Energy landscape and band-structure tuning in realisticMoS2/MoSe2heterostructures

Abstract

While monolayer forms of 2D materials are well-characterised both experimentally and theoretically, properties of bilayer heterostructures are not nearly so well-known. We employ high-accuracy linear-scaling DFT calculations utilising non-local van-der-Waals functionals to explore the possible constructions of the MoS2/MoSe2 interface. Utilising large supercells, we vary rotation, translation and separation of the layers without introducing unrealistic strain. The energy landscape shows very low variations under rotation, with no strongly preferred alignments. By unfolding the spectral function into the primitive cells, we show that the monolayers are more independent than in homo-bilayers, and that the electronic bandstructure of each layer is tunable through rotation, thus influencing hole effective masses.

Multipurpose Black-Phosphorus/hBN Heterostructures

“…11 Secondly, the decrease of the band gap in BP stacks implies that only the monolayer is usable for near-IR optoelectronic applications, limiting the external quantum efficiency of such devices. This band gap decrease cannot be avoided by simply misaligning the BP layers, as we have previously shown that stacked layers always interact at Γ in reciprocal-space, 30 exactly where the BP direct band-gap is. Lastly, due to the band gap being smaller than that of TMDCs, the current on/off ratio for BP transistors is lower; therefore, pristine BP channels are not at first sight as appealing as TMDCs in ultra-low power applications.…”

“…41 We utilise the optB88-vdW functional for exchange and correlation, due to its proven trackrecord in describing both covalent and weak interactions in 2D materials. 30 The projectoraugmented-wave (PAW) formalism 42 was employed for all the LS-DFT calculations, using the atomic datasets developed by Garrity et al, 43 which have been validated for a wide range of covalent compounds.…”

“…In this manner, we also gain means of direct comparison with angular-resolved photoemission spectroscopy experiments (ARPES), as explained in previous works. 30,53 To access only the Brillouin zone of the BP primitive cell, we need to unfold the supercell spectral function by projecting the spectral function operator onto the monolayer of interest and afterwards changing the representation basis to the primitive-cell eigenstates of the monolayer in question:…”

Tunneling Photocurrent Assisted by Interlayer Excitons in Staggered van der Waals Hetero‐Bilayers

“…To identify the origin of X 1 and X 2 peaks, we show the predicted band alignment of the MoSe 2 /MoS 2 HB in terms of the exciton transition energies, band renormalization, the binding energies of intralayer and interlayer excitons, and the valance band offsets (Figure b,c). In what follows, we assume that the binding energy () of interlayer excitons for the MoSe 2 /MoS 2 HB is similar to that of MoSe 2 /WSe 2 (≈0.2 eV) .…”

Van der Waals Heterostructures with Tunable Tunneling Behavior Enabled by MoO3 Surface Functionalization

“…Among these, the TFETs have attracted great attention owing to the potential to open up new avenues for low‐power and fast switching devices. Nevertheless, many vdWHs based on semiconducting TMDs exhibit the type II band alignment, which is not suitable for TFETs . The changeless conduction behavior of the vdWHs also limits the device tunability and performance in optoelectronic application.…”