Ultrathin nanoparticle ZnS and ZnS : Mn films: surface sol-gel synthesis, morphology, photophysical properties

Ultrathin films of ZnS and Mn-doped ZnS were grown on silicon substrates us ing surface sol-gel reactions, and the film growth process was characterize d by ellipsometry, atomic force microscopy, X-ray photoelectron spectroscop y, UV-visible absorbance and photoluminescence (PL) spectroscopy. The Si su bstrates were pre-treated by chemical oxidation. On the oxidized Si/SiOx su rface, nanoparticulate films of ZnS and Mn-doped ZnS were grown by sequenti al immersion in aqueous metal acetate and sodium sulfide solutions. During the first four adsorption cycles, there was little film growth, but thereaf ter the amount of material deposited was linear with the number of adsorpti on cycles. This behavior is consistent with the formation of ZnS nuclei at low coverage, followed by particle growth in subsequent cycles. PL spectra are consistent with incorporation of Mn2+ into the ZnS nanoparticles. (C) 2 000 Elsevier Science S.A. All rights reserved.