Synthesis of well-aligned boron nanowires and their structural stability under high pressure

Abstract

Owing to its unusual bonding and vast variety of unique crystal structures, boron is one of the most fascinating elements in the periodic table . Here we report the large-scale synthesis of well-ordered boron nanowires and their structural stability at high pressure. Boron nanowires with uniform diameter and length grown vertically on silicon substrates were synthesized by radio-frequency magnetron sputtering with a target of pure boron using argon as the sputtering atmosphere without involvement of templates and catalysts. Detailed characterization by high-resolution transmission electron microscopy and electron diffraction indicates that the boron nanowires are amorphous. Structural stability of the boron nanowires at room temperature has been investigated by means of in situ high-pressure energy-dispersive x-ray powder diffraction using synchrotron radiation in a diamond anvil cell. No crystallization was observed up to a pressure of 103.5 GPa, suggesting that the amorphous structure of boron nanowires is stable under high pressure at ambient temperature.

Free standing double walled boron nanotubes

“…Although the natural phases of bulk boron do not possess laminar structures, recent experimental studies [8] confirmed the existence of quasiplanar clusters of 10-15 B atoms which have been previously predicted by first principle calculations [9]. Furthermore, single walled boron nanotubes (SWBNTs) have also been declared beforehand by Boustani and coworkers [10][11][12][13] which have also been synthesized experimentally [14,15] a few years ago with a radius of nearly 18Å, after the fabrication of crystalline [16] and amorphous [17] boron nanowires with diameters as small as 20 nm. A recent review article about boron nanotubes which may serve as a basic orientation for any reader interested in pure boron chemistry can be found in [18].…”

Recent progress in boron nanomaterials

“…The authors concluded that this process might enable the creation of nanometer-size heterojunctions of a wide variety of one-dimensional (1D) nanostructures [ 103 ]. Since no crystallization was observed up to a pressure of 103.5 GPa for these boron nanowires, the amorphous structure of boron nanowires is concluded as stable under high pressure at ambient temperature [ 104 ]. Here, it should be noted that according to a subsequent report by Wang and Duan [ 105 ], the amorphous structure of boron nanowires made by a similar radio frequency magnetron sputtering method can be converted to a rhombohedral crystalline structure (β-boron) with lattice parameters of a = 10.95 Å and c = 23.82 Å by annealing at 1050 °C under a high vacuum for 3 hours followed by a quench.…”

Synthesis of Pure Boron Single-Wall Nanotubes

“…Boron nanowires have been produced by radio frequency magnetron sputtering. [4][5][6][7][8][9][10] Both amorphous 11 and crystalline 12 boron nanowires were obtained by laser ablation, while chemical vapor deposition produced crystalline boron nanowires. 13 Here we report the synthesis of single-wall boron nanotubes by reaction of BCl 3 with H 2 over an Mg-MCM-41 14 catalyst with parallel, uniformdiameter (36 ( 1 Å) cylindrical pores.…”