Enhanced Stability and Epitaxial Growth Mechanism of the Honeycomb Borophene Monolayer on a Two-Dimensional Ti<sub>2</sub>C Substrate
Kaiwen Pu, Xianying Dai, Yuyu Bu, Yiwei Guo, Jin Qiu, Jianjun Song, Tianlong Zhao, Tianmin Lei
Abstract
The stability enhancement mechanism of honeycomb borophene on a typical MXene material, known as Ti2C, was investigated systematically by theoretical energetic and kinetic studies. On this basis, the epitaxial growth model has been proposed by comparative total energy calculations of boron adatoms and islands. Our results reveal that the planar honeycomb borophene layer is energetically favorable on a Ti2C substrate with desirable kinetic and thermodynamic stability. Strong substrate-induced interactions, including charge redistribution, orbital hybridization, and covalent bond formation, are crucial factors for enhanced stability. Boron adatoms easily migrate and form clusters along hollow sites on the surface due to the limit of the potential energy surface, resulting in the formation of six-membered boron islands as the local minimum. Adatoms are preferred to bond with dangling bonds at the step edge of clusters, leading to the spread or combination of islands. Our calculating results indicate that Ti2C is a potential substrate for the epitaxial growth of honeycomb borophene, which may provide important insights into searching potential two-dimensional substrates.