Electronic stripes and transport properties in borophene heterostructures

Abstract

We performed a theoretical investigation of the structural and electronic properties of (i) pristine, and (ii) superlattice structures of borophene. In (i), by combining first-principles calculations, based on the density functional theory (DFT), and simulations of the X-ray Absorption Near-Edge Structure (XANES) we present a comprehensive picture connecting the atomic arrangement of borophene and the X-ray absorption spectra. Once we have characterized the electronic properties of the pristine systems, we next examined the electronic confinement effects in 2D borophene superlattices (BSLs) [(ii)]. Here, the BSL structures were made by attaching laterally two different structural phases of borophene. The energetic stability, and the electronic properties of those BSLs were examined based on total energy DFT calculations. We find a highly anisotropic electronic structure, characterized by the electronic confinement effects, and the formation of metallic channels along the superlattices. Combining DFT and the Landauer-Büttiker formalism, we investigate the electronic transport properties in the BSLs. Our results of the transmission probability reveal that the electronic transport is ruled by π or a combination of π and σ transmission channels, depending on the atomic arrangement and periodicity of the superlattices. Finally we show that there is huge magnification on the directional dependence of the electronic transport properties in BSLs, in comparision with the pristine borophene phase. Those findings indicate that BSLs are quite interesting systems in order to design conductive nanoribbons in a 2D platform.

Polymorphism in Post-Dichalcogenide Two-Dimensional Materials

“…The 2D boron polymorphs observed experimentally are all metallic in character, which is consistent with multiple computational studies. ,,,, A potential exception is the α sheet (ν 1/9 ), which Wu et al calculated to be a narrow bandgap semiconductor, but the experimental observation of this structure requires further investigation . In a study by Silvestre et al, the ν 0 structure was found to exhibit a more anisotropic band structure than the ν 1/6 and ν 1/5 structures . Additionally, the authors found that the π* states in the ν 1/6 structure are more localized than in the ν 1/5 structure.…”

“…Furthermore, multiple studies report the coexistence of the ν 1/6 and ν 1/5 structures, attesting to the polymorphism of borophene. ,,, An STM image of a region containing intermixed ν 1/6 and ν 1/5 domains is presented in Figure b. As suggested by Silvestre et al, the formation of periodically alternating domains of the ν 1/6 and ν 1/5 phases could be leveraged to form electronic stripes or transport channels …”

“…Polymorphic Engineering and Functionality: Higher-order materials engineering and functionalities can be enabled by accessing and engineering 2D polymorphs. (f) Right: the self-assembly of lateral “stripes” of 2D borophene polymorphs could lead to nanoscale transport channels . Adapted with permission from ref .…”

“…As suggested by Silvestre et al, the formation of periodically alternating domains of the ν 1/6 and ν 1/5 phases could be leveraged to form electronic stripes or transport channels. 52 In contrast to Ag(111), Vinogradov et al observed only a single a phase of borophene grown via MBE on Ir (111). 71 The proposed structure for their STM observations consists of a HH density of ν = 1/6; however, the HHs are arranged differently from the ν 1/6 polymorph discussed above.…”

“…51 In a study by Silvestre et al, the ν 0 structure was found to exhibit a more anisotropic band structure than the ν 1/6 and ν 1/5 structures. 52 Additionally, the authors found that the π* states in the ν 1/6 structure are more localized than in the ν 1/5 structure. However, the distinctions are subtle, and experimental measurements show that the ν 1/6 and ν 1/5 structures on Ag(111) are electronically similar.…”