Epitaxy Growth of Robust Mono‐Oriented Rhombohedral NbSe2 Ribbons on c‐Plane Sapphire

Developing two‐dimensional (2D) transition metal dichalcogenides (TMDs) that possess uniform crystal orientation and controlled interlayer stacking is essential for next‐generation electronic and quantum devices. However, precise control over both lattice alignment and stacking polytype in materials like NbSe2 remains challenging, primarily due to the small energy difference favoring the hexagonal (H)‐stacked phase and the significant lattice mismatch with conventional substrates. Here, we demonstrate the successful growth of mono‐oriented rhombohedral‐stacked (R‐stacked) NbSe2 ribbons on c‐plane sapphire substrates via step‐guided epitaxy. This approach utilizes the interaction between atomic steps on the sapphire surface and the NbSe2 layers: the steps control the orientation and stacking of the NbSe2 layers. Combined experimental and theoretical analyses reveal that these atomic steps simultaneously guide unidirectional alignment and stabilize the R‐stacking configuration. The synthesized NbSe2 ribbons exhibit promising superconducting properties, with a superconducting transition temperature of 5.6 K and a residual resistance ratio of 4.5. This work paves the way for large‐scale integration of single‐crystal R‐stacked NbSe2 ribbons, holding immense potential for future applications in superconducting electronics and beyond.