Harnessing Plateau-Rayleigh Instability in GeS Nanowires for Nanoscale Optoelectronic Heterojunctions.

Periodic shell formation in one-dimensional structures is a classical outcome of the Plateau-Rayleigh (P-R) instability, yet its manifestation in van der Waals (vdW) crystals has remained unexplored. Here, we demonstrate P-R instability in GeS vdW nanowires, synthesized by vapor-liquid-solid growth. Under elevated temperatures and continuous precursor supply, GeS nanowires transition from smooth sidewalls to periodic core-shell architectures. A quasi-liquid amorphous surface layer reorganizes into sulfur-rich shells surrounding a crystalline core. By tuning growth duration, both shell diameters and intershell pitches can be systematically controlled, consistent with theoretical predictions. Furthermore, these nanowires define site-specific nanoscale junctions in mixed-dimensional heterostructures. When integrated with monolayer WSe2, GeS shells create localized heterojunctions that drive charge transfer and excitonic modulation. Photoluminescence mapping and spectral analysis reveal exciton redshifts, trion enhancement, and localized quenching. These findings extend P-R instability to vdW materials and establish periodic nanowires as a platform for optoelectronic patterning.