Resonant dynamics governed by interlayer frozen bubbles in h-BN/graphene heterostructures

The graphene–hexagonal boron nitride (h-BN) heterostructures represent a pivotal platform for the exploration of dynamic characteristics of nanoelectromechanical systems, unconventional quantum Hall effects, and related phenomena. However, the inevitable formation of interfacial bubbles during the stacking process of these heterostructures significantly compromise device performance. Consequently, it is imperative to attain a more profound comprehension of the electromechanical properties under the conditions of bubble interfaces in the h-BN/graphene system. Beyond conventional quasi-static methodologies (e.g., STEM imaging, AFM-based techniques, blister tests), initiating from the resonant response of nanoelectromechanical systems offers a dynamic approach to probe interfacial interactions. Herein, we have utilized the pickup technique with h-BN to accomplish the stacking of h-BN/graphene heterostructures and the assembly of dual-clamped resonators in a single step. At conditions of 5 K, we analyzed its unique resonant dynamical response, which is attributed to the domination of interlayer frozen bubbles. We discovered that these “frozen bubbles” consistently maintain the coupling effect between the two layers of materials, even when the heterostructure exhibits independent vibrational modes due to significant gate-induced electrostatic pulling. Simultaneously, the thicker layer of h-BN masks the influence of graphene's negative thermal expansion coefficient, dominating the temperature response of the heterostructure's resonance, thus providing a possible means for localized modulation of interfaces. Our work furnishes further insights into comprehending the impact of interlayer bubbles on the electromechanical response within van der Waals heterostructures at cryogenic temperatures.