Curvature-Induced Raman Anisotropy and Excitonic Resonance Shifts in Scrolled Monolayer MoS₂and WSe₂

Monolayer transition metal dichalcogenides (TMDs) such as MoS₂ and WSe₂ exhibit D₃h point group symmetry, yielding an isotropic out-of-plane A₁′ Raman mode under co-polarized excitation. Here, we report that this isotropy is broken when the monolayers are transformed into quasi-one-dimensional scrolls. The transformation is induced by immersing CVD-grown monolayer TMDs in organic solvents such as ethanol. Upon drying, spontaneous Marangoni-driven forces roll the initially triangular or hexagonal monolayers into filament-like scrolls without any mechanical manipulation. Raman measurements reveal a pronounced polarization dependence of the A₁′ mode in the scrolled structures: its intensity is maximized when the excitation polarization is aligned parallel to the scroll axis and suppressed when perpendicular. The silicon substrate’s Raman signal served as an internal polarization reference to validate the measurement geometry. This emergent anisotropy indicates curvature-induced perturbations to phonon eigenmodes and the local dielectric environment, effectively lowering the crystal symmetry and coupling out-of-plane vibrations to in-plane optical fields. Under 473 nm excitation, monolayer MoS₂ and WSe₂ domains display a distinct 2LA resonance associated with the C exciton, whereas this feature vanishes in the scrolled configurations, suggesting that curvature detunes the C exciton resonance and modifies electron-phonon coupling. To further probe the structure, selected nanoscrolls were transferred onto TEM grids for detailed imaging, complemented by AFM characterization of the scroll morphology.