| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2018) | |
| Nanomaterials | Monday Sessions |
| Session NM-MoM |
| Session: | Nanocharacterization |
| Presenter: | Bruno Schuler, Lawrence Berkeley National Laboratory |
| Authors: | B. Schuler, Lawrence Berkeley National Laboratory D. Qiu, University of California Berkeley S. Rafaely-Abramson, Lawrence Berkeley National Laboratory C. Kastl, Lawrence Berkeley National Laboratory K. Cochrane, Lawrence Berkeley National Laboratory S. Barja, Lawrence Berkeley Lab, USA C.T. Chen, Lawrence Berkeley National Laboratory N. Borys, Lawrence Berkeley National Laboratory R. Koch, Lawrence Berkeley National Laboratory F. Ogletree, Lawrence Berkeley National Laboratory S. Aloni, Lawrence Berkeley National Laboratory A.M. Schwartzberg, Lawrence Berkeley National Laboratory S. Louie, University of California Berkeley J. Neaton, Lawrence Berkeley National Laboratory A. Weber-Bargioni, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
The advent of transition metal dichalcogenides (TMDs) and other two-dimensional (2D) materials has attracted considerable attention due to unique material properties emerging from their reduced dimensionality. Because of this strong confinement, structural defects greatly modify such properties and have therefore become of increasing interest to the 2D materials community. Particularly the creation of in-gap defect states is decisive for their optoelectronic properties and catalytic activity.
Using low-temperature scanning probe microscopy with CO functionalized tips we identified and characterized common point defects in monolayer WS2 (see Fig. 1).
Contrary to previous reports, we suggest that the most abundant defect is an O substitution at a S site, not a S vacancy, with a distinctively different electronic structure.
In contrast to O decorated S vacancies, a W substitutional defect and pristine S vacancies create distinct defect states within the band gap of WS2. Interestingly, both types of point defects exhibit spin-orbit split defect states with a large splitting of 80 meV and 280 meV, respectively. Moreover, these defects exhibit electron-induced luminescence with a characteristic bias dependence. Spectrally integrated luminescence maps resemble the defect orbitals.
The same sample was also characterized with nano-ARPES and photoluminescence spectroscopy, which shows that thermally grown graphene on SiC constitutes a suitable platform for cross-correlation microscopy of TMD materials (and potentially other van der Waals materials) in both, UHV and ambient conditions.
The atomic-scale characterization allows an unprecedentedly detailed picture on the structure and functionality of point defects in 2D-TMDs.