Quantum wells formed in transition-metal dichalcogenide nanosheet-superlattices: stability and electronic structures from first principles

The possibility of forming quantum wells (QWs) in transition-metal dichalcogenide nanosheet assembled superlattices (SLs) was investigated by using the first principles calculations. The interfacial binding energies and electronic structures of MoS2/MX2 (MX2 = MoSe2, WS2, and WSe2) SLs were calculated. The interfacial binding energies show that all the SLs are stable, and the most stable atomic configuration is that where M atoms are located right above S atoms. By calculating the band offsets in the SLs, it was found that a QW with a depth of 0.17 eV can be formed in the MoS2 layer in MoS2/WSe2 SLs. The calculated band structure shows that this SL has an indirect band gap due to the tensile strained state of the MoS2 layer. The charge transfer between the two layers is very small, which is in favor of the QWs' formation. In particular, the depth of the QW in the SLs can be adjusted by strain engineering, which can be attributed to the different strain dependencies of the two materials' band gaps. These findings will guide the choice of future nanosheet assembled SLs to work on and suggest a new route to facilitate the design of QW based optoelectronic devices.