Detachment Dynamics of Graphene Nanoribbons on Gold

Abstract

Metal−surface physisorbed graphene nanoribbons (GNRs) constitute mobile nanocontacts whose interest is simultaneously mechanical, electronic, and tribological. Previous work showed that GNRs adsorbed on Au(111) generally slide smoothly and superlubrically owing to the incommensurability of their structures. We address here the nanomechanics of detachment, as realized when one end is picked up and lifted by an AFM cantilever. AFM nanomanipulations and molecular-dynamics (MD) simulations identify two successive regimes, characterized by (i) a progressively increasing local bending, accompanied by the smooth sliding of the adhered part, followed by (ii) a stick−slip dynamics involving sudden bending relaxation associated with intermittent jumps of the remaining adhered GNR segment and tail end. AFM measurements of the vertical force exhibit oscillations which, compared with MD simulations, can be associated with the successive detachment of individual GNR unit cells of length 0.42 nm. Extra modulations within one single period are caused by steplike advancements of the stillphysisorbed part of the GNR. The sliding of the incommensurate moirépattern that accompanies the GNR lifting generally yields an additional long-period oscillation: while almost undetectable when the GNR is aligned in the standard "R30" orientation on Au(111), we predict that such feature should become prominent in the alternative rotated "R0" orientation on the same surface, or on a different surface, such as perhaps Ag(111).

Registry-Dependent Peeling of Layered Material Interfaces: The Case of Graphene Nanoribbons on Hexagonal Boron Nitride

“… Quasi-static peeling of a 20 nm long GNR from an h-BN substrate calculated using the protocol of ref ( 44 ). The vertical peeling force (left axis) and contact length (right axis) as functions of peeling distance are presented for three different orientations of the GNR with respect to the h-BN substrate: (a) θ = 0°, (b) θ = 90°, and (c) θ = 45°.…”

Well-defined sub-nanometer graphene ribbons synthesized inside carbon nanotubes

“…More recently ribbons with more complex topologies were grown which have coved zigzag, chevron or chiral type structures [7,9,10]. The ribbons are usually grown on Au substrates from preselected and properly designed flat poly-aromatic hydrocarbon molecules (PAHs) [11]. In this case the PAHs are vacuum deposited on the substrate and subsequently transformed to polymeric units with nanoribbon structure.…”

Registry dependent potential for interfaces of gold with graphitic systems

“…Gold and graphene are two very stable materials that can be produced with a high level of crystallinity and cleanness over large surface areas. For these reasons the gold/graphene interface has been the prototypical choice for a large number of case studies, including diffusing and sliding gold nanoclusters [1][2][3][4][5][6], nanomanipulation of graphene nanoribbons [7][8][9], plasmon-enhanced optics [10,11], sensing and biomedical applications [12], surfaceenhanced Raman scattering [13,14], among many others.…”

“…In superlubric systems the corrugation energy (CE) -the energy barrier resisting sliding -can decrease to values much below the meV per interface atom. Therefore, studies aiming at describing superlubricity, often considering a combination of metals and graphitic materials [3,[7][8][9][24][25][26], are critically sensitive to the chosen experimental or theoretical setup.…”

“…For example, Torres et al measured an adhesion energy (AE) E a = 7687.1 mJ•m −2 in the case of graphene-covered gold nanoparticles [27], while a pulloff force of F a = 45.7 ± 5.1 nN was measured by Li et al for gold-coated AFM probes forming a ∼ 200 nm 2 contact with a graphite substrate [23]. Other experiments provide only indirect information based on empirically fitted models or simulations [6,7,9,28]. The comparison with experiments is further complicated by the presence of surface reconstruction at the gold surface, usually neglected in first-principles calculations due to the large supercell size required to encompass its long (∼ 6.3 nm) wavelength.…”