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Abstract BaTiS₃, a quasi-1D complex chalcogenide, has gathered considerable scientific and technological interest due to its giant optical anisotropy and electronic phase transitions. However, the synthesis of high-quality BaTiS₃crystals, particularly those featuring crystal sizes of millimeters or larger, remains a challenge. Here, we investigate the growth of BaTiS₃crystals utilizing a molten salt flux of either potassium iodide, or a mixture of barium chloride and barium iodide. The crystals obtained through this method exhibit a substantial increase in volume compared to those synthesized via the chemical vapor transport method, while preserving their intrinsic optical and electronic properties. Our flux growth method provides a promising route toward the production of high-quality, large-scale single crystals of BaTiS₃, which will greatly facilitate advanced characterizations of BaTiS₃and its practical applications that require large crystal dimensions. Additionally, our approach offers an alternative synthetic route for other emerging complex chalcogenides. Graphical Abstract 

Abstract A key open question in the study of layered superconducting nickelate films is the role that hydrogen incorporation into the lattice plays in the appearance of the superconducting state. Due to the challenges of stabilizing highly crystalline square planar nickelate films, films are prepared by the deposition of a more stable parent compound which is then transformed into the target phaseviaa topotactic reaction with a strongly reducing agent such as CaH₂. Recent studies, both experimental and theoretical, have introduced the possibility that the incorporation of hydrogen from the reducing agent into the nickelate lattice may be critical for the superconductivity. In this work, we use secondary ion mass spectrometry to examine superconducting La_1−xX_xNiO₂/ SrTiO₃(X= Ca and Sr) and Nd₆Ni₅O₁₂/ NdGaO₃films, along with non-superconducting NdNiO₂/ SrTiO₃and (Nd,Sr)NiO₂/ SrTiO₃. We find no evidence for extensive hydrogen incorporation across a broad range of samples, including both superconducting and non-superconducting films. Theoretical calculations indicate that hydrogen incorporation is broadly energetically unfavorable in these systems, supporting our conclusion that extensive hydrogen incorporation is not generally required to achieve a superconducting state in layered square-planar nickelates. 

Interfacial behavior of quantum materials leads to emergent phenomena such as quantum phase transitions and metastable functional phases. Probes for in situ and real time surface-sensitive characterization are critical for control during epitaxial synthesis of heterostructures. Termination-switching in complex oxides has been studied using a variety of probes, often ex situ; however, direct in situ observation of this phenomena during growth is rare. To address this, we establish in situ and real time Auger electron spectroscopy for pulsed laser deposition with reflection high energy electron diffraction, providing structural and compositional surface information during film deposition. Using this capability, we show the direct observation and control of surface termination in heterostructures of SrTiO3 and SrRuO3. Density-functional-theory calculations capture the energetics and stability of the observed structures, elucidating their electronic behavior. This demonstrates an exciting approach to monitor and control the composition of materials at the atomic scale for control over emergent phenomena and potential applications. 

Abstract Vapor‐pressure mismatched materials such as transition metal chalcogenides have emerged as electronic, photonic, and quantum materials with scientific and technological importance. However, epitaxial growth of vapor‐pressure mismatched materials are challenging due to differences in the reactivity, sticking coefficient, and surface adatom mobility of the mismatched species constituting the material, especially sulfur containing compounds. Here, a novel approach is reported to grow chalcogenides—hybrid pulsed laser deposition—wherein an organosulfur precursor is used as a sulfur source in conjunction with pulsed laser deposition to regulate the stoichiometry of the deposited films. Epitaxial or textured thin films of sulfides with variety of structure and chemistry such as alkaline metal chalcogenides, main group chalcogenides, transition metal chalcogenides, and chalcogenide perovskites are demonstrated, and structural characterization reveal improvement in thin film crystallinity, and surface and interface roughness compared to the state‐of‐the‐art. The growth method can be broadened to other vapor‐pressure mismatched chalcogenides such as selenides and tellurides. This work opens up opportunities for broader epitaxial growth of chalcogenides, especially sulfide‐based thin film technological applications. 

Abstract As one of the most fundamental physical phenomena, charge density wave (CDW) order predominantly occurs in metallic systems such as quasi‐1D metals, doped cuprates, and transition metal dichalcogenides, where it is well understood in terms of Fermi surface nesting and electron–phonon coupling mechanisms. On the other hand, CDW phenomena in semiconducting systems, particularly at the low carrier concentration limit, are less common and feature intricate characteristics, which often necessitate the exploration of novel mechanisms, such as electron–hole coupling or Mott physics, to explain. In this study, an approach combining electrical transport, synchrotron X‐ray diffraction, and density‐functional theory calculations is used to investigate CDW order and a series of hysteretic phase transitions in a diluted‐band semiconductor, BaTiS₃. These experimental and theoretical findings suggest that the observed CDW order and phase transitions in BaTiS₃may be attributed to both electron–phonon coupling and non‐negligible electron–electron interactions in the system. This work highlights BaTiS₃as a unique platform to explore CDW physics and novel electronic phases in the dilute filling limit and opens new opportunities for developing novel electronic devices.