Prof. David C. Bell

School of Engineering and Applied Science, Harvard University, Cambridge, MA 02134

“Recent Advances in Microscopy:  STEM and Helium Ion Microscopy”

Recent work has focused on improvements to Scanning Transmission Electron Microscopy (STEM) technology for the applications of atomic resolution electron energy-loss (EELS) and imaging, such as enhancement of collection optics of the spectrometer entrance aperture and minimization the elastic scattering artifacts. A single analytical platform featuring STEM probe Cs corrector, monochromator, in-column energy filter and twin x-ray detection sensitivity serves an exceptional foundation for simultaneous signal collection and an approach towards the realization of simultaneous atomic-column EELS and  X-ray microanalysis.

The Helium ion microscope presents new and compelling prospects in terms of imaging and characterization of nanomaterials and composites. Since its official launch it has been actively used by researchers around the world to establish new avenues for imaging and modification of various materials, as highlighted in a recent special edition on Helium Ion Microscopy in the journal Scanning.  The image formation principle in the helium ion microscope involves interaction of a relatively low energy He ion with the specimen that produces secondary electron signal that is mainly confined to the surface of the material [2]. The resulting secondary signal exhibits superb resolution and image fidelity.