Abstract:
The crystal structure of lead sulfide (PbS) films produced by chemical deposition onto a glass substrate is studied by X-ray diffraction analysis. The thickness of the synthesized films is $\sim$120 nm, the dimensions of the regions of coherent scattering are 70–80 nm, and the magnitude of microstrains is $\sim$0.20%. It is established that the crystal structure of the synthesized PbS films and of the same films annealed at the temperature 293–423 K is cubic (space group $Fm\bar3m$) and corresponds to the $D0_3$ type that differs from the $B1$ type typical of coarse-grained PbS. In the cubic structure of the PbS nanofilms, there is a latent nonstoichiometric distribution of S atoms and vacancies among octahedral sites 4$(b)$ and tetrahedral positions 8$(c)$. The optical transmittance of the nanocrystalline PbS films is measured in the wavelength range from 200 to 3270 nm. The most pronounced variations in the transmittance is observed in the wavelength range from 700–800 to 1600–2000 nm (corresponding to the photon energy range from $\sim$1.8 to $\sim$0.7 eV). It is established that the band gap E g is 0.83–0.85 eV, i.e., it is larger than the band gap of single-crystal PbS, 0.41 eV.
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