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.