Wednesday, March 20, 2019, 10:00 am

Hosted by: Oleg Gang

Functional materials with exciting novel properties are often disordered, posing challenges to structural characterization. The conventional laboratory X-ray powder diffraction breaks down when the material is nanocrystalline or amorphous. Atomic pair distribution function (PDF) calculated from synchrotron X-ray total scattering, on the other hand, is the tool of choice for studying local structure of disordered materials. In the beginning part of my talk, I will introduce PDF technique, and its applications on extracting structural details of emerging two-dimensional nanomaterials. Despite the ubiquitous importance of nanoparticles in the modern scientific and technological materials landscape, it is notoriously difficult to find an experimental answer to questions as simple as "do bonds get weaker or stronger in a nanocluster compared to the bulk", yet the answer to these questions is critical to understanding properties such as catalytic activity or optical response. I will present our recent work on examining size dependence of lattice dynamics of cadmium selenide quantum dot nanoparticles via high resolution inelastic X-ray scattering (HERIX). Finally, I will summarize my research progress in applying synchrotron X-ray techniques in studying pharmaceutical soft materials [6-8] and conclude the talk with future plans.

Thursday, March 28, 2019, 10:00 am

Hosted by: Oleg Gang

Organic semiconductors have been studied extensively in recent decades due to their potential to reduce both the material and production costs of electronic devices. Materials developed for applications such as organic photovoltaics (OPVs), organic light emitting diodes (OLEDs), and organic field effect transistors (OFETs) often have similar chemical structures and functionality, and thus can be expected to share similar structure-property relationships. In this talk, I highlight a series of studies where I use and develop synchrotron X-ray techniques to elucidate the morphology of organic semiconducting materials in order to advance our understanding of how nanostructure impacts performance. In the first half of my talk, I will show how wide angle X-ray scattering (WAXS) can be used to monitor the crystal structure of poly(3-hexylthiophene) (P3HT), in situ, during electrochemical doping. By simultaneously probing crystal structure and electrochemical performance, a clear picture of the electrochemical doping process in P3HT emerges. The results found for this model P3HT system have been shown to be consistent with several other studies of OFET devices, demonstrating the generalized nature of the doping process. The second half of my talk is focused on developing resonant soft X-ray reflectivity (RSoXR) as technique to probe the through-film structure of organic thin films. I begin by demonstrating how resonant-enhanced X-ray contrast can be utilized to detect phase segregation in thin films of small-molecule/polymer semiconductor blends, which enables their remarkable performance in OFET devices. Next, I discuss how polarized soft X-rays can enable the study of molecular orientation in thin films. Finally, using a small-molecule model system, I demonstrate how polarized-RSoXR can be used to depth-profile molecular orientation, even in amorphous single-component films. Although these studies are focused on organic electronic

Wednesday, April 17, 2019, 8:00 am

Thursday, April 18, 2019, 8:00 am

Friday, April 19, 2019, 8:00 am

Friday, April 26, 2019, 4:00 pm

Hosted by: Donald DiMarzio

In this talk, I discuss our recent research activity in electromagnetics, nano-optics, quantum optics, acoustics and mechanics, showing how suitably tailored meta-atoms and suitable arrangements of them open exciting venues to realize non-reciprocal devices for light, radio-waves and sound, largely breaking Lorentz reciprocity and realize isolation without the need of magnetic bias. Our approaches are based on using suitably tailored mechanical motion, spatio-temporal modulation, and large nonlinearities in coupled resonator systems, and have enabled magnetic-free circulators and isolators for sound, microwaves, THz and optical frequencies, non-reciprocal antennas, emitters and absorbers breaking Kirchhoff's law, self-induced isolation for high-intensities triggered by nonlinearities, and a new generation of topological insulators for light, sound, and static systems in mechanics. In the talk, I will also discuss the impact of these concepts from basic science to practical technology from classical light to quantum optics and computing. Andrea Alù is the Founding Director and Einstein Professor at the Photonics Initiative, CUNY Advanced Science Research Center. He received his Laurea (2001) and PhD (2007) from the University of Roma Tre, Italy, and, after a postdoc at the University of Pennsylvania, he joined the faculty of the University of Texas at Austin in 2009, where he was the Temple Foundation Endowed Professor until Jan. 2018. Dr. Alù is a Fellow of IEEE, OSA, SPIE and APS, and has received several scientific awards, including the ICO Prize in Optics (2016), the NSF Alan T. Waterman award (2015), the OSA Adolph Lomb Medal (2013), and the URSI Issac Koga Gold Medal (2011).

Thursday, May 2, 2019, 4:00 pm

Hosted by: Andrey Tarasov

Thursday, June 6, 2019, 4:00 pm

Hosted by: Chang-Yong Nam