The structure of graphene on graphene/C₆₀/Cu interfaces: a molecular dynamics study

Abstract

Two experimental studies reported the spontaneous formation of amorphous and crystalline structures of C60 intercalated between graphene and a substrate. They observed interesting phenomena ranging from reaction between C60 molecules under graphene to graphene sagging between the molecules and control of strain in graphene. Motivated by these works, we performed fully atomistic reactive molecular dynamics simulations to study the formation and thermal stability of graphene wrinkles as well as graphene attachment to and detachment from the substrate when graphene is laid over a previously distributed array of C60 molecules on a copper substrate at different values of temperature. As graphene compresses the C60 molecules against the substrate, and graphene attachment to the substrate between C60s ("C60S" stands for plural of C60) depends on the height of graphene wrinkles, configurations with both frozen and non-frozen C60s structures were investigated in order to verify the experimental result of stable sagged graphene when the distance between C60s is about 4 nm and height of graphene wrinkles is about 0.8 nm. Below the distance of 4 nm between C60s, graphene becomes locally suspended and less strained. We show that this happens when C60s are allowed to deform under the compressive action of graphene. If we keep the C60s frozen, spontaneous "blanketing" of graphene happens only when the distance between them are equal or above 7 nm. Both above results for the existence of stable sagged graphene for C60 distances of 4 or 7 nm are shown to agree with a mechanical model relating the rigidity of graphene to the energy of graphene-substrate adhesion. Although the studies of intercalation of molecules on interfaces formed by graphene-substrate are motivated by finding out ways to control wrinkling and strain in graphene, our work reveals the shape and structure of intercalated molecules and the role of stability and wrinkling on final structure of graphene. In particular, this study might help the development of 2D confined nanoreactors that are considered in literature to be the next advanced step on chemical reactions.

Молекулы Фуллерена C-=sub=-60-=/Sub=- Под Однослойным Графеном На Металлической Подложке

“…Предельная поверхностная плотность молекул в интеркалированном слое равна 2/( √ 3a 2 ), где a = 1.01 нм -расстояние между центрами соседних молекул. В качестве материала подложки будем рассматривать медь [7,9]. Предполагается, что межатомные взаимодействия в системе не приводят к деформациям молекул, графена и поверхности подложки.…”

“…где z означает расстояние от центра молекулы фуллерена до поверхности подложки в формуле (8) и графена в формуле (9). Подставляя (1) в (8), ( 9) и выполняя интегрирование, получаем…”

“…Система, состоящая из однослойного графена, молекул фуллерена и медной подложки, теоретически изучалась в [9] методом молекулярной динамики. Исследовались устойчивость графена, покрывающего фуллерены, а также процесс возникновения и стабильность складок графена при различных расстояниях между молекулами.…”

“…Метод молекулярной динамики в данном случае оказался достаточно успешным, однако один важный момент остался без внимания. Моделирование в [9] проводилось в том числе и для высокой температуры 1000 K, т. е. не так далеко от температуры плавления массивной меди (1358 K). Известно, что для меди при температуре ∼ 900 K начинается так называемое поверхностное плавление [10].…”

Reduction of Interlayer Interaction in Multilayer Stacking Graphene with Carbon Nanotube Insertion: Insights from Experiment and Simulation

“…The benefits of suspended Gr include ultra-high carrier mobility and ballistic transport. ,− However, the single-atom layer structure of Gr results in its low stiffness to bending deformation . The adsorption interaction among Gr layers results in the bending of Gr and a decrease in interlayer distance. − Thus, negative factors, including strong interlayer coupling, electron scattering, and a decrease in the surface-to-volume ratio, will appear. Thus, investigating the real effect of CNT insertion on the microstructure of Gr and the CNT composite system is necessary to comprehensively understand and optimize their interaction.…”