Controllable Synthesis of Se Microwires and Mixed-Dimensional Se/MoS2 Vertical Heterostructures for Nonlinear Optical Applications

Selenium (Se), as a typical elemental semiconductor, has garnered significant attention due to its excellent carrier mobility, outstanding photoconductivity, and broad spectral response. However, Se micro- and nanostructures exhibit inherently low nonlinear optical coefficients, necessitating substantial enhancement of their nonlinear optical properties. In this study, trigonal Se (t-Se) microwires (MWs) and t-Se/MoS 2 mixed-dimensional vertical heterostructures are synthesized using the atmospheric pressure vapor phase deposition method. the influence of precursor concentration on the growth of t-Se MWs is systematically investigated, and computational fluid dynamics simulations are employed to elucidate the growth mechanism. Open-aperture Z-scan measurements reveal that the nonlinear optical properties of t-Se/MoS 2 mixed-dimensional vertical heterostructures are significantly enhanced compared to those of t-Se MWs and monolayer MoS 2 nanosheets. First-principles calculations based on density functional theory, along with surface potential measurements indicate that effective charge transfer across the interfaces of the vertical heterostructures is critical for enhancing their nonlinear optical properties. This study provides valuable insights into the development of next-generation nonlinear optical materials and advanced devices.