Periodic elastic nanodomains in ultrathin tetrogonal-like BiFeO3 films

TL;DR

This study uses synchrotron x-ray diffraction to analyze the domain structure of ultrathin BiFeO3 films, revealing periodic nanodomains, a shear strain mechanism, and deviations from classical domain scaling laws.

Contribution

It uncovers the existence of periodic elastic nanodomains in ultrathin BiFeO3 films and details a shear strain mechanism, expanding understanding of domain behavior at nanoscale thicknesses.

Findings

Periodic nanodomains exist down to 6 nm thickness.

Nanodomain periodicity increases with film thickness.

Disappearance of periodic modulation above 90°C.

Abstract

We present a synchrotron grazing incidence x-ray diffraction analysis of the domain structure and polar symmetry of highly strained BiFeO3 thin films grown on LaAlO3 substrate. We revealed the existence of periodic elastic nanodomains in the pure tetragonal-like BFO ultrathin films down to a thickness of 6 nm. A unique shear strain accommodation mechanism is disclosed. We further demonstrated that the periodicity of the nanodomains increases with film thickness but deviates from the classical Kittel's square root law in ultrathin thickness regime (6 - 30 nm). Temperature-dependent experiments also reveal the disappearance of periodic modulation above 90C due to a MC-MA structural phase transition.