Regensburg 2019 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 48: Two-dimensional Materials IV (joint session HL/CPP)
HL 48.3: Talk
Friday, April 5, 2019, 10:00–10:15, H36
Towards an Atomistic Understanding of Defects in 2D Materials - Correlating Defects, Band Structure and Excitons — •Christoph Kastl1, Roland Koch1, Chris Chen1, Bruno Schuler1, Johanna Eichhorn1, Soren Ulstrup2, Aaron Bostwick1, Chris Jozwiak1, Nicholas Borys3, Francesca Toma1, Shaul Aloni1, Alexander Weber-Bargioni1, Eli Rotenberg1, and Adam Schwartzberg1 — 1Lawrence Berkeley National Laboratory, Berkeley, United States — 2Aarhus University, Denmark — 3Montana State University, Bozeman, United States
Despite their importance, a detailed understanding of defects in 2D materials and their impact on excitonic and electronic properties is lacking. We use spatially resolved, angle resolved photoemission spectroscopy (nano-ARPES) to map the variations in band structure and defect density of monolayer WS2 down to a resolution of 150 nm. [1] By correlating nano-ARPES with photoluminescence, we reveal the interplay between local defect density, band structure, and excitons. We compare this to atomic force and scanning tunneling microscopy, where we unambiguously identify defects at the atomic level. Surprisingly, the chalcogen vacancy is not present in as-grown monolayers, although it is commonly inferred to be the dominant point defect.[2] Instead, we find that substitutional oxygen effectively passivates chalcogen vacancies, which removes the electronic in-gap state and renders correct assignment of the defect challenging.
[1] C. Kastl et al., 2D Mater. 5, 045010, 2018. [2] arXiv:1810.02896, arXiv:1810.03364.