Back-scattered electron visualization of ferroelectric domains in a BiFeO3 epitaxial film

Abstract

Three-dimensional orientation of the ferroelectric (FE) domain structure of a BiFeO3 epitaxial film was investigated by scanning electron microscopy (SEM) using back-scattered electrons and piezoresponse-force microscopy (PFM). By changing the crystallographic orientation of the sample and the electron collection angle relative to the detector, we establish a link between the orientation of polarization vectors (out-of-plane and in-plane) in BiFeO3 film and the backscattered electron image contrast in agreement with PFM investigations. The different FE polarization states in the domains correspond to altered crystalline environments for the impingent primary beam electrons. We postulate that the resultant back-scattered electron domain contrast arises as the result of either differential absorption (through a channelling effect) or through back-diffraction from the sample which leads to a projected diffraction pattern superposed with the diffuse conventional back-scattered electron intensity. We demonstrate that SEM can be sensitive for both out-of-plane and in-plane polarization directions using BSE detection mode and can be used as a non-destructive and fast method to determine 3D FE polarization orientation of domains.

Structural and photoelectric properties of tensile strainedBiFeO3

“…Due to the lack of a bottom electrode, conventional piezo force microscopy measurements of the polarisation and domains are not possible. Instead we use SEM measurements to image the domains, as demonstrated by Alyabyeva et al [30]. Figure 2(b) shows an image demonstrating the domain structure, where a stripe domain structure can be seen with width of ∼ 30 as well as a longer range bundles of domains.…”

“…Figure 2(b) shows an image demonstrating the domain structure, where a stripe domain structure can be seen with width of ∼ 30 as well as a longer range bundles of domains. It is assumed, from comparison BFO with typical 71 • domains [30,31], that each bundle has the same out-of-plane polarisation component, but the stripes within correspond to varying in-plane polarisation. This differs from the purely orthorhombic BFO-NSO system demonstrated by Yang et al [21] where the polarisation vector was purely in-plane.…”

Modified cantilevers to probe unambiguously out-of-plane piezoresponse

“…2(a)] in agreement with literature. 13,14,22 The magnitude of the phase shift is less than 180° and the presence of domain pattern contrast for both amplitude and phase in OP PFM images [ Fig. 1(a, c)] similar to the IP contrast [ Fig.…”

Characterization of ferroelectric domain walls by scanning electron microscopy

“…Trivially, but very important, clean and flat surfaces with a root mean square roughness in the order of 1 nm, as obtained from proper polishing, eliminate topographic contrast that can dominate over weak domain and domain wall contrast. Finally, it should be noted that both SE 42,69,77 and BSE 78,79 detection modes have been reported to give domain and domain wall contrast, but not necessarily work equally well on the same material. From our experience, the best contrast is achieved using an in-lens detector biased for SE imaging.…”