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

Abstract

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.