NanoCrystallites of lead sulfide in hybrid films prepared by sol-gel process

The synthetic procedure, optical and electrical properties of various sizes and concentrations of PbS nanocrystals (NCs) in hybrid thin films prepared by the sol-gel procedure are presented. Zirconium oxide and Zirconia-Silica- Urethane (ZSUR) matrices with different concentration of di-urethane-silica (DURS-0-12.5 mole%), are used as host materials. TEM and absorption measurements showed that the average diameter of the PbS NCs varied between 2.0 and 8.0 nm with an increase in the temperature treatment and with an increase of the concentration of DURS and the PbS volume fraction (5-30 mole%). An increase in the PbS concentration (40-50 mole%) results in a uniform layer of PbS formed spontaneously, with a thickness of about 10-30 nm on the zirconia substrate containing PbS NCs. I-V characteristics were measured for three configurations of the films: one layer uniform PbS NCs in hybrid film, (ITO/PbS-hybrid film/Au) structure exhibiting nearly symmetric nonlinear characteristics; two-layer structure (ITO/PbS-hybrid film/PbS bulk/Au) depending on the DURS concentration in hybrid matrix exhibiting rectifying behavior with rectifying ratio 50-200 at 1 V; and the third uniform PbS thin film (Au/PbS thin fim/Au) structure with thickness dependence of specific conductivity.