Hidden by graphene – Towards effective screening of interface van der Waals interactions via monolayer coating

Abstract

Recent atomic force microscopy (AFM) experiments [ACS Nano 2014, 8, 12410-12417] conducted on graphene-coated SiO2 demonstrated that monolayer graphene (G) can effectively screen dispersion van der Waals (vdW) interactions deriving from the underlying substrate: despite the singleatom thickness of G, the AFM tip was almost insensitive to SiO2, and the tip-substrate attraction was essentially determined only by G. This G vdW opacity has far reaching implications, encompassing stabilization of multilayer heterostructures, micromechanical phenomena or even heterogeneous catalysis. Yet, detailed experimental control and high-end applications of this phenomenon await sound physical understanding of the underlying physical mechanism. By quantum many-body analysis and ab-initio Density Functional Theory, here we address this challenge providing theoretical rationalization of the observed G vdW opacity for weakly interacting substrates. The non-local density response and ultra slow decay of the G vdW interaction ensure compensation between standard attractive terms and many-body repulsive contributions, enabling vdW opacity over a broad range of adsorption distances. vdW opacity appears most efficient in the low frequency limit and extends beyond London dispersion including electrostatic Debye forces. By virtue of combined theoretical/experimental validation, G hence emerges as a promising ultrathin shield for modulation and switching of vdW interactions at interfaces and complex nanoscale devices.

Comparison of dispersion-corrected exchange-correlation functionals using atomic orbitals

“…We mention that the kernels entering Eq. 3, such as VV10 and rVV10, are usually two-body approximations without multilayer screening effects [64], extremely strong screening in 2D systems [65,66], long-range scaling, and dimensional crossovers [64,[67][68][69][70]. Even if the long-range vdW is described by a 2-body approximation, the intermediate and short-range dispersions depend on the semilocal functional as well.…”

Faraday cage screening reveals intrinsic aspects of the van der Waals attraction

“…Related parallel work demonstrates how ionic forces can control typical scenarios associated with dispersion ( 14 ), as well as scenarios in which general solvent effects including dispersion control structure ( 15 , 16 ). Alternatively, at long distances, the Casimir dispersion effect becomes critical ( 17 – 19 ), as well as other exotic phenomena associated with the wavelike nature of charge polarization in nanoscale objects ( 4 ). While answers to each of the issues raised can be formed in isolation, a generally useful understanding of the vdW force remains elusive.…”

“…This becomes particularly significant for long-ranged interactions between low-dimensional metallic conductors ( 26 , 50 , 51 ), but, in undoped graphene at T = 0 K, it is less important ( 22 ). It leads on ( 21 ) to the Casimir effect ( 17 – 19 ), something that can become very important in large systems ( 52 ).…”

Van der Waals Density Functional Theory vdW-DFq for Semihard Materials

“…It is worth noting that it is not evident a priori that self consistency should necessarily lead to higher accuracy: although self-consistent, vdW-DF and related methods still imply a number of approximations which may be way larger than self-consistency vdW effects. One of these is the lack of long-range many body effects which may amount to more than 10% of the total dispersion energy (see [69][70][71], and can lead to unexpected features in highly anisotropic systems [72,73].…”