Characterization of Excited-State Magnetic Exchange in Mn2+-Doped ZnO Quantum Dots Using Time-Dependent Density Functional Theory

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• 作者：Ekaterina Badaeva ; Joseph W. May ; Jiao Ma ; Daniel R. Gamelin ; Xiaosong Li
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：November 3, 2011
• 年：2011
• 卷：115
• 期：43
• 页码：20986-20991
• 全文大小：914K
• 年卷期：v.115,no.43(November 3, 2011)
• ISSN：1932-7455

文摘

Absorption spectra of Mn²⁺-doped ZnO quantum dots have been studied with the linear-response time-dependent density functional theory. Spectral changes caused by excited state dopant-carrier and dopant鈥揹opant magnetic exchange couplings are investigated. The excitonic transition maximum shifts to higher energy and decreases in intensity with increasing Mn²⁺ concentration. The lowest excitonic transitions split in the spin-up and spin-down manifolds due to sp鈥?i>d magnetic exchange between the Mn²⁺ and ZnO conduction and valence band carriers. Increased Mn²⁺ concentration leads to a broadening and increase in the intensity of the midgap charge-transfer electronic absorption band. The charge-transfer band broadening results from excited-state splitting arising from double exchange magnetic interactions involving Mn²⁺ ions and the photogenerated hole. The excited-state double exchange leads to stabilization of the ferromagnetic configuration in the charge-transfer state. The strength of this ferromagnetic double exchange interaction depends on the inter-Mn²⁺ distance within the quantum dot.