Elastocapillary cleaning of twisted bilayer graphene interfaces

Abstract

Although layered van der Waals (vdW) materials involve vast interface areas that are often subject to contamination, vdW interactions between layers may squeeze interfacial contaminants into nanopockets. More intriguingly, those nanopockets could spontaneously coalesce into larger ones, which are easier to be squeezed out the atomic channels. Such unusual phenomena have been thought of as an Ostwald ripening process that is driven by the capillarity of the confined liquid. The underlying mechanism, however, is unclear as the crucial role played by the sheet’s elasticity has not been previously appreciated. Here, we demonstrate the coalescence of separated nanopockets and propose a cleaning mechanism in which both elastic and capillary forces are at play. We elucidate this mechanism in terms of control of the nanopocket morphology and the coalescence of nanopockets via a mechanical stretch. Besides, we demonstrate that bilayer graphene interfaces excel in self-renewal phenomena.

Time-Dependent Pinning of Nanoblisters Confined by Two-Dimensional Sheets. Part 1: Scaling Law and Hydrostatic Pressure

“…On the one hand, interfacial nanoscale blisters are found almost inevitable in van der Waals (vdW) heterostructures, − which are stacks of different atomically thin two-dimensional (2D) materials. In spite of being detrimental to the functioning of vdW heterostructures which requires cleaning methods, ,− such blisters show promising benefits. For example, high hydrostatic pressures expected in such nanoblisters inspired studies of high-pressure chemistry of confined molecules inside them. , High strains in graphene nanoblisters were shown to be able to induce great pseudomagnetic fields and photoluminescence emission .…”

Time-Dependent Pinning of Nanoblisters Confined by Two-Dimensional Sheets. Part 2: Contact Line Pinning

“…3−9,20−22 Studies have suggested that liquid water is the most likely substance inside the blisters. [3][4][5][6][7][8]22 Our observation of residual wetting ridge structures in this work provides further evidence that the confined substance in our sample is liquid. The blisters are determined to be confined between the two graphite flakes since the graphite−SiO 2 interface is found to have no such features.…”

Deep Elastic Strain Engineering of 2D Materials and Their Twisted Bilayers

“…15 Thus, on the basis of the vdW interaction, stacking engineering of the homo/heterostructures, with a nearly perfect interface without defects, provides new and efficient approaches to modulate properties of them. 16 Similar to monolayer 2D materials, the properties of 2D vdW homo/heterostructure can be further modified under mechanical strain. 17 Again, because of the weak vdW interaction, the stacking angle can be tailored without introducing interlayer defects.…”

“…Compared to traditional chemical epitaxial growth methods (such as molecular beam epitaxy) and physical vapor deposition, the interlayer weak van der Waals interaction provided a low-energy material-integration method to assemble novel 2D material systems without the requirements of precise lattice matching and processing compatibility . Thus, on the basis of the vdW interaction, stacking engineering of the homo/heterostructures, with a nearly perfect interface without defects, provides new and efficient approaches to modulate properties of them . Similar to monolayer 2D materials, the properties of 2D vdW homo/heterostructure can be further modified under mechanical strain .…”