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Perovskite chalcogenides are gaining substantial interest as an emerging class of semiconductors for optoelectronic applications. High-quality samples are of vital importance to examine their inherent physical properties. We report the successful crystal growth of the model system, BaZrS 3 and its Ruddlesden–Popper phase Ba 3 Zr 2 S 7 by a flux method. X-ray diffraction analyses showed the space group of Pnma with lattice constants of a = 7.056(3) Å, b = 9.962(4) Å, and c = 6.996(3) Å for BaZrS 3 and P 4 2 / mnm with a = 7.071(2) Å, b = 7.071(2) Å, and c = 25.418(5) Å for Ba 3 Zr 2 S 7 . Rocking curves with full width at half maximum of 0.011° for BaZrS 3 and 0.027° for Ba 3 Zr 2 S 7 were observed. Pole figure analysis, scanning transmission electron microscopy images, and electron diffraction patterns also establish the high quality of the grown crystals. The octahedral tilting in the corner-sharing octahedral network is analyzed by extracting the torsion angles. 

Abstract The making of BaZrS₃thin films by molecular beam epitaxy (MBE) is demonstrated. BaZrS₃forms in the orthorhombic distorted‐perovskite structure with corner‐sharing ZrS₆octahedra. The single‐step MBE process results in films smooth on the atomic scale, with near‐perfect BaZrS₃stoichiometry and an atomically sharp interface with the LaAlO₃substrate. 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.