Mechanical Engineering Seminar
Strain & Defect Engineering at the Atomic-Limit in 2D Nanoelectronics
Tara Peña, Ph.D
NSF Mathematical & Physical Science Ascend Postdoctoral Fellow
Stanford University
Abstract:
Two-dimensional (2D) materials are naturally excellent candidates for hyper-scaled devices, because of their atomic thinness and desirable optical, electrical, and mechanical properties. The unique potential of 2D materials could usher the next generation of nanoelectronics, such as high performance transistors, wearable/flexible electronics, and quantum technologies. However, 2D materials and their devices have been plagued by disorder and variability, such as local randomized strains and defect sites at the atomic scale.
In this talk, I will discuss how to intentionally design strain in 2D materials and their heterostructures, to precisely tune their (opto)electronic properties. Specifically, I explore how to use process-induced strain engineering techniques, which were first introduced by Si technology in 2003. I show that thin film stressed capping layers can be utilized to study interfacial mechanics and how these control resulting spatial strain profiles. Incomplete out-of plane strain transfer is especially pronounced in 2D heterostructures due to their van der Waals bonds, allowing this approach to introduce systematic heterostrain for moiré heterostructures. Next, I will cover how fabrication-induced disorder can be mitigated in top-down patterned 2D monolayers with reduced width dimensions (nanoribbons). With careful process optimization, I demonstrate single-gated transistors composed of monolayer MoS2, WS2, and WSe2 nanoribbons with record high current densities and widths down to 25 nm. Finally, I will conclude with prospective research directions for further commanding strain and defects with atomic precision, and the implications that this work has for future nanotechnology.
Bio:
Tara Peña earned her B.S. in Physics at Adelphi University, then her M.S. and Ph.D. in Electrical & Computer Engineering at the University of Rochester. Her graduate work examined on-chip strain engineering techniques for two-dimensional (2D) materials, heterostructures, and devices. She is currently an NSF Mathematical & Physical Science Ascend postdoctoral fellow at Stanford University, where she works towards large-scale synthesis of 2D materials and optimizing their nanoscale transistors.