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Investigation of phase change separation processes (APT)

Nanoscale characterization of phase change materials with Atom Probe Tomography
Thanks to unique spatial resolution analytical capabilities (subnanometer lateral and depth resolution), the CAMECA Atom Probes perform benchmark atomic scale quantitative analysis in materials.

In the present study, the LEAP Atom Probe was used to investigate the phase separation process in Ge15Sb85, a material used in optical as well as electronic data storage devices.

2 analyses were performed: one on a as-deposited sample (left side), the second one on an annealed sample (right side).

While the distribution of Ge and Sb atoms is homogeneous on the 3D mapping of the as-deposited sample (top left), Ge-enriched areas are clearly visible on the 3D reconstruction of the annealed sample (top right right). Data comparison between the 2 samples reveals the nanoscale phase separation occurring during heat treatment.

By extracting a 1nm-thick slice in the perpendicular direction and using false color on the quantitative atomic concentration scale from the nanovolume, one provides even clearer evidence of the phase separation. Note that the size of the phase separation is only few nm.

Atom Probe Tomography is the only analytical technique that provides both quantitative composition and atomic scale 3D elemental mapping of chemical heterogeneities in a material. As with STM, a single atom and its neighbors can be imaged, but the 3D Atom Probe offers 2 major advantages:
  • Elemental analysis, which allows each single detected atom to be chemically identified
  • Depth resolution, which makes the chemical map of the atoms truly 3-dimensional 

Courtesy of M. Salinga and M. Wuttig (Department of Physics, RWTH Aachen, Germany)