Systematic study of electronic structure and band alignment of monolayer transition metal dichalcogenides in Van der Waals heterostructures

TLDR

Two-dimensional transition metal dichalcogenides (TMDs) are promising low-dimensional materials that can produce diverse electronic properties and band alignment in van der Waals heterostructures. The study uses systematic DFT calculations on 24 TMD monolayers and their bilayer heterostacks, and applies a charge equilibration model to derive a quantitative formula for the highest occupied state of all 552 bilayer combinations. DFT reveals that monolayer TMDs can be semiconducting, metallic, or semimetallic, and the calculated band alignments, validated by the CEM predictions, offer quantitative guidance for designing TMD-based van der Waals heterostructure devices.

Abstract

Two-dimensional transition metal dichalcogenides (TMDs) are promising low-dimensional materials which can produce diverse electronic properties and band alignment in van der Waals heterostructures. Systematic density functional theory (DFT) calculations are performed for 24 different TMD monolayers and their bilayer heterostacks. DFT calculations show that monolayer TMDs can behave as semiconducting, metallic or semimetallic depending on their structures; we also calculated the band alignment of the TMDs to predict their alignment in van der Waals heterostacks. We have applied the charge equilibration model (CEM) to obtain a quantitative formula predicting the highest occupied state of any type of bilayer TMD heterostacks (552 pairs for 24 TMDs). The CEM predicted values agree quite well with the selected DFT simulation results. The quantitative prediction of the band alignment in the TMD heterostructures can provide an insightful guidance to the development of TMD-based devices.