Size-driven phase evolution in ultrathin relaxor films

Jieun Kim ^1,2, Yubo Qi ^3,4, Abinash Kumar ⁵

¹Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, USA.
²Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.
³Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA.
⁴Department of Physics, University of Alabama at Birmingham, Birmingham, AL, USA.
⁵Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
⁶Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
⁷Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China.
⁸Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, CA, USA.
⁹Rice Advanced Materials Institute, Rice University, Houston, TX, USA.
¹⁰Department of Physics, University of California Berkeley, Berkeley, CA, USA.
¹¹Department of Materials Science and Nanoengineering, Rice University, Houston, TX, USA.
¹²Department of Physics and Astronomy, Rice University, Houston, TX, USA.
¹³Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. lwmartin@rice.edu.
¹⁴Department of Materials Science and Nanoengineering, Rice University, Houston, TX, USA. lwmartin@rice.edu.
¹⁵Department of Physics and Astronomy, Rice University, Houston, TX, USA. lwmartin@rice.edu.
¹⁶Rice Advanced Materials Institute, Rice University, Houston, TX, USA. lwmartin@rice.edu.
¹⁷Department of Chemistry, Rice University, Houston, TX, USA. lwmartin@rice.edu.

⁰Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, USA.

Nature Nanotechnology +

|

February 11, 2025

View abstract on PubMed

Summary

Relaxor ferroelectric thin films exhibit thickness-dependent behavior. Polar nanodomains rotate and stabilize relaxor properties as films approach 25-30 nm, but properties collapse below 6-10 nm.

Area Of Science

Materials Science
Condensed Matter Physics
Solid State Chemistry

Background

Relaxor ferroelectrics are characterized by polar nanodomains (PNDs), slim hysteresis loops, and dielectric relaxation.
Thin-film relaxors are crucial for applications like nanoelectromechanical systems and energy harvesting.
Understanding relaxor behavior in ultrathin films is vital for fundamental science and technological advancement.

Purpose Of The Study

To investigate the evolution of relaxor phases and PNDs in thin films as a function of thickness.
To determine the critical length scales governing relaxor behavior at the nanoscale.

Main Methods

Epitaxial growth of 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 films with varying nanometer thicknesses using pulsed-laser deposition.
Characterization through ferroelectric and dielectric measurements, temperature-dependent synchrotron X-ray diffuse scattering, scanning transmission electron microscopy, and molecular dynamics simulations.

Main Results

As film thickness approaches the PND long axis (25-30 nm), electrostatic forces induce PND rotation towards the film plane, stabilizing relaxor behavior.
Anisotropic phase evolution occurs along out-of-plane and in-plane directions.
Relaxor behavior collapses when film thickness reaches the PND smallest dimension (6-10 nm).

Conclusions

Polar nanodomains dictate the critical length scale for relaxor behavior evolution in ultrathin films.
Thickness-dependent phase instabilities and PND rotation are key mechanisms governing nanoscale relaxor properties.
The study establishes a fundamental understanding of nanoscale relaxor ferroelectrics for advanced material design.

Related Concept Videos

Atomic Nuclei: Types of Nuclear Relaxation

Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...