| AVS 54th International Symposium | |
| MEMS and NEMS | Tuesday Sessions |
| Session MN-TuM |
| Session: | Integration and Packaging in MEMS/NEMS |
| Presenter: | B. Ilic, Cornell University |
| Authors: | B. Ilic, Cornell University S. Krylov, Tel Aviv University, Israel M. Kondratovich, Cornell University H.G. Craighead, Cornell University |
| Correspondent: | Click to Email |
Excitation of biologically functional micro and nanomechanical structures using optical fields is a recently emerging arena of research that couples the fields of optics, fluidics, electronics and mechanics with potential of generating novel chemical and biological sensors. We present experimental and theoretical elucidation of optical excitation of higher order flexural and torsional modes in resonant nanoelectromechanical systems (NEMS). The modulated optical fields were coupled directly into the NEMS device layer causing amplified mechanical vibrations. Dynamic detection of vibrational characteristics of nanomechanical resonators, fabricated from low-stress silicon nitride and mono-crystalline silicon thin film layers, was accomplished using optical interferrometry. As a model system, 200nm and 250nm thick single crystal silicon cantilevers with dissimilar lengths and widths ranging from 6 to 12µm and 500nm to 1µm, respectively, were fabricated using surface micromachining techniques. We have analyzed the actuation mechanism using finite element modeling, and we found that the dominant actuation mechanism in close proximity of the clamped end was primarily thermal. In contrast, mechanical traveling waves are attributed as possible excitation mechanisms in the far-field regime. Higher order modes of slender cantilevers, calculated using linear Euler-Bernoulli beam model, differed significantly from the measured values. Three dimensional finite element analysis incorporating shear, rotational inertia, deplanation and non-ideal boundary conditions due to the structural undercut, are shown to adequately describe the dynamics of the nanomechanical structures. The quality factor of a particular in-plane harmonic was consistently higher than the transverse mode. The increased dissipation of the out of plane mode was attributed to material and acoustic loss mechanisms.