Single Crystalline Alkaline-Earth Metal Hexaboride One-Dimensional (1D) Nanostructures: Synthesis and Characterization

Abstract

Catalytic material-assisted growth of alkaline-earth metal hexaboride (MB6, M = Sr, Ba) 1D nanostructures was achieved by pyrolysis of diborane (B2H6) over alkaline-earth metal oxide (MO) powders at elevated temperature (∼840−870 °C) and low pressure (∼165 mTorr). The as-synthesized MB6 1D nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Results show that the MB6 nanostructures are single crystalline with the preferred growth direction along [001]. The SrB6 nanowires are ∼20−100 nm in diameter and ∼2−5 μm in length. The BaB6 nanostructures have a rectangular cross section (width ∼20−300 nm) and are ∼5−20 μm in length. The growth of these MB6 nanostructures can be attributed to a nontraditional vapor−solid−liquid (VLS)-like growth mechanism. The as-synthesized MB6 1D nanostructures are promising n-type low-dimensional thermoelectric materials.