Growing and nanomanipulating heterostructures of α-bismuthene in a nearly isolated state

The growth of vertical heterostructures, which incorporate bismuthene with minimal coupling to adjacent materials, is pursued to fully exploit the exceptional properties intrinsic to the 2D allotropic forms of bismuth. Here, the growth of vertical heterostructures of ultrathin α-bismuthene and one-atom-thick layers of hexagonal boron nitride (h-BN) supported on Rh(110) surfaces is reported. Scanning tunneling microscopy (STM) characterization shows that the sample morphology is dominated by the presence of ultrathin α-bismuthene islands, with a lower thickness limit of a paired bilayer, randomly scattered over the h-BN surface. Unlike previous studies on heterostructures combining α-bismuthene with different 2D materials, which only allowed specific relative angles between the atomic lattices of both constituents, the Bi structures grown here can adopt any in-plane orientation relative to the underlying h-BN/Rh(110) surface, although certain twist angles are preferred. The greater rotational variety found in this study suggests a weaker interaction between bismuthene and h-BN, meaning that these islands could be the most weakly coupled 2D Bi nanocrystals to a substrate reported to date. Additionally, in pursuit of precise control over the spatial distribution of the islands on the h-BN/Rh(110) surface, they have been nanomanipulated using the STM tip.