摘要:
基于石墨烯二维材料的诸多应用需要将其大面积、高质量地转移到目标基底上,迫切需要了解石墨烯在剥离和转移过程中与基底之间的相互作用特性.本文采用经典分子动力学方法探索了铜基底表面凹槽的几何特征尺寸对石墨烯吸附和剥离过程中凹槽基底对石墨烯吸附作用的影响机理和规律.结果表明:对于固定边界条件下的单层石墨烯,当基底表面的凹槽宽度固定不变时,吸附过程中基底对石墨烯的吸附力随二者间距的减小,呈现先增大后减小的趋势;其最大吸附力随凹槽深度的增加而增大,而当凹槽深度继续增大至石墨烯未能吸附进入凹槽底部的临界值时,吸附力迅速减小;剥离过程中,石墨烯完全剥离的临界作用力随凹槽深度的增加同样呈现先增大后减小的趋势,且与剥离前石墨烯与凹槽基底的相互作用面积有关;当基底表面凹槽的深度固定不变时,吸附和剥离过程中石墨烯-基底之间的吸附力随间距的变化规律取决于石墨烯在基底凹槽处的稳态吸附构型.
Abstract:
The two-dimensional material graphene is usually required to be transferred on the target substrate for some special applications, thus it is important to understand the adsorption properties in the graphene transferring and stripping processes. In this paper, the adsorption properties of a single-layered graphene on the grooved copper substrate are investigated using molecular dynamics simulations. The influence of geometric characteristic size of the groove on the adsorption force of the graphene deriving from the substrate is explored. For the fixed boundary conditions of the graphene, the adsorption force increases up to maximum and then decreases with reducing the distance between the graphene and substrate in the adsorbing process. The maximum adsorption force increases with groove depth increasing, with the groove width kept constant. Nevertheless, as the groove depth increases continuously, the adsorption force decreases greatly until the graphene cannot be adsorbed into the groove. In the graphene stripping process, the critical force that can strip the graphene completely from the substrate increases first and then decreases with the increase of the groove depth, which is also dependent on the steady adsorbing configuration of the system before stripping. With the groove depth kept constant, the magnitude of the adsorption force between the graphene and substrate is determined by the steady adsorbing configuration of the graphene in the groove region. The adsorption force versus the distance between the graphene and the grooved substrate can be divided into two groups according to whether the graphene can be adsorbed into the groove. In both adsorbing and stripping processes, the adsorption force for the graphene adsorbed into the groove is obviously larger than that for the graphene covered on the groove. Moreover, the influence of the boundary condition of the graphene on the adsorption properties in the groove region on the substrate is considered preliminarily. It indicates that the tensile plane stress within the graphene sheet induced by the fixed boundaries can hinder the graphene from being adsorbed into the groove. The findings may be helpful for the graphene-based fabrication of nano-apparatus and functionalized surface modification.
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