The structure of porous 2D boron crystals

TL;DR

This paper predicts new porous 2D boron structures with unique coordination and electronic properties, including a semimetallic borophene that can become semiconducting through lattice expansion, broadening potential applications.

Contribution

It introduces a new class of porous borophenes with smaller atomic densities and explores their electronic properties, including a transition from metallic to semiconducting behavior.

Findings

Porous borophenes with 5-coordinated boron atoms are predicted.

A semimetallic borophene can become a semiconductor with a 0.3 eV gap upon lattice expansion.

Lattice expansion of 10% induces a significant electronic transition.

Abstract

In this work, we foresee the structure of a new class of borophenes with smaller 2D densities of atoms than those explored so far for 2D boron crystals. Boron atoms in the porous borophenes tend to be $5$-coordinated in contrast to commonly investigated structures with hexagonal holes for which the number of nearest neighbors of each atom varies from $3$ to $6$. High metallic character is the usual feature of borophenes, however, we have also identified a semimetallic borophene that turns into semiconductor upon unit cell expansion. A $10\%$ increase in lattice constant of this structure gives rise to an energy gap of $0.3\,\textnormal{eV}$. This extends to semiconductor industry the possible application of 2D boron crystals.