First-principles study of a MoS2-PbS van der Waals heterostructure inspired by naturally occurring merelaniite

[Marco E. Ciriotti]

Referenza:
▪ Degaga, G.D., Kaur, S., Pandey, R., Jaszczak, J.A. (2021): First-Principles Study of a MoS2-PbS van derWaals Heterostructure Inspired by Naturally Occurring Merelaniite. Materials, 14. 1649.

Abstract:
Vertically stacked, layered van der Waals (vdW) heterostructures offer the possibility to design materials, within a range of chemistries and structures, to possess tailored properties. Inspired by the naturally occurring mineral merelaniite, this paper studies a vdW heterostructure composed of a MoS2 monolayer and a PbS bilayer, using density functional theory. A commensurate 2D heterostructure film and the corresponding 3D periodic bulk structure are compared. The results find such a heterostructure to be stable and possess p-type semiconducting characteristics. Due to the heterostructure’s weak interlayer bonding, its carrier mobility is essentially governed by the constituent layers; the hole mobility is governed by the PbS bilayer, whereas the electron mobility is governed by the MoS2 monolayer. Furthermore, we estimate the hole mobility to be relatively high (~106 cm2V􀀀1s􀀀1), which can be useful for ultra-fast devices at the nanoscale.

[Marco E. Ciriotti]

Referenza:
▪ Bindi, L., Dasgupta, A., Mukherjee, P., Gao, J., Yang, X., Jaszczak, J.A. (2022): Misfit-generated structural and optical anisotropies of the natural MoS2−PbS van der Waals heterostructure merelaniite. Physical Review Materials, 6, 115202.

Abstract:
Significant efforts developing MoS2−PbS-based heterostructure devices with several different architectures show promise for photosensor, solar cell, and chemical sensor applications. Merelaniite (Mo4Pb4VSbS15) is a newly discovered natural van der Waals heterostructure of the cylindrite type, composed predominantly of heavily modulated pseudotetragonal PbS layers and pseudohexagonal MoS2 layers with large misfit-induced anisotropy. For an incommensurate modulated structure, the refined structural model from single-crystal x-ray diffraction analysis is in reasonable agreement with the results obtained by high-resolution scanning transmission electron microscopy, especially in light of the fact that that the two isolated single-crystal domains used for the x-ray and electron diffraction experiments were extracted from two different whiskers and subjected to different sample preparation methods. The effects of the misfit-induced structural anisotropy are studied using angle-resolved polarized Raman spectroscopy. The intensities of 12 Raman modes are studied as a function of incident polarization angle relative to merelaniite's whisker axis, and show maximal intensity with the polarization direction perpendicular to the whisker axis. Polarization-dependent anisotropic third-harmonic generation from ultrathin mechanically exfoliated flakes reveals the anisotropy of the third-order nonlinear susceptibility tensor. Merelaniite demonstrates an expanded structure-chemistry space for engineering stable layered materials for potential device applications.