Freestanding Honeycomb Research Articles

Diffractive dipolar coupling in non-Bravais plasmonic lattices.

Honeycomb plasmonic lattices are paradigmatic examples of non-Bravais lattices. We experimentally measure surface lattice resonances in effectively free-standing honeycomb lattices composed of silver nanospheres. By combining numerical simulations with analytical methods, we analyze the dispersion relation and the near-field properties of these modes along high symmetry trajectories. We find that our results can be interpreted in terms of dipole-only interactions between the two non-equivalent triangular sublattices, which naturally lead to an asymmetric near-field distribution around the nanospheres. We generalize the interaction between the two sublattices to the case of variable adjacent interparticle distance within the unit cell, highlighting symmetry changes and diffraction degeneracy lifting associated to the transition between Bravais and non-Bravais lattices.

CrAs Monolayer: Low Buckled 2D Half‐Metal Ferromagnet

Ab initio calculations based on density functional theory (DFT) are performed to study the structural, electronic, and magnetic properties of 2D free‐standing honeycomb CrAs. It is shown that CrAs has a low buckled stable structure. Magnetic CrAs has larger buckling than nonmagnetic CrAs. 2D CrAs is a ferromagnetic semiconductor at lattice constant , and above this lattice constant CrAs is a half‐metal ferromagnet. 2D CrAs is shown to be half‐metal ferromagnetic with a magnetic moment of 3.0 μB per unit cell, at equilibrium structure. The orbital of the band is completely empty in the spin‐down state, whereas it is almost occupied in the spin‐up state, and the magnetic moment in the band is mainly dominated by the orbital of Cr. The and orbitals of the band are partially occupied in the spin‐up state and behave like a metal, whereas they are insulators in the spin‐down state. Phonon calculations confirm the thermodynamic stability of 2D CrAs. The ferromagnetic (FM) and antiferromagnetic (AFM) interactions between the Cr atoms reveal that the FM state is more stable than the AFM state of 2D CrAs.

How is Honeycomb Borophene Stabilized on Al(111)?

Because of the electron deficiency, freestanding honeycomb borophene (HB) is predicted to be kinetically unstable. Very recently, the honeycomb phase of two-dimensional boron, nevertheless, has bee...

Band engineering of B2H2 nanoribbons**Project supported by the National Natural Science Foundation of China (Grant Nos. 61888102, 61390501, and 51872284), the CAS Pioneer Hundred Talents Program, the Strategic Priority Research Program of Chinese Academy of Sciences (Grant Nos. XDB30000000 and XDB28000000), the Beijing Nova Program, China (Grant No. Z181100006218023), and the University of Chinese Academy of Sciences.

Freestanding honeycomb borophene is unstable due to the electron-deficiency of boron atoms. B2H2 monolayer, a typical borophene hydride, has been predicted to be structurally stable and attracts great attention. Here, we investigate the electronic structures of B2H2 nanoribbons. Based on first-principles calculations, we have found that all narrow armchair nanoribbons with and without mirror symmetry (ANR-s and ANR-as, respectively) are semiconducting. The energy gap has a relation with the width of the ribbon. When the ribbon is getting wider, the gap disappears. The zigzag ribbons without mirror symmetry (ZNR-as) have the same trend. But the zigzag ribbons with mirror symmetry (ZNR-s) are always metallic. We have also found that the metallic ANR-as and ZNR-s can be switched to semiconducting by applying a tensile strain along the nanoribbon. A gap of 1.10 eV is opened under 16% strain for the 11.0-Å ANR-as. Structural stability under such a large strain has also been confirmed. The flexible band tunability of B2H2 nanoribbon increases its possibility of potential applications in nanodevices.

Honeycomb Boron Allotropes with Dirac Cones: A True Analogue to Graphene.

We propose a series of planar boron allotropes with honeycomb topology and demonstrate that their band structures exhibit Dirac cones at the K point, the same as graphene. In particular, the Dirac point of one honeycomb boron sheet locates precisely on the Fermi level, rendering it as a topologically equivalent material to graphene. Its Fermi velocity (vf) is 6.05 × 105 m/s, close to that of graphene. Although the freestanding honeycomb B allotropes are higher in energy than α-sheet, our calculations show that a metal substrate can greatly stabilize these new allotropes. They are actually more stable than α-sheet sheet on the Ag(111) surface. Furthermore, we find that the honeycomb borons form low-energy nanoribbons that may open gaps or exhibit strong ferromagnetism at the two edges in contrast to the antiferromagnetic coupling of the graphene nanoribbon edges.

Porous Graphene: Functional Free‐Standing Graphene Honeycomb Films (Adv. Funct. Mater. 23/2013)

A scalable and solution-processable strategy called the “on water spreading” method is developed to create free-standing graphene honeycomb films. As reported by Xiaodong Chen and co-workers on page 2972, the free-standing honeycomb films obtained can be easily transferred to the substrates of interest while retaining their original sizes and structures. They exhibit broad spectrum antibacterial activity and enhanced efficiency of photoconversion.

Fabrication of freestanding honeycomb films with through-pore structures via air/water interfacial self-assembly

Highly ordered freestanding honeycomb films with asymmetric through-pore structures were prepared from polystyrene/gold-nanoparticles (PS/AuNPs) nanocomposite at an air/water interface using a one-step interfacial self-assembly method.