石墨烯纳米网中的声子干涉效应

Phonon interference effects in graphene nanomesh

石墨烯纳米网(GNM)是一种具有周期性纳米孔分布的单层石墨烯,在热电能量转换、热能存储、场效应晶体管等领域具有广阔的应用前景.本文采用非平衡分子动力学与晶格动力学的方法对GNM的热输运机理进行研究.结果表明:GNM的导热系数随纳米孔数量的增加而减小,部分原因归因于声子布拉格散射引起的带隙产生和声子群速度的降低;横向和纵向纳米孔的间距共同影响GNM热输运过程,当水平间距较小时,GNM的导热系数随纵向间距的增大单调减小,随横向间距的增大单调增大;随着水平间距的增大,在声子干涉和散射的共同作用下,导热系数产生明显的波动.这些结论可为GNM中的热输运调控提供理论参考.

Graphene nanomesh(GNM)is a single-layer graphene material that has a periodic distribution of nanoscale pores.GNM shows great potential applications in various fields such as thermoelectric energy conversion,energy storage,and field-effect transistors.In this study we utilize non-equilibrium molecular dynamics and lattice dynamics method to investigate the thermal transport mechanism of GNM.The thermal conductivity of GNM is mainly affected by the number of nanoscale pores and their horizontal and vertical spacing.Our study finds that as the number of nanoscale pores increases,the thermal conductivity of GNM decreases significantly.Additionally,the increase of the number of nanoscale pores causes phonon branch to be folded and confined,which results in a flatter dispersion curve,wider bandgap,and slower phonon group velocity.Moreover,the horizontal and vertical spacing of the nanoscale pores jointly affect the thermal transport process of GNM.When the horizontal spacing is small,the thermal conductivity of GNM decreases monotonically with the increase of vertical spacing,and increases monotonically with an increase of horizontal spacing.However,as the horizontal spacing increases,the interference effect caused jointly by phonon reflection and superposition leads to significant fluctuations in thermal conductivity.The analysis of the spectral heat flow,density of states,participation rate,and group velocity of GNM indicate that the variation in vertical spacing leads to different phonon contributions to heat flow,resulting in fluctuations in the thermal conductivity of GNM.These findings could serve as a reference for controlling the thermal transport of graphene nanomesh,and are of great significance in regulating the thermal conductivity and designing nanoscale pores in GNM.