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 crystals of varying size and size distribution by varying the deposition parameters, in particular the nature of the complexing agent, the complex-to-lead ion ratio, the film thickness, and the deposition temperature. Crystal size and size distribution were measured by transmission electron microscopy and correlated with the increase in effective optical bandgap estimated from the optical absorption spectra of the films. Postdeposition treatments (annealing and treatment in hydroxide solutions) were used to induce controlled crystal growth and the bandgaps of the treated films were correlated with the crystallite size. The experimental 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 quantized films was intrinsic, with the Fermi level close to the center of the effective bandgap.