STROBE Seminar

We show that targeted energy input from an electron beam in a transmission electron microscope (TEM), often combined with concurrent heating in a MEMS holder, drives atomic defect formation and phase transitions across four classes of low-dimensional materials: (1) few-layer transition metal phosphorus trichalcogenides (TMPTs), (2) graphene sandwich structures encapsulating either lithium droplets (2a) or a benzenehexathiol-based two-dimensional conjugated metal-organic framework (2b), (3) platinum nanocrystals on graphene, and (4) noble metals confined within carbon nanotubes.

While electron microscopy enables imaging of individual atoms, the sample thickness is typically limited to a few hundred nanometers. Although super-resolution optical microscopy permits high-resolution visualization of subcellular structures, it requires staining of the sample. In contrast, EUV and X-ray microscopy allow imaging of entire biological cells and other thick specimens with spatial resolutions down to ~10 nm.

Atomic electron tomography (AET) enables the determination of 3D atomic structures by acquiring a sequence of 2D TEM projection measurements of a particle and then computationally solving for its underlying 3D representation. AET is a challenging and labor-intensive experiment! In this talk, we offer two computational methods to alleviate these challenges and make the reconstruction procedure more robust.

Abstract: Ultrafast infrared spectroscopy in its extension to nano-imaging provides access to vibrational and low energy carrier dynamics in molecular, semiconductor, quantum, or polaritonic materials. In addition, to simultaneously probe both ground and excited state dynamics we have developed ultrafast heterodyne pump-probe nano-imaging with far-from-equilibrium excitation.

Dr. Colum O'Leary, a Research Associate at the SLAC National Accelerator Laboratory, presents, “X-Ray and Electron Tomography: From Images to Volumes to Knowledge.”

Abstract: CryoEM and cryoET enable imaging of biological specimens frozen in vitreous ice, revealing 3D molecular or cellular structures at high resolution and in their native state. However, cryoET is limited by the “missing-wedge” problem due to restricted tilt angles, and cryoEM often suffers from preferred orientation, resulting in uneven sampling of angular views and leaving parts of Fourier space poorly covered.

Optics and coatings are often considered as commodity in the laser systems
across different applications. And yet, these are the main factors limiting
the efficiency, power, and lifetime of lasers and optical layouts. Moreover,
coating engineers, just like masters of dark magic, have their own language.
I will cover a variety of topics and questions, which will help to grow
awareness about the critical characteristics of optics. Answers to those
questions will also help to learn some of the language coating engineers

Abstract: