Novel dDesign of Epitaxial Quasi-2D Bi₂O₂(S, Se)

Since the discovery of graphene, the field of two-dimensional materials (2DMs) has emerged prominently and captivated researchers. This is primarily due to their exceptional characteristics, such as tunable bandgaps, distinctive planar structures, and high thermal and electrical conductivity. Moreover, these properties remain consistent even at atomic-scale thickness. Among the diverse range of 2DMs, bismuth oxychalcogenides (Bi₂O₂X, where X = S, Se, Te) have garnered significant attention in recent years due to their high electron mobility, air stability, and excellent photoelectric properties. Based on this foundation, bismuth oxychalcogenides are also considered candidates for the next generation of semiconductor materials. Therefore, precise control over the properties of these novel quasi-2D materials is crucial for practical applications. In this study, we aim to synthesize epitaxial thin films of Bi₂O₂(S, Se) with a compositional gradient of sulfur (S) and selenium (Se). Bi₂O₂S and Bi₂O₂Se exhibit strikingly similar structures, facilitating meticulous control over their blending ratios by tuning deposition proportions. This approach allows the modulation of electronic behaviors and crystal structures through variations in elemental composition. Our findings reveal that the lattice constants, band gaps, and electrical properties of the thin film exhibit nuanced shifts dependent on varying composition concentrations. Further, compared to the Bi₂O₂Se mobility of 148.7 cm²/Vs, we have observed an increase in mobility to 191.1 cm²/Vs in the Bi₂O₂(S, Se) compound. The outcome is expected to exhibit superior performance in electronic devices. With these efforts, this work not only establishes a pathway toward the development of novel designs for 2D materials but also holds the potential to significantly impact the field of materials science and engineering, opening new avenues for more applications in the future.