Making BaZrS3 Chalcogenide Perovskite Thin Films by Molecular Beam Epitaxy

Abstract The making of BaZrS 3 thin films by molecular beam epitaxy (MBE) is demonstrated. BaZrS 3 forms in the orthorhombic distorted‐perovskite structure with corner‐sharing ZrS 6 octahedra. The single‐step MBE process results in films smooth on the atomic scale, with near‐perfect BaZrS 3 stoichiometry and an atomically sharp interface with the LaAlO 3 substrate. The films grow epitaxially via two competing growth modes: buffered epitaxy, with a self‐assembled interface layer that relieves the epitaxial strain, and direct epitaxy, with rotated‐cube‐on‐cube growth that accommodates the large lattice constant mismatch between the oxide and the sulfide perovskites. This work sets the stage for developing chalcogenide perovskites as a family of semiconductor alloys with properties that can be tuned with strain and composition in high‐quality epitaxial thin films, as has been long‐established for other systems including Si‐Ge, III‐Vs, and II‐VIs. The methods demonstrated here also represent a revival of gas‐source chalcogenide MBE.