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Single Atom Spectroscopy

M. Varela2, A. R. Lupini2, H. M Chrwisten2, A. Y. Borisevich2, S. J. Pennycook2, N. Dellby3, O. J. Krivanek3, P. D. Nellist3, S. D. Findlay4, M. P. Oxley4, L. J. Allen4

Physical Review Letters, 92, 095502 (2004)

Full Article (PDF 872 KB)

The ability to detect, identify and perform spectroscopic studies of individual atoms in their active environment within materials or on their surfaces would unravel unsolved mysteries in catalysis, structural materials, electronic materials and nanoscience. Researchers at Oak Ridge National Laboratory have shown how electron energy loss spectroscopy in a scanning transmission electron microscope can now achieve single atom sensitivity. Spectra below locate and identify a single Lanthanum (La) atom inside a crystal of calcium titanate. A strong La M4/5 ionization signal is detected when the beam is passed down one particular calcium column, and the atom depth can be deduced by comparison with simulations.

   
 
 Figure 1

  Figure 1: Electron energy loss spectra obtained from individual columns of a calcium titanate crystal. The red spectrum reveals the presence of a single La atom within the calcium column circled in red. The signal is substantially reduced from neighboring columns.
 
Figure 2
  Figure 2: Dynamical simulation of the La spectroscopic image along the green arrow. The ratio of signals on adjacent columns indicates the depth of the atom in the crystal. This atom is approximately 100 Å below the surface.
 
 
  1. CMSD, Oak Ridge National Laboratory
  2. Nion Co., 1102 8th St., Kirkland, WA 98033
  3. Dept. of Physics, University of Melbourne, Australia

 Oak Ridge National Laboratory