Theory of Epitaxial Growth of Borophene on Layered Electride: Thermodynamic Stability and Kinetic Pathway

TL;DR

This study uses first-principles calculations to demonstrate that layered electrides like Mg2O can serve as effective substrates for the epitaxial growth of stable, electronically weakly perturbed honeycomb borophene, offering a promising alternative to metal substrates.

Contribution

It introduces layered electrides as novel substrates for epitaxial growth of 2D materials, specifically demonstrating the thermodynamic and kinetic feasibility for borophene on Mg2O.

Findings

Thermodynamically stable h-borophene on Mg2O confirmed

Kinetic pathways favor 2D growth mode

Weak substrate perturbation of borophene band structure

Abstract

Based on first-principles calculations, we propose that a layered electride Mg2O can serve as an effective substrate, in place of metal substrate, to grow honeycomb borophene (h-borophene). We first confirm the thermodynamic stability of h-B@Mg2O heterostructure by energetics analysis and dynamic stability by absence of imaginary frequency in phonon spectra. Then, kinetically, we identify the atomistic pathways for a preferred 2D growth mode over 3D growth, and reveal a growth transition from 2D compact islands to h-borophene at ~13-atom cluster size, indicating the feasibility of epitaxial growth of h-borophene on Mg2O. The h-borophene is found to be stabilized by nearly one electron transfer from Mg2O to h-borophene based on the Bader charge analysis. Moreover, the intrinsic band structure of the free-standing h-borophene is only weakly perturbed by the Mg2O substrate, a significant advantage over metal substrate. We envision that layered electrides provide an attractive family of substrates for epitaxial growth of a range of 2D materials that can otherwise only be grown on undesirable metal substrates.