Epitaxial Antiferroelectric Bi₂O₂S Films with Superior Photoresponse

Two-dimensional bismuth oxychalcogenide is a rising material system with superior electronic properties. However, a lack of high-quality synthesis impedes the exploration of fundamental understanding and practical applications. This work presents high-quality epitaxial Bi₂O₂S films on (LaAlO₃)_0.3(Sr₂TaAlO₆)_0.7 with diverse properties by taking advantage of lattice compatibility. The atomically resolved sharp interface of Bi₂O₂S/(LaAlO₃)_0.3(Sr₂TaAlO₆)_0.7 heteroepitaxy is observed with the verification of centrosymmetric breaking through microscopic evidence and macroscopic characterizations. Such an epitaxial feature of the Bi₂O₂S film provides an essential step for applications compared to those of chemically synthesized nanomaterials. The interior polarization and piezoelectricity can be investigated through atomic-scale observation and RhB degradation of BOS. Meanwhile, this synthesized system can achieve a strong photoresponse with an on/off ratio of ∼10⁴ and a responsivity of ∼60 mA/W in the range of red light (620-750 nm). With these advantages, the demonstrated epitaxial Bi₂O₂S shows a huge potential for applications in high-performance optoelectronic devices.