Pb0.8Sn0.2Te thin films were grown on Si(100) substrates using intermediate BaF2/CaF2 buffer layers in a molecular beam epitaxy system. Atomic force microscopy showed that the PbSnTe films become more flat as deposition rate increases, and substrate temperature decreases. The optimal substrate temperature was found to be about 350 degrees C. Fourier-transform infrared spectroscopy and variable angle spectroscopic ellipsometry were used for the optical characterization of the PbSnTe films in the infrared and visible to ultraviolet range of the light, respectively. It was found that the PbSnTe film grown at about 350 degrees C with higher deposition rate has the most pronounced optical characteristics as well as smoothest surface. The charge carrier concentrations and mobilities of the Pb0.8Sn0.2Te films were determined by means of infrared spectroscopy and also using conventional Hall-effect measurements, these results were then compared and analyzed. The different values obtained using these two techniques are explained by the grain structure of the surface and by occurrence of the microcracks in the PbSnTe films. The thicker PbSnTe films have the higher values of carrier mobility. (C) 2009 Elsevier B.V. All rights reserved.