掺杂原子质量对硅声子散射的影响

Effect of Atomic Mass of Dopants on Phonon Scattering in Si

本文采用分子动力学方法,重点研究了掺杂原子质量对硅晶格振动行为的影响,在原子尺度上清楚地展示出目前实际无法展现的点缺陷影响声子散射的演化过程。结果表明:同位素掺杂的存在会在特定声子频率区引起共振,使透射率显著减少,掺杂原子质量较大时共振区域明显扩大,且透射率随掺杂浓度增加下降得越快,会使材料导热性变差;掺杂原子质量相同时,共振区中最小透射率对应的频率值不随浓度变化而改变。在大于共振频率时,有明显LA到TA声子模式的转变,随掺杂原子质量的增加TA模式所占比例增大。这些结果对深入认识点缺陷对晶格导热微观机制的影响有积极意义。

By using molecular dynamics simulation the effect of atomic mass of dopants on lattice vibration in silicon has been researched,the evolution of phonon scattering from point defects has been explicitly displayed in the atomic scale,which can not be currently observed by actual experiments.The results show that： the isotope dopants can lead to a dramatic drop of transmission coefficient in the specific phonon frequency region,which attributes to the local resonance caused by dopants.Heavier dopants make larger resonant region and greater decrease of transmission coefficients with increasing dopant concentration, these could lead to poorer thermal conductivity of the materials. The frequency where the minimum transmission coefficient occurs is almost not affected by the dopant concentration with same atomic mass of dopants. When the frequency is greater than the resonant frequene~~, there is obvious conversion from LA to TA phonon mode, and the proportion of TA mode increases as the atomic mass increases. These results could be significant for through understanding of the microcosmic mechanism of point defect effect on lattice heat transfer.