title: 3D lattice distortions and defect structures in ion-implanted nano-crystals.
abstract: Focussed Ion Beam (FIB) milling is a mainstay of nano-scale machining. By manipulating a tightly focussed beam of energetic ions, often gallium (Ga+), FIB can sculpt nanostructures via localised sputtering. This ability to cut solid matter on the nano-scale revolutionised sample preparation across the life, earth and materials sciences. Despite its widespread usage, detailed understanding of the FIB-induced structural damage, intrinsic to the technique, remains elusive. Here we examine the defects caused by FIB in initially pristine objects. Using Bragg Coherent X-ray Diffraction Imaging (BCDI), we are able to spatially-resolve the full lattice strain tensor in FIB-milled gold nano-crystals. We find that every use of FIB causes large lattice distortions. Even very low ion doses, typical of FIB imaging and previously thought negligible, have a dramatic effect. Our results are consistent with a damage microstructure dominated by vacancies, highlighting the importance of free-surfaces in determining which defects are retained. At larger ion fluences, used during FIB-milling, we observe an extended dislocation network that causes stresses far beyond the bulk tensile strength of gold. These observations provide new fundamental insight into the nature of the damage created and the defects that lead to a surprisingly inhomogeneous morphology.
authors.affiliation: Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, UK.
authors.forename: Felix
authors.initials: F
authors.lastname: Hofmann
authors.affiliation: Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK.
authors.forename: Edmund
authors.initials: E
authors.lastname: Tarleton
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Ross J
authors.initials: RJ
authors.lastname: Harder
authors.affiliation: ARC Centre for Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia.|CSIRO Manufacturing Flagship, Parkville 3052, Australia.
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: Phillips
authors.affiliation: Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, UK.
authors.forename: Pui-Wai
authors.initials: PW
authors.lastname: Ma
authors.affiliation: Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
authors.forename: Jesse N
authors.initials: JN
authors.lastname: Clark
authors.affiliation: Condensed Matter Physics and Materials Department, Brookhaven National Laboratory, 734 Brookhaven Avenue, Upton, NY, 11973, USA.
authors.forename: Ian K
authors.initials: IK
authors.lastname: Robinson
authors.affiliation: ARC Centre for Advanced Molecular Imaging, Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Victoria 3086, Australia.
authors.forename: Brian
authors.initials: B
authors.lastname: Abbey
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK.
authors.forename: Christian E
authors.initials: CE
authors.lastname: Beck