This review examines the recent literature that has focused on uniaxial compression experiments of single crystals at the micrometer scale. Collectively, the studies discovered new regimes of plastic flow that are size-scale dependent and that occur in the absence of strong strain gradients. However, the quantitative comparison of the flow curves between independent studies is hampered by differences in the particular implementations of the testing methodology. Modeling of microcompression experiments using 3-D discrete dislocation simulations has provided valuable insight into the mechanisms that control plastic flow in FCC metals. These efforts identified the importance of the initial dislocation density and distribution of mobile dislocation segments, the influence of free surfaces on that distribution, as well as altered multiplication and hardening responses due to the finite source statistics. Microcrystal experiments also provide a new pathway to characterize the global system dynamics of dislocati...

Plasticity of Micrometer-Scale Single Crystals in Compression

Cu specimens were exposed to Ga + ion bombardment for varying conditions of ion energy, ion dose, and incident angle in a focussed ion beam workstation Conventional transmission electron microscopy investigations were employed to analyze the Ga + ion induced damage The extent of visible damage was minimized by reducing the ion energy and furthermore by using grazing incident ions Concentration depth profiles of the implanted Ga were measured by Auger electron spectroscopy Concentrations of up to 20 at% Ga were found several nanometers below the surface Ga contents of more than 2 at% were detected within a depth of up to ∼50 nm Mechanical consequences in terms of possible hardening mechanisms are discussed, taking into account the experimental findings along with Monte Carlo simulations A non-negligible influence of the ion damage is predicted for submicron-sized samples

FIB damage of Cu and possible consequences for miniaturized mechanical tests

Sample preparation for atomic-resolution STEM at low voltages by FIB.

Review: Developments in micro/nanoscale fabrication by focused ion beams

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.

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3D lattice distortions and defect structures in ion-implanted nano-crystals

TEM investigation of FIB induced damages in preparation of metal material TEM specimens by FIB

Cross-sectional TEM observation of iron–zinc intermetallic Γ and Γ1 phases in commercial galvannealed IF steel sheets

In order to investigate the structure of Fe-Zn r phase in a commercial galvannealed IF steel sheet, the electron diffraction and composition of r phase in a commercial galvannealed IF steel sheet were studied by transmission electron microscope (TEM) and X-ray energy dispersive spectroscopy (EDX). The cross-sectional TEM specimen was prepared using focused ion beam (FIB) technique which was also introduced briefly. The results show that there exist superlattice reflections in the selected area diffraction patterns (SADPs) of r phase which indicate that the r phase is a kind of ordered intermetallic compound. The results of computer simulation of electron diffraction patterns based on the single crystals X-ray diffraction of previous researchers give a advice to the atomic coordinates of r phase in a commercial galvannealed IF steel sheets.

Electron Diffraction Study on Fe–Zn Γ intermetallic Phase of a Galvannealed IF Steel Sheet

Electron diffraction study on iron-zinc Γ1 intermetallic phase in a galvannealed IF steel sheet

Morphology significantly affects material's electronic, catalytic, and magnetic properties, especially for 2D crystals. Abundant achievements have been made in the morphology engineering of high‐symmetry 2D materials, but for the emerging low‐symmetry ones, such as ReS2, both the morphology control technique and comprehension are lacking. Here, the lateral shape and vertical thickness engineering of 2D ReS2 by tailoring the growth temperature and the substrate symmetry using chemical vapor deposition, is reported. The temperature increase induces an isotropic‐to‐anisotropic transition of domain shapes, as well as a monotonic decrease of the domain thickness, which promotes the electrocatalytic performance. The substrate rotational symmetry determines the shape anisotropy of polycrystalline ReS2 monolayers via a diffusion‐limited mechanism, leading to highly oriented square, triangular, and strip‐like domains synthesized on the fourfold symmetry SrTiO3 (001), threefold symmetry c‐sapphire, and twofold symmetry a‐sapphire substrates, respectively. Various stacking configurations in bilayers are unclosed at the atomic scale. Some are predicted to adopt a type‐II band alignment with great potential in photovoltaics. The results give insights into the morphological engineering of a unique class of 2D material with low in‐plane lattice symmetry and weak interlayer coupling, which are crucial for their high‐quality synthesis and industrial applications.

Jinshan Yu

Papers

TEM investigation of FIB induced damages in preparation of metal material TEM specimens by FIB

Cross-sectional TEM observation of iron–zinc intermetallic Γ and Γ1 phases in commercial galvannealed IF steel sheets

Electron Diffraction Study on Fe–Zn Γ intermetallic Phase of a Galvannealed IF Steel Sheet

Electron diffraction study on iron-zinc Γ1 intermetallic phase in a galvannealed IF steel sheet

Lateral and Vertical Morphology Engineering of Low‐Symmetry, Weakly‐Coupled 2D ReS2