【作者】 乌达巴拉；

【导师】 赵国军；

【作者基本信息】 内蒙古大学 ， 物理学， 2018， 硕士

【摘要】 拉曼光谱技术由于高灵敏性、快速性、信息丰富等优点,在研究晶格内部的结构时扮演着重要的角色。然而,作为一种间接性的检测技术,在相关实验研究中常会遇到光谱重叠、光谱非线性变化等问题。我们在理论上用第一性原理计算二维材料拉曼振动特性,为实验设计和相关研究提供理论依据。本文对单层和双层In Se进行结构优化并计算声子色散谱,以此为基础得出其拉曼散射光谱图,研究晶格结构、晶格振动、以及空间对称性等特点。另外,还计算了单层InSe拉曼散射退偏比。最后研究了单层InSe拉曼散射强度随入射光角度的变化规律,分别讨论了入射光与散射光偏振平行/垂直,且在xy/xz平面的四种情况。计算结果表明:单层In Se结构具有较好的稳定性。对单层In Se二维材料,拉曼光谱中出现四个峰,且对应模A’的峰较为明显。而双层的InSe材料,其拉曼光谱中出现多个峰,且A₁可激发较明显的拉曼散射现象;我们通过计算单层InSe退偏比得出,模A’激发的拉曼散射可完全退偏;对单层InSe,当入射光与散射光偏振平行,且在xy平面时,拉曼张量A’和E’产生的拉曼散射不会随入射光的角度发生变化。当入射光与散射光偏振垂直,且在xy平面时,张量A’不产生拉曼散射现象。这表明入射光和散射光的夹角也影响拉曼散射强度。当入射光与散射光偏振平行,且偏振在xz平面时,张量A’对应的散射强度除了与入射光角度θ有关以外,还与拉曼张量矩阵元素b和a的比值有关。在入射光与散射光偏振垂直,且偏振在xz平面时,拉曼张量矩阵元素b和a的比值有较小的值时,张量A’才可产生明显的拉曼散射现象。更多还原

【Abstract】 Raman spectroscopy plays an important role in studying the structure of lattice because of its high sensitivity,rapidity and rich information.However,there are still some difficulties in relevant experimental studies,such as overlapping band of different components in a mixture,nonlinear mixture effects of spectra and so on.We use the first principle to calculate the Raman vibration characteristic of 2D material,which provides theoretical basis for the experimental design and related research.In the paper,we optimize the structure and calculate the phonon dispersion of monolayer and bilayer InSe.Based on this results,we obtain their Raman spectrum,and study the characteristics of crystal structure,lattice vibration,and structure symmetry.We also calculate the depolarization ratio of monolayer InSe.Finally,we study the variation of the Raman scattering intensity of monolayer In Se with incident light,and discuss four situations in which the polarization of incident light and scattered light are parallel/perpendicular and in the xy/xz plane.Our results indicate that the monolayer InSe has stable structure.There are four peaks in the Raman spectrum of monolayer InSe,and an dominant peak corresponding to mode A’.We investigate that several peaks in the Raman spectrum.And A₁ modes can simulate obvious Raman scattering phenomenon;we also obtain the depolarization of mode A’ with two peaks are highly polarized bands according to the depolarization ratio.For monolayer In Se,the Raman tensor A’ and E’corresponding Raman scattering do not change with the angle of incident light,when the polarization of incident light is parallel to the scattered light,and is in the xy plane.When the polarization of incident light is perpendicular to the scattered light,and is in the xy plane,the Raman tensor A’ dose not cause the Raman scattering phenomenon.This indicates that the angel between incident light and scattered light also affects Raman scattering intensity.When the polarization of incident light is parallel to the scattered light,and is in the xz plane,Raman tensor A’ corresponding to the Raman scattering intensity is not only related to the angle of incident light,but also the ratio of b to a of the Raman tensor matrix.When the polarization of incident light is perpendicular to the scattered light,and is in the xz plane,the ratio of elements b and a of Raman tensor needs to have a smaller value.In this case,Raman tensor A’ can cause obvious Raman scattering phenomenon.更多还原