Optical properties of nanostructured lead sulfide films with a D03 cubic structure

The optical transmittance of nanostructured cubic PbS (lead sulfide) films with a D03 structure is measured in the wavelength range 300 to 3200 nm. The film thicknesses are in the range ∼120 to ∼400 nm. Electron microscopy of the microstructure shows that about half of the films' particles are 60 nm or smaller in size. As the average particle size is decreased, the band gap Eg increases from 0.85 to 1.5 eV, being noticeably larger than the band gap of coarse-grained PbS, 0.41 eV. This is indicative of a blue shift of the optical absorption band in nanostructured PbS films.