Heterostructures of transition metal dichalcogenides

The structural, electronic, optical, and photocatalytic properties of out-of-plane and in-plane heterostructures of transition metal dichalcogenides are investigated by (hybrid) first principles calculations. The out-of-plane heterostructures are found to be indirect band gap semiconductors with type-II band alignment. Direct band gaps can be achieved by moderate tensile strain in specific cases. The excitonic peaks show blueshifts as compared to the parent monolayer systems, whereas redshifts occur when the chalcogen atoms are exchanged along the series S-Se-Te. Strong absorption from infrared to visible light as well as excellent photocatalytic properties can be achieved.

Figure 1

Out-of-plane heterostructures for different stackings.

Figure 2

Band structures of the out-of-plane heterostructures obtained using the PBE (left) and HSE06 (right) functionals. The black dashed conduction bands are obtained under strain; see the text for details.

Figure 3

Orbitally weighted HSE06 band structures of the out-of-plane heterostructures, taking into account the spin-orbit coupling.

Figure 4

Imaginary part of the dielectric function of the out-of-plane (black) and in-plane (red) heterostructures as compared to the parent monolayer systems.

Figure 5

In-plane heterostructures.

Figure 6

Band structures of the in-plane hetero-structures obtained using the PBE (left) and HSE06 (right) func-tionals.

Figure 7

Valence and conduction band edge potentials for the out-of-plane (orange) and in-plane (yellow) heterostructures. The values are obtained by HSE06 (black) and ${\mathrm{GW}}_0$ (blue) calculations. The dashed lines represent the water reduction $\left({\mathrm{H}}^{+}/{\mathrm{H}}_2\right)$ and oxidation $\left({\mathrm{H}}_2\mathrm{O}/{\mathrm{O}}_2\right)$ potentials.