Sliding-friction-dependent stress at the graphene/LiNbO3 interface around the critical temperature of the stress-free state

Abstract

The graphene/LiNbO3 structure exists in an interfacial stress-free state at the temperature at which the graphene was transferred onto the LiNbO3 substrate surface. Coupling of a surface acoustic wave with this structure revealed drastic changes in the properties of the propagating elastic wave around the critical temperature of the stress-free state. Three states, namely, tensile stress, stress-free, and compressive stress, were successively observed at the surface of the LiNbO3 substrate as the temperature was increased through the critical point. The interfacial stress increased prior to the occurrence of sliding friction and approached a constant value when the frictional force exceeded the van der Waals interaction between the graphene and LiNbO3. Consequently, the interfacial stress exhibited a step-like temperature dependence around the critical temperature of the stress-free state. The results obtained in this study indicate that the temperature used to prepare graphene layers on a substrate is a crucial parameter owing to the instability of the electrical and mechanical properties of the graphene/substrate in the vicinity of this temperature. Therefore, in the fabrication of graphene-based electronic devices, room temperature should be avoided during the preparation of the graphene layers on the substrate.

Possible pair-graphene structures govern the thermodynamic properties of arbitrarily stacked few-layer graphene

“…If the temperature change is sufficiently large, sliding friction appears and stick–slip behavior occurs 58 . In fact, we reported abnormal behavior regarding parameters of SAWs that pass through the penta-layer graphene/LiNbO 3 interface in our previous research 30 . Discontinuous changes occur in both the SAW intensity and frequency near the transfer temperature.…”

“…It acts as a compressive stress as the temperature increases, resulting in an increase in . Third, the temperature at which the instability occurs corresponds to the graphene layer transfer temperature 30 . Fourth, temperature-dependent stress occurs because of interfacial stick–slip friction that is dependent on the graphene and LiNbO 3 crystal lattice structures.…”

“…Also, discontinuous changes in are observed at 306 K for the tri-layer sample and at 292 K for the penta-layer sample. The temperature range of the discontinuous change is approximately 2 K 30 . The discontinuous changes correspond to thermal contraction and expansion stresses at the LiNbO 3 surface for the tri- and penta-layer samples, respectively.…”

“…This corresponded to the IDT distance of 16 mm. Detailed information on SAW devices and signal processing techniques was reported in our previous paper 30 . The SAW fundamental frequency, attenuation, and delay time were measured to characterize interactions of the SAWs with the few-layer graphene films.…”

“…Surface acoustic wave (SAW) propagation is a powerful method of investigating the mechanical and electrical properties of low-dimensional materials such as 2D electron gases 27 , 28 , graphene 29 , 30 , 1D carbon nanotubes 31 , 32 , and zero D quantum dots 33 , 34 . In this study, we investigated the thermodynamic properties of deformed few-layer graphene by analyzing the propagation velocities, frequencies and attenuation characteristics of SAWs that passed through the graphene layers.…”