F.-R. Chen1, D. Van Dyck2, C. Kisielowski3
1Dept. of Engineering and System Science, National Tsing Hua University, Hsin Chu, Taiwan, E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
2EMAT, Department of Physics, University of Antwerp, 2020 Antwerpen, Belgium. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
3Lawrence Berkeley National Laboratory, The Molecular Foundry and Joint Center for Artificial Photosynthesis, One Cyclotron Road, Berkeley California 94720 USA. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
To address Feynman’s dream, it is important to extract 3D atomic coordinates in a nano-object [1]. So far, there are two approaches, namely, STEM-tilt series [2] and in-line holography [3] have been demonstrated to achieve the atomic resolution tomography for fulfilling Feynman’s dream to understand physical and chemical properties of nano-object. Most noticeable bottleneck is the large accumulated electron dose required to produce tilt series of atomic resolution images, because electron dose are commonly chosen large (10 4 -10 5 eÅ 2 s -1 ) to achieve a needed resolution around 1Å and single atom sensitivity. Any such single image can exhibit uncontrolled electron beam-induced surfaces alterations or even bulk modifications, in particular if particles are small or for the organic materials such as protein or molecules. For biological sample, protein, the 3D structure are usually reconstructed from images recorded at the cryo-mode to slow down the electron radiation damage. But drawbacks of cryo-microscopy is that at the low temperature the shape of the protein will be deformed. And the proteins are required exists high symmetry for cryo-microscopy with single particle reconstruction. In my talk, we present a self-consistent approach to recover the 3D atomic structure of nanocrystalline particles from single projections by exploiting the dynamic nature of electron scattering and pursuing a quantitative interpretation of the electron exit wave reconstructed from focal series of high-resolution images recorded at low dose mode. Beyond investigations of radiation hard periodic matter, the approach offers intrinsic advantages to study beam-sensitive materials such as catalysts and molecules because dose-rate dependences can be exploited to help reducing beam-sample interactions so that atomic resolution and single atom sensitivity may be achieved without altering the pristine structure of radiation sensitive matter. In my talk, we demonstrate the the 3D information of the atomic position in encoded in the exit wave function reconstructed from simulated focus series images. The positions of exit surface atom, and therefore the surface profile, can be determined from the maximum intensity of the propagation wave with an accuracy of atomic resolution [3]. The number of atom in a column can be quantitatively counted from the relative phase angle of the focus corrected wave and the vacuum wave [3]. Several cases of the reconstructed atomic resolution tomograms, such as Au nano-bridge, Ge wedge crystal, and MgO nano-cube will be demonstrated.
References
[1] Feynman, R. P. (1960) There is plenty of room at the bottom. Eng. Sci. 23, 22–36.
[2] Scott, M. C. et al. (2012) Electron tomography at 2.4-ångstrom resolution. Nature 483, 444–447, https://doi.org/10.1038/nature10934
[3] Chen, F.-R., Van Dyck, D. & Kisielowski, C. (2016) In-line three-dimensional holography of nanocrystalline objects at atomic resolution. Nat. Commun. 7, 10603, https://doi.org/10.1038/ncomms10603
