Temperature‐Dependent Adhesion in van der Waals Heterostructures

Abstract

physical properties pave the way for a greater range of functionality in materials and devices. [3] The adhesion characteristics between 2D materials are not only of fundamental interest for understanding the bonding and properties of heterostructures, but also for the development of fabrication pathways involving transfer by vdW pickup, as well as growth mechanisms of 2D crystals. [4] The adhesive properties of 2D materials have been studied using a variety of approaches at micro-and nanoscopic scales, addressing adhesion to metal and oxide substrates, and increasingly between 2D materials. [5][6][7] In particular, nanomechanical atomic force microscopy (AFM) techniques have been employed for the direct measurement of the interactions between graphene and the tip material. [8,9] Advances in the coating of AFM tips with graphitic materials have not only led to improved wear resistance and electrical characterization, [10][11][12][13][14] but also the possibility for probing interlayer interactions between 2D materials. Li et al. conducted a qualitative comparison of the adhesion between a ≈10 nm graphite-wrapped AFM tip and flakes of MoS 2 and h-BN. [15] Using tip-attached 2D crystals, Rokni and Lu recentlyThe interlayer coupling between 2D materials is immensely important for both the fundamental understanding of these systems, and for the development of transfer techniques for the fabrication of van der Waals (vdW) heterostructures. A number of uncertainties remain with respect to their adhesion characteristics due to the elusive nature of measured adhesion interactions. Moreover, it is theoretically predicted that the intrinsic ripples in 2D materials give rise to a temperature dependence in adhesion, although the vdW interactions themselves are principally independent of temperature. Here, direct measurements of the adhesion between reduced graphene oxide -coated by solution deposition on atomic force microscopy tips -and graphene, h-BN, and MoS 2 supported on SiO 2 substrates and as freestanding membranes are presented. The in situ nanomechanical characterization reveals a prominent reduction in the adhesion energies with increasing temperature which is ascribed to the thermally induced ripples in the 2D materials.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admi.202100838.

Interlayer Friction in Graphene/MoS2, Graphene/NbSe2, Tellurene/MoS2 and Tellurene/NbSe2 van der Waals Heterostructures

“…Deng et al show theoretical studies that (Deng and Berry, 2016), with the increase of temperature, atomic thermal vibration intensifies, and nanoscale ripples will inevitably appear in two-dimensional materials, resulting in the reduction of effective contact area and the reduction of adhesion force. The conclusion that the interlayer adhesion force of two-dimensional materials decreases with increasing temperature has been confirmed by experiments (Polfus et al, 2021).…”

Nanoscale Adhesion and Material Transfer at 2D MoS2–MoS2 Interfaces Elucidated by In Situ Transmission Electron Microscopy and Atomistic Simulations

“…The error bars represent the standard deviations of the six trial runs. The W adh was estimated using the Derjaguin–Müller–Toporov (DMT) , approximation for hard spherical contacts as W adh = false F pull − off 2 π R where F pull‑off is the maximum tensile force ( i.e ., the negative-most force on the curves shown in Figure a) required to separate the two surfaces, and R is the composite radius of the probe tip pair, which is given as 1 R = 1 R 1 + 1 R 2 Here, R 1 and R 2 are the respective radii of the tips in the contacting pair. Using the outer radii of the coated tips, the effective tip radius, R , is then calculated to be 3.52 nm.…”

Heterogeneous Material Integration via Autogenous Transfer Printing Using a Graphene Oxide Release Layer

“…These results indicate that the GO layer and Si substrate bond through weak van der Waals interactions, resulting in a moderate adhesion energy of 185 mJ/m 2 . This van der Waals heterostructure generally offers an optimal interfacial condition for the efficient delamination of the upper layer. − Second, the required peeling force can be predicted with the work of adhesion and angle of microcrack using the simplified Kendall model F b = W Si / GO 1 − cos α where F represents the required peeling force for delamination of the layer, b is the width of the layer, and α is the inclination angle of the microcrack which is defined as the angle between the length and height of the microcrack. To quantify α, the surface profiler examined the morphology of microcracks over varying reduction times, as depicted in Figure S1.…”