Carbon nanotip arrays were prepared from carbon films deposited on silicon by plasma-enhanced hot filament chemical vapor deposition using CH4, NH3 and H-2 as reaction gases. The carbon films and arrays were investigated by atomic force microscopy, scanning electron microscopy and micro-Raman spectrometry. The results indicate that the formation of the carbon nanotip arrays greatly depends on the etchant gas ratio of NH3 to H-2. The theory related to plasma and sputtering was applied to explain the formation of the carbon nanotip arrays under different gas ratios. (c) 2006 Elsevier B.V. All rights reserved.