Bottom-Up Synthesized B₃N₃-Doped Amorphous Carbon Monolayer

Research on amorphous carbon monolayers (ACMs) has accelerated in recent years, driven by their intriguing structural and electronic properties and the vast potential for applications. To date, ACMs have been mainly synthesized by chemical vapor deposition methods. Here, we present an alternative bottom-up synthesis approach and demonstrate the formation of a B₃N₃-substituted amorphous carbon monolayer (B₃N₃-ACM), thus introducing multiple dopant heteroatoms. In particular, we follow an ultrahigh-vacuum-based on-surface synthesis strategy by using a tailored B₃N₃-functionalized precursor to achieve uniform, large-area B₃N₃-ACMs. The characterization of the on-surface reaction products via low-temperature scanning tunneling microscopy and noncontact atomic force microscopy provides insight into their structure at the atomic scale. The covalent monolayers, formed upon thermal activation of the precursors at high coverage, were transferred onto Si/SiO₂ and a transmission electron microscope grid. Atomically-resolved electron microscope imaging combined with Raman spectroscopy confirmed the freestanding, amorphous monolayer structure of the material, incorporating nanocrystallites in disordered areas. X-ray photoelectron spectroscopy proved the presence of B and N in the 2D material after the transfer. Our on-surface synthesis protocol, combined with the demonstrated transfer abilities, showcases the potential for producing tailored heteroatom-doped amorphous materials using custom-designed molecular precursors and integrating such complex 2D architectures into devices.