Field emission from a periodic amorphous silicon pillar array fabricated by modified nanosphere lithography.

We prepare an array of amorphous silicon nanopillars by using a modified nanosphere lithography method. The fabrication process includes three steps: (1) 70 nm thick a-Si film was deposited on a crystalline silicon substrate; (2) the substrate was coated with a monolayer of polystyrene (PS) spheres to form an ordered structure on the a-Si thin film surface; (3) the sample was etched by reactive ion etching to produce the amorphous silicon pillar array. The results of field emission measurements show a low turn-on electrical field of about 4.5 V microm(-1) at a current density of 10 microA cm(-2). A relatively high current density exceeding 0.2 mA cm(-2) at 9 V microm(-1) was also obtained. The field enhancement factor is calculated to be about 1240 according to the Fowler-Nordheim (FN) relationship. The good field emission characteristics are attributed to the geometrical morphology, crystal structure and the high density of the field emitter of the silicon nanopillar.