A polycrystalline lead sulfide PbxS1-x alloys with various Pb concentration (x=0.50, 0.51, 0.52, 0.54 and 0.55) has been prepared successfully. PbₓS₁-ₓ films of thickness 1.5 μm have been deposited on n-Si substrates by flash thermal evaporation method at room temperature (RT) under vacuum 10^-6 torr and deposition rate 0.83x10^-3 μm/sec. These films have been annealed at different annealing temperatures (Ta = RT, 323, 373, 423, 473 and 523 K). The optical measurement showed that PbₓS₁-ₓ films have a direct energy band gap, which increases with increasing Ta and decreases with increasing Pb concentration. The absorption coefficient, refractive index, extinction coefficient, dielectric constant, and the width of the tails of localized states in the gap decreases with decreasing Ta and increase with increasing Pb concentration.
