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

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.