Metal-like single crystalline boron nanotubes: synthesis and in situ study on electric transport and field emission properties

Unveiling the Atomic Structure of Single‐Wall Boron Nanotubes

“…Several models for boron sheets and nanotubes (BNTs) with different underlying lattice structures have been proposed [8][9][10][11][12][13] and first successes in growing pure BNTs were reported. [14][15][16] In contrast to carbon nanotubes, which can be either semiconducting or metallic depending on their diameter and chiralities, BNTs are predicted to be metallic only [8][9][10] and highly conductive. 17,18 For small-diameter BNTs related to the α-sheet (diameter < 1.7 nm), some density functional theory (DFT) calculations predict that the nanotubes are semiconducting due to a curvature-induced out-of-plane buckling of certain atoms.…”

“…Recently Liu et al reported conductivity measurements on large-diameter (10 to 40 nm) multi-walled BNTs which seem to confirm this prediction. 15 Besides the metallic sheets and nanotubes there is a growing body of literature on semi-conducting boron nanostructures that are probably related to the known bulk crystal structures. [22][23][24][25][26] These developments indicate the rise of a very promising branch of nanoscience based on boron nanostructures.…”

Semimetallic Two-Dimensional Boron Allotrope with Massless Dirac Fermions

“…While at least 16 forms of boron (some of which were probably impurity-stabilized) have been reported, the existence as pure polymorphs of boron has been established for the α rhombohedral, β rhombohedral, two tetragonal phases, and the recently discovered orthorhombic highpressure partially ionic γ phase [2]. Boron has been investigated both theoretically and experimentally as bulk boron, nanotubes, clusters, quasi planar, monolayer, and bilayer sheets [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Novel boron nanobelts or nanowires have been successfully synthesized [13,14], and experimentally shown to be semimetals or narrow-gap semiconductors, but the exact atomic structures are still not fully resolved [14].…”

“…The extension to 2D structure prediction has been implemented and is now available in the uspex code. In these calculations, initial structures are randomly produced using plane group symmetry with a user-defined initial thickness (the energetic stability is sensitive to the constraint of thickness; we want to study the monolayer and bilayer 2D structures mostly, according to the experimental evidence for the spacing (∼ 3.2Å) between two adjacent layers of multiwalled boron nanotubes [15], the initial thickness was set to 3Å, and allowed to change during relaxation), and all newly produced structures are relaxed, and relaxed energies are used for selecting structures as parents for the new generation of structures (produced by well-designed variation operators, such as heredity and softmutation). The target is to find the most stable 2D structures.…”

Elasticity, Flexibility, and Ideal Strength of Borophenes

“…Since the advent of graphene, 2 twodimensional (2D) materials that are one or several atoms thick reign the current field of materials research. As boron has demonstrated striking similarity to carbon, forming planar clusters 1,[3][4][5][6][7][8] , cage-like fullerences [9][10][11][12][13][14][15] and 1D nanotubes 7,[16][17][18][19][20][21] , extensive theoretical efforts have been devoted to exploring graphene analogues of boron-borophenes [22][23][24][25][26] . Unlike graphene or hexagonal boron nitride (h-BN) that have exclusively stable honeycomb lattice, the borophene is predicted to be polymorphic 27 with numerous states near the ground-state energy line, due to a highly variable network of hollow hexagons (HHs) in a reference triangular lattice.…”