Optical and physical properties of vacuum-deposited PbS films

Abstract

We describe the film density, void volume, thickness, species, reflectivity and crystal size of vacuum-deposited PbS films. Film densities, as determined from film thickness and areal film density measurements, were approximately one-half that of bulk PbS, resulting in a calculated average film void volume of about 60%. Film thicknesses ranging from 160 to 890 nm measured with the stylus and interferometer measuring methods were accurately determined for PbS films overlaid with approximately 100 nm of aluminum. The ion backscattering measuring method yielded an average [S]/[Pb] ratio of 0.955±0.07 or 1.00 (within experimental errors). The specular reflectivity of the glass-film interface of prism substrates, measured at an angle of incidence of 45° and at λ = 1060 nm, decreased as deposition time increased. The PbS films exhibited two sizes of crystals with the smaller located near the glass-film interface. The stylus, interferometer and ion backscattering measuring methods are useful in determining the density, void volume, thickness and species of vacuum-deposited films.