SiO_2薄膜TO与LO振动模式的数值研究

Numerical experiment research on TO and LO vibrational modes of SiO_2 film

对Si-SiO2基底薄膜系统进行数值实验,将SiO2薄膜的能损函数与透过率光谱和反射椭圆偏振光谱进行对比,讨论了在红外透过率光谱和反射椭偏光谱中激发的SiO2薄膜TO和LO振动模式。在正入射的红外透过率光谱中,仅能发现SiO2薄膜的TO振动模式;在倾斜入射的s偏振透过率光谱中没有激发的LO模式;在倾斜入射的p偏振透过率光谱中,当入射角小于60°时,三个TO振动模式全部被激发;当入射角大于60°时,三个LO振动模式都被激发,而TO模式仅能激发两个。在反射椭偏光谱中,TO模式未被激发,仅能激发LO模式。在透过率光谱和反射椭偏谱中,振动频率分别具有向高波数和低波数方向频移的现象。

The system of Si substrate and SiO2 film was researched by numerical experiment. Compared energy loss function of SiO2 film with transmission spectrum and reflection elliptically polarized spectrum of SiO2 film, TO and LO vibrational modes of SiO2 film were researched by infrared transmission spectrum and reflection elliptically polarized spectrum. In the infrared transmission spectrum with normal incidence, only TO vibrational mode of SiO2 film was found. In the s- polarized infrared transmission spectrum with oblique incidence, there was no excitation LO vibrational mode for SiO2 film. When the ncidence angle is less than 60 degree, three TO vibrational modes were all excited. When the incidence angle is more than 60 degree, three LO vibrational modes were all excited, but only two TO vibrational modes were excited. In the reflection elliptically polarized spectrum, TO vibrational mode could not be excited and only LO vibrational mode was excited. In the transmission spectrum and reflection elliptically polarized spectrum of SiO2 film, their vibrational frequencies individual shifted to long wavenumber and short wavenumber.