Optical properties of films of the PbTe-SnS system

Optical absorption and reflection spectra of thin films of (PbTe)/sub 1-x/(SnS)/sub x/ (0 < x < 0.2) deposited on monocrystalline barium fluoride substrate have been investigated. The dependences of the squared refractive index and of the dielectric constant on squared wavelength for films with different compositions are given and discussed. The absorption coefficients of the films are calculated over the whole interference range from optical transmission spectra. The dependence of the squared absorption coefficient on the photon energy gives evidence that direct optical transmissions are characteristic of films and the band gap drops with increasing SnS concentration