All-Inorganic Bismuth Halide Perovskite-Like Materials A₃Bi₂I₉ and A₃Bi_1.8Na_0.2I_8.6 (A = Rb and Cs) for Low-Voltage Switching Resistive Memory

Abstract

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.

Ion Migration: A “Double‐Edged Sword” for Halide‐Perovskite‐Based Electronic Devices

“…h) I – V curves of forming step for all‐inorganic perovskite memory devices. Reproduced with permission . Copyright 2018, American Chemical Society.…”

Dual‐Phase All‐Inorganic Cesium Halide Perovskites for Conducting‐Bridge Memory‐Based Artificial Synapses

“…In the α‐CsPbI 3 phase, I − migrates along the linearly aligned PbI 6− octahedron edge, and Cs + migrates to adjacent V′ Cs sites (Figure b) . Further, in the Cs 3 Bi 2 I 9 phase (Figure c), I − migration is achieved through the 0D face‐sharing octahedrons of [Bi 2 I 9 ] 3− , and Cs + migration occurs along the adjacent V′ Cs sites . However, in the orthorhombic δ‐CsPbI 3 phase, the direction of defect migration is not uniform due to the arrangement of the square bipyramidal units of the PbI 6− octahedrons in different directions, as illustrated in Figure S9c (Supporting Information) .…”

Recent Advances in Halide Perovskite Memristors: Materials, Structures, Mechanisms, and Applications

“…As previously mentioned, Cuhadar et al found that for Rb 3 Bi 2 I 9 perovskite, when 10% Bi 3+ cations were substituted with Na + cations, the average value of V forming significantly decreased, and some of these devices were completely electroforming‐free. [ 72 ] However, even without doping, many halide perovskite memristors are also electroforming‐free, and the reasons need to be further explored. Another controversial focus is the selection of metal electrodes.…”

“…In 2018, Cuhadar et al fabricated all‐inorganic lead‐free Rb 3 Bi 2 I 9 and Cs 3 Bi 2 I 9 perovskite memristors. [ 72 ] The device had a structure of Si/SiO 2 /Ti/Pt/A 3 Bi 2 I 9 /Au (A = Rb, Cs). Both devices showed instantaneous switching phenomena in the SET and RESET processes.…”