Anomalous domain periodicity observed in ferroelectric PbTiO3 nanodots with 180o stripe domains

TL;DR

This study reveals an unexpected increase in domain width with decreasing size in PbTiO3 nanodots below a critical thickness, challenging classical scaling laws and attributed to surface effects.

Contribution

It uncovers anomalous domain periodicity in ferroelectric nanodots, highlighting the impact of surface layers and size effects beyond classical models.

Findings

Domain width increases as nanodot thickness decreases below 35 nm.

Classical LLK scaling law does not hold for ultra-thin nanodots.

Presence of nonferroelectric surface layer influences domain behavior.

Abstract

PbTiO3-based nano-scale dots and tubes have received a great deal of attention owing to their potential applications to nonvolatile memories and multi-functional devices. As for the size effect of 180o stripe domains in ferroelectric thin films, there have been extensive reports on the thickness-dependent domain periodicity. All these studies have revealed that the domain periodicity of 180o stripe domains scales with the film thickness (d) according to the classical Landau-Lifshitz-Kittel (LLK) scaling law down to the thickness of ~2 nm. In the case of PbTiO3 nanodots, however, we obtained a quite striking correlation that for the thickness less than a certain critical value, dc (~35 nm), the domain width even increases with decreasing thickness of the nanodot, which surprisingly indicates a negative value in the LLK scaling-law exponent. On the basis of theoretical considerations of dc, we attribute this anomalous domain periodicity to the presence of a nonferroelectric surface layer, in addition to the finite lateral-size effect of a ferroelectric nanodot.