Improving 3D Reconstruction from STEM Data

The successful implementation of spherical aberration correction in the scanning transmission electron microscope (STEM) is one of the most significant accomplishments in electron optics in the last few decades. Correction of magnetic lens aberrations to the third order has led to significant improvements in point resolution and signal-to-noise ratio, expanding the range of accessible lattice spacings into the sub-Ångstrom regime [1]. The greatly reduced depth of field of the aberrationcorrected STEM probes has also enabled three-dimensional imaging by optical sectioning [2]. Fig. 1 shows a 3D rendered STEM data set of a (Pt, Au)/TiO2 catalyst sample. The data has been acquired using a VG Microscopes HB603U STEM at ORNL. The metal particles appear elongated in the depth direction, reflecting the defocus spread of the STEM probe. Deconvolution techniques similar to those used in confocal optical microscopy can help achieve closer correspondence with the real structure of the material [2].