Direct measurement of electron channeling in a crystal using scanning transmission electron microscopy

L. Fitting Kourkoutis, M. K. Parker, V. Vaithyanathan, D. G. Schlom, and D. A. Muller
Phys. Rev. B 84, 075485 – Published 17 August 2011

Abstract

Self-focusing of an atomic-scale high-energy electron wave packet by channeling along a zone axis in crystalline silicon is directly measured by scanning transmission electron microscopy using thin epitaxial SrTiO3(100) islands grown on Si(100) as test objects. As the electron probe propagates down a silicon atom column, it is progressively focused onto the column, resulting in a fourfold increase in the scattered signal at the channeling maximum. This results in an enhancement of the visibility of the SrTiO3 islands, which is lost if the sample is flipped upside down and the channeling occurs only after the probe scatters off the SrTiO3 layer. The evolution of the probe wave function calculated by the multislice method accurately predicts the trends in the channeling signal on an absolute thickness scale. We find that while electron channeling enhances the visibility of on-column atoms, it suppresses the contribution from off-column atoms. It can therefore be used as a filter to selectively image the atoms that are most aligned with the atomic columns of the substrate. By using this technique, coherent islands can be distinguished from relaxed islands. For SrTiO3 films formed in a topotactic reaction on Si(100), we show that only 55% of the SrTiO3 is aligned with the Si atom columns. The fraction of coherent SrTiO3 islands on Si(100) can be increased by choosing growth conditions away from equilibrium.

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  • Received 11 April 2011

DOI:https://doi.org/10.1103/PhysRevB.84.075485

©2011 American Physical Society

Authors & Affiliations

L. Fitting Kourkoutis1,*, M. K. Parker1,†, V. Vaithyanathan2,‡, D. G. Schlom3,4, and D. A. Muller1,4

  • 1School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA
  • 2Department of Material Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802-5055, USA
  • 3Department of Material Science and Engineering, Cornell University, Ithaca, New York 14853, USA
  • 4Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA

  • *lf56@cornell.edu
  • Current address: Department of Geology and Geophysics, Yale University, New Haven, CT 06520.
  • Current address: MEMC Electronic Materials, Inc., St. Peters, MO 63376.

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Issue

Vol. 84, Iss. 7 — 15 August 2011

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