Designer 2D Materials and Machine-Learning Assisted Characterization

2D materials offer enormous opportunities to build designer structures with widely tunable properties. The precise atomic engineering and quick characterization approach are critical to advance the application of designer 2D materials. This talk will introduce new optical features of designer 2D materials [1-5], including dipole-induced mechanical behavior, phonon interference, and single photon emission. The engineering of 2D materials presents unique opportunities for optoelectronic devices and quantum information platforms. When designing optoelectronic devices of 2D materials, spectroscopic permittivity of 2D material is a key parameter. While ellipsometry has been used to measure permittivity, it requires simple device structure, non-trivial parameter fitting, and special setup. This talk will also present a new machine-learning assisted approach to measure permittivity of 2D materials embedded in complex device structures without model fitting, which can facilitate a quick, accurate, and in-situ characterization of 2D and other thin film materials [6].<br/><br/><b>References</b><br/>[1] Q. Qian, et al. “Photoluminescence Induced by Substitutional Nitrogen in Single-Layer Tungsten Disulfide,” <i>ACS Nano</i>, 16 (5), 7428-7437 (2022).<br/>[2] K. Zhang, et al. “Enhancement of van der Waals Interlayer Coupling Through Polar Janus MoSSe,” <i>Journal of the American Chemical Society</i>, 142 (41), 17499-17507 (2020).<br/>[3] K. Zhang, et al. “Spectroscopic signatures of interlayer coupling in Janus MoSSe/MoS2 heterostructures,” <i>ACS Nano</i>, 15 (9), 14394-14403 (2021).<br/>[4] N. T. Hung, et al. “Nonlinear Optical Responses of Janus MoSSe/MoS2 Heterobilayers Optimized by Stacking Order and Strain,” <i>ACS Nano</i> 17, 20, 19877–19886 (2023)<br/>[5] Q. Qian, et al. “Chirality-Dependent Second Harmonic Generation of MoS2 Nanoscroll with Enhanced Efficiency,” <i>ACS Nano</i>, 14 (10), 13333–13342 (2020).<br/>[6] Z. Wang, et al. “Measuring complex refractive index through deep-learning-enabled optical reflectometry,” <i>2D Materials</i>, 10, 025025 (2023).