Speaker
Description
Domain walls in ferroelectric materials are an exciting new type of graphene-like 2D functional interface with properties that can differ significantly from the surrounding bulk. Like graphene, they can display various transport regimes, such as semiconducting, metallic, and even superconducting, behaviour. Domain walls are a part of the ferroelectric microstructure (they are interfaces that separate polar domain variants) that can be created, erased or moved by applied voltages, and in this sense are reconfigurable. A decade of research has focused on exploiting this reconfigurable electrical property variation seen within domain walls with an aim to create voltage configurable nanoelectronic devices. Lab-level transistor [1] and memristor devices [2] have been reported, where device functionality is derived entirely from the number of electrically conducting domain walls connecting device electrodes, thereby enabling a tuneable device resistance for multi-state memory applications. However, much less is known about the fundamental electrothermal properties of domain walls and their influence on device operation, despite similar studies in resistive switching memories where self-heating and local temperature are key to operation [3]. We have been using Scanning Thermal Microscopy (SThM), supported by finite-element modelling, to investigate the self-heating properties of domain walls in electroded thin-film ferroelectric LiNbO3 devices. Electrically conducting domain walls were introduced into the material by an electrical poling procedure. The devices were cross-sectioned using a Focused Ion Beam procedure such that the domain wall microstructure in the 500nm thick ferroelectric layer could be visualised directly using Piezoresponse Force Microscopy. Finite-element modelling of the self-heating of the domain walls is being used to inform the ongoing SThM investigations of biased cross-sectioned devices.
[1] X Chai et.al, Nat. Commun. 11, 2811 (2020).
[2] J. P. V. McConville et.al, Adv. Funct. Mater. 30, 2000109 (2020).
[3] W. S. Deshmukh et al. Sci. Adv. 8, eabk1514 (2022).
