Quantitative piezoelectric force microscopy: Influence of tip shape, size, and contact geometry on the nanoscale resolution of an antiparallel ferroelectric domain wall

TL;DR

This study uses quantitative piezoelectric force microscopy to analyze how tip shape and contact geometry affect the nanoscale resolution of ferroelectric domain walls, revealing a linear relationship between tip radius and measured profile width.

Contribution

It introduces a calibrated probe method and analytical modeling to accurately measure ferroelectric domain wall widths at the nanoscale, accounting for tip geometry effects.

Findings

Profile width linearly proportional to tip radius

Piezoelectric coefficient magnitude independent of tip size

Observed ferroelectric wall widths range from 20 to 200 nm

Abstract

The structure of a single antiparallel ferroelectric domain wall in LiNbO3 is quantitatively mapped by piezoelectric force microscopy (PFM) with calibrated probe geometry. The PFM measurements are performed for 49 probes with the radius varying from 10 to 300 nm. The magnitude and variation of the experimental piezoelectric coefficient across a domain wall matches the profiles calculated from a comprehensive analytical theory, as well as 3-dimensional finite element method simulations. Quantitative agreement between experimental and theoretical profile widths is obtained only when a finite disk-type tip radius that is in true contact with the sample surface is considered, which is in agreement with scanning electron microscopy images of the actual tips after imaging. The magnitude of the piezoelectric coefficient is shown to be independent of the tip radius, and the PFM profile width is linearly proportional to the tip radius. Finally we demonstrate a method to extract any intrinsic material broadening of the ferroelectric wall width. Surprisingly wide wall widths of 20- 200nm are observed.