Imaging Ferroelectric Nanodomains in Strained BiFeO3 Nanoscale Films Using Scanning Low-Energy Electron Microscopy: Implications for Low-Power Devices

Precise control of ferroelectric and multiferroic domain states at the nanoscale is of considerable interest due to the potential to boost the development of next-generation low-energy-consumption nanoelectronic components. Progress in this field is closely related to advances in spatially resolved characterization methods. In this regard, scanning electron microscopy (SEM) as a powerful and highly versatile imaging technique with diversified inner detectors possesses huge potential for scale-bridging microscopy studies (spanning from micrometers to nanometers). Here, both the phase variants and the ordered ferroelectric nanodomains of the tetragonal-like (T) phase in the rhombohedral-like (R) and T mixed-phase BiFeO3 nanoscale film are acquired simultaneously using the surface-sensitive scanning low-energy electron microscopy (SLEEM) for the first time. In particular, backscattered electron (BSE) signals, which bring abundant polarization information, can be utilized to discern polarized discrepancy in mixed-phase BiFeO3 nanoscale films. Furthermore, it is demonstrated that the polarization contrast of nanodomains increases with increasing ratio of the low-loss BSEs in the collected signal. Electron trajectories simulation enables us to optimize and separate morphological and polarization contrast in angle-selective BSEs imaging in the presence of a deceleration field. SLEEM combines with other nanocharacterization and fabrication techniques, such as three-dimensional (3D) atom probe tomography, opening up new opportunities for tackling the complex nanoscale physics and defect chemistry of ferroelectric nanomaterials.

Automated summary

The precise control of ferroelectric and multiferroic domain states at the nanoscale is important for the development of low-energy-consumption nanoelectronic components. Scanning low-energy electron microscopy (SLEEM) was used for the first time to simultaneously acquire information on phase variants and ordered ferroelectric nanodomains in BiFeO3 nanoscale films. Electron trajectories simulation allowed for optimization and separation of morphological and polarization contrast in angle-selective backscattered electron imaging with a deceleration field.