MEMS/MatSci Seminar: Mechanical Properties of Two-Dimensional Metal Halide Perovskites: From Bulk Crystals to Molecular Sheets
Wednesday, September 29, 2021 - 12:00pm
Two-dimensional (2D) metal halide perovskites (MHPs) are emerging low-cost, high performance semiconductor materials with great promises in optoelectronics and other semiconductor devices. Mechanical strain is ubiquitous in these materials during device fabrication and operation, which could induce stability issues and/or impact the device performance. This calls for a comprehensive understanding of the mechanical behaviors of 2D MHPs. In this talk, I will present a series nanomechanical studies by scanning probe techniques and instrumental nanoindentation to elucidate the structure-mechanical-property relationship of 2D MHPs along both in-plane and out-of-plane directions. While in 3D MHPs, the metal-halide framework dictates the mechanical performance of the materials, the mechanical properties of 2D MHPs receive impacts from the inorganic metal halide framework, the organic spacer molecules and the interfaces between the 2D layers. The vast compositional space of 2D MHPs also allows engineering the mechanical behaviors of 2D MHPs over a wide range. Furthermore, the unique response of the organic spacer molecules to temperature results in a strong abnormal thermo-mechanical behavior that is different from the anharmonic thermo-mechanical expectation found in other low dimensional material systems such as graphene and nanoparticle thin films. This talk will be concluded by a briefly discussion of new opportunities in mechanical induced phenomena and electromechanical coupling in 2D MHPs. Bio: Dr. Qing Tu is an assistant professor in the Department of Materials Science & Engineering at Texas A&M University (TAMU). He received his B.S. in Theoretical & Applied Mechanics from Peking University in 2011 and PhD in Mechanical Engineering & Materials Science with Outstanding Dissertation Award from Duke University in 2017. During his PhD, he also obtained a certificate (minor) in Nanoscience and M.A. in Economics. He then did a postdoc in the Department of Materials Science & Engineering at Northwestern University, during which he was selected as a recipient of American Vacuum Society Electronic Materials & Photonics Division Postdoctoral Travel Award in 2019. He is interested in understanding and engineering the surfaces and interfaces in advanced functional materials (e.g., 2D materials, hybrid organic-inorganic perovskites) from a mechanics perspective to design and optimize their functional properties for applications.