Investigation On Method Of Phonon Scattering In Isotope-doped Si

Phonon scattering from point defect is one of key mechanism of affecting the thermal transfer for electronic insulators, in which the phonon frequency and the isotope-doped concentrations are significant factors. This paper focuses on the phonon frequency effect and the isotope-doped concentrates effect on the phonon scattering in isotope-doped Si. The effect of phonon frequency and isotope-doped concentrates is described quantitatively by generating the phonon wave packet with well-defined frequency and determining related parameters and building MD model, and then performing the MD simulation, and analyzing the relative amounts of energy transmitted from defect field. The procedure of phonon scattering from doped field is explicitly displayed in atomic scale. In the region of resonance frequency the MD results are well fitted by the improved R.O.Pohl's equation for the system with single defect, 4 defects and 8 defects respectively. Under low isotope-doped concentrations, the studies on LA and TA phonons indicate that, the total energies are mainly constituted by LA phonons in the lower frequency region than the resonant frequency. But in the resonance region and higher frequency region, the energy presenting by TA phonons changed with the phonon frequency and the isotope-doped concentrations can not be neglected. The MD results in 3.53THz and in 3.68THz indicate that, the independent scattering model only fits in lower isotope-doped concentrations. When the isotope-doped concentrations increase, the coherence of scattering between doped atoms increases also, and the MD results deviate from the independent scattering model. This paper also has some deductive work about the transmitted rate of phonons in higher isotope-doped concentrations, some of which are approved by other researcher's work. Finally, three classical theories on point defects effect effect are introduced , and the adaptability of the MD simulations for isotope-doped Si are discussed. These results could be helpful both for formulizing the phonon thermal conductivity in a wider frequency region including non dispersive and dispersive phonon and for performing our further work.