PREPARATION OF II-VI QUANTUM-DOT COMPOSITES BY ELECTROSPRAY ORGANOMETALLIC CHEMICAL-VAPOR-DEPOSITION

New thin film composites consisting of a ZnSe matrix and CdSe nanocrystals (NCs) have been prepared by a novel technique combining electrospray and organometallic chemical vapor deposition (OMCVD). CdSe NCs, synthesized in solution by controlled growth of CdSe nuclei, were derivatized with pyridine or overcoated with a thin ZnSe layer. The derivatized NCs were dispersed in a pyridine/ acetonitrile mixture and transferred into the growth zone of an OMCVD reactor using an electrospray. The transferred NCs were co-deposited with ZnSe grown by OMCVD from hydrogen selenide and diethyl zinc at temperatures ranging from 150 to 250 degrees C. The absorption and emission spectra of the composites show characteristic transitions of the NCs. The emission wavelength can be tuned by selecting the size of the NCs. A pre-formed ZnSe passivation layer, also synthesized in solution, improves thermal stability of the NCs during the co-deposition, and enhances the photoluminescence emission efficiency of the composites. The elemental composition and microstructure of the materials are probed by Auger electron spectroscopy, X-ray fluorescence spectroscopy, and high-resolution transmission electron microscopy.