Browsing by Author "Ti, C."

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    Dynamics of NEMS resonators across dissipation limits
    (AIP Publishing LLC, 2022-07-12) Ti, C.; McDaniel, J. G.; Liem, A.; Gress, H.; Ma, M.; Kyoung, S.; Svitelskiy, O.; Yanik, C.; Kaya, I. I.; Hanay, M. S.; González, M.; Ekinci, K. L.
    The oscillatory dynamics of nanoelectromechanical systems (NEMS) is at the heart of many emerging applications in nanotechnology. For common NEMS, such as beams and strings, the oscillatory dynamics is formulated using a dissipationless wave equation derived from elasticity. Under a harmonic ansatz, the wave equation gives an undamped free vibration equation; solving this equation with the proper boundary conditions provides the undamped eigenfunctions with the familiar standing wave patterns. Any harmonically driven solution is expressible in terms of these undamped eigenfunctions. Here, we show that this formalism becomes inconvenient as dissipation increases. To this end, we experimentally map out the position- and frequency-dependent oscillatory motion of a NEMS string resonator driven linearly by a non-symmetric force at one end at different dissipation limits. At low dissipation (high Q factor), we observe sharp resonances with standing wave patterns that closely match the eigenfunctions of an undamped string. With a slight increase in dissipation, the standing wave patterns become lost, and waves begin to propagate along the nanostructure. At large dissipation (low Q factor), these propagating waves become strongly attenuated and display little, if any, resemblance to the undamped string eigenfunctions. A more efficient and intuitive description of the oscillatory dynamics of a NEMS resonator can be obtained by superposition of waves propagating along the nanostructure.
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    Optimization of piezoresistive motion detection for ambient NEMS applications
    (Institute of Electrical and Electronics Engineers, 2020) Ti, C.; Arı, A.; Orhan, E.; Gonzalez, M.; Yanık, C.; Kaya, İ. İ.; Hanay, Mehmet Selim; Ekinci, K. L.
    Electrical readout of nanomechanical motion in ambient pressure and temperature imposes an important challenge for emerging applications of nanoelectromechanical systems (NEMS). Here, we optimize a metallic piezoresistive motion transducer for NEMS resonators in air. The nanomechanical motion of the NEMS resonator serves as a signal down-mixer and enables the detection of the motional signal by a low-frequency circuit. A balanced circuit in the detection loop reduces some of the unwanted background and allows for detection without significant losses. We explore the detection parameter space and use an optimized parameter set to detect the fundamental, second and third harmonic resonances of a NEMS doubly-clamped beam resonator. Our simple circuit model agrees with experimental observations and points the way for further optimization.