Selective heteroepitaxial synthesis of 2D bismuth-based mixed-anion compounds with interfacial spin–orbit interaction via atmospheric solution routes

Abstract

We demonstrate the synthesis of nanoscale-thick epitaxial thin films of Bi₂OS₂ and Bi₃O₂S₂Cl, which are two-dimensional Bi-based mixed anion systems, by mist chemical vapor deposition. Despite the common precursors, the single- and dual-source configurations of the synthesis method resulted in the formation of Bi₂OS₂ and Bi₃O₂S₂Cl, respectively, due to the different reaction schemes in the mist droplets and on the substrates. The Bi₃O₂S₂Cl thin films showed better crystallinity and higher electrical conductivity compared to the Bi₂OS₂ thin films. In addition, an almost pure k-cubic spin–orbit interaction was confirmed through the two-dimensional weak antilocalization effect at the interface between the Bi₃O₂S₂Cl thin film and oxide substrate.