Direct Thermal Imaging of Domain Wall Hot Spots in LiNbO3

Abstract

Ferroelectric domain wall devices offer a promising route to low-voltage, reconfigurable nanoelectronics by confining currents to nanoscale conducting interfaces within an insulating bulk. However, the potential for resistive heating and unregulated temperature increases due to domain wall conduction remains unexplored. Here, scanning thermal microscopy is employed to directly image hot spots in thin-film lithium niobate domain wall devices. Piezoresponse force microscopy shows that the hot spots correlate with nanodomain structure, and thermal mapping reveals surface temperature rises of ~20 K at most, levels that are unlikely to negatively affect device performance. This is due to the moderate electrical conductivity of domain walls, their voltage-tunable erasure, and distributed current pathways, which inherently limit power dissipation and peak temperatures. Finite element electrothermal modelling indicates that domain walls behave as pseudo-planar heat sources, distinct from the filament-based heating typically observed in resistive switching oxides. These findings highlight the potential for domain wall devices as an energy-efficient, thermally stable platform for emerging memory and logic applications.