Nanoscale piezoresponse studies of ferroelectric domains in epitaxial BiFeO3 nanostructures

Abstract

We report the dependence of the ferroelectric domain configuration and switching behavior on the shape ͑square versus round͒ of epitaxial BiFeO 3 ͑BFO͒ nanostructures. We fabricated ͑001͒ oriented BFO͑120 nm͒ / SrRuO 3 ͑SRO, 125 nm͒ film layers on ͑001͒ SrTiO 3 single crystals by rf magnetron sputter deposition, and patterned them to square ͑500ϫ 500 nm 2 ͒ and round ͑502 nm in diameter͒ shaped nanostructures by focused ion-beam lithography. The surface morphology and the crystalline structure of the nanostructures were characterized by scanning electron microscopy and x-ray diffraction, respectively, while the domain configuration was investigated using piezoelectric force microscopy. We found that the square-shaped nanostructures exhibit a single variant domain configuration aligned along the ͓111͔ direction, whereas the round-shaped nanostructures exhibit seven variants of domain configuration along the ͓111͔, ͓111͔, ͓111͔, ͓111͔, ͓111͔, ͓111͔, and ͓111͔ directions. Moreover, local d 33 piezoelectric coefficient measurements showed hysteresis loops with a strong displacement in the voltage axis ͑strong imprint͒ for the square-shaped nanostructures, while the round-shaped ones exhibited more symmetric loops. These findings have critical implications for the development of nanocapacitors for gigabyte to terabyte nonvolatile ferroelectric memories.

Anisotropic relaxation and crystallographic tilt in BiFeO3 on miscut SrTiO3 (001)

“…Rebecca J. Sichel, 1 Alexei Grigoriev, 1,a͒ Dal-Hyun Do, 1 Seung-Hyub Baek, 1 Ho-Won Jang, 1 Chad M. Folkman, 1 Chang-Beom Eom, 1 Zhonghou Cai, 2 Epitaxial BiFeO 3 thin films on miscut ͑001͒ SrTiO 3 substrates relax via mechanisms leading to an average rotation of the crystallographic axes of the BiFeO 3 layer with respect to the substrate. The angle of the rotation reaches a maximum in the plane defined by the surface normal of the film and the direction of the surface miscut.…”

“…The piezoelectricity and ferroelectric domain structure of ferroelectric and multiferroic oxides can be modified by epitaxial stresses, which distort the crystallographic unit cell, and in extreme cases can lead to changes in the structural phase. 1,2 The relaxation of stress and its influence on the resulting structure of complex heterostructures involving materials of different crystallographic symmetries is particularly challenging. BiFeO 3 , for example, is a rhombohedrally distorted perovskite with a pseudocubic bulk lattice constant of 3.96 Å that is often grown as a thin film on cubic substrates such as SrTiO 3 .…”

Structure-property relationships in self-assembled metalorganic chemical vapor deposition–grown CoFe2O4–PbTiO3 multiferroic nanocomposites using three-dimensional characterization

“…v-PFM was used to reconstruct the 3 D polarization domains of the nanocomposites. 18,32,33 Figure 5(a) shows the topography of the area of interest and Fig. 5(b) shows the relationship between crystallographic orientation of the STO substrate and the direction of the measured components of polarization.…”

Nanoscale study of perovskite BiFeO3/spinel (Fe,Zn)3O4 co-deposited thin film by electrical scanning probe methods

“…Recently, multiferroic BFO has attracted much attention due to his ferroelectric/magnetic properties and is a promising material for memory device [5]. The nanoscale ferroelectric properties of this material have been intensively studied in a broad range from BFO thin films [6] to nanostructures [7].…”