Experimental Realization and Phase Engineering of a Two-Dimensional SnSb Binary Honeycomb Lattice

Binary two-dimensional (2D) materials comprising main group elements with several phases of AB and AB2 stoichiometry provide significantly rich physics and application potentials. We present the epitaxial growth of two phases of atomically thin SnSb on a Cu2Sb surface alloy under ultrahigh-vacuum (UHV) conditions. Theoretical studies predict that these 2D SnSb sheets adopt the atomic configurations similar to those of black and blue phosphorene but with Sb-Sn-Sn-Sb motif (R- and H-phases) holding an indirect band gap of 0.20 and 0.85 eV, respectively. Our low-temperature (77 K) scanning tunneling microscopy characterizations, and first-principles theoretical calculations, reveal the atomic structures and semiconducting properties of the most stable H-phase, displaying a commensurate lattice growth mode on Cu2Sb(111) but a weak interfacial interaction. Strain-engineered band gap, effective mass, and Young's Modulus of the most stable H-phase are further explored theoretically. These results suggest that 2D SnSb with intriguing properties has great potential for electronics in an atomically thin platform.