Hybrid carbon nanostructures based on single walled carbon nanotubes (SWNT) and single layer graphene (SLG) are drawing much attention lately for their applications in a range of efficient hybrid devices. Few recent studies, addressing the interaction behavior at the heterojunction, consider charge transfer between the constituents (SWNT and SLG) to be responsible for changes in the electronic and vibrational properties in their hybrid system. We report the effect of various factors, arising due to the interactions between atoms of SWNT and SLG, on the structural and vibrational roperties of hybrid nanostructures investigated computationally within the framework of tight-binding DFT. These factors such as the van der Waal’s (vdW) forces, structural deformation and the charge transfer, are seen to affect the Raman active phonon frequencies of SWNT and SLG in the hybrid nanostructure. These factors are already known to affect the vibrational properties on SWNT and SLG separately and in this work, we have explored their role and interplay between these factors in hybrid systems. The contribution of different factors to the total shift observed in phonon frequencies are estimated and it is perceived from our findings that not only the charge transfer but the structural deformations and the vdW forces also affect the vibrational properties of components within the hybrid, with structural deformation being the leading factor. With decreasing separation between SWNT and SLG, the charge transfer and the vdW forces, both increase. However, the increase in vdW forces is relatively much higher and likely to be the main cause for larger Raman shifts observed at smaller separations.

中文翻译：

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石墨烯-单壁碳纳米管结的结构和振动特性的紧密结合研究

基于单壁碳纳米管（SWNT）和单层石墨烯（SLG）的混合碳纳米结构近来因其在一系列有效混合设备中的应用而备受关注。很少有研究针对异质结处的相互作用行为进行研究，认为成分（SWNT和SLG）之间的电荷转移是造成其混合系统电子和振动性质变化的原因。我们报告了各种因素的影响，由于SWNT和SLG原子之间的相互作用，对在紧密结合DFT框架内进行计算研究的杂化纳米结构的结构和振动拉索的影响。这些因素包括范德华力（vdW），结构变形和电荷转移，据观察，在混合纳米结构中，SWNT和SLG的拉曼活性声子频率受到影响。众所周知，这些因素分别影响SWNT和SLG的振动特性，在这项工作中，我们探索了它们在混合系统中的作用和相互作用。估计了不同因素对声子频率中总位移的贡献，并且从我们的发现可以看出，不仅电荷转移，而且结构变形和vdW力还会影响混合动力内组件的振动特性，并发生结构变形。是主要因素。随着SWNT和SLG之间的间隔减小，电荷转移和vdW力都增加。然而，