Ferroelectric nanostructures fabricated by focused-ion-beam milling in epitaxial BiFeO₃thin films

Abstract

We studied a suitable route to fabricate ferroelectric islands by focused-ion-beam milling in bismuth ferrite epitaxial thin films. Piezoresponse force microscopy shows that the damage induced by the milling process is extended to 1 µm away from the edge of the focused-ion-beam patterned islands. After a combined vacuum and oxygen atmosphere annealing procedure, ferroelectricity is fully recovered in structures with sizes down to 500 nm, while for 250 nm islands the defects at the interfaces induce polarization direction pinning.

Mask assisted fabrication of nanoislands of BiFeO3 by ion beam milling

“…Both behaviors may be due to defects at the BFO/SRO interface and on the sidewalls of the islands, shifting the coercive voltage values by modification of the internal bias field [4], and pinning the polarization at the interfaces [14]. This pinning effect is very much reduced compared to that for 250 nm islands obtained by direct FIB milling of BFO at the most commonly used accelerating voltage, 30 keV [9]. This proves that the defective pinned volume of the BFO structures is much reduced by the new developments to our technique, since such volume is not large enough to lead to a complete polarization pinning through all the structure.…”

“…Fabrication methods based on bottom-up approaches, successfully employed for size effects studies in other ferroelectric materials [5][6] [7], are quite challenging in the case of BFO, given the complexity of its phase diagram [8]. Therefore top-down methods have been recently developed for production of nanostructures in BFO, such as use of focused ion beam (FIB) milling followed by double step annealing procedure [9] leading to ferroelectric islands down to a minimum of 250nm in lateral size. Another method is based on differential etching of prepoled polarization patterns [10] giving the possibility of producing islands down to 170nm in diameter but with rounded lateral profile and no complete separation from the surrounding material of the film.…”

Epitaxial Ferroelectric Nanostructures Fabricated by FIB Milling

“…2.1), consists of material removal from a bare BFO epitaxial thin film in order to obtain the desired structures [49]. This is done by milling grooves around the structures to isolate them from the rest of the BFO film.…”

Strain dependent microstructural modifications of BiCrO3 epitaxial thin films

“…One of the above mentioned materials that possesses intrinsic multiferroic properties is BiCrO3 (BCO) [6,7,8]. BCO has not been explored much yet, unlike BiFeO3 (BFO), which is quite appealing due to its large FE polarisation at room temperature (RT) [9,10,11,12].…”