AFM-based Functional Tomography-To Mill or not to Mill, that is the Question!

TL;DR

This paper demonstrates AFM-based tomography in YbMnO3, revealing complex domain microstructures up to 1.8 micrometers deep, and discusses its potential and limitations for studying ferroelectric materials.

Contribution

It provides the first detailed AFM tomography analysis of YbMnO3 at significant depths and introduces a model for current distribution in interconnected domain walls.

Findings

AFM tomography mapped YbMnO3 domain structure up to 1.8 μm depth

Interconnected domain walls act as current dividers

Identified challenges include tip-blunting and subsurface amorphisation

Abstract

The electrical response of ferroelectric domain walls is often influenced by their geometry underneath the sample surface. Tomographic imaging in these material systems has therefore become increasingly important for its ability to correlate the surface-level functional response with subsurface domain microstructure. In this context, AFM-based tomography emerges as a compelling choice because of its simplicity, high resolution and robust contrast mechanism. However, to date, the technique has been implemented in a limited number of ferroelectric materials, typically to depths of a few hundred nanometers or on relatively soft materials, resulting in an unclear understanding of its capabilities and limitations. In this work, AFM tomography is carried out in YbMnO3, mapping its complex domain microstructure up to a depth of around 1.8 um along with its current pathways. A model is presented, describing the impact of interconnected domain walls within the network, which act as current dividers and codetermine how currents distribute. Finally, challenges such as tip-blunting and subsurface amorphisation are identified through TEM studies, and strategies to address them are also put forward. This study highlights the potential of AFM tomography and could spur interest within the ferroics community for its use in the investigation of similar material systems.