QUANTUM-SIZE EFFECTS IN CHEMICALLY DEPOSITED, NANOCRYSTALLINE LEAD SELENIDE FILMS

Quantum size effects have been studied in chemical solution deposited films of nanocrystalline PbSe. Films have been deposited containing cr ystals of varying size and size distribution by varying the deposition parameters, in particular the nature of the complexing agent, the com plex-to-lead ion ratio, the film thickness, and the deposition tempera ture. Crystal size and size distribution were measured by transmission electron microscopy and correlated with the increase in effective opt ical bandgap estimated from the optical absorption spectra of the film s. Postdeposition treatments (annealing and treatment in hydroxide sol utions) were used to induce controlled crystal growth and the bandgaps of the treated films were correlated with the crystallite size. The e xperimental increases in bandgap were compared with theoretical models for increase in bandgap as a function of nanocrystallite size. X-ray photoelectron spectroscopy showed that the PbSe in the highly quantize d films was intrinsic, with the Fermi level close to the center of the effective bandgap.