Phase Noise and Frequency Stability of Very-High Frequency Silicon Nanowire Nanomechanical Resonators

We report measurements and analyses of noise characteristics of very-high frequency (VHF) silicon nanowire (SiNW) nanoelectromechanical systems (NEMS). VHF SiNW resonators vibrating at ~200MHz typically have displacement sensitivity of ~5fm/Hz
^1/2
and force sensitivity of 50~250aN/Hz
^½
, set by thermomechanical fluctuations. They have ~1nm critical amplitude and intrinsic dynamic range of 90~110 dB. Amplifier noise and resistor thermal noise dominate the resonance detection, resulting in in compromised displacement noise floor (typically ≥30fm/Hz
^½
), dynamic range (reduced to 70~90dB), and phase noise (≥20~30dB degradation). We develop SiNW-NEMS-based phase-locking techniques to investigate the phase noise and frequency stability performance. Frequency stability of ~0.1ppm and 71 resonant mass sensitivity of ~10zg(1zg=10
^-21
g) have been achieved.