Recently, organic-inorganic halide perovskite (OHP) has been suggested as an alternative to oxides or chalcogenides in resistive switching memory devices due to low operating voltage, high ON/OFF ratio, and flexibility. The most studied OHP is 3-dimensional (3D) MAPbI. However, MAPbI often exhibits less reliable switching behavior probably due to the uncontrollable random formation of conducting filaments. Here, we report the resistive switching property of 2-dimensional (2D) OHP and compare switching characteristics depending on structural dimensionality. The dimensionality is controlled by changing the composition of BAMAPbI (BA = butylammonium, MA = methylammonium), where 2D is formed from n = 1, and 3D is formed from n = ∞. Quasi 2D compositions with n = 2 and 3 are also compared. Transition from a high resistance state (HRS) to a low resistance state (LRS) occurs at 0.25 × 10 V m for 2D BAPbI film, which is lower than those for quasi 2D and 3D. Upon reducing the dimensionality from 3D to 2D, the ON/OFF ratio significantly increases from 10 to 10, which is mainly due to the decreased HRS current. A higher Schottky barrier and thermal activation energy are responsible for the low HRS current. We demonstrate for the first time reliable resistive switching from 4 inch wafer-scale BAPbI thin film working at both room temperature and a high temperature of 87 °C, which strongly suggests that 2D OHP is a promising candidate for resistive switching memory.
As silicon-based metal oxide semiconductor field effect transistors get closer to their scaling limit, the importance of resistive random-access memory devices increases due to their low power consumption, high endurance and retention performance, scalability, and fast switching speed. In the last couple of years, organic-inorganic lead halide perovskites have been used for resistive switching applications, where they outperformed conventional metal oxides in terms of large on/off ratio and low power consumption. However, there were scarce reports on lead-free perovskites for such applications. In this report, we prepared lead-free Au/ABiI/Pt/Ti/SiO/Si (A is either Cs or Rb) devices and tested their resistive switching characteristics. They showed a forming step prior to repeating switching, low operating voltage (0.09 V for RbBiI and 0.1 V for CsBiI), large on/off ratio (>10), relatively high endurance (200 cycles for RbBiI and 400 cycles for CsBiI cycles), and high retention (1000 s). Such low voltage could be explained by grain boundary-modulated ion drift. Difference in endurance was speculated to be due to the difference in the surface roughness of films because CsBiI films are smoother. To get rid of the forming step, 10% of the Bi cations were substituted with Na cations. However, this method only worked on Rb-based structures. This phenomenon was explained by the defect formation energy, which can only be negative in a corner-sharing RbBiI structure compared to a face-sharing octahedral CsBiI structure. As a result, the forming step was removed, and 100 cycles endurance and 1000 s retention performance were obtained. Similarly, the lower endurance is suspected to be due to the poor surface quality of the film.
Organic–inorganic halide perovskite is regarded as one of the potential candidates for next generation resistive switching memory (memristor) material because of fast, millivolt‐scale switching, multilevel capability, and high On/Off ratio. Here, resistive switching property of HC(NH2)2PbI3 (FAPbI3) depending on structural phase is reported. It is found that 1D hexagonal FAPbI3 (δ‐FAPbI3), formed at relatively low temperature, is active in memristor, while 3D trigonal FAPbI3 (α‐FAPbI3), formed at temperature higher than 150 °C, is inactive. Failure of switching from low resistance state to high resistance state is found for α‐FAPbI3, while δ‐FAPbI3 shows stable switching behavior. Density functional calculation reveals that iodine cluster in isotropic 3D α‐FAPbI3 is so stable after forming filament that the filament is hard to be ruptured at off state. However, for anisotropic δ‐FAPbI3, iodine cluster is not stable and migration barrier is much lower for c‐axis (0.48 eV) than for ab‐plane (0.9 eV), which is beneficial for switching. The memristor devices based on δ‐FAPbI3 demonstrate endurance up to 1200 cycles with On/Off ratio (>105), retention time up to 3000 s, multilevel storage capacity, and working even at 80 °C.
Studies on the compositional engineering of imidazolium lead iodide revealed that 1-dimensional hexagonal stoichiometric (Im)PbI3 showed the best endurance and retention characteristics.
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