Center for Functional Nanomaterials Seminar

The Helium Ion Microscope (HIM) has been described as an impact technology offering new views into nanoscale imaging. Combining a high brightness Gas Field Ion Source (GFIS) with unique sample interaction dynamics, the Helium Ion Microscope provides images offering unique contrast and complementary information to existing charged particle imaging instruments such as the SEM and TEM. Formed by a single atom at the emitter tip, the helium probe can be focused to below 0.25nm offering the highest recorded resolution for secondary electron images. The helium beam has a high secondary electron yield, i.e. each incoming helium ion produces between 3 and 8 electrons depending on the material, which results in a strong and differential contrast between heavy and light elements. The small interaction volume between the helium beam and the sample and the low energies with which the secondary electrons are emitted results in images with stunning surface detail. Furthermore, the stopping dynamics of a helium ion beam leaves certain sensitive samples undamaged, even for high beam energy. Sample charging effects that hamper traditional SEM or VP-SEM efforts, can be easily compensated for in the He Ion Microscope with an electron flood gun offering the ability to image insulating samples at high resolution without coating the sample. A small convergence angle offers a large depth of field (~5X of FE-SEM) giving the ability to keep tall structures in focus within a single image. In addition to high resolution imaging, the helium beam can be used for performing materials analysis. Using the properties of backscattered helium - specifically their energy and scattering angle - the mass of the scattering nuclei can be determined. The unique combination of ion scattering spectroscopy and sub-nanometer resolution microscopy opens the door to new and so far unexplored applications in materials analysis and process control.