Patterning enhanced tetragonality in BiFeO3 thin films with effective negative pressure by helium implantation

C. Toulouse*, J. Fischer, S. Farokhipoor, L. Yedra, F. Carla, A. Jarnac, E. Elkaim, P. Fertey, J-N Audinot, T. Wirtz, B. Noheda, R. Garcia, S. Fusil, I. Peral Alonso, M. Guennou, J. Kreisel

*Corresponding author for this work

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Helium implantation in epitaxial thin films is a way to control the out-of-plane deformation independently from the in-plane strain controlled by epitaxy. In particular, implantation by means of a helium microscope allows for local implantation and patterning down to the nanometer resolution, which is of interest for device applications. We present here a study of bismuth ferrite (BiFeO3) films where strain was patterned locally by helium implantation. Our combined Raman, x-ray diffraction, and transmission electron microscopy (TEM) study shows that the implantation causes an elongation of the BiFeO3 unit cell and ultimately a transition towards the so-called supertetragonal polymorph via states with mixed phases. In addition, TEM reveals the onset of amorphization at a threshold dose that does not seem to impede the overall increase in tetragonality. The phase transition from the R-like to T-like BiFeO3 appears as first-order in character, with regions of phase coexistence and abrupt changes in lattice parameters.

Original languageEnglish
Article number024404
Number of pages9
JournalPhysical Review Materials
Issue number2
Publication statusPublished - 9-Feb-2021

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