Optical Transduction for Vertical Nanowire Resonators

We describe an optical transduction mechanism to measure the flexural mode vibrations of vertically aligned nanowires on a flat substrate with high sensitivity, linearity, and ease of implementation. We demonstrate that the light reflected from the substrate when a laser beam strikes it parallel to the nanowires is modulated proportionally to their vibration, so that measuring such modulation provides a highly efficient resonance readout. This mechanism is applicable to single nanowires or arrays without specific requirements regarding their geometry or array pattern, and no fabrication process besides the nanowire generation is required. We show how to optimize the performance of this mechanism by characterizing the split flexural modes of vertical silicon nanowires in their full dynamic range and up to the fifth mode order. The presented transduction approach is relevant for any application of nanowire resonators, particularly for integrating nanomechanical sensing in functional substrates based on vertical nanowires for biological applications.
This work was supported by the ERC CoG Grant 681275 “LIQUIDMASS” and by the Spanish Science, Innovation and Universities Ministry through project “EXOFLUX” (ref: PGC2018-101762-B-I00). We acknowledge the service from the Micro and Nanofabrication Laboratory at IMN-CNM, funded by the Comunidad de Madrid (Project S2018/NMT4291 TEC2SPACE) and by MINECO (Project CSIC13-4E1794 with support from FEDER, FSE). E.G.S. acknowledges financial support by Fundacion General CSIC (Programa ́ ComFuturo), as well as Marie-Sklodowska Curie Actions (H2020-MSCA-IF-2015) under NOMBIS project (703354). We acknowledge partial open access support by CSIC through URICI initiative.