Parametric amplification is widely used in diverse areas from optics to electronic circuits to enhance low level signals by varying relevant system parameters. Parametric amplification has also been performed in several micro-nano resonators including nano-electromechanical system (NEMS) resonators based on a two-dimensional (2D) material. Here, we report the enhancement of mechanical response in a MoS drum resonator using degenerate parametric amplification. We use parametric pumping to modulate the spring constant of the MoS resonator and achieve a 10 dB amplitude gain. We also demonstrate quality factor enhancement in the resonator with parametric amplification. We investigate the effect of cubic nonlinearity on parametric amplification and show that it limits the gain of the mechanical resonator. Amplifying ultra-small displacements at room temperature and understanding the limitations of the amplification in these devices is key for using these devices for practical applications.
We use sapphire substrate for fabrication of the device to reduce parasitic capacitance. Low parasitic capacitance allows us to use homodyne electrical measurement technique. Homodyne electrical measurement scheme offers a simpler set-up and is faster technique compared to the other techniques such as heterodyne frequency mixdown and frequency modulation technique. 1 To fabricate the device, a metal gate Ti/Pt (15/10 nm) is deposited on the substrate using thermal deposition. Next, 300 nm thick is deposited using plasma enhanced chemical vapor deposition SiO 2 (PECVD). A circular window is exposed, covering the remaining with Cr mask. The circular SiO 2 trench is obtained by etching the exposed using reactive ion etching (RIE). For the source-SiO 2 drain metal contact pads, Cr/Au (5/50 nm) is deposited a few away from the trench. To suspend μm membrane, a PDMS sheet with exfoliated flake is placed on top of the circular trench MoS 2 MoS 2 and the flake is transferred over it such that the membrane also makes contacts with source-drain pads. 2
This paper discusses the interaction of an interfacial cavity/crack with an internal crack in a bimaterial plane under uniform loading at infinity. The point dislocation solution is used to simulate internal crack by using the distributed dislocation technique. The resulting singular integral equation is solved numerically and the stress intensity factor variations are plotted for some cases of internal crack interacting with interfacial cavity/crack.
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