Experimental Study Of Graphene Nanoelectromechanical Resonators

Graphene,the first layered two-dimensional(2D)crystal,since its discovery by A.K.Geim and K.S.Novoselov in 2004,has attracted tremendous research interests worldwide.Guaranteed by the outstanding electrical and excellent mechanical properties,graphene is an ideal material for use in Nanoelectromechanical Systems(NEMS).In this thesis,we focus on the performance of few-layer graphene NEMS resonators in ribbon geometry.We will discuss the experimental techniques and studies on their intrinsic properties,nonlinear dynamics and quality factor.We report the first demonstration of strong coupling between graphene nanoelectromechanical resonators and quantum dot,and the direct transduction between an electrical signal and a mechanical signal.Then we study the strong coupling between two graphene resonators,and we have observed the synchronization of frequency locking by switching the drive microwave's power and relative phase.Furthermore,we've realized the tunable strong coupling of two distant graphene resonators by tuning the resonance frequency of the center mechanical resonator.The main content of this thesis includes:1.A brief introduction about the concepts of Nanoelectromechanical Systems and its research background.We also introduced some basic concepts about quantum dots and mechanical resonator and strong coupling etc.2.An introduction of the nanofabrication technologies and the equipment induced in preparing the suspended graphene mechanical resonators.Then,we introduced the 2D materials transfer platform and three transfer techniques.The fabrication processing steps and some recipes have been discussed.Finally,we show a new technique for suspending graphene by inducing a sacrificial layer.3.An extensive discussion about the measurements of typical graphene NEMS resonators.We focus on the three electrical transduction schemes of the mechanical signal,including:frequency mixing,microwave cavity coupling and direct transduction.4.We have fabricated a hybrid system of an extremely narrow graphene constriction,which can act as a mechanical resonator and also a quantum dot.In this system we realize the strong coupling between a single electron tunneling and a mechanical motion.In this situation,the resonator act as a detector and also a signal transducer,which provides a possibility of using mechanical resonators as a quantum data bus.5.We realize the strong coupling between two distant graphene mechanical resonators.By increasing the drive microwave's power and switching the relative phase,we have observed the synchronization between two strongly coupled mechanical motions.6.We have demonstrated a phonon coupling switch in graphene mechanical resonator system.By tuning the resonance frequency of the center resonator,the distant coupling between the two distant mechanical resonators can be tuned from weak to strong.The main innovations of this thesis are:1.For the first time,we have fabricated suspended few layers graphene ribbons through the all-dry transfer technique.Meanwhile,in this hybrid system,the graphene acts as a mechanical resonator and also a single electron transistor.2.We have reported the first experimental realization of strong coupling between single-electron transport and mechanical motion in a graphene nanoribbon.3.For the first time,we have measured the strong coupling between two individual graphene mechanical resonators.Also,we have observed the frequency locking in two coupled mechanical motions.4.For the first time,we have realized the tunable distant strong coupling between two distant graphene mechanical resonators.