Kinetically Confined Sulfurization for Continuous Growth of Layered SnS Films

We present a novel approach for synthesizing continuous, single-phase SnS thin films through the kinetically confined sulfurization of SnO. The process utilizes a chemically inert Al2O3 confinement layer to enable kinetically controlled sulfurization, effectively suppressing surface migration while allowing H2S diffusion. This confinement addresses the discontinuity issues frequently encountered in conventional deposition and sulfurization techniques. The method achieves uniform film coverage at a minimal thickness of 4 nm. Structural and compositional analyses confirm the formation of stoichiometric SnS with high phase purity and a preferred orientation of van der Waals (040) planes parallel to the substrate. Mechanistic studies reveal that sulfurization predominantly initiates at the surface and proceeds inward, with rapid grain boundary diffusion resulting in localized acceleration of the transformation. The Al2O3 layer can be selectively removed without compromising the integrity of the SnS film. This strategy provides a scalable route for the fabrication of high-quality SnS and holds potential for application to other metal chalcogenide systems.