Study on the noise of silicon capacitive resonant mass sensors in ambient atmosphere

This article reports on the resolution of mass detection by optical and capacitive methods in ambient atmosphere using very thin single-crystalline silicon microcantilevers. The detectable minimum mass by optical sensing increases slightly with decreasing cantilever size due to temperature fluctuation noise. Using capacitive detection, a detectable minimum mass of below 1×10^-14 g can be obtained using cantilevers with resonance frequencies of 78–80 kHz. From an experimental comparison, we find that the detectable minimum mass by capacitive detection is slightly smaller than that obtained by optical detection using a cantilever with resonant frequency of 78 kHz. Using theoretical modeling and experimental results relevant to gas adsorption-desorption to the sensor surface, it is found that the adsorption-desorption noise by gases with infinitesimal partial pressure in the air surrounding a cantilever significantly influences the resonance frequency fluctuation of the cantilever in the high resonance frequency region.