Elastic relaxation and correlation of local strain gradients with ferroelectric domains in (001) BiFeO3 nanostructures

Abstract

We report an elastic relaxation and increase in local strain variation correlated with ferroelectric domains within epitaxial BiFeO 3 thin film nanostructures fabricated by combined electron-beam and focused ion-beam nanolithography. Nano-focused x-ray diffraction microscopy provided new insights into the relationship between film strain and ferroelectric domains in nanostructures, namely: (i) an out-of-plane (C-axis) elastic relaxation of as much as À1.8% Dc/c in a BFO film-based nanostructure relative to the planar film lattice constant; (ii) an out-of-plane rotation trending from the center towards all released edges of the nanostructure; and (iii) an increase of inter-domain strain variation within the nanostructure of approximately 10 times the inter-domain variation found within the planar film, correlated with ferroelectric domain boundaries as confirmed by piezoresponse-force microscopy. These results indicate that the release of in-plane BFO/SRO mismatch strain in a planar film is taken up by the local ferroelectric domain structure after patterning, resulting in greatly increased mechanical strain gradients within the structure.

Strain accommodation through facet matching in La1.85Sr0.15CuO4/Nd1.85Ce0.15CuO4 ramp-edge junctions

“…The former has become a powerful tool for selective analysis thanks to the development of high brilliance synchrotron sources that employ micro and nano-focused beams. 8 This allows nXRD to combine sub-micron lateral resolution with high k-space resolution [9][10][11][12][13][14][15][16][17] for the nondestructive study of the crystal structures of buried layers. HAADF-STEM complements the nXRD measurements by providing a local cross-section of Z contrast with atomic resolution.…”

Nanostructuring Ferroelectrics via Focused Ion Beam Methodologies

“…In the round capacitors, seven domain variants were visible and the hysteresis curves showed no obvious imprint. The strain gradients in these nanostructures were later investigated, with the results indicating a significant internal mechanical strain, replacing the strain imposed via the substrate clamping prior to FIB patterning . In a follow‐up study, the same group highlighted one aspect of the research into FIB processed ferroelectrics that cannot be understated and must be correctly utilised – PFM .…”

Investigation of AFM-based machining of ferroelectric thin films at the nanoscale

“…[24][25][26][27] As such, studies have also involved fabrication of ferroelectric nanostructures as a means to alter the mechanical boundary conditions imposed on the ferroelectric material and provide further physical insight into different ferroelectric phenomena mediated though the release of mechanical constraints. 26,28,29 Such nanostructures have conventionally been fabricated through a range of bottom-up (mask-assisted pulsed laser deposition, 30 block co-polymer selfassembly 31 ) and top-down (focussed ion beam (FIB), 32 electron beam writing 33 and AFM-assisted crystallisation 34 ) techniques. In ferroelectric samples, tomography investigations have typically been achieved by carefully polishing relaxor ferroelectric ceramic samples, 35 repeated surface chemical etching of bulk Pb(Zr,Ti)O 3 , 36 or via non-destructive confocal Raman microscopy of both periodically poled as well as more complex dendritic electrically-induced domains in LiNbO 3 .…”