Weak Van der Waals Stacking, Wide-Range Band Gap, and Raman Study on Ultrathin Layers of Metal Phosphorus Trichalcogenides

TLDR

Metal phosphorus trichalcogenides (MPS₃ and MPSe₃) have been synthesized, crystallized, and exfoliated into monolayer 2D semiconductors. The study proposes using these monolayers as building blocks for van der Waals heterostructures with potential ferroelectric and magnetic functionalities. Raman analysis confirms structural stability of monolayer FePS₃ and 3‑layer FePSe₃, while tunable band gaps from 1.3 to 3.5 eV and low cleavage energies relative to graphite indicate promising optoelectronic and heterostructure applications.

Abstract

2D semiconducting metal phosphorus trichalcogenides, particularly the bulk crystals of MPS3 (M = Fe, Mn, Ni, Cd and Zn) sulfides and MPSe3 (M = Fe and Mn) selenides, have been synthesized, crystallized and exfoliated into monolayers. The Raman spectra of monolayer FePS3 and 3-layer FePSe3 show the strong intralayer vibrations and structural stability of the atomically thin layers under ambient condition. The band gaps can be adjusted by element choices in the range of 1.3–3.5 eV. The wide-range band gaps suggest their optoelectronic applications in a broad wavelength range. The calculated cleavage energies of MPS3 are smaller than that of graphite. Therefore, the monolayers used for building of heterostructures by van der Waals stacking could be considered as the candidates for artificial 2D materials with unusual ferroelectric and magnetic properties.