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Intercalation and functionalization in 2D materials
Presented by Prof. Judy Cha
Hosted by Prof. Delor
Judy J. Cha is Professor in the Department of Materials Science and Engineering at Cornell University. She received her Ph.D. in Applied Physics from Cornell University in 2009 and did her post-doc research at Stanford University in the Department of Materials Science and Engineering. Before joining Cornell in 2022, she was a faculty member in the Dept. of Mechanical Engineering and Materials Science at Yale University. She is a recipient of the SRC Young Faculty Award (2021), 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), and the IBM Faculty Award (2014).
The large surface areas and interlayer gaps of 2D materials enable surface functionalization and intercalation as effective post-synthesis design knobs to tune the properties of 2D materials using ions, atoms, and organic molecules. For complete engineering control, detailed understanding of the interactions between the 2D materials and the molecules adsorbed on 2D materials surface or between the 2D materials and the intercalants is necessary.
I will first discuss surface functionalization to tune the electrical properties of 2D materials. We developed an experimental approach to quantitatively measure the doping powers of organic electron donors (OEDs) to monolayer MoS2. Using novel and previously studied OEDs, we demonstrate experimentally that the measured doping power is a sensitive function of molecule’s reduction potential, size, surface coverage, and orientation to 2D materials [1, 2].
I will then discuss electrochemical intercalation into 2D materials to induce novel phases that were previously undetected and to study heterointerface effects on the intercalation induced phase transition [3, 4]. We discover a new structural phase in Td-WTe2 with lithium intercalation and this new phase is semiconducting even though the initial WTe2 is semimetallic and lithium ions donate electrons to WTe2. In the lithium intercalation-induced phase transition from the 2H to 1T’ phase of MoS2, we show that the nucleation of the 1T’ phase proceeds via heterogeneous nucleation where the nature of heterointerface dictates the thermodynamics of the phase transition.
 Advanced Electronic Materials 7, 2000873 (2021).
 Nano Letters 22, p.4501 (2022).
 ACS Applied Materials & Interfaces 13, p.10603-10611 (2021).
 Advanced Materials 34, 2200861 (2022).