Nila A, Baltog I, Dragoman D, Baibarac M, Mercioniu I
Laboratory of Optical Processes in Nanostructured Materials, National Institute of Material Physics, PO Box MG-7, Magurele-Bucharest 077125, Romania. Faculty of Physics, University of Bucharest, POB MG-11, Magurele-Bucharest 077125, Romania.
J Phys Condens Matter. 2017 Sep 13;29(36):365702. doi: 10.1088/1361-648X/aa7cb3. Epub 2017 Jun 30.
The exciton-phonon interaction, considered as a stimulated Raman scattering process, is studied in different semiconductor mixtures: PbI/TiO, PbI/Si and CdS/Si. Raman spectra recorded at excitation wavelengths of 514.5 and 488 nm for PbI and CdS, respectively, reveal a strong enhancement of the Raman lines peaked at 97 and 305 cm, evaluated by the ratio I /I between the relative intensities of the spectra recorded in the temperature range of 88-300 K. It is found that PbI and CdS exhibit a decrease in the Raman intensity modes with decreasing temperature, while in TiO and Si an increase in the Raman lines intensities peaked at 138 and 520 cm is observed. This behavior can be explained by an energy transfer process from PbI or CdS towards TiO and Si. This explanation is supported by the schematic potential energy levels diagram obtained from the density of states, which is calculated using the density functional theory. According to this energy levels diagram, the electrons are expected to migrate directly from the conduction band (CB) energetic levels of the PbI and CdS towards the CB levels of TiO and Si.
激子 - 声子相互作用被视为一种受激拉曼散射过程，在不同的半导体混合物中进行了研究：碘化铅/二氧化钛（PbI/TiO）、碘化铅/硅（PbI/Si）和硫化镉/硅（CdS/Si）。分别在514.5纳米和488纳米的激发波长下记录的碘化铅和硫化镉的拉曼光谱显示，通过在88 - 300 K温度范围内记录的光谱相对强度之比I /I评估，在97和305厘米处出现峰值的拉曼线有显著增强。研究发现，随着温度降低，碘化铅和硫化镉的拉曼强度模式降低，而在二氧化钛和硅中，观察到在138和520厘米处出现峰值的拉曼线强度增加。这种行为可以通过从碘化铅或硫化镉向二氧化钛和硅的能量转移过程来解释。这种解释得到了从态密度获得的示意性势能能级图的支持，该图是使用密度泛函理论计算得出的。根据这个能级图，预计电子将直接从碘化铅和硫化镉的导带（CB）能级迁移到二氧化钛和硅的CB能级。
