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Synthesis and Optical Properties of CdSe Core and Core/Shell Semiconductor Nanocrystals

Dr Joel Van Embden

Centre for Micro-Photonics,
Swinburne University of Technology

3:30 pm Friday, 11 July 2008, EN101 (Ground Floor, EN Building), Hawthorn.

The synthesis of nanocrystals is unique compared to the formation of larger micon-sizes species as the final crystal sizes are not much larger than the primary nuclei. As a consequence the final outcome of a nanocrystal synthesis i.e mean crystal size, concentration and standard deviation is almost solely determined by the end of the nucleation phase. Directing the growth of crystals beginning from aggregates of only tens of atoms into mature monodisperse nanocrystals requires that the the governing kinetics are strictly controlled at every moment of the reaction. Some experimental data and numerical modeling of nucleation and growth of cadmium selenide (CdSe) nanocrystals will be presented.

The ultimate success of applications based on nanocrystals requires the increasing ability to control and manipulate both the chemical and electronic behaviour of the crystals. Considering that the phase transfer of these crystals into non-ideal environments is predominantly the first step toward usable nano-devices, the crystals themselves require protection from degradation of their desired properties. Overcoating the core with a "shell" of a wider band gap material provides a means to physically and electronically isolate the chromophore from its environment. Despite the fact that core/shell materials are a vital part of impending semiconductor technologies on the nanoscale, to date there has still been little detailed studied on the properties of core-shell materials. Refining the methods of core/shell synthesis toward the production of high-quality well defined core/shells will act not only to improve the way shell coatings are conducted, but via optial investigations deepen our understanding of how the shell functions. Data on the synthesis and optical properties of CdSe/CdS heterostructures will be presented

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