Imaging and identification of single atoms/molecules is an ultimate goal of all analytical techniques. In 2000, we reported the first successful elemental identification of individual atoms by means of electron spectroscopy [1]. It came 200 years after the establishment, at the end of the 18th century, of Dalton’s atomic theory, which first proposed distinct elements among atoms [2].

Advances of nanotechnology increasingly rely on the advancement of atomic technologies and therefore the progress of electron microscopies, which are capable of visualizing and analysing constituent atoms in individual nanostructures. Electron spectroscopy based on a scanning transmission electron microscope equipped with an energy-loss spectrometer enables us to obtain the chemical composition of individual quantum objects with high sensitivity and high resolution, which are crucial to detect dopants or impurities in materials at atomic level.

Also, a phase contrast of high-resolution transmission electron microscopy with high time resolution and high sensitivity allows dynamic observation of individual atoms and visualization of individual molecular structures. Point defects such as vacancies and pentagons, as well as the Frenkel pair defects in carbon nanotubes, can be also visualized during formation and annihilation. This work highlights our achievements in atomic-scale characterization of individual nanostructures, involving the individual molecular imaging, the single atom spectroscopy, and the point defect detection.

[1] K. Suenaga et al., Science 290 (2000) 2280
[2] J. Dalton, A New System of Chemical Philosophy, by Russell, (1808)

Figure) The first report of single-atom EELS. (Left) The specimen was Gd@C82 metallofullerenes encapsulated in single-walled carbon nanotubes. (Bottom) EELS spectra recorded on Gd atomic sites shows the signal of Gd M-edge. (Right) The constructed chemical maps for Gd, for carbon, and a colour map (red: Ge, blue: carbon).