The optical properties of PbTe films in the 5–20 μm wavelength region
Abstract PbTe films have been prepared by a variety of evaporation techniques using a range of substrate temperatures and source compositions. It has proved possible to prepare films exhibiting low absorption (> 25 cm −1 ) over a wide spectral range (6–20 μm) combined with a high refractive index, 5.6, with very little dispersion. The techniques used flash evaporation of tellurium rich PbTe onto unheated substrates. Although X-ray studies and Hall measurements have been performed on these samples and reveal intriguing variations, only limited correlation is possible with the detailed variation of the optical properties. A very simplified explanation is offered by the results of thermal probe measurements which indicate that the transparent films are those with very few electrical carriers present.