Modulating the electronic and magnetic properties of bilayer borophene via transition metal atoms intercalation: from metal to half metal and semiconductor

Abstract

Borophene, a two-dimensional monolayer made of boron atoms, has attracted wide attention due to its appealing properties. Great efforts have been devoted to fine tuning its electronic and magnetic properties for desired applications. Herein, we theoretically investigate the versatile electronic and magnetic properties of bilayer borophene (BLB) intercalated by 3d transition metal (TM) atoms, TM@BLBs (TM = Ti-Fe), using ab initio calculations. Four allotropes of AA-stacking (α -, β-, β- and χ -) BLBs with different intercalation concentrations of TM atoms are considered. Our results show that the TM atoms are strongly bonded to the borophene layers with fairly large binding energies, around 6.31 ∼ 15.44 eV per TM atom. The BLBs with Cr and Mn intercalation have robust ferromagnetism, while for the systems decorated with Fe atoms, fruitful magnetic properties, such as nonmagnetic, ferromagnetic or antiferromagnetic, are identified. In particular, the α- and β-BLBs intercalated by Mn or Fe atom can be transformed into a semiconductor, half metal or graphene-like semimetal. Moreover, some heavily doped TM@BLBs expose high Curie temperatures above room temperature. The attractive properties of TM@BLBs entail an efficient way to modulate the electronic and magnetic properties of borophene sheets for advanced applications.

Room-Temperature Ferromagnetism in Transition Metal Embedded Borophene Nanosheets

“…The χ 3 borophene characterizes in a planar structure with periodic hexagon boron vacancies . As a start, we investigate the adsorption behavior of a single Cr atom on χ 3 borophene and find the hexagon boron vacancy is the only stable adsorption site, consistent with previous studies. − Initial adsorptions on other sites are automatically relaxed to the hexagon boron vacancy after fully structural optimization. Because of the relatively low diffusion barriers (the vertical and lateral diffusion barrier is 0.59 and 0.77 eV, respectively; see Figure S1), transition metal adatoms are expected to diffuse easily between different hexagon boron vacancies on borophene surface.…”

“…As an analogue of graphene, borophene has been successfully grown in experiment. − However, owing to the electron deficiency of boron, 2D borophene exhibits much richer bonding chemistry and possesses several tens of allotropes as a result of different concentrations and locations of hexagon boron vacancies, leading to versatile mechanical, electronic, and optical properties. − Unfortunately, all borophenes are intrinsically nonmagnetic, which severely hinders their application in spintronics. Note previous works suggest to introduce ordered spin in borophenes by adsorption of magnetic transition metals (TM); − however, TM adatoms are rather easy to diffuse between different adsorption sites, which would cause serious stability problems in information storage. Inducing stable spin order in borophenes, especially room-temperature ferromagnetism, still challenges the physical chemistry world.…”

Magnetism and perfect spin filtering in pristine MgCl2 nanoribbons modulated by edge modification

“…Half-metallic materials are considered to be ideal for applications in spintronics since they possess completely polarized spin channels that can be accessed independently. Some studies have predicted the existence of the half-metallic state in pristine two-dimensional materials, 10,13–16 but the half-metallic state has been more commonly obtained by means of selective doping, 17–21 the application of an external electric field, 22–26 strain, 27–30 in bilayers, 31–33 nanoribbons, 34–39 and using many other techniques.…”

Prediction of superconductivity in bilayer borophenes

“…Besides, some unique properties appear in few-layer borophenes. For example, the in-plane negative Poisson’s ratios in the monolayer become positive in the layered borophene, while out-of-plane negative Poisson’s ratios are preserved; 57 the electronic and magnetic properties of BL borophene can be modulated by transition metal atoms intercalation; 58 P6̄-boron possesses a topologically nontrivial Dirac nodal line, which is protected by the mirror reflection symmetry. 59 BL-α borophene has been synthesized recently and it has a higher crystallinity and local work function, but it can’t maintain a free-standing structure without the supportive substrate.…”