Core–Shell to Doped Quantum Dots: Evolution of the Local Environment Using XAFS

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• 作者：Avijit Saha ; Soma Chattopadhyay ; Tomohiro Shibata ; Ranjani Viswanatha
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：August 25, 2016
• 年：2016
• 卷：120
• 期：33
• 页码：18945-18951
• 全文大小：516K
• 年卷期：0
• ISSN：1932-7455

文摘

Internal structure study at an atomic level is a challenging task with far reaching consequences to its material properties, specifically in the field of transition metal doping in quantum dots. Diffusion of transition metal ions in and out of quantum dots forming magnetic clusters has been a major bottleneck in this class of materials. Diffusion of the magnetic ions from the core into the nonmagnetic shell in a core/shell heterostructure architecture to attain uniform doping has been recently introduced and yet to be understood. In this work, we have studied the local structure variation of Fe as a function of CdS matrix thickness and annealing time during the overcoating of Fe₃O₄ core with CdS using X-ray absorption spectroscopy. The data reveals that Fe₃O₄ core initially forms a core/shell structure with CdS followed by alloying at the interface eventually completely diffusing all the way through the CdS matrix to form homogeneously Fe-doped CdS QDs with excellent control over size and size distribution. Study of Fe K-edge shows a complete change of Fe local environment from Fe–O to FeS.