Efficient internal electrostatic transduction of the 41st radial mode of a ring resonator

This paper reports internal electrostatic transduction of the 41^st radial bulk-mode of a ring resonator at 2.75 GHz with a quality factor of 7200 in air. The transducer electrodes are integrated within the vibrating structure in a dense serpentine pattern and strategically placed on the nodal lines to excite the 41^st order bulk radial mode. The serpentine dielectric transduction results in a low motional resistance of 475 ¿ detected by direct two-port measurements. This resonator is fabricated by a double nanogap process, where 30 nm Si₃N₄ sidewall layers are formed using a combination of optically defined trenches and deposition of a high-¿ dielectric followed by a doped polysilicon layer.