Field emission properties of carbon coated Si nanocone arrays on porous silicon

Silicon nanocone arrays are formed on porous silicon substrates by plasma etching in a hot filament chemical vapour deposition system. The as-formed Si nanocones were characterized by means of scanning electron microscopy, hi-h resolution transmission electron microscopy, energy dispersive x-ray analysis, and Raman spectroscopy. The results indicate that the nanocone is composed of a silicon core coated with a thin amorphous carbon (a-C) layer produced by carbon-bearing plasma etching. Plasma etching is a key factor in the formation of the nanocone arrays, while re-condensation of evaporated silicon atoms on the tip of the as-etched cone also occurs. Field emission measurements show that the a-C coating can effectively enhance the field emission ability of the nanocone arrays due to the decrease of the surface work function from 4.15 to 2.37 eV.