CAREER: Understanding Strain and Strain Relaxation Mechanisms in Complex Two-Dimensional Materials

This Faculty Early Career Development (CAREER) award supports research to investigate how two-dimensional (2D) films deform to release strain, and how to leverage this knowledge to engineer new applications of 2D materials. Deformation mechanisms and defects play a critical role in the mechanical, electrical, and chemical properties of 2D materials due to their atomic thinness. However, a fundamental understanding of how strain relaxation in these materials differ from their bulk counterparts remains elusive due to challenges in characterization at multiple length scales. This project aims to develop new electron microscopy approaches to observe and understand novel strain relaxation mechanisms. The insights gained from this study will advance the use of complex 2D materials in flexible electronics, quantum computing, catalysis, and protective coatings. Additionally, the project will support several activities to support broader participation in STEM, with a focus on underrepresented minorities and women, including a Research Experience for Teachers program for local high school teachers, interactive science demonstrations for young learners in collaboration with a local museum, and integration of research and education through curriculum development. Conventional understanding of strain relaxation in bulk materials have not been successful in describing the deformation behavior of 2D materials and heterostructures. The central hypothesis of this project is that additional novel deformation mechanisms besides the traditionally observed dislocation-based mechanisms contribute towards stress relaxation in 2D materials. To investigate this possibility, this project will use state-of-the-art four-dimensional scanning transmission electron microscopy (4D-STEM) and related techniques to map the lattice strain and deformations in 2D heterostructures. By investigating various sizes and shapes of 2D epitaxial heterostructures, a comprehensive understanding of novel deformations mechanisms in complex 2D materials is expected. This knowledge will enable precise and predictable engineering of strain and defects in these materials and their heterostructures, with significant implications for the development of advanced devices. This project is jointly funded by the Mechanics of Materials and Structures (MoMS) program in the Division of Civil, Mechanical and Manufacturing Innovation (CMMI) and the Solid State and Materials Chemistry (SSMC) program in the Division of Materials Research (DMR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.