Uniform amorphous tungsten cone arrays in high density were fabricated by Ar+ reduction etching of WO3 nanowire film. The etching process was performed in the analysis chamber of an X-ray photoelectron spectroscopy (XPS) system. SEM and TEM results revealed that the tip radius of the etched cones was 10 nm, and the cones were amorphous with a high aspect ratio of over 250. XPS analysis proved the cones to be metallic tungsten. In the aspect of field-emission property, the tungsten cone arrays had a lower turn-on field of 3 MV m (1) compared with 5 MV m (1) of the as-grown original WO3 nanowire film. (c) 2009 Elsevier B.V. All rights reserved.