Oriented Spiral Growth of Two-Dimensional Materials

Abstract

Two-dimensional (2D) spiral growth is crucial for scalable moiré superlattices, yet controlled large-area synthesis remains an outstanding challenge. Here, we report a rational epitaxial strategy for synthesizing oriented spiral WS2 films on a-plane sapphire, where unidirectionally aligned R-stacked domains serve as templates and substrate tilting acts as the key trigger for spiral growth. Comprehensive characterization confirms high density, identical crystallographic orientation, zero interlayer twist, well-defined R-stacking, and excellent crystalline quality across these structures. We propose a two-stage growth model: dual-coupling-guided formation of aligned R-stacked domains transitions into a dual-mode process for simultaneous lateral coalescence and vertical screw-dislocation-driven growth. The unique configuration of these oriented-spiral films endows photodetectors with superior performance and an extended spectral response. Our work represents a significant advance in 2D spiral materials, establishing a key step toward robust and scalable twistronics.