Supertwisted WS₂ spirals synthesized on step-edge non-Euclidean surfaces: Twist angle modulation and optical properties

Twisted two-dimensional (2D) layered materials have attracted significant attention due to their twist angle-related superconductivity and moiré exciton phenomena. In twisted layered materials, supertwisted spirals exhibit multiple layers of continuous twisted structures, which give rise to their unique optoelectronic properties. Previous studies have primarily focused on the influence of conical non-Euclidean surfaces on the growth of twisted spirals, revealing their dominant role in determining the twist angle. However, few studies have systematically analyzed the additional factors influencing the variation of twist angles during the growth of such structures. In this work, we demonstrated the synthesis of supertwisted WS₂ spirals on the edges of WS₂ nanoribbons with nanoparticles, where the twist angle deviates from the theoretical value due to the additional influence of the nanoribbons during growth. Beyond the dominant role of nanoparticles in determining the twist angle of the spirals, we found that larger step heights or contact areas of the nanoribbons lead to larger twist angles. Furthermore, photoluminescence (PL) and Raman spectroscopy revealed the unique optical properties of the twisted spirals. PL spectra exhibited thickness-dependent abnormal variation in luminescence intensity, attributed to the decoupling and recoupling of interlayer interactions, while Raman spectra demonstrated the thickness-dependent and twist angle-dependent variations in the dominant atomic vibrations of interlayer van der Waals (vdW) interactions. These findings not only provide new insights into the regulation of twist angles in twisted spiral structures, but also contribute to a deeper understanding of the optical characteristics of twisted 2D layered materials, paving the way for their potential applications in various fields.