Ultrafast carrier dynamics in ZnO nanorods

Chi-Kuang Sun; Shih-Ze Sun; Kung-Hsuan Lin; Kenneth Yi-Jie Zhang; Hsiang-Lin Liu; Sai-Chang Liu; Jih-Jen Wu
July 2005
Applied Physics Letters;7/11/2005, Vol. 87 Issue 2, p023106
Academic Journal
Free exciton and above-band-gap free carrier dynamics in ZnO nanorods have been investigated at room temperature with a femtosecond transient transmission measurement. Following the photoexcitation of above-band-gap free carriers, an extremely fast external thermalization time on the order of 200 fs can be observed. Under high excitation, hot phonon effects were found to delay the carrier cooling process. While the photoexcitation energy was tuned to match the free exciton transition, stable exciton formation can be uncovered while no evident exciton ionization process can be found unless the photoexcited exciton density exceeded the Mott density.


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