Silicon tip arrays with ultrathin amorphous diamond apexes

Silicon (Si) tip emitter arrays with uniform, smooth, and ultrathin (∼2 nm) amorphous diamond $(a-D)$ apexes were fabricated. Aqueous buffer hydrofluoric acid and $H2/Ar$ plasma have been employed to remove the native oxide layer of Si tips, prior to the $a-D$ film deposition. Scanning electron microscopy study showed that uniform $a-D$ coatings were highly localized on the apex of individual Si tips. Study using high-resolution transmission electron microscopy and x-ray energy dispersive spectroscopy confirmed that the $Si/a-D$ junction is free from the oxide interlayer. Field-emission measurements demonstrated that the removal of the native oxide layer and the $a-D$ apex coating are important to stabilize and enhance the electron emission from Si field emitters.