Nanoscale Mapping of Nanosecond Time-scale Electro-Mechanical Phenomena in Graphene NEMS

Atomically thin layers of two-dimensional (2D) materials such as graphene, MoS2 and h-BN have immense potential as sensors and electronic devices thanks to their highly desirable electronic, mechanical, optical and heat transport properties. In particular their extreme stiffness, tensile strength and low density allows for high frequency electronic devices, resonators and ultra-sensitive detectors providing realistic avenues for down-scaling electronic devices and nanoelectromechanical systems (NEMS). Whilst nanoscale morphology and electronic properties of 2D materials can be studied using existing electron or scanning probe microscopy approaches, time-dependant phenomena on the ns and shorter time-scales cannot be readily explored. Here we use the heterodyne principle to reach into this ns time-scale and create a local nanoscale probe for electrostatically induced actuation of a graphene resonator, with amplitude sensitivity down to pm range and time sensitivity in the ns range. We experimentally observed response times of 20-120 ns for resonators with beam lengths of 180 nm to 2.5 um in line with the theoretical predictions for such NEMS devices.