48.1: Ultimate Sensing with an Ultrathin Single Crystalline Silicon Resonator

摘要

Miniaturization of resonating sensors is promising method to reduce the thermo-mechanical noise and raise the mass and force sensitivity. Fabrication technique based on SOI (silicon on insulator) wafer was developed for making ultrathin single-crystalline structures down to 20 nm thick. Mechanical Quality factor (Q-factor) of the cantilever decreases with decreasing the thickness due to the energy dissipation on the surface, however heating in Ultra-high vacuum (UHV) make the surface clean in atomic scale, result in dramatic increase of the Q-factor. All measurements were performed in an UHV chamber equipped with a laser Doppler vibrometer. Leaving the cleaned cantilever in UHV, small quantities of molecule adsorbed on the cantilever and lower the Q-factor. These behaviors are measured on both of 170 nm thick Si(100) and 50 nm thick Si(111) cantilevers. Using these ultra-thin resonators, mass change below pico gram and external force loaded on the cantilever are demonstrated.