Twinning in two-dimensional materials and its application to electronic properties

Abstract

Ever since its discovery, graphene has been revolutionizing the field of materials science and engineering, showing promise towards use in a variety of applications. Examples of some of the many remarkable properties of graphene include allowance of the electric field-effect at room temperature [1], high thermal mobility and electronic conductivity [2, 3], and unprecedented high-strength and quantum effects (e.g. the quantum Hall effect and relativistic behavior of carriers) [4]. The discovery of graphene has expanded the area of quantum materials, leading to the discovery of additional 2D materials-such as dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), silicene, germanene, black phosphorene [5, 6]-with similarly-intriguing properties.Despite the inherently-remarkable properties associated with these materials, engineering intervention is still sometimes necessary to achieve certain, otherwise-unattainable properties. For instance, device-driven applications necessitate modification of a candidate material's electronic structure. Probabilistic factors hinder the ability to control these properties, although contemporary engineering techniques-such as doping and strain engineering [7, 8]-have curbed the extent of these probabilistic factors, allowing for the tuning of material properties on demand.Similarly, nanodevices with multiple layers of 2D materials have been developed [9][10][11] in order to expand the envelope of attainable properties. In these devices, the layers weakly interact by van der Waals forces and the atoms form Moiré patterns when subjected to rotations. Interestingly, recent studies have shown that the

Charge-carrier transmission across twins in graphene

“…The calculations reveal that graphene twins open transport gaps depending on the twin geometry up to maximum of 1.15 eV. This value is consistent with band gaps of up to 1.2 eV reported by Rojas et al [22]. As previously reported for grain boundaries [32], we find that localized states arise at dislocation cores in the twin boundaries that introduce peaks near the Fermi level.…”

“…In addition, since the average deformation following twinning may differ from the identity, twinning provides an accommodation mechanism. Graphene twins have been investigated computationally [21,22] by introducing twin boundaries in the graphene lattice ab initio. Arca et al [23] have presented numerical evidence that twinning in fact operates as an accom- modation and relaxation mechanism in graphene, i.e., twins may arise spontaneously in graphene layers containing arrays of dislocations and results in a significant reduction in energy.…”

“…In the present work, we investigate charge-carrier transmission across the twin structures in graphene using the Landauer-Büttiker (LB) formalism [24][25][26] in combination with a tight-binding model [27]. These methods have been combined in multiple works before [5,16,22,28,29]. We verify the approach through selected comparisons with density functional theory (DFT) and nonequilibrium Green's function (NEGF) calculations using the codes SIESTA and TRANSIESTA [30,31].…”

Solvent Mediated Nanoscale Quasi‐Periodic Chirality Reversal in Self‐Assembled Molecular Networks Featuring Mirror Twin Boundaries

“…Such twinned crystals are often observed in a 3D space. [7][8][9][10][11][12] In 2D space, 2D twining has been observed for atomically thin inorganic sheet materials, [13][14][15] and some monolayer molecular crystals also have the feature of twinning. [16][17][18][19] The intermolecular interactions at the domain boundary were most often not the result of an engineering effort, nor did they involve a large intermolecular contact area.…”