Capacitive resonant mass sensor with frequency demodulation detection based on resonant circuit

In this letter, capacitive mass sensing with a 250-nm-thick single-crystalline silicon cantilever is investigated. The mass sensor employs the frequency modulation detection method using an electrical LC oscillator, in which the capacitance of the sensor serves as the component of the oscillator. The displacement noise of the demonstrated capacitive detection is 0.05 nm/(Hz)(0.5), which is equivalent to the capacitance change of 2.4x10(-21) F. It is experimentally shown that the capacitive detection is less affected to temperature fluctuation noise than optical detection. The detectable minimum mass of 1x10(-14) g is achieved using capacitive detection in ambient atmosphere. (c) 2006 American Institute of Physics.