Abstract

Semiconductor crystallites which are 10s to 100s of Angstroms in diameter occupy a special niche in between bulk solids and isolatedmolecules. These cluster compounds are large enough to exhibit a crystalline core, but small enough that solid state electronic and vibrational band structures is not yet developed. We use solution based methods for the synthesis of high quality nanometer sice (1-10 nm) II-VI semiconductor crystallites with narrow size distributions, emphasizing CdSe, CdS, and CdTe crystallites. The crystallites are characterized using x-ray and electron diffraction techniques. Optical characterization of their electronic structure using hole-burning techniques luminescence, DC Stark and Zeeman techniques reveals both molecular and bulk-like characteristics as well as properties which are unique to nanometer size crystallites. We observe a number of discrete electronic transitions and study their dependence on crystallite diameter. We find that the electron-hole pair dynamics following photoexcitation are dominated by surface effects which are especially important in these crystallites since a large fraction of the atoms are "surface" atoms.

© 1993 Optical Society of America