Mapping Polar Distortions using Nanobeam Electron Diffraction and a Cepstral Approach

Area of Science:

• Materials Science
• Condensed Matter Physics
• Crystallography

Background:

• Accurate measurement of local polar ordering is crucial for understanding ferroelectricity in thin films, particularly those with small domains or disorder.
• Scanning nanobeam electron diffraction (NBED) is a powerful tool for probing local lattice parameters, fields, and polarization in materials.
• Quantifying polarization vectors from NBED data presents significant challenges.

Purpose of the Study:

• To develop a robust method for quantitatively extracting polarization vector magnitudes and directions from NBED patterns.
• To enable precise mapping of local polar displacements driving ferroelectricity in thin films.
• To overcome the limitations of existing methods in analyzing complex ferroelectric systems.

Main Methods:

• Utilizing a cepstral analysis approach, analogous to a pair distribution function, applied to NBED patterns.
• Exploiting the asymmetry in diffraction pattern intensity caused by polar distortions.
• Recovering underlying polar displacements from the imaginary part of the cepstrum transform.

Main Results:

• Demonstrated the ability to precisely determine local polar displacements from NBED data.
• Achieved an unprecedented precision of approximately 1.1 picometers in measurements.
• Successfully mapped polar displacements with nanometer resolution in experimental samples.

Conclusions:

• The cepstral method offers an efficient and accurate way to quantify ferroelectric polarization from NBED.
• This technique significantly advances the study of ferroelectricity in nanoscale and disordered systems.
• The findings pave the way for improved characterization and understanding of advanced ferroelectric materials.