Intermodal Coupling as a Probe for Detecting Nanomechanical Modes

Abstract

Nanoelectromechanical systems provide ultrahigh performance in sensing applications. The sensing performance and functionality can be enhanced by utilizing more than one resonance mode of a nanoelectromechanical-systems device. However, it is often challenging to measure mechanical modes at high frequencies or modes that couple weakly to output transducers. In this paper, we propose the use of intermodal coupling as a mechanism to enable the detection of such modes. To implement this method, a probe mode is continuously driven and monitored using a phase-locked loop, while an auxiliary drive signal scans for other modes. Each time the auxiliary drive signal excites the corresponding mode by matching the mechanical frequency, the effective tension within the structure increases, which in turn causes a frequency shift in the probe mode. The location and width of these frequency shifts can be used to determine the frequency and quality factor of mechanical modes indirectly. Intermodal coupling can be used as a tool to obtain the spectrum of a mechanical structure even if some of these modes cannot be detected conventionally.

Comparison of geometric and drive-induced nonlinearities in doubly clamped,thermoelastic nanoelectromechanical systems

“…In the particular case of Figure 1, the structural material is silicon nitride and the metal used in electrodes is gold. The fabrication of the device is detailed previously in [15]. In summary, it consists of three electron beam lithography steps, followed by gold depositions in the first two steps for metallic interconnects, and by copper deposition in the final one as the etch mask.…”

“…Thermoelastically driven NEMS have been first developed to drive the multiple modes of a nanomechanical structure simultaneously [14]. This device family was later used for the two-mode experiments to weigh single proteins in real time [9], and continues to be a potent platform for performing multimode dynamical experiments [15] and quality factor studies [16]. For this reason, charting the linear regime of operation is important for this device family.…”

Measurement and Characterization of Nano-Electro-Mechanical Systems Using Laser Interferometry

“…The nano-electro-mechanical systems used in this work are suspended doubly-clamped beams, fabricated on a siliconnitride layer over a silicon substrate [16]. Each beam has two nanofabricated gold electrodes (one at each extremity) that are used for actuation of the devices.…”

Observation of coupled mechanical resonance modes within suspended 3D nanowire arrays

“…depending on its coupling strength to the excited mode. [37][38][39][40][41] Hence, a higher coupling strength is expected between two collective modes sharing common vibrating NWs.…”

“…S7 †). Thus, as reported elsewhere, 41 one mode can now be kept at resonance using a phase-locked-loop (PLL) circuit, while an open-loop measurement is simultaneously performed for the second mode ( f sweep ). This way, pumping mode i induces a resonance frequency change (Δf j /f j ) for the mode j, such that the frequency change is proportional to the intermodal coupling strength (δ ij ).…”