Wednesday Colloquium: Dr. Juan Idrobo (ORNL)
Title: Exploring the universe one atom at the time: A brief glimpse into the world of electron microscopy
Abstract: Our vision of the universe was drastically enhanced after the Hubble Space Telescope was carried into the Earth’s orbit in the beginning of the 1990’s. For instance, the age of the universe was measured with better precision than ever before, which allowed to determine the rate at what the universe expands, as well as the first evidence of the presence of extrasolar planets. These discoveries were possible because of the improved optics on the Hubble Space Telescope. A similar revolution occurred ten years later in the world of electron microscopy when, after more than 50 years since its theoretical description, it was finally viable to correct the inherent aberrations present in the optics of electron microscopes. Now, thanks to aberration correction, using an electron microscope it is literally possible to study materials one atom at the time! In this talk, I will present our recent results on two-dimensional materials, including graphene, boron-nitride and dichalcogenides, studied using a combination of aberration-corrected scanning transmission electron microscopy and first-principles calculations. In particular, I will show examples that include: the optical response arising from individual atoms, the direct determination of two- and three-dimensional bonding of individual atoms, the visualization of reversible molecular dynamics of clusters, the optical response of van der Waals heterostructures, and the conditions required to produce twodimensional dilute magnetic semiconductors.