Defects, band bending and ionization rings in MoS2

Iolanda Di Bernardo; James Blyth; Liam Watson; Kaijian Xing; Yi-Hsun Chen; Shao-Yu Chen; Mark T Edmonds; Michael S Fuhrer

doi:10.1088/1361-648X/ac4f1d

Defects, band bending and ionization rings in MoS₂

J Phys Condens Matter. 2022 Feb 24;34(17). doi: 10.1088/1361-648X/ac4f1d.

Authors

Iolanda Di Bernardo^{1

2}, James Blyth^{1

2}, Liam Watson^{1

2}, Kaijian Xing², Yi-Hsun Chen^{1

2}, Shao-Yu Chen^{1

2}, Mark T Edmonds^{1

2

3}, Michael S Fuhrer^{1

2

3}

Affiliations

¹ Australian Research Council Centre of Excellence in Future Low-Energy Electronics Technologies, Monash University, Clayton, 3800, VIC, Australia.
² School of Physics and Astronomy, Monash University, Clayton, 3800, VIC, Australia.
³ Monash Centre for Atomically Thin Materials, Monash University, Clayton, 3800, VIC, Australia.

PMID: 35081526
DOI: 10.1088/1361-648X/ac4f1d

Abstract

Chalcogen vacancies in transition metal dichalcogenides are widely acknowledged as both donor dopants and as a source of disorder. The electronic structure of sulphur vacancies in MoS₂however is still controversial, with discrepancies in the literature pertaining to the origin of the in-gap features observed via scanning tunneling spectroscopy (STS) on single sulphur vacancies. Here we use a combination of scanning tunnelling microscopy and STS to study embedded sulphur vacancies in bulk MoS₂crystals. We observe spectroscopic features dispersing in real space and in energy, which we interpret as tip position- and bias-dependent ionization of the sulphur vacancy donor due to tip induced band bending. The observations indicate that care must be taken in interpreting defect spectra as reflecting in-gap density of states, and may explain discrepancies in the literature.

Keywords: MoS2; STM; TMDs; defects; ionization rings.