Peculiar bonding associated with atomic doping and hidden honeycombs in borophene

TL;DR

This study reveals that borophene's unique bonding structure, involving atomic doping and hidden honeycombs, enables tunable electronic and thermal properties, confirmed by both experiments and first-principles calculations.

Contribution

It uncovers a peculiar bonding mechanism in borophene with atomic doping and hidden honeycombs, supported by experimental and theoretical evidence.

Findings

B atoms act as electron donors filling sigma bonding states

Weak bonding leads to highly tunable properties via strain

High thermal conductance surpassing graphene

Abstract

Engineering atomic-scale structures allows great manipulation of physical properties and chemical processes for advanced technology. We show that the B atoms deployed at the centers of honeycombs in boron sheets, borophene, behave as nearly perfect electron donors for filling the graphitic $\sigma$ bonding states without forming additional in-plane bonds by first-principles calculations. The dilute electron density distribution owing to the weak bonding surrounding the center atoms provides easier atomic-scale engineering and is highly tunable via in-plane strain, promising for practical applications, such as modulating the extraordinarily high thermal conductance that exceeds the reported value in graphene. The hidden honeycomb bonding structure suggests an unusual energy sequence of core electrons that has been verified by our high-resolution core-level photoelectron spectroscopy measurements. With the experimental and theoretical evidence, we demonstrate that borophene exhibits a peculiar bonding structure and is distinctive among two-dimensional materials.