Chemical bath deposited PbSe films were subjected to post-deposition treatment with aqueous (typically 0.25 - 0.5 M) KOH. For films deposited using a citrate complex, this treatment resulted in dissolution of surface lead oxides (seen from XPS and EXAFS mesurements) and growth of the nanocrystals (from ca. 5 to as much as 20 nm, measured by XRD and TEM) by an Ostwald ripening mechanism and formation of a porous network. For films deposited using KOH-complexed Pb, this growth did not occur. The latter films are made up of PbSe crystals (ca. 4 nm) embedded in an amorphous matrix of lead oxide. Successful etching of the crystallite surface passivation is found to be critical fo the growth progress. While the KOH treatment removed most of this matrix, the individual crystals of PbSe still remained passivated with a surface where Pb was apparently bonded to both O and Se. Using a concentrated KOH solution (3 M) for long times (> 1 h), this surface could be removed and crystal growth occurred to give a network of PbSe crystals several nm in size.
Citation: Chemistry of Materials
Pub Type: Journals
nanocrystals, Ostwald ripening, PbSe, surface treatment