Small-angle x-ray scattering and inhomogeneities of the electron density in polycrystalline and epitaxial PbS films

The dependence of the characteristics of the macro- and microporosity on the condensation temperature has been studied for condensation temperatures from 30 to 450°C by small-angle x-ray scattering, hydrostatic weighing, and low-temperature desorption of argon in polycrystalline and single-crystal lead sulfide films with thickness 3–5 μm condensed for normal incidence of the molecular beam on polycrystalline and single-crystal substrates. The porosity of the polycrystalline films is an order of magnitude greater than in the epitaxial films. In polycrystalline condensates, the pores are elongated and are oriented along the normal to the film. The pores in the epitaxial films have a platelet form with faces along the {100} planes and are parallel to the direction of growth of the condensate. At high substrate temperature (about 400°C), more nearly equiaxial pores, with additional {110} faces are formed, as a result of the plastic deformation of the condensate by thermal macrostresses.