Tunable band structures of polycrystalline graphene by external and mismatch strains

Abstract

Lacking a band gap largely limits the application of graphene in electronic devices. Previous study shows that grain boundaries (GBs) in polycrystalline graphene can dramatically alter the electrical properties of graphene. Here, we investigate the band structure of polycrystalline graphene tuned by externally imposed strains and intrinsic mismatch strains at the GB by density functional theory (DFT) calculations. We found that graphene with symmetrical GBs typically has zero band gap even with large uniaxial and biaxial strain. However, some particular asymmetrical GBs can open a band gap in graphene and their band structures can be substantially tuned by external strains. A maximum band gap about 0.19 eV was observed in matched-armchair GB (5, 5) | (3, 7) with a misorientation of θ = 13• when the applied uniaxial strain increases to 9%. Although mismatch strain is inevitable in asymmetrical GBs, it has a small influence on the band gap of polycrystalline graphene.

Floquet Engineering of Multifold Fermions

“…Analogously, we observe the maximum band gap opening up for cases where the original band structure showed the maximal tilt along the (1, 1, 1) direction. This matches Weyl semimetal studies where it has been shown that lifting the degeneracy in a fully centrosymmetric Weyl semimetal is difficult 42 . It has also been shown that tilted Weyl semimetals have a better response to light, and they can support significant photocurrents while centrosymmetric Weyls cannot 43 .…”

Mechanics and Mechanically Tunable Band Gap in Single-Layer Hexagonal Boron-Nitride

“…when the stress component in the transverse direction is fully relaxed to be zero, remains unknown. Furthermore, it is recognized that the presence of defects in graphene can significantly alter the mechanical and electrical properties of graphene [25][26][27][28]; therefore, it is critical to understand how defects affect the properties of h-BN if these defects present in h-BN. In this work, we perform a systematic investigation on several critical mechanical properties of single-layer h-BN, including Young's modulus, the Poisson's ratio, bending rigidity, the mechanical properties of h-BN with antisite defects and the band structure tunability by mechanical strain.…”

The influence of Gaussian strain on sublattice selectivity of impurities in graphene

“…As a matter of fact, the determining factor is the adsorption location, which means that similar features should be seen with impurities that have the same bonding geometry as hydrogen, i.e., top-bonded impurities. It is well known that realistic graphene samples have a multitude of surface effects such as ripples and corrugations [44,45], and that certain defects can modify the electronic structure and the chemical doping of graphene [46][47][48]. While the calculations with hydrogen in this work show a slight decrease in the binding energy of hydrogen between pristine and strained graphene, it is a possibility that other impurities and/or strain profiles could produce enhanced chemical doping.…”