Step-Edge Epitaxy for Borophene Growth on Insulators

Borophene, the two-dimensional (2D) single-layer boron, has drawn tremendous attention due to its unique structures and intriguing properties. The state-of-art synthesis methodology employs the use of metal substrates that provides strong binding with borophene atoms, stabilizing two-dimensional structure and enabling the growth of various borophene phases. However, the strong borophene adhesion to metal surfaces[1] prevents subsequent exfoliation and therefore hinders stand-alone characterization and practical application. On the other hand, the weak-interacting substrates that should enable post-growth exfoliation do not provide sufficient areal interaction to enable 2D growth resulting in a significant nucleation barrier. Following our recent work on the lateral nature of the 2D epitaxy[2] we investigate the possibility of borophene growth stabilization through dimensionality reduction on the nucleation stage. Using ab initio calculations of the epitaxial borophene growth on the h-BN surface we propose a novel growth methodology near naturally present 1D-defects.[3] We demonstrate an order of magnitude reduction in the nucleation barrier due to covalent bonding to the exposed substrate while maintaining minimal areal adhesion. This approach not only exemplifies the importance of the lateral epitaxy mechanism in the growth of 2D materials but also provides a practical approach to the synthesis of novel nanomaterials.<br/>[1] Liu, X.; Wang, L.; Yakobson, B. I.; Hersam, M. C. Nanoscale Probing of Image-Potential States and Electron Transfer Doping in Borophene Polymorphs. Nano Lett. 2021, 21 (2), 1169–1174.<br/>[2] Bets, K. V.; Gupta, N.; Yakobson, B. I. How the Complementarity at Vicinal Steps Enables Growth of 2D Monocrystals. Nano Lett. 2019, 19, 2027–2031.<br/>[3] Ruan, Q.; Wang, L.; Bets, K. V.; Yakobson, B. I.; Step-Edge Epitaxy for Borophene Growth on Insulators, ACS Nano, just accepted.