Micromachining of ultrananocrystalline diamond

Ultrananocrystalline diamond (UNCD) with grain sizes in the range of 2 - 5 nm is produced using a microwave plasma chemical vapor deposition process with argon-rich C 60 or CH 4 plasmas. This material has excellent mechanical properties: high hardness and Young modulus, and an extremely low friction coefficient (approximately 0.01). It is resistant to chemical attack, and is potentially biocompatible. These properties make UNCD a very good candidate for a diamond-based microelectromechanical systems (MEMS) technology. We report on the micromachinability of this material by selective seeding, selective growth and reactive ion etching, in conjunction with SiO 2 sacrificial layers for fabricating 3-D structures with freestanding or movable parts. These micromachining techniques are used to develop a totally UNCD-made turbine as a demonstration for UNCD-based MEMS.