Indium thin film (∼20 nm) deposited on intrinsic lead sulfide films leads to the formation of an n-type composite layer when annealed in nitrogen atmosphere at 350–400°C. The formation of metallic lead and indium oxide is observed in the X-ray diffraction patterns of the films. The dark conductivity of the PbS+In films after nitrogen annealing at 400°C attains a value of 500 Ω −1 cm −1, which is higher by five orders of magnitude compared with as-prepared PbS films. Modifications in the optical and electrical properties of PbS+In films after annealing are attributed to the presence of metallic lead and indium oxide in the films.