Title: Optical Properties and Applications of Colloidal Semiconductor Nanocrystals
Speaker: Pro. Min Xiao
Time: July. 08. 2008. 4:20 P.M.
Venue: Room A101 At WNLO
Abstract:
In the past twenty years, the fields of nanosciences and nanotechnologies have been expanded and developed extremely fast, and have entered into many areas of sciences and technologies. Comparing to the MBE-grown nanostructures, the chemically-synthesized colloidal nanocrystas can be made with very simple setups, like the one with a chemical beaker on a hot plate. The nanocrystals can be made with heated chemical solutions by injecting the right elements at the right temperature. By controlling the concentrations of the composite elements, temperature, growth time, and right injection speed, et al, colloidal nanocrystals of certain desired sizes (by taking them out at selected growth time) can be made with narrow size distributions, typically 5—10%. Nanocrystals with different diameters emit at different wavelengths, therefore very useful in applications. Many colloidal nanocrystals, such as CdSe, CdS, ZnSe, InP, and many others, have been synthesized with very high qualities. Some of the nanocrystals can have very high quantum efficiency, up to 90% quantum yield. In order to protect the surfaces of the nanocrystals and make the nanocrystals stable for long periods of time, sometime, protective shells are grown on the quantum-dot cores, making the core/shell structure such as CdSe/CdS, with CdS having a larger bandgap than Cd. Such core/shell nanocrystals are now commercially available. New kinds of colloidal nanocrystals are been made using different techniques and elements.
Nanoscience and nanotechnology are very active research fields and cover very broad areas, therefore it is impossible for me to make a comprehension review for the fields involving colloidal nanocrystals. I will use some experiments that we have done in the past few years to illustrate the interesting properties of such colloidal nanocrystals, and at the end to point out some potential applications.
