Block copolymer templated halide perovskite memristors

Abstract

Scaling down of transistors in modern ICs has been made increasingly difficult due to the encroachment of inevitable adverse effects at this length scale. Moreover, the quest to increase computing density and power has also been stifled due to the Von Neumann bottleneck, where separate “process” and “memory” modules in the current architecture limit computational performance. One approach being explored is neuromorphic electronics, which aim to emulate biological neurons and synapses, allowing for a computational architecture of separate memory and process units to overcome the aforementioned bottleneck. A promising candidate in this category is a class of devices called memristors. Lead halide perovskites (LHPs) possess resistive switching behaviour, enabling multilevel resistance states which make them suitable for use in memristors. However, LHPs are notorious for their instability in ambient conditions and inconsistent switching behaviour due to the arbitrary nature of conductive filament (CF) formation.

In this study, thin films were fabricated by using PS-b-P2VP, a block copolymer (BCP) to template and confine LHP crystallization within nanostructures via a selective coordination between the LHP precursors and the P2VP block. Structures ranging from lamellae to vertical cylinders were observed by Atomic Force Microscopy (AFM) upon spin coating of the film. The selective coordination was confirmed via Fourier Transform Infrared (FTIR) spectroscopy data. The composite also showed enhanced photoluminescent quantum yield (PLQY) which further supports the confinement of LHP crystals. Memristors assembled from the films via thermal evaporation of silver (Ag) electrodes indicated CF formation as the main resistive switching behaviour. Fabricated memristors show a high ON/OFF ratio of 10^4, a retention of >1000s, a low device-to-device variation and an ability to retain switching performance after 16 days in ambient air, showing remarkable stability The effects of varying LHP loading and film thicknesses on film structure and device performance are also discussed.

These observations highlight the potential of the LHP/PS-b-P2VP-based memristors as a candidate for use in the field of neuromorphic electronics, as well as the possibility of leveraging self-assembly in BCPs for other optoelectronic applications.