SYNTHESIS AND CHARACTERIZATION OF NEARLY MONODISPERSE CDE (E = S, SE,TE) SEMICONDUCTOR NANOCRYSTALLITES

A simple route to the production of high-quality CdE (E = S, Se, Te) s emiconductor nanocrystallites is presented. Crystallites from approxim ately 12 angstrom to approximately 115 angstrom in diameter with consi stent crystal structure, surface derivatization, and a high degree of monodispersity are prepared in a single reaction. The synthesis is bas ed on the pyrolysis of organometallic reagents by injection into a hot coordinating solvent. This provides temporally discrete nucleation an d permits controlled growth of macroscopic quantities of nanocrystalli tes. Size selective precipitation of crystallites from portions of the growth solution isolates samples with narrow size distributions (<5% rms in diameter). High sample quality results in sharp absorption feat ures and strong ''band-edge' emission which is tunable with particle s ize and choice of material. Transmission electron microscopy and X-ray powder diffraction in combination with computer simulations indicate the presence of bulk structural properties in crystallites as small as 20 angstrom in diameter.