Hovden Robert, Ercius Peter, Jiang Yi, Wang Deli, Yu Yingchao, Abruña Héctor D, Elser Veit, Muller David A
School of Applied & Engineering Physics and Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY 14853, USA.
National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Ultramicroscopy. 2014 May;140:26-31. doi: 10.1016/j.ultramic.2014.01.013. Epub 2014 Feb 20.
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.
迄今为止，对扩展物体进行三维（3D）高分辨率（<1纳米）成像尚无法实现。一种被称为克劳瑟准则的限制使得通过断层扫描进行3D重建时，在物体尺寸和分辨率之间不得不进行权衡。此外，像差校正电子显微镜的亚埃分辨率伴随着景深的大幅减小，导致较大标本（>6纳米）的区域出现模糊或缺失。在此，我们展示了一种三维成像方法，该方法通过结合焦深切片和传统倾斜系列断层扫描来克服这两个限制，从而在所有三个维度上以高分辨率重建扩展物体。像差校正仪器中的大会聚角现在成为了高质量重建的优势而非障碍。对一个包含100多个脱合金化和纳米多孔PtCu催化剂颗粒的390纳米3D碳载体进行的焦深重建，以亚纳米级细节揭示了由脱合金化不稳定性产生的广泛且相互连接的内部孔隙结构。
