Growth‐Pathway‐Controlled van der Waals Epitaxy of Phase‐Selective Tin Sulfides

ABSTRACT

Controlling crystalline phase and interfacial strain remains a central challenge in van der Waals (vdW) epitaxy for polymorphic two‐dimensional (2D) materials. Tin sulfides represent an ideal platform, yet deterministic phase control and growth‐pathway effects on phase stability and strain accommodation remain unexplored. Here, we demonstrate growth‐pathway‐controlled vdW epitaxy of phase‐selective tin sulfides on WSe ₂ using a two‐zone chemical vapor deposition (CVD) system. Under sulfur‐rich conditions, tin sulfide adopts a hexagonal SnS ₂ structure that shares the trigonal symmetry of WSe ₂ , enabling a unique in‐plane epitaxial alignment despite a large lattice mismatch. Under sulfur‐deficient conditions, tin sulfide stabilizes in orthorhombic SnS, whose symmetry is incompatible with WSe ₂ . As a result, SnS nucleates with multiple energetically comparable epitaxial registries. Direct growth of SnS on WSe ₂ generates substrate‐mediated strain, leading to local lattice distortion and phase evolution from α‐ to β′‐SnS. Through sequential control of the precursor temperature, SnS is grown on a pre‐formed SnS ₂ rather than directly on WSe ₂ . This sequential growth suppresses substrate‐induced strain and yields deformation‐free α‐SnS via a SnS ₂ vdW buffer layer. These findings establish growth‐pathway‐controlled vdW epitaxy as a strategy for decoupling epitaxial alignment from strain accommodation, enabling deterministic phase control and structural integrity in lattice‐mismatched vdW heterostructures.