Theoretical analysis of the combined effects of sulfur vacancies and analyte adsorption on the electronic properties of single-layer MoS₂

Abstract

We report a first-principles theoretical investigation on the electronic structure and electron transport of defective single-layer (SL) MoS2, as well as of corresponding structures adsorbed with benzyl viologen (BV), which was shown to provide improved performance of a field effect transistor. O2 adsorption was included to gain an understanding of the response upon air-exposure. Following analysis of the structure and stability of sulfur single vacancy and line defects in SL MoS2, we investigated the local transport at the adsorbed sites via a transport model that mimics a scanning tunneling spectroscopy experiment. Distinct current-voltage characteristics were indicated for adsorbed oxygen species at a sulfur vacancy. The electronic structures of defective MoS2 indicated the emergence of impurity states in the bandgap due to sulfur defects and oxygen adsorption. Electron transport calculations for the MoS2 surface with an extended defect in a device setting demonstrated that physisorption of BV enhances the output current, while facile chemisorption by O2 upon air-exposure causes degradation of electron transport.

Various Structures of 2D Transition‐Metal Dichalcogenides and Their Applications

“…Meanwhile, the density of states (DOS) showed that it has a half‐metal behavior and obtained the whole spin polarization (Figure d,e). Furthermore, Akdim et al reported that when the O 2 molecule is adsorbed at vacancy‐defected MoS 2 , the impurity states emerge at the bandgap (Figure f) . Meanwhile, the impurity states lead to a decrease of the transport properties of the system (Figure g).…”

“…g) I – V characteristics when the tip is positioned on S in pristine single‐layer (SL) MoS 2 , on a sulfur vacancy (SV), and on oxygen for the corresponding SV+O 2 adsorbed structure. f,g) Reproduced with permission . Copyright 2016, IOP Publishing Ltd.…”

“…Furthermore, Akdim et al reported that when the O 2 molecule is adsorbed at vacancy-defected MoS 2 , the impurity states emerge at the bandgap (Figure 5f). [88] Meanwhile, the impurity states lead to a decrease of the transport properties of the system (Figure 5g). In addition, Ataca and Ciraci found that H 2 O molecules can be dissociated into O and H atoms at specific vacancy defects of single-layer MoS 2 .…”

Adsorption of small inorganic molecules on a defective MoS2monolayer

“…25,26 Very recently, different groups have analyzed the interactions of some molecules in a defective MoS 2 monolayer. [27][28][29][30][31][32] The first two works show both experimentally and theoretically the molecular chemisorption or dissociation for O 2 molecules on MoS 2 defects. Li et al extended the study to other molecules on a S vacancy, 29 while Sahoo and coworkers applied a similar analysis for an antisite, i.e.…”

Molecular detection on a defective MoS2 monolayer by simultaneous conductance and force simulations

“…Two good examples are the oxidation of the MoS 2 borders [28] and the sulfur vacancy self-healing using thiol molecules [29]. Even the molecular dissociation of O 2 molecules over MoS 2 defects has been shown very recently, both experimentally and theoretically [31,32].…”