Unraveling the origin of ferroelectric resistance switching through the interfacial engineering of layered ferroelectric-metal junctions

Abstract

Ferroelectric memristors have found extensive applications as a type of nonvolatile resistance switching memories in information storage, neuromorphic computing, and image recognition. Their resistance switching mechanisms are phenomenally postulated as the modulation of carrier transport by polarization control over Schottky barriers. However, for over a decade, obtaining direct, comprehensive experimental evidence has remained scarce. Here, we report an approach to experimentally demonstrate the origin of ferroelectric resistance switching using planar van der Waals ferroelectric α-In2Se3 memristors. Through rational interfacial engineering, their initial Schottky barrier heights and polarization screening charges at both terminals can be delicately manipulated. This enables us to find that ferroelectric resistance switching is determined by three independent variables: ferroelectric polarization, Schottky barrier variation, and initial barrier height, as opposed to the generally reported explanation. Inspired by these findings, we demonstrate volatile and nonvolatile ferroelectric memristors with large on/off ratios above 104. Our work can be extended to other planar long-channel and vertical ultrashort-channel ferroelectric memristors to reveal their ferroelectric resistance switching regimes and improve their performances.

Two‐dimensional In2Se3: A rising advanced material for ferroelectric data storage

“…The characterizations of the samples show that In 2 Se 3 exhibits regular shapes and boundaries when the thickness is ≥2 nm, indicating good crystallinity, while when the thickness decreases below 1.3 nm, it exhibits irregular shapes 49 . Limited by the trade‐off between thickness and crystal quality, the thickness of the In 2 Se 3 in the current reported devices is mainly tens of nanometers 54–57,96,117,119 . Therefore, it is urgent to seek a method for mass‐produce high‐quality 2D In 2 Se 3 toward industrial applications.…”

“…The consistent PFM phase and electric potential at the interface in high and low resistance states suggest that the principle of resistance switching in this planar memristor is not the inversion of polarization at the metal-ferroelectric interface. However, the authors suggest that the change in band offset between the ferroelectric-electrode interface and the ferroelectric 96 Copyright 2021, Springer Nature channel caused by the ferroelectric switching may be responsible for the ferroelectric resistance switching. 99 The next year, Xue et al explored the resistance switching mechanism of p-FSJ-based ferroelectric memristors through an interfacial engineering approach.…”

“…Owing to the excellent property of 2D In 2 Se 3 , its various electronic devices are successfully fabricated soon after the theoretical prediction 54–60,95–97 . Although memory or computing devices based on ferroelectric materials were considered a promising technology, the problem of depolarization field that plagues ferroelectrics is particularly prominent in the era of device miniaturization for high‐density data applications 98 .…”

“…Although memory or computing devices based on ferroelectric materials were considered a promising technology, the problem of depolarization field that plagues ferroelectrics is particularly prominent in the era of device miniaturization for high‐density data applications 98 . Now, the development of 2D In 2 Se 3 will significantly promote the research of nano‐scaled devices such as FeFETs, ferroelectric semiconductor channel field‐effect transistors (FeS‐FETs, also called FeCTs), ferroelectric memristors, and ferroelectric semiconductor junctions (FSJs) 54–57,96,99 . Investigations on these devices not only demonstrate the practicability of 2D In 2 Se 3 , but also reflect the challenges and thus show the directions for future optimizations.…”

“…These devices differ in the work function height of the metal electrodes and the degree of interfacial screening of the ferroelectric polarization charges. Through electrical and PFM measurements, the authors found that ferroelectric resistance switching is affected together by ferroelectric polarization, variation of the Schottky barrier during operation, and the initial Schottky barrier height 96 …”