Self-Assembly Growth of Single-Crystal Spiral Graphene on Liquid Heterogeneous Substrates
Spiral graphene, characterized by Bernal-stacked layers and unique electronic properties, holds promise for advanced quantum and optoelectronic devices. However, its controlled synthesis remains challenging. Here, we report the self-assembly growth of single-crystal spiral graphene on a liquid heterogeneous substrate via chemical vapor deposition (CVD). A 50-μm-thick Cu foil was placed on a Ni support and heated to 1083 °C, the melting point of pure Cu, ensuring a fully molten Cu layer on solid Ni. Growth proceeded for 30 minutes under optimized conditions. The resulting spiral graphene exhibits a uniform Bernal stacking configuration, as confirmed by transmission electron microscopy and selected-area electron diffraction. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling and isotope-labeling experiments reveal that carbon incorporation occurs predominantly at the spiral step edges, following a self-assembly mechanism driven by the liquid substrate's dynamic surface. Control experiments on solid Cu-Ni alloys yield no spiral morphology, underscoring the critical role of the liquid phase. The liquid heterogeneous substrate facilitates rapid carbon diffusion and step-edge attachment, enabling the growth of high-quality single-crystal spirals with controlled layer number. This work provides a scalable route to synthesize spiral graphene with tailored stacking, advancing its application in twistronics and high-performance electronics.