Imparting α-Borophene with High Work Function by Fluorine Adsorption: A First-Principles Investigation

Abstract

Increasing the work function of borophene over a large range is crucial for the development of borophene-based anode materials for highly efficient electronic devices. In this study, the effect of fluorine adsorption on the structures and stabilities, particularly on the work function, of α-borophene (BBP), was systematically investigated via first-principles density functional theory. The calculations indicated that BBP was well-stabilized by fluorine adsorption and the work functions of metallic fluorineadsorbed BBPs (F n -BBPs) sharply increased with increasing fluorine content. Moreover, the work function of F-BBP was close to that of the frequently used anode material Au and even, for other F n -BBPs, higher than that of Pt. Furthermore, we have comprehensively discussed the factors, including substrate deformation, charge transfer, induced dipole moment, and Fermi and vacuum energy levels, affecting the improvement of work function. Particularly, we have demonstrated that the charge redistribution of the substrate induced by the bonding interaction between fluorine and the matrix predominantly contributes to the observed increase in the work function. Additionally, the effect of fluorine adsorption on the increase in the work function of BBP was significantly stronger than that of silicene or graphene. Our results concretely support the fact that F n -BBPs can be extremely attractive anode materials for electronic device applications.

Effects of adatom species on the structure, stability, and work function of adatom-α-borophene nanocomposites

“…S12 and S13, ESI,† respectively). Essentially, the F site can be regarded as a special T site, and thus the adsorption sites of F/BBP and Cl/BBP are in agreement with the reported adsorption positions of the ground state configurations for F/BBP (F site), 39 F(Cl)-adsorbed δ 6 -borophene, 23,72 and χ 3 -borophene (T site). 73 Similarly, the F site is also the most energetically favorable adsorption site for Br/BBP and I/BBP (Fig.…”

“…Among them, Δ h is defined as the lifting height of the NB from the initial position in the pristine BBP plane, which can well describe the deformation degree of NBs for the halogen/BBP systems with only one NB. 39,73 R z and R̄ z were computed according to eqn (2) and (3), respectively.where z h and z l refer to the two z coordinates of the NBs with the farthest distance along the z -axis of M/BBP, m represents the total number of NBs in a 2 × 2 lattice cell, and z m(M/BBP) and z m(BBP) correspond to the z coordinates of the m th NB atom in M/BBP and BBP, respectively.…”

“…Among them, Dh is defined as the lifting height of the NB from the initial position in the pristine BBP plane, which can well describe the deformation degree of NBs for the halogen/BBP systems with only one NB. 39,73 R z and % R z were computed according to eqn (2) and (3), respectively.…”

“…11,20,[30][31][32] Generally, p-and n-type doping aim to increase and decrease the work function of the nanomaterial, respectively. Previous studies focusing on tuning the work function of typical 2D nanomaterials using the atomadsorption method are summarized in Table S1 (ESI †); [33][34][35][36][37][38][39][40][41][42] these studies lay the foundation for the atom-scale design of work function-tunable 2D nanomaterials.…”

“…In addition to 2D nanographene, borophene has emerged as a prominent member of the Xenes family, and thus the work function engineering of borophene has attracted increasing attention. [43][44][45][46][47][48] To date, it has been shown theoretically that H doping can improve the work function of d 6 -borophene from 5.31 eV to 5.88 eV, 23 while F adsorption increases the work function of a-borophene from 4.14 eV to 5.36-7.78 eV, 39 which enhances their prospects as future anode materials. Moreover, studies by Yu et al indicate that Li, 13,36,37 Na, 37 K, 37 and Cs 38 adsorption can reduce the work functions of mono/bilayer aand a 1 -type borophenes, down to a minimum value of 0.11 eV, 38 confirming that these nanocomposites are promising cathode materials for electronic devices.…”