Stokes shift and fine structure splitting in composition-tunable Zn_xCd_1−xSe nanocrystals: Atomistic tight-binding theory

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• 作者：Worasak Sukkabot ^{w.sukkabot@gmail.com}
• 关键词：Tight-binding theory ; ZnxCd1&minus ; xSe ; Alloy ; Nanocrystals ; Stokes shift ; Fine structure splitting
• 刊名：Physica B: Condensed Matter
• 出版年：2017
• 出版时间：1 February 2017
• 年：2017
• 卷：506
• 期：Complete
• 页码：192-197
• 全文大小：937 K
• 卷排序：506

文摘

I report on the atomistic correlation of the structural properties and excitonic splitting of ternary alloy ZnxCd1−xSe wurtzite nanocrystals using the sp3s* empirical tight-binding method with the description of the first nearest neighbouring interaction and bowing effect. Based on a successful model, the computations are presented under various Zn compositions (x) and diameters of alloy ZnxCd1−xSe nanocrystals with the experimentally synthesized compositions and sizes. With increasing Zn contents (x), the optical band gaps and electron-hole coulomb energies are improved, while ground electron-hole wave function overlaps, electron-hole exchange energies, stokes shift and fine structure splitting are reduced. A composition-tunable emission from blue to yellow wavelength is obviously demonstrated. The optical band gaps, ground electron-hole wave function overlaps, electron-hole interactions, stokes shift and fine structure splitting are progressively decreased with the increasing diameters. Alloy ZnxCd1−xSe nanocrystal with Zn rich and large diameter is the best candidate to optimistically be used as a source of entangled photon pairs. The agreement with the experimental data is remarkable. Finally, the present systematic study on the structural properties and excitonic splitting predominantly opens a new perspective to understand the size- and composition-dependent properties of ZnxCd1−xSe nanocrystals with a comprehensive strategy to design the optoelectronic devices.