强激光辐照对3C-SiC晶体结构稳定性的影响

Effect of intense laser irradiation on the structural stability of 3C-SiC

使用基于密度泛函微扰理论的线性响应方法,模拟研究了强激光辐照对闪锌矿结构的碳化硅晶体结构稳定性的影响.通过计算在不同电子温度下3C-SiC晶体的声子色散曲线,发现3C-SiC的横声学声子频率随电子温度的升高会出现虚频,其临界电子温度是3.395 eV.结果表明,在强激光辐照下3C-SiC晶体变得不稳定,这与以前对金刚石结构的碳、硅和闪锌矿结构的砷化镓、锑化铟的研究结果非常类似.电子温度在0—4.50 eV范围内时,3C-SiC晶体在Γ点的LO-TO分裂度随电子温度的升高而增大,超过4.50 eV后随电子温度的升高而减小.这表明只有在足够强的激光辐照下,电子激发才会削弱晶体的离子性强度.

Using the linear response method based on the density functional perturbation theory, we simulate the effect of intense laser irradiation on the zinc-blende structural stability of silicon carbide crystal. By calculating the phonon dispersion curves for the 3C-SiC crystal of the zinc-blende structure at different electronic temperatures, we find that the transverse acoustic phonon frequencies of 3C-SiC become imaginary as the electron temperature increases. The critical electronic temperature is 3.395 eV. This means that the lattices of 3C-SiC become unstable under the intense laser irradiation. These results are very similar to the previous results for the diamond structure（C and Si） and the zinc- blende structure （GaAs and InSb）. In an electron temperature range of 0-4.50 eV, the LO-TO splitting at F gradually increases with the increase of electronic temperature. When the electron temperature is beyond 4.50 eV, the splitting decreases. The results indicate that only under the intense enough laser irradiation, the ionic strength can be weakened by the electronic excitation.