非晶介质中硅纳米晶的拉曼尺寸效应研究

Study on Raman Size Effect of Silicon Nanocrystals Embedded in Amorphous Matrix

摘要:

区别于传统的尺寸模型,本文基于唯象声子受限理论,综合考虑声子波失q-标准偏差σ-介质受限系数β三者的统 一,建立相应的函数关系,着重探讨了非晶包覆硅纳米晶因尺寸效应引起的拉曼频移和非对称性宽化。结果表明,对于非晶介质中的硅纳米晶,受限系数β考虑了非晶介质的受限势垒高度对峰位频移的影响；随着硅纳米晶尺寸减小到玻尔半径以下,布里渊区内波失由准连续转变为离散形式参与散射,此离散波失能更准确地拟合小尺寸硅纳米晶的拉曼谱线；进一步改变标准偏差σ,精细化调整拉曼谱峰的非对称性。最后,本文建立的理论模型与课题组实验结果、文献数据进行比较,发现综合考虑三者的协同效应,有助于更准确地评估非晶包覆型硅纳米晶的尺寸效应、纳米晶的存在形态及其相对比例。

Abstract:

Different from the traditional size model, this paper is based on the phenomenological phonon confinement model. The phonon wave vector q, standard deviation σ and confinement coefficient β were comprehensively considered and their relative functional relationship was established. The discussions focused on the Raman shift and asymmetry broadening of the amorphous coated silicon nanocrystals brought by the size effect. The results showed that, for the silicon nanocrystals embedded in amorphous matrix, the confinement coefficient β involved the influence of the limitation barrier height to the Raman shift. As the size of the silicon nanocrystals decreased, the q changed from quasi-continuous form to discrete form participating the scattering and this discrete q can more accurately fit the Raman spectral lines of small-sized silicon nanocrystals. Standard deviation σ was further changed to precisely adjust the asymmetry of Raman peaks. Finally, the theoretical model established in this paper was compared with the experimental results and literature data of the research group, and found that the comprehensive consideration of the synergistic effect of the q, σ and β was conducive to evaluating the size effect, crystal morphology and relative proportion of amorphous coated silicon nanocrystals.