Size Effects of Raman and Photoluminescence Spectra of CdS Nanobelts
Size Effects of Raman and Photoluminescence Spectra of CdS Nanobelts
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DOI：
10.1021/jp407272u
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发表时间：
2013-10-10
影响因子：
3.7
通讯作者：
Lu, Junfeng
中科院分区：
文献类型：
--
作者：
Hu, Chuan;Zeng, Xianghua;Lu, Junfeng
在800、850和900 ℃下通过在Au涂覆的硅衬底上热蒸发CdS粉末来合成不同尺寸的CdS纳米带，并用于研究拉曼散射和光致发光光谱的尺寸效应。CdS纳米带的拉曼光谱清楚地显示出一阶和二阶纵向光学（LO）拉曼峰、表面声子峰和多声子过程。激子-声子耦合机制主要与Frohlich相互作用有关，激子-声子耦合强度随横向尺寸的增大而增大.与较大的CdS纳米带相比，较窄的纳米带表现出较大的拉伸应变。从低温PL光谱中鉴定了自由激子（FX）、与中性杂质结合的激子（A（0）X）和供体-受体对（DAP）的解离。当温度低于123 K时，由于单轴拉伸应变的增大，FX能随横向尺寸的减小而发生红移;在高于类似于123 K的温度下，FX能量的红移随着横向尺寸的增加而发生，这是因为发射光在较厚的带内被再吸收，这表明FX能量受到纳米带中的拉伸应变和表面耗尽诱导的量子限制（发射光的再吸收）两者的影响。
Different sizes of CdS nanobelts were synthesized at 800, 850, and 900 degrees C by the thermal evaporation of CdS powders on Au-coated silicon substrates and were used to study the size effects of Raman scattering and photoluminescent spectra. The Raman spectra of CdS nanobelts clearly exhibit first- and second-order longitudinal optical (LO) Raman peaks, surface phonon peaks, and multiphonon processes when excited using a wavelength of 532 nm. The mechanism of exciton-phonon coupling was observed to be mainly associated with the Frohlich interaction, and the coupling strength of the exciton-phonon increases with increasing lateral size. Compared with a larger CdS nanobelt, a narrower nanobelt exhibits a larger tensile strain. Recombination of free excitons (FX), excitons bound to neutral impurities (A(0)X), and donor-acceptor pairs (DAP) were identified from a low-temperature PL spectrum. At temperatures below similar to 123 K, a red shift of the FX energy occurs with decreasing lateral size due to a larger uniaxial tensile strain; at temperatures above similar to 123 K, a red shift of the FX energy occurs with increasing lateral size because of the reabsorption of the emitted light inside the thicker belt, indicating that the FX energy is affected by both the tensile strain and the surface-depletion-induced quantum confinement (the reabsorption of the emitted light) in the nanobelt.