Probing Single Dopant Atoms in 2D Semiconductors via Scanning Probe Microscopy

Two-dimensional (2D) semiconductors provide an exciting platform to engineer atomic quantum states in a robust, yet tunable solid-state system. In this talk, I will present our efforts to unravel the interesting physics behind single dopant atoms in transition metal dichalcogenide (TMD) monolayers by means of high-resolution scanning probe microscopy [1-8].

Our recent research on transition metal doped TMDs such as (n-type) Re-doped MoS₂ and (p-type) V-doped WSe₂ reveals the significance of the charge state in the spectroscopic signature of these defects. By substrate chemical gating, we can stabilize three charge states of Re_Mo, where two of the charge states exhibit symmetry broken electronic orbitals and a distorted atomic configuration that we assign to a pseudo Jahn-Teller effect [9]. Negatively charged V dopants and dopant pairs in WSe₂ exhibit a series of occupied p-type defect states above the valence band edge, accompanied by an intriguing electronic fine-structure that we attribute to many-body electron interactions [10].

I will also introduce our efforts to probe excitation dynamics on the ultrafast time scales using a newly developed THz-pulse-driven STM [11].



References

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   S. Barja et al., Nat. Commun. 10, 3382 (2019)
   
   K. Cochrane et al., 2D Mater. 7, 031003 (2020)
   
   M. Aghajanian et al., Phys. Rev. B 101 081201(R) (2020)
   
   B. Schuler et al., Sci. Adv. 6, eabb5988 (2020)
   
   K. Cochrane et al., Nat. Commun. 12, 7287 (2021)
   
   E. Mitterreiter et al., Nat. Commun. 12, 3822 (2021)
   
   F. Xiang*, L. Huberich* et al. Arxiv: 2308.0220 (in review)
   
   S. Stolz et al. ACS Nano (in press)
   
   J. Allerbeck et al. ACS Photonics (2023)