Tuning Local Conductance to Enable Demonstrator Ferroelectric Domain Wall Diodes and Logic Gates

• Published in: Advanced Physics Research Vol. 2; no. 5
• Main Authors: Suna, Ahmet, McCluskey, Conor Joseph, Maguire, Jesi Rit, Holsgrove, Kristina Mary, Kumar, Amit, McQuaid, Raymond Gerard Peter, Gregg, John Marty
• Format: Journal Article
• Language: English
• Published: Edinburgh John Wiley & Sons, Inc 01.05.2023; Wiley-VCH
• Subjects: Bias; Boolean; Diodes; domain wall electronics; Domain walls; Electric contacts; Electrical conduction; Electrodes; ferroelectric domain walls; Ferroelectric domains; Ferroelectricity; Gates; Inclination angle; Lithium; lithium niobate; Lithium niobates; Logic circuits; logic gates; Microscopy; Point defects; Thick films; Thin films
• ISSN: 2751-1200; 2751-1200
• DOI: 10.1002/apxr.202200095

Fundamentally, lithium niobate is a good electrical insulator. However, this can change dramatically when 180° domain walls are present, as they are often found to be strongly conducting. Conductivities depend on the inclination angles of walls with respect to the polarization axis and so, if these angles can be altered, then electrical conduction can be tuned, or toggled on and off. In ≈500 nm thick z‐cut ion‐sliced thin films, localized wall angle variations can be controlled by both the sense and magnitude of applied electrical bias. It is shown that this results in diode‐like behaviour, allowing half‐wave rectification at modest frequencies. Importantly, it is experimentally demonstrated that these domain wall diodes can be used to construct “AND” and inclusive “OR” logic gates, where “0” and “1” output states are clearly distinguishable. Extrapolation to more complex arrangements shows that output states can still be distinguished in two‐level cascade logic. Insights show that simple logic circuits can be realized by localized manipulation of domain wall conductivity. Our research complements that by Jie Sun et al. (Adv. Funct. Mater. 2207418 (2022)), where NOT, NOR, and NAND gates are realized by moving conducting domain walls to make or break electrical contacts. In thin film lithium niobate capacitors, localized bias‐induced changes in domain wall tilt (and associated changes in polar discontinuities) are found to induce strong diode‐like current–voltage characteristics. As a result, domain wall rectifiers, as well as “OR” and “AND” logic gates, are successfully demonstrated and modeled to be effective, even in two‐level cascade logic.