Mo6S3Br6: An Anisotropic 2D Superatomic Semiconductor

Abstract

Two-dimensional (2D) van der Waals materials with in-plane anisotropy are of great interest for directional transport of charge and energy, as exemplified by recent studies on black phosphorus and α-phase molybdenum trioxide (α-MO3). Here, a layered van der Waals semiconductor with in-plane anisotropy built upon the superatomic units of Mo6S3Br6 is reported. This material possesses robust 2D characteristics with a direct gap of 1.64 eV, as determined by scanning tunneling spectroscopy and first-principles calculations. Polarization-dependent Raman spectroscopy measurement and density functional theory calculation reveal strong in-plane anisotropy. These results suggest an effective strategy to explore anisotropic 2D electronic and optoelectronic properties from superatomic building blocks with multifunctionality, emergent properties, and hierarchical control.