Credit: © 2009 NPG

For decades the performance of electron microscopes was limited by spherical aberration in the optics that handled the electron beams, rather than the de Broglie wavelength of the electrons. However, the introduction of aberration-corrected electron microscopes led to significant improvements in resolution. For instance, scanning transmission electron microscopes (STEM) can now routinely achieve resolutions of better than 0.1 nm, but the performance of scanning electron microscopes (SEM) — which image secondary and backscattered electrons, rather than electrons that have passed through the sample — is no better than 0.4 nm. Now Yimei Zhu and co-workers at the Brookhaven National Laboratory and Hitachi have shown that it is possible to routinely achieve resolutions of 0.1–0.15 nm with an aberration-corrected SEM1.

The aberration correction reduces the size of the beam and increases the beam current. An improved detector design and an increase in the operating voltage also boost the performance. Zhu and co-workers demonstrate the ability of their new microscope to image single atoms by studying a variety of samples, including a cuprate superconductor.

By using a combined SEM/STEM instrument, the Brookhaven–Hitachi team was able to probe both the surface and the bulk structure of their samples. Moreover, it should be possible to combine this new approach with various diffraction and spectroscopy techniques to learn even more about the properties and behaviour of materials on the nanoscale.