|May 28, 2013
Bldg. 440, A105-106
"Aberration-Corrected Scanning Transmission Electron Microscopy: Including Light Elements," by Patrick Phillips, University of Illinois at CHicago, Hosted by Yuzi Liu
Abstract: Scanning transmission electron microscopy (STEM) offers a multitude of characterization techniques for a wide range of relevant materials, most commonly realized through chemical analysis combined with high-angle annular dark-field (HAADF) imaging. However, with the recent advent of annular bright-field (ABF) STEM, it is now possible to image light and heavy elements simultaneously. By coupling ABF imaging to HAADF and chemical analyses, a full-scale materials characterization can be performed.
The first part of this talk will focus on the STEM-based characterization of AlxGa1xN nanowires for UVLED applications. To assist subsequent growth processes while striving for optimum efficiency, both structural and chemical characterization methods are necessary, which can be provided at sufficiently high resolutions by advanced STEM instruments. Specifically, structural characterization will focus on determining layer thicknesses and wire polarity, as well as visualizing any short-range ordering and/or stacking faults that may be present. Chemically, both energy dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies will be discussed in various capacities, ranging fromquantum well composition (EDX) to N K-edge fine structure of both GaN and AlN (EELS).
The second portion of the talk will present numerous example materials that required structural, chemical, and/or electronic characterization via aberration-corrected STEM methods. Additionally, the technique of ABF STEM (coupled with HAADF) will be discussed in terms of imaging very thin samples. Notably, preliminary research has indicated that some of the phenomenological theory of ABF breaks down in the limit of thin specimens. Where necessary, supporting STEM multislice image simulations will be presented.
|June 7, 2013
Bldg. 440, A105-106
"Molecular biophotonics for diagnostics and treatment," by Jonathan T.C. Liu, Stonybrook University, hosted by Il Woong Jung
Abstract: The molecular biophotonics lab, directed by Dr. Jonathan Liu, is developing optical strategies for biomedical diagnostics and therapy. These endeavors require multidisciplinary advances in optical devices, contrast agents, image processing, and preclinical/clinical studies.
For example, over the past few years, our lab has published on the simulation and development of a miniaturized advanced volumetric microscopy technology to enable real-time point-of-care pathology, as well as the development of a molecularly targeted fluorescent contrast agent to guide tumor resection in the brain. These complementary technologies have the potential to revolutionize patient care by providing surgeons with a real-time alternative to invasive biopsy and frozen-sectioning pathology for confirming the status of tissues at the final stages of surgery.
In addition, our lab is developing spectral imaging devices in conjunction with multiplexed Raman nanoparticles for endoscopic visualization of large panels of disease biomarkers. This has the potential to allow physicians to better visualize and understand the molecular mechanisms of disease progression for improved early detection and to monitor the molecular response to personalized therapies.