Tool Talks Express with Ondrej Krivanek and Tracy Lovejoy
Join us to learn from NION experts on the key developments in aberration-corrected STEM and ultra-high energy resolution EELS, as well as open-source software advantages and limitations.
September 28, 2018
10am–noon
12-0168, MIT.nano (basement level)
60 Vassar Street (rear)
Cambridge, MA
Aberration-corrected STEM: past, present and future
Ondrej L. Krivanek
The capabilities of scanning transmission electron microscopes (STEMs) have advanced very significantly in the last two decades. Nion contributed to this progress by developing the first successful STEM aberration corrector, delivering the first commercial EM aberration corrector in the world (in 2000), and by pushing aberration-corrected STEM in new and often unexpected directions. This talk will review major aberration correction milestones, from the successful proof-of-principle STEM corrector built into a 20-year old microscope in the other Cambridge (the UK one, in 1997), to the latest instruments that cover a wide range of operating voltages, have ultra-bright and very stable cold field emission guns, ultra-high vacuum in the sample chamber, flexible and user-friendly operating software, and several revolutionary new capabilities. It will provide a number of real-life application examples, such as the first direct sub-Å imaging achieved in electron microscopy, spectroscopic analysis of single atoms by electron energy-loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDXS), efficient elemental mapping of large sample areas, both by EELS and EDXS, and damage-free analysis of organic materials by vibrational EELS. It will conclude by discussing current limitations of STEM imaging and analytical techniques, and briefly reviewing likely future developments.
Key developments in analytical STEM: ultra-high energy resolution EELS and open-source software
Tracy C. Lovejoy
Electron energy loss spectroscopy (EELS) is a powerful analytical technique with a rich history and several major recent advances. This talk will review its general capabilities and then focus on key developments which were thought to be impossible just 10 years ago but have now become standard. These include: efficient atomic-resolution elemental mapping of large sample areas, EELS of individual atoms that gives information on their bonding, and ultra-high energy resolution EELS that has allowed vibrational spectroscopy to be performed in the electron microscope. The last technique is very promising and open-ended: in a major first in electron microscopy, it is able to analyze organic and biological materials at a spatial resolution of 10-30 nm (i.e., orders of magnitude better than equivalent optical techniques), while side-stepping radiation damage. The talk with conclude by describing the Nion open-source data acquisition, processing and analysis software: Python-based Nion Swift. The Nion approach is to provide user-friendly tools for operating the microscope and obtaining “regular” data such as atomic-resolution images and elemental maps, and to provide advanced users with easy customization and ready access to a wide choice of analysis tools that are available in the Python open-source community. Examples of how this works out in practice will be given, and the advantages and limitations of the open-source approach will be discussed.