title: Breaking the Crowther limit: combining depth-sectioning and tilt tomography for high-resolution, wide-field 3D reconstructions.
abstract: To date, high-resolution (<1 nm) imaging of extended objects in three-dimensions (3D) has not been possible. A restriction known as the Crowther criterion forces a tradeoff between object size and resolution for 3D reconstructions by tomography. Further, the sub-Angstrom resolution of aberration-corrected electron microscopes is accompanied by a greatly diminished depth of field, causing regions of larger specimens (>6 nm) to appear blurred or missing. Here we demonstrate a three-dimensional imaging method that overcomes both these limits by combining through-focal depth sectioning and traditional tilt-series tomography to reconstruct extended objects, with high-resolution, in all three dimensions. The large convergence angle in aberration corrected instruments now becomes a benefit and not a hindrance to higher quality reconstructions. A through-focal reconstruction over a 390 nm 3D carbon support containing over 100 dealloyed and nanoporous PtCu catalyst particles revealed with sub-nanometer detail the extensive and connected interior pore structure that is created by the dealloying instability.
authors.affiliation: School of Applied & Engineering Physics and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA. Electronic address: rmh244@cornell.edu.
authors.forename: Robert
authors.initials: R
authors.lastname: Hovden
authors.affiliation: National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Ercius
authors.affiliation: Department of Physics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Deli
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Yingchao
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Héctor D
authors.initials: HD
authors.lastname: Abruña
authors.affiliation: Department of Physics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Veit
authors.initials: V
authors.lastname: Elser
authors.affiliation: School of Applied & Engineering Physics and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Muller
keywords: 3D imaging; Aberration correction; Catalysts; Crowther criterion; Depth of field; Depth sectioning; Electron microscopy; Nanoparticles; STEM; Scanning transmission electron microscopy; TEM; Through focal imaging; Tomography