Synthesis and characterization of large-area single-crystal sheets of borophene on various metal surfaces

Borophene, an atomically thin covalently bonded boron sheet, has attracted great attention as a novel quantum material because of its structural tunability and potential utilization in next-generation electronics. Here, we report the synthesis of borophene on various single-crystal substrates and nanometer-scale thick crystallized metal films on sapphire. With real-time feedback from low-energy electron microscopy and diffraction, we have developed a process of enlarging monocrystal borophene domains, by repeated submersion of boron into substrates at high temperature, resurfacing and re-crystallization at low temperature. We demonstrate the synthesis of borophene as faceted micrometer-size monocrystal islands or as full-monolayer sheets. The process is scalable to wafer size; moreover, metallic buffers could be sacrificed, and sapphire substrate reused. Our work opens the door for new experiments and applications.

R. Wu et al., “Large-area single-crystal sheets of borophene on Cu(111) surfaces”, Nature Nanotechnology 14, 44 (2019).
R. Wu, A. Gozar, I. Bozovic, “Large-area borophene sheets on sacrificial Cu(111) films promoted by recrystallization from subsurface boron”, npj Quantum Materials 4, 40 (2019)