14 October 2004 Comparison of the femtosecond time-resolved excited state dynamics in copper oxide and copper sulfide quantum dots
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Abstract
The relaxation dynamics of Cu2O and Cu1.8S quantum dots (QDs) are compared via time-resolved femtosecond pump probe experiments. It is found that Cu2O shows extremely long-lived excited states on the microsecond time scale and Cu1.8S exhibits much shorter lifetimes in the picosecond time regime. While copper sulfide systems are described in the literature as p-type direct band gap materials, the Cu2O system is direct band gap, however it has a forbidden lowest-energy state. These differences are expressed in the different lifetimes displayed in the time-resolved femtosecond and nanosecond measurements. Moreover, it is confirmed by photoluminescence spectroscopy that reveals that only the Cu1.8S QDs show efficient PL and the Cu2O QDs do not luminescence. In all of the systems, carrier trapping is probably the lifetime limiting process for the conduction band edge depopulation.
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Yongbing Lou, Clemens Burda, Ming Yin, Stephen O'Brien, "Comparison of the femtosecond time-resolved excited state dynamics in copper oxide and copper sulfide quantum dots", Proc. SPIE 5513, Physical Chemistry of Interfaces and Nanomaterials III, (14 October 2004); doi: 10.1117/12.556695; https://doi.org/10.1117/12.556695
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