Quasi-Two-Dimensional\nSe-Terminated Bismuth Oxychalcogenide\n(Bi₂O₂Se)

Abstract

Since\nthe discovery of graphene, van der Waals (vdW) two-dimensional\n(2D) materials have attracted considerable attention for various potential\napplications. Recently, a Se-terminated bismuth oxychalcogenide, Bi₂O₂Se, has been fabricated using the vapor deposition\nmethod. Bi₂O₂Se is not a vdW 2D material, but\nthe as-grown substance shows 2D characteristics. For example, Bi₂O₂Se exhibits layer number-dependent absorption\nspectra in experiments, but until now, there has been no reasonable\nexplanation as to why. Here, we propose a 50% Se-passivation surface\nmodel, which elucidates the production of such spectra. Our model\nis also consistent with recent observations using scanning tunneling\nmicroscopy. Moreover, high-resolution transmission electron microcopy\nobservations show a broken zipper-like structure in Bi₂O₂Se. We ascribe Bi₂O₂Se as a zipper\n2D material, and we summarize the characteristics of zipper 2D materials\nwhile proposing the development of others. Zipper 2D materials not\nonly are an important subset of 2D materials but also bridge the gap\nbetween vdW 2D materials and traditional 3D materials. Because they\nare a big family, including insulators, semiconductors, and magnetic\nmetals, zipper 2D materials lend themselves to a plethora of applications.