Short-range Order in Semiconductor Alloys: Does it Exist or Matter?
Speaker
Tianshu Li
Department of Civil and Environmental Engineering, George Washington University
About This Talk
Chemical short-range order (SRO) in alloys refers to a statistical deviation from a random distribution of atoms in lattice within a short atomic distance. Although SRO has been linked to important properties in metallic alloys and ceramics, its existence and relevance in semiconductor alloys have remained virtually unknown. In early studies we predicted SRO in group IV semiconductor alloys and the induced significant change in electronic and topological properties. However, the subtlety and intricacy of SRO elude conventional characterization approaches, sometimes even state-of-the-art techniques. An explicit demonstration of the existence and relevance of SRO requires synergistic efforts from both characterization and modeling on the same spatial scale. In this talk, Tianshu discuss his recent advance to enable a close modeling-experiment synergy for explicitly exploring SRO in semiconductor alloys. This includes (1) A physics-informed, statistical approach that overcomes the limited spatial resolution in atom-probe tomography (APT) to recover SRO parameter in alloys, and (2) A highly efficient and accurate machine-learning potential framework to model SRO on the same spatial scale of four-dimensional scanning transmission electron microscopy (4D-STEM) and APT. Applying these new methods through a close collaboration with 4D-STEM, APT, HRTEM, and EXAFS, we show explicitly that SRO not only exists in group IV and III-nitrides semiconductor alloys but also leads to a substantial variation in key properties. Tianshu will also discuss the ubiquity of SRO in a wide range of alloys and routes for potentially controlling SRO to harness novel properties via SRO engineering.
Biography
Dr. Tianshu Li obtained his Bachelor’s and Master’s degrees in Materials Science and Engineering from Tsinghua University in 1999 and 2001, respectively. He completed his Ph.D. in Materials Science from University of California, Berkeley in 2005. From 2006 to 2010, Dr. Li continued his research as a post-doctoral associate with Prof. Giulia Galli in Department of Chemistry at University of California, Davis. He then joined in the George Washington University as a faculty in 2010. Dr. Li’s research is focused on modeling materials’ behaviors using classical, quantum, and machine-learning approaches. His current research interests include understanding the thermodynamics and kinetics of crystal nucleation and unraveling complex structures and properties of materials.
About the MSE Seminar Series
The Materials Science and Engineering (MSE) Seminar Series features distinguished speakers from leading institutions, offering a platform for sharing groundbreaking research, innovative ideas, and entrepreneurial experiences. Held multiple times each semester, these seminars bring global perspectives world to MIT’s materials research community, exposing students, faculty, and postdocs to cutting-edge concepts and valuable networking opportunities.