Effect of interlayer spacing in layered perovskites on resistive switching memory

Abstract

We report here the effect of interlayer spacing in 2-dimensional (2D) perovskites of [C₆H₅(CH₂)_nNH₃]₂PbI₄ (anilinium (An) for n = 0, benzylammonium (BzA) for n = 1 and phenylethylammonium (PEA) for n = 2) on resistive switching properties. X-ray diffraction (XRD) reveals that the interlayer spacing of layered PbI₂ is increased from 6.98 Å to 13.29 Å for (An)₂PbI₄, 14.20 Å for (BzA)₂PbI₄ and 15.92 Å for (PEA)₂PbI₄, which leads to a monolayer of organic cations with stacked benzene rings between inorganic PbI₄²⁻ layers. All the samples in the device structure of Ag/PMMA (polymethyl methacrylate)/perovskite/Pt show bipolar switching behavior, where the SET voltage is near +0.2 V and the RESET voltage is less than −0.5 V. The ratio of LRS (low resistance state) to HRS (high resistance state), also called the ON/OFF ratio, is increased from 10⁶ to 10⁸ as interlayer spacing is increased due to the gradual increase in resistance in the HRS. Endurance is slightly improved from 1.3 × 10² for An to 2.2 × 10² for PEA, whereas substantial improvement in retention is observed from 2 × 10³ to 5.5 × 10³. This indicates that the enhanced 2D structure is beneficial to the kinetics of forming and rupturing the conducting filaments. The ohmic-like conduction mechanism in the LRS and the hopping mechanism in the HRS are observed for all three samples. This work finds that the resistive switching properties and conduction mechanism in the HRS depend on interlayer spacing in 2D perovskites.