Periodic Superlattice Modulation of Monolayer Borophene by Adsorption of Boron Clusters.

Elemental boron exhibits remarkable polymorphism and strong substrate dependence in phase formation due to its intrinsic electron deficiency and highly delocalized bonding nature. These unique characteristics pose significant chance for the controlled synthesis of well-defined boron-based phases through substrates engineering. In this study, we demonstrate the structure modulation of monolayer borophene (MLB) with atomic precision by the adsorption of small boron clusters on Cu(100). Through combined scanning tunneling microscopy (STM) and first-principles calculations, we identify these small clusters as B7 and reveal their non-close-packed selective adsorption behaviors, which templates the formation of distinct boron cluster chain configurations. The strong interfacial coupling between B7 clusters and the MLB induces spontaneous migration of boron atoms from dislocation sites, leading to dynamic and periodic modulation of the boron superlattice in MLB. Our work establishes a novel paradigm for the bottom-up construction of low-dimensional boron phases and realizes the periodic superlattice modulation of MLB through adsorption of boron clusters, providing new insight into fabricating polymorphs of borophene beyond the choice of substrates.