Friday, January 31, 11:00 AM, 214 Mudd
Professor Judy Cha
Yale University

Phase Transformations of Nanoscale Systems Using In Situ TEM

Many nanoscale systems undergo phase transformations in response to stimuli, which subsequently change the properties of the systems, providing opportunities to create smart devices. Here, we employ in situ transmission electron microscopy (TEM) to study how phase transformations occur, deviate, and are controlled at the nanoscale under electrical biasing, heating, and cooling, and examine their effects on materials properties.

I will discuss three examples of phase transformation: IBM’s confined phase change memory (PCM) device with a surfactant layer, which showed a record endurance of 2x1012 programming cycles [1], metallic glass nanostructures that are crystallized to test the limits of classical nucleation theories [2], and the ferroelectric transition of topological crystalline insulator SnTe nanowires, which has implications for the recently observed novel superconductivity [3]. In all three examples, in situ TEM investigations reveal detailed and unexpected phenomena and rich structural and chemical heterogeneities, guiding us to build better models and theories for nanoscale phase transformations.

If time allows, I will also discuss our recent results on the phase transformations of two-dimensional transition metal dichalcogenides induced by electrochemical intercalation of Li+ and their energy applications [4].

[1] Adv. Mater. 30, 1705587 (2018).
[2] Nat. Comm. 6:8157 (2015); Nat. Comm. 8:1980 (2017); Nat. Comm. 10:915 (2019).
[3] Nano Lett. 15, 3827 (2015); APL Materials 5, 076110 (2017); arXiv:1907.04199
(2019); Nat. Mater. Rev. 4, 479 (2019).
[4] Adv. Mater. 30, 1706076 (2018); Small 15, 1900078 (2019).

Bio of the speaker
Judy J. Cha is the Carol & Douglas Melamed Associate Professor in the Department of Mechanical Engineering and Materials Science at Yale University. Prior to Yale, she was a post-doctoral researcher at Stanford University in the Department of Materials Science and Engineering. She received her Ph.D. in Applied Physics from Cornell University in 2009. Notable awards she received include the Gordon & Betty Moore EPiQS Synthesis Investigator Award (2019), the NSF CAREER (2018), the Canadian Institute for Advanced Research (CIFAR) Azrieli Global Scholar for quantum materials (2017), the Yale Arthur Greer Memorial Prize (2016), the IBM Faculty Award (2014), the Presidential Student Award from Microscopy Society of America (2010), and the Graduate Student Silver Award at the Spring Materials Research Society meeting (2008).

Her research focuses on synthesis and transport measurements of topological nanomaterials and two-dimensional transition metal dichalcogenides; in situ TEM studies of phase transformations of nanomaterials; and potential applications of these systems in quantum computing and energy.