We report the discovery of vertically aligned nano-scale diamond tips grown on the rugged polycrystalline diamond/Si substrates in a planar microwave plasma enhanced chemical vapor deposition system. The diamond nanotips exhibit three different morphologies (C-, cone-, and rod-like-shape) that can be monitored by varying substrate temperature and bias voltage. Experimental results indicate that the rod-like nanotips exhibit the best diamond quality, C-shape nanotips the second best, and the cone-shape nanotips the worst. (c) 2005 Elsevier B.V. All rights reserved.