A review on role of tetra-rings in graphene systems and their possible applications

Abstract

Inspired by the success of graphene, various two-dimensional (2D) non-hexagonal graphene allotropes having sp 2 -bonded tetragonal rings in free-standing (hypothetical) form and on different substrates have been proposed recently. These systems have also been fabricated after modifying the topology of graphene by chemical processes. In this review, we would like to indicate the role of tetra-rings and the local symmetry breaking on the structural, electronic and optical properties of the graphene system. First-principles computations have demonstrated that the tetragonal graphene (TG) allotrope exhibits appreciable thermodynamic stability. The band structure of the TG nanoribbons (TGNRs) strongly depends on the size and edge geometry. This fact has been supported by the transport properties of TGNRs. The optical properties and Raman modes of this graphene allotrope have been well explored for characterisation purposes. Recently, a tight-binding model was used to unravel the metal-to-semiconductor transition under the influence of external magnetic fluxes. Even the introduction of transition metal atoms into this non-hexagonal network can control the magnetic response of the TG sheet. Furthermore, the collective effect of B-N doping and confinement effect on the structural and electronic properties of TG systems has been investigated. We also suggest future directions to be explored to make the synthesis of T graphene and its various derivatives/allotropes viable for the verification of theoretical predictions. It is observed that these doped systems act as a potential candidate for carbon monoxide gas sensing and current rectification devices. Therefore, all these experimental, numerical and analytical studies related to non-hexagonal TG systems are extremely important from a basic science point of view as well as for applications in sensing, optoelectronic and photonic devices.

Phononic and electronic features of diamond nanowires

“…Due to confinement, the electronic states become less dispersive in comparison with the bulk diamond. The fully occupied states are extended in an energy interval of 21.24 eV, which is well comparable to the previously reported energy distribution of the occupied states in bulk diamond [15]. In the interval between about -22 to −10 eV below valence band, the band structure of the wire is dominated by the carbon 2s bonding interactions and represents the expected parabolic behavior with k. The higher occupied bands, based on the s-bonding of carbon 2p orbitals, start in about -8 eV at G-point from the top of the valence band.…”

“…Our results show that the closed-shell fully hydrogenated DNWs are non-magnetic materials. However, defects can induce magnetism in carbon allotropes [15]. We found that the local atomic magnetic moment may be induced in the DNWs if there is a free dangling bond on the surface that is not passivated by for example a hydrogen atom.…”

The topology and robustness of two Dirac cones in S-graphene: A tight binding approach

“…structural deformation or chemical functionalizations 4,5 . However, the only dispute that restrict the potential application of graphene in modern opto-electronic devices is its zero band gap nature 6,7 . Afterwards, a plethora of investigations have been performed on graphene in order to tune its band structure [8][9][10] .…”

Dirac Materials in a MatrixWay

“…That gives rise to various important aspects of topological insulators [28]. The SOC effect is negligible for graphene while it is prominent for systems with large atomic number [29][30][31][32][33].…”