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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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