Anisotropic etching of microscale β-FeSi2 particles: Formation, mechanism, and quantum confinement of β-FeSi2 nanowhiskers

Needle-shaped β-FeSi2 nanowhiskers with diameters of 1–5 nm and lengths of 20–100 nm are produced by chemical etching of β-FeSi2 powders with microscale particles. The nanowhiskers mainly exhibit a <400> growth direction due to the anisotropic etching following the lowest etching rate of the Fe atomic facets. The absorbance spectra show that the energy gap of the β-FeSi2 nanowhiskers increases from 0.81 (bulk) to 0.94 eV, demonstrating distinct quantum size effect.