在不同应力下石墨烯中拉曼谱的G峰劈裂的变化

应用计及五阶近邻的力常数模型,研究了单轴应力下的石墨烯和芳香烃分子三明治型贴层的石墨烯中拉曼谱的G峰劈裂.计算结果表明对称性的降低解除了G峰对应的在Γ点的面内的纵波光学模声子和横波光学模声子能量简并,从而G峰劈裂为G⁺和G^- 两个峰.在单轴应力作用下,C—C键的伸长致使力常数减小,软化了面内的光学模声子,导致两个G峰都红移;芳香烃分子对石墨烯产生的沿分子长短边方向不同的应力作用,使得G峰对应的两支光学模声子的频率一支发生蓝移,而另一支发生红移.这解关键词：力常数模型石墨烯拉曼G峰劈裂

Variation of graphene Raman G peak splitting with strain

Variation of graphene Raman G peak splitting due to uniaxial strain and absorption of polyaromatic moleculars on both sides are studied by fifth-nearest neighbor force-constant model. The calculation results show that symmetry lowering is responsible for the G peak splitting, where G peak splits into G⁺ and G^- peaks by lifting the energy degeneracy of in-plane longitudinal and transverse optical phonons at Γ point. Under uniaxial strain, the elongation of C—C bonds reduces the force-constant and softens the in-plane optical phonons which induce red shifts of both G⁺ and G^- peaks. The different strains produced by polyaromatic molecules along its long and short edges lead to red shift and blue shift of the two in-plane optical phonons relevant to G^- and G⁺ peaks, which gives a plausible explanation to the different G peak splitting of the recent Raman experiment on graphene with uniaxial strain and graphene sandwiched by the polyaromatic molecules.