FIB Lift-Out and Milling of Cylindrical Specimens for Electron Tomography (or Atom Probe Field Ion Microscopy)

Abstract

Electron tomography using transmission electron microscopy (TEM) and related techniques (e.g., scanning transmission electron microscopy (STEM) or energy filtered TEM (EFTEM)) allow for 3-D microstructural and elemental mapping of specimens, and has been used successfully in the biological sciences where mass-thickness contrast dominates these mostly amorphous materials. Z-contrast STEM imaging via high angle annular dark field (HAADF) tomography has also been used successfully in the physical sciences. STEM, EFTEM, and holography tomography are more useful techniques for crystalline materials, since diffraction contrast in conventional TEM images can hinder image reconstruction. Typical tomography routines utilize conventional electron transparent foils, whereby the dimensions of the specimen perpendicular to the electron beam may be orders of magnitude greater than the specimen thickness parallel to the electron beam. Using this conventional specimen geometry, the effective specimen thickness increases as the specimen is tilted through the ± 70 degrees necessary for the tomographic acquisition process.