MSSI/Bernal Institute Research Forum 17/08
A New Era in High Spatial and Energy Resolution Electron Microscopy: From Fingerprinting Single Atom Bonding to Vibrational Spectroscopy
Professor Quentin Ramasse SuperSTEM Laboratory Daresbury United Kingdom
Modern aberration-corrected scanning transmission electron microscopes (STEMs) have been optimised to provide improved data collection ability and greater flexibility even at low acceleration voltages, spurring what could be arguably described as a new era in nano-scale materials characterisation. A wealth of complementary analytical signals is now available from a single experiment: when combining atomic resolution chemically-sensitive Z-contrast and bright field STEM imaging, 2D chemical mapping using analytical techniques such as electron energy loss spectroscopy (EELS) or energy dispersive X-ray spectroscopy (EDXS) together with advanced image analysis, it is possible to fully characterise the chemical and bonding environment of materials down to the single atom level. These in turn can be related to accurately measured atomic displacements and to the electronic properties of the material determined through theoretical calculations. There are further exciting times ahead, with the advent of ultra-high energy resolution monochromators, which are boosting the resolution of STEM-EELS into the sub 10 meV range and are now opening the door to vibrational and phonon spectroscopy at unprecedentedly high spatial resolution.
Quentin Ramasse is the Director of the SuperSTEM Laboratory, the EPSRC UK National Facility for Aberration-Corrected STEM, and holds a visiting associate Professorship at the University of Leeds, UK. He obtained his PhD in Physics from the University of Cambridge working on optical aberration measurements methodologies for aberration-corrected STEM. Before taking up his post at SuperSTEM, he held a Staff Scientist position at the National Center for Electron Microscopy (NCEM) in Berkeley, a US Department of Energy-funded user facility where he took part in the TEAM project which saw development of the world's first 0.5 A electron microscope. Quentin has published extensively in the field of STEM-EELS, with a dual focus on STEM technique development and on applications to a wide range of energy harvesting materials, from 2-dimensional materials such as graphene and MoS2 nano-catalysts to complex oxides.
DATE: Thursday, 17 November 2016 TIME: 15h00 VENUE: MSG-025 Materials Surface Science Institute (MSSI) Building Extension, University of Limerick
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