Temperature-dependent photoluminescent and Raman studies on type-II CdS/ZnSe core/shell and CdS/CdZnS-ZnCdSe/ZnSe core/intermediate/shell nanoparticles
Temperature-dependent photoluminescent and Raman studies on type-II CdS/ZnSe core/shell and CdS/CdZnS-ZnCdSe/ZnSe core/intermediate/shell nanoparticles
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DOI：
10.1016/j.jallcom.2016.10.223
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发表时间：
2017-03-15
影响因子：
6.2
通讯作者：
Nghia, N. X.
中科院分区：
文献类型：
--
作者：
Ca, N. X.;Bau, N. Q.;Nghia, N. X.
由于ii型半导体纳米晶体在光电器件中的应用前景广阔，人们对这种材料体系进行了大量的研究。许多先前的工作研究了它们在室温下的紫外可见吸收和光致发光（PL）特性。然而，没有对温度相关的PL和拉曼散射（RS）光谱进行详细的研究来了解它们的光学性质。为了进一步了解这一问题，我们制备了CdS、CdS/ZnSe核/壳层（C/S）和CdS/CdZnS-ZnCdSe/ZnSe核/中间体/壳层（C/I/S）纳米粒子，并研究了它们的拉曼、紫外吸收和PL性能。室温下的光谱研究表明，C/S和C/I/S样品属于ii型结构。对它们在10-300 K温度范围内的PL光谱的详细分析表明，光谱参数发生了不寻常的变化，特别是在160 - 250 K温度范围内。基于温度相关的RS研究结果，我们认为这种不寻常的变化主要是由于核心和外壳部分以及周围环境的热膨胀系数差异产生的压缩应变。我们还指出，在核壳之间形成的中间层对降低晶格应变起着重要的作用，并且可以提高PL的量子产率。(C) 2016 Elsevier B.V.版权所有
Due to promising applications in optoelectronic devices of type-II semiconducting nanocrystals, much effort has been made to study this material system. Many previous works investigated their UV-vis absorption and photoluminescent (PL) features at room temperature. However, no detailed study on temperature-dependent PL and Raman-scattering (RS) spectra has been carried out to learn about their optical properties. To further understand this problem, we prepared CdS, CdS/ZnSe core/shell (C/S), and CdS/CdZnS-ZnCdSe/ZnSe core/intermediate/shell (C/I/S) nanoparticles, and then studied their Raman, UV evis absorption and PL properties. Spectroscopic studies at room temperature demonstrated the C/S and C/I/S samples belonging to the type-II structure. Detailed analyses of their PL spectra in a temperature range of 10-300 K indicated unusual changes in the spectral parameters, particularly at temperatures from about 160 to 250 K. Based on the results obtained from temperature-dependent RS studies, we suggest that such the unusual variations are predominantly due to compressive strain generated from the difference in the thermal expansion coefficients of the core and shell parts, and surroundings. We also point out that the intermediate layer formed between the core and shell plays an important role in reducing lattice strain, and can improve the PL quantum yield. (C) 2016 Elsevier B.V. All rights reserved.