Electrothermally Tunable Graphene Resonators Operating at Very High Temperature up to 1200 K

Abstract

The unique negative thermal expansion coefficient and remarkable thermal stability of graphene make it an ideal candidate for nanoelectromechanical systems (NEMS) with electrothermal tuning. We report on the first experimental demonstration of electrothermally tuned single- and few-layer graphene NEMS resonators operating in the high frequency (HF) and very high frequency (VHF) bands. In single-, bi-, and trilayer (1L, 2L, and 3L) graphene resonators with carefully controlled Joule heating, we have demonstrated remarkably broad frequency tuning up to Δ f/ f ≈ 310%. Simultaneously, device temperature variations imposed by Joule heating are monitored using Raman spectroscopy; we find that the device temperature increases from 300 K up to 1200 K, which is the highest operating temperature known to date for electromechanical resonators. Using the measured frequency and temperature variations, we further extract both thermal expansion coefficients and thermal conductivities of these devices. Comparison with graphene electrostatic gate tuning indicates that electrothermal tuning is more efficient. The results clearly suggest that the unique negative thermal expansion coefficient of graphene and its excellent tolerance to very high temperature can be exploited for engineering highly tunable and robust graphene transducers for harsh and extreme environments.

Frequency Tuning of Graphene Nanoelectromechanical Resonators via Electrostatic Gating

“…At different built-in strain levels, we find three frequency tuning behaviors: resonance frequency increases monotonically with | V g |, it decreases monotonically with | V g |, and it first decreases, then increases with increasing | V g |. All these cases are observed in existing experiments [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] for both of doubly clamped and circular drumhead graphene resonators. Figure 3 shows simulated frequency tuning of the doubly clamped and circular drumhead single-layer (1L) graphene resonators, with typical effective mass ratio = 2, air gap z 0 = 300 nm, length L = 1 μm and diameter D = 1 μm, respectively.…”

“…These attributes have made graphene an attractive and promising candidate for highly miniaturized and aggressively scaled resonant-mode nanoelectromechanical systems (NEMS) with unprecedented device performance. To date, mainly doubly clamped [ 5 , 6 , 7 , 8 ] membranes and ribbons, and circumference-clamped circular drumhead graphene resonators [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] have been prototyped, and fundamental device physics and basic device characteristics have been studied. Further, potential applications of these graphene 2D NEMS resonators in sensing of external stimuli and perturbations [ 17 ], and components for radio frequency (RF) signal processing and communications (e.g., oscillators [ 11 ]), have been attempted.…”

“…Indeed, strong frequency tunability has been quite heavily pursued in more conventional and state-of-the-art microelectromechanical systems (MEMS) based resonators and oscillators; however, tuning range is often limited up to 5% due to their high stiffness [ 18 ]. Thanks to ultra-strong yet highly stretchable crystals and their related material properties, graphene NEMS resonators can exhibit remarkably broad tunability of resonance frequency, with Δ f res / f res > 300% [ 12 ].…”

“…Among various device platforms and resonance excitation and detection methods, including photothermal and electrothermal schemes, electrostatic excitation and control of graphene 2D NEMS devices are always attractive for on-chip integration with mainstream technologies, and are particularly promising toward achieving wide frequency tuning ranges [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. In the electrostatic scheme, device structures form a capacitor between a suspended 2D material and a bottom (or top) gate, enabling electrostatic control of electrical and mechanical device performance by applying direct current (DC) electric potential (i.e., DC gate voltage).…”

“…More importantly, in the electromechanical domain, frequency tuning can be easily achieved by applying the gate DC voltage, which modifies the effective spring constants of the devices by electrostatic-mechanical coupling. The reported frequency tuning results in the electrostatic scheme to date, however, exhibit complicated behavior including frequency downshifts and upshifts [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 16 ]. Several attempts have been made to develop frequency tuning models that can be used to describe and explain the precise tuning mechanisms of devices [ 6 , 9 , 10 , 19 , 20 , 21 , 22 , 23 , 24 ].…”