| Popis: |
Two-dimensional non-layered materials have attracted considerable attention owing to their potential for innovative applications. Chromium sulfide (Cr2S3) is a ferrimagnetic material with special spin states and thickness-dependent conduction-type transition properties. However, a fundamental understanding of Cr2S3 is limited, and a comprehensive study of its structural properties is essential for practical applications. In this study, facile salt-assisted chemical vapor deposition (CVD) was used to synthesize ultrathin non-van der Waals 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. For the 2D specimen, we studied the transition from a disorder-Cr1/3 layer of R-Cr2S3 to trigonal-Cr2S3, and trigonal-Cr2S3 to monoclinic-Cr3S4; for the quasi-1D specimen, we studied the transition from a disorder-Cr1/3 layer of R-Cr2S3 to monoclinic-Cr3S4 and monoclinic-Cr3S4 to trigonal-Cr5S6. The rearrangement of atoms during the phase transition was driven by the loss of sulfur atoms at elevated temperatures, resulting in increased free energy. The effect of the ratio of (001) plane on the structural transformation temperature was also discussed. A decrease in the ratio of (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. |
