broaden the application of pillar[n]arene.

Refining the Negative Differential Resistance Effect in a TiOx-Based Memristor

The N-type negative difference resistance (NDR) is characterized by the peak/valley voltage (V_p/V_v) and the corresponding current (I_p/I_v). The N-type NDR is observed in the resistive switching (RS) memory device of Ag|TiO₂|F-doped SnO₂ at room temperature. After the TiO₂ film is equipped with a nanoporous array, the ∼1.2 V gap voltage between V_p and V_v is effectively downscaled to ∼0.5 V, and the gap current of ∼7.23 mA between I_p and I_v is improved to ∼30 mA. It demonstrates that a lower power consumption and faster switching time of the NDR can be obtained in the memristor. Compensations and synergies among the nanoscale conduction filaments (OH^-, Ag⁺, and V_o) are responsible for the refining NDR behavior in our devices. This work provides an efficient method to construct a high-performance N-type NDR effect at room temperature and gives a new horizon on the coexistence of this type of NDR effect and RS memory behaviors.

Features of the crystallization of multicomponent solutions: a dipeptide, its salt and potassium carbonate

Various stages of crystallization of the dipeptide potassium salt on graphite and gold. Possible molecular structures of the dipeptide (a) and its potassium salt (b).