  We report actuation and detection of gigahertz-range resonance frequencies in
nano-crystalline diamond mechanical resonators. High order transverse vibration
modes are measured in coupled-beam resonators exhibiting frequencies up to
1.441 GHz. The cantilever-array design of the resonators translates the
gigahertz-range resonant motion of micron-long cantilever elements to the
displacement of the central supporting structure. Use of nano-crystalline
diamond further increases the frequency compared to single crystal silicon by a
factor of three. High clamping losses usually associated with micron-sized
straight beams are suppressed in the periodic geometry of our resonators,
allowing for high quality factors exceeding 20,000 above 500 MHz.
