Large-area, vertical, periodic silicon nanowire (SiNW) arrays on Si(100) substrates were fabricated by nanosphere lithography and metal-assisted catalytic etching. Immersion in KOH solution uniformly reduced the diameter of SiNWs, enabling the diameter to be tuned from 60 to 150 nm. The etching rates of SiNW in 20 wt% KOH solution at different temperatures were measured, and the activation energy was calculated from Anhenius plots to be about 0.6 eV. The field emission properties were improved by reducing the diameter of the SiNWs. Excellent field emission properties of the SiNW arrays were found: they had a turn-on field of 4 V mu m(-1) and a field enhancement factor of 3821. The excellent field emission characteristics are attributed to the vertically well-aligned, high aspect ratio and highly ordered arrangement of the single crystalline SiNW field emitters. (C) 2013 The Electrochemical Society. All rights reserved.