Graduate Student Seminar
March 13, 2026
10:00 a.m. ET
CUC McConomy Auditorium
Dislocations as Emerging Conduction Pathways in Semiconducting BiSb Alloys
The continuing miniaturization of semiconductor chips with ever-increasing functionality is driven by understanding point, line, and extended defects and the new functionalities that they may offer. In addition to providing key “designer impurities”, point defects may be harnessed for quantum information. Line and extended defects often limit the performance of electronics but they may also provide new opportunities in classical and quantum computing. For example, in strong topological insulators, with a conducting surface and an insulating bulk, select dislocations are predicted to host 1D topological states and act as spin-state preserving conduction paths. Recently, uniaxial compression of semiconducting Bi-Sb alloys was reported to lead to conductivity enhancements presumed to be associated with 1-2μm-length dislocations. However, the nature of the dislocations and their role in enhancing conduction remains unknown.
Here, we report on a new approach to identify conduction pathways associated with extended defects in semiconducting Bi-Sb alloys. We characterize the structure and physical properties using high-angle annular dark field scanning transmission electron microscopy and electron-channeling contrast imaging in conjunction with magnetotransport measurements. Using high magnetic fields, we suppress bulk conduction, enabling the identification of the residual conductivity associated with extended defects. In addition to reporting on these findings, we examine the nature of multiple-micron-length {011}〈100〉dislocations generated during cyclic uniaxial [2̅11] compression and (111) nano-indentation. We also discuss progress towards probing electronic states associated with these dislocations using a Corbino geometry to suppress bulk and side-surface conduction.
Rachel Goldman
Maria Goeppert Mayer Professor of Materials Science and Engineering, Physics, and Electrical Engineering and Computer Science
University of Michigan
Goldman is the Director of the UM Materials Research Science and Engineering Center and leads a Multidisciplinary University Research Initiative supported by the Air Force Office of Scientific Research. In addition, she serves as an Associate Editor for the Journal of Applied Physics and as elected Councilor for the Division of Materials Physics of the American Physical Society (APS).
Prof. Goldman received degrees from the UM (B.S. Physics, 1988), Cornell University (M.S. Applied Physics, 1992), and the University of California, San Diego (PhD Materials Science, 1995). Following her PhD, she was a postdoctoral fellow (1995-1996) at Carnegie Mellon University prior to returning to UM in 1997 as the Dow Corning Assistant Professor. She was promoted to Associate Professor in 2003 and to Professor in 2007. She has served as Graduate Chair of Materials Science and Engineering (2008-2012) and as Associate Director of the Applied Physics Program (2010-2025).
Goldman’s research encompasses materials physics, with an emphasis on processing-structure-property relationships in epitaxial semiconductor films, nanostructures, and heterostructures. A current focus involves understanding the role of local solute configurations on emergent phenomena and novel functionalities of exotic alloys, nanowires, and quantum materials. She has published > 160 papers on processing-structure-property correlations in semiconductors; she holds a U.S. patent on “ion-cut-synthesis”, a novel approach for simultaneous synthesis and integration of nanocomposite materials with virtually any substrate. Recently, she pioneered the incorporation of Writing to Learn pedagogies into introductory materials science and engineering courses.
Goldman’s achievements have been recognized by numerous awards, including the Peter Mark Memorial Award from the AVS Science and Technology Society (formerly the American Vacuum Society), the Augustus Anson Whitney Fellowship from the Radcliffe Institute at Harvard University, the 50th Anniversary Distinguished Alumna of the Electronic Devices and Materials Group at the University of California, San Diego, and the Distinguished Faculty Achievement Award from UM. She is Fellow of the APS, the AVS Science and Technology Society, and the American Association for the Advancement of Science.
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