The deep-acceptor nature of the chalcogen vacancies in 2D transition-metal dichalcogenides

Abstract

Chalcogen vacancies in the semiconducting monolayer transition-metal dichalcogenides (TMDs) have frequently been invoked to explain a wide range of phenomena, including both unintentional p-type and n-type conductivity, as well as sub-band gap defect levels measured via tunneling or optical spectroscopy. These conflicting interpretations of the deep versus shallow nature of the chalcogen vacancies are due in part to shortcomings in prior first-principles calculations of defects in the semiconducting two-dimensional (2D) TMDs that have been used to explain experimental observations. Here we report results of hybrid density functional calculations for the chalcogen vacancy in a series of monolayer TMDs, correctly referencing the thermodynamic charge transition levels to the fundamental band gap (as opposed to the optical band gap). We find that the chalcogen vacancies are deep acceptors and cannot lead to n-type or p-type conductivity. Both the (0/$-1$) and ($-$1/$-$2) transition levels occur in the gap, leading to paramagnetic charge states S=1/2 and S=1, respectively, in a collinear-spin representation. We discuss trends in terms of the band alignments between the TMDs, which can serve as a guide to future experimental studies of vacancy behavior.

References in corpus (10)

• Observation of giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor
• Vertical Field Effect Transistor based on Graphene-WS2 Heterostructures for flexible and transparent electronics
• Elastic properties of freely suspended MoS2 nanosheets
• Electrical suppression of all nonradiative recombination pathways in monolayer semiconductors
• Thickness dependence of work function, ionization energy, and electron affinity of Mo and W dichalcogenides from DFT and GW calculations
• Effect of Point Defects on the Optical and Transport Properties of MoS2 and WS2
• Self-consistent potential correction for charged periodic systems
• Electronic Band Structure of Transition Metal Dichalcogenides from Ab Initio and Slater-Koster Tight-Binding Model
• Tunable magneto-optical properties in MoS${}_2$ via defect-induced exciton transitions
• Vacancy localization effects on MX2 transition metal dichalcogenides: a systematic ab-initio study

Cited by in corpus (1)

• Transition Metal Dichalcogenide MoS${}_2$: oxygen and fluorine functionalization for selective plasma processing