Molecular Beam Epitaxy and Electronic Structure of Atomically Thin Oxyselenide Films.

Abstract

Atomically thin oxychalcogenides have been attracting intensive attention for their fascinating fundamental properties and application prospects. Bi2 O2 Se, a representative of layered oxychalcogenides, has emerged as an air-stable high-mobility 2D semiconductor that holds great promise for next-generation electronics. The preparation and device fabrication of high-quality Bi2 O2 Se crystals down to a few atomic layers remains a great challenge at present. Here, molecular beam epitaxy (MBE) of atomically thin Bi2 O2 Se films down to monolayer on SrTiO3 (001) substrate is achieved by co-evaporating Bi and Se precursors in oxygen atmosphere. The interfacial atomic arrangements of MBE-grown Bi2 O2 Se/SrTiO3 are unambiguously revealed, showing an atomically sharp interface and atom-to-atom alignment. Importantly, the electronic band structures of one-unit-cell (1-UC) thick Bi2 O2 Se films are observed by angle-resolved photoemission spectroscopy (ARPES), showing low effective mass of ≈0.15 m0 and bandgap of ≈0.8 eV. These results may be constructive to the synthesis of other 2D oxychalcogenides and investigation of novel physical properties.