Capacitive resonant mass sensing using a single-crystalline silicon resonator with an electrical LC oscillator was demonstrated in ambient atmosphere. Using capacitive detection method, the detectable minimum mass of 1× 10-14 g was obtained in the self-oscillation of cantilever with a thickness of 250 nm. The noise amplitude of the sensor output corresponds to a vibration amplitude of 0.05 nm (Hz)0.5 in the frequency domain compared with the actuation signal, which is equivalent to the detectable minimum capacitance variation of 2.4× 10-21 F. Using the capacitive detection method, mass/stress induced resonance frequency shift due to the adsorption of ethanol and moist vapor in a pure N2 gas as a carrier is successfully demonstrated. These results show the high potential of capacitive silicon resonator for high mass/stress-sensitive sensor.
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