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The detailed study of the effects of spin recipe and GaAs substrate doping (i.e., semi-insulating, n-type, or p-type) on the structural and optical properties of spin-cast CdSe-CdS core-shell CQDs provides insight into the surface adsorption and charge transfer mechanisms that will influence any potential optoelectronic device. The hypotheses of this study are: i) it is possible to establish spin-casting recipes that yield a thin film of CQDs with large surface density and uniform size, and ii) it is possible to control the optical response of CQDs by varying the GaAs substrate doping to influence charge transfer processes. As a result of these measurements, we have been able to demonstrate a strong dependence of spin-cast CQD structural properties on the doping type of the GaAs substrate, as well as evidence from measured optical properties to support the idea that hot carriers photoexcited in the GaAs substrate are transferred either to the CQD surface states through organic surface ligands or directly to confined states within the CQD.
Date of Publication: July 2007