Epitaxial Growth of Monolayer SnP₃ with High Mobility and Chiral Boundary Junctions

Two-dimensional materials with layered structures, appropriate band gaps, and high carrier mobility have attracted tremendous interest for their potential applications. Here we report the growth of monolayer SnP₃ on Au(111) surfaces by molecular beam epitaxy. The kinetic processes for the growth and the crystalline properties are studied by scanning tunneling microscopy. The weak interaction between SnP₃ and its Au(111) substrate is signified by the random crystal orientation distributions of SnP₃ nanosheets. The electronic structures exhibit a band gap of ∼0.25 eV and high charge carrier mobility comparable to that of black phosphorus engineered by compressive strain. Additionally, domain boundary junctions with opposite chirality are observed, resulting from the strained film in the epitaxial growth process. Our work provides a method to fabricate high-quality monolayer SnP₃ and suggests that the monolayer SnP₃ is a promising candidate for applications in nanoelectronics and optoelectronics.