22:T437,In this study, facile salt-assisted chemical vapor deposition (CVD) was used to synthesize ultrathin non-van der Waals chromium sulfide (Cr₂S₃) with a thickness of ∼1.9 nm. The structural transformation of as-grown Cr₂S₃ was studied using advanced in situ heating techniques combined with transmission electron microscopy (TEM). Two-dimensional (2D) and quasi-one-dimensional (1D) samples were fabricated to investigate the connection between specific planes and the dynamic behavior of the structural variation. The rearrangement of atoms during the phase transition was driven by the loss of sulfur atoms at elevated temperatures, resulting in increased free energy. A decrease in the ratio of the (001) plane led to an overall increase in surface energy, thus lowering the critical phase transition temperature. Our study provides detailed insight into the mechanism of structural transformation and the critical factors governing transition temperature, thus paving the way for future studies on intriguing Cr-S compounds.23:T45b,Recently, perovskite (PV) oxides with ABO₃ structures have attracted considerable interest from scientists owing to their functionality. In this study, CaFeO_x is introduced to reveal the resistive switching properties and mechanism of oxygen vacancy transition in PV and brownmillerite (BM) structures. BM-CaFeO_2.5 is grown on an Nb-STO conductive substrate epitaxially. CaFeO_x exhibits excellent endurance and reliability. In addition, the CaFeO_x also demonstrates an electroforming-free characteristic and multilevel resistance properties. To construct the switching mechanism, high-resolution transmission electron microscopy is used to observe the topotactic phase change in CaFeO_x . In addition, scanning TEM and electron energy loss spectroscopy show the structural evolution and valence state variation of CaFeO_x after the switching behavior. This study not only reveals the switching mechanism of CaFeO_x , but also provides a PV oxide option for the dielectric material in resistive random-access memory (RRAM) devices.

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