Bobbitt N Scott, Chelikowsky James R
Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
Departments of Physics and Chemical Engineering, Center for Computational Materials, Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712, USA.
J Chem Phys. 2016 Mar 28;144(12):124110. doi: 10.1063/1.4943970.
We examine the vibrational properties and Raman spectra of Si-Ge core-shell nanostructures using real-space pseudopotentials constructed within density functional theory. Our method uses no empirical parameters, unlike many popular methods for predicting Raman spectra for nanocrystals. We find the dominant features of the Raman spectrum for the Si-Ge core-shell structure to be a superposition of the Raman spectra of the Ge and Si nanocrystals with optical peaks around 300 and 500 cm(-1), respectively. We also find a Si-Ge "interface" peak at 400 cm(-1). The Ge shell causes the Si core to expand from the equilibrium structure. This strain induces significant redshift in the Si contribution to the vibrational and Raman spectra, while the Ge shell is largely unstrained and does not exhibit this shift. We find that the ratio of peak heights is strongly related to the relative size of the core and shell regions. This finding suggests that Raman spectroscopy may be used to characterize the size of the core and shell in these structures.
我们使用在密度泛函理论框架下构建的实空间赝势来研究硅锗核壳纳米结构的振动特性和拉曼光谱。与许多预测纳米晶体拉曼光谱的常用方法不同，我们的方法不使用经验参数。我们发现硅锗核壳结构拉曼光谱的主要特征是锗和硅纳米晶体拉曼光谱的叠加，其光学峰分别位于300和500 cm⁻¹ 附近。我们还在400 cm⁻¹ 处发现了一个硅锗“界面”峰。锗壳使硅核从平衡结构发生膨胀。这种应变在硅对振动光谱和拉曼光谱的贡献中引起显著的红移，而锗壳基本无应变且未表现出这种位移。我们发现峰高比与核和壳区域的相对尺寸密切相关。这一发现表明拉曼光谱可用于表征这些结构中核和壳的尺寸。
Zotero 插件