Patterning enhanced tetragonality in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Bi</mml:mi><mml:mi>Fe</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math> thin films with effective negative pressure by helium implantation

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