Time-dependant electrostatic and electro-mechanical phenomena in Graphene NEMS

The impact Graphene has had on nano-electro-mechanical systems (NEMS) has been profound due to its high in-plane stiffness as well as low mass density, ideal properties for such devices. To understand NEMS manufactured from Graphene we introduce a technique called electrostatic heterodyne force microscopy (E-HFM). E-HFM allows for NEMS structures to be operated at frequencies around their primary resonance but due to heterodyne detection allows the down shifting of the signal, making measurements simple. By down-shifting the response signal it is possible to probe NEMS actuation amplitude with pm resolution and time-dependant behavior with ps resolution. By using E-HFM we probe the amplitude of vibration and response time of various NEMS structures and compare with the theoretical expectations. If Graphene is to be implemented into ultra-sensitive NEMS then it is not only important to understand the behavior of the device but the effects of the surroundings on the device. Properties such as trapped surface charges underneath the Graphene layers can dope the device and as such the reliability of its performance. With E-HFM we observe trapped subsurface charges beneath resonator structures quantitatively and link it with an observed change in the NEMS performance.