Investigation of Nonlinearities and Piezoelectricity in 2D NEMS

Nanoelectromechanical systems (NEMS) have drawn considerable attention towards several sensing applications such as force, spin, charge and mass. These devices due to their smaller size, operate at very high frequencies (MHz - GHz) and have very high quality factors (102 -105). However, the early onset of nonlinearity limits the linear dynamic range of these devices. My doctoral research is primarily on the investigation of the nonlinearities and their effect on the performance of graphene based NEMS. Electromechanical devices based on 2D materials are extremely sensitive to strain. I studied the effect of strain on the performance of single layer Graphene NEMS and have shown how the strain in Graphene NEMS can be tuned to manipulate the linear operational range. I have also studied the frequency stability of graphene resonators. Frequency stability analysis indicates departure from the nominal frequency of the resonator with time. I have used Allan Variance as a tool to characterize the frequency stability of the device. 

In my postdoctoral research, I have investigated 2D material-based piezoelectric NEMS. By using the atomically-thin layers that do not have inversion symmetry, it is possible to implement 2D piezoelectric transduction. Experimental values have been reported for MoS2, but contradicting results open the possibility for unprecedented effects, i.e. with a gigantic response several orders of magnitude above any piezoelectric material known. This has the potential to cast profound effect on ultrasensitive sensors, biomechanical energy harvesters and self-powered wireless devices with unseen resolution and bandwidth.