The role of annealing temperature and lead content on optical properties of Pb xS 1 − x films

Abstract

Films of Pb x S 1 − x were prepared and investigated for optical properties. Alloys of the material were initially prepared with different contents of lead and later thermally evaporated to grow the films. Optical properties of the Pb x S 1 − x films were studies for two Pb content [ x = 0.50 and 0.53] and various annealing temperatures ( T a) between 303 and 673 K. The results showed that films have both direct and indirect optical transitions. Optical energy gap ( E g) increased with increasing annealing temperature whereas it decreased with increased Pb content ( x). In contrast, the widths of localized tail states in the gap decreased with increasing T a and increased with x. Further, increasing T a caused a decrease in the optical constants (refractive index, extinction coefficient and real and imaginary dielectric constants), whereas they increased with increasing Pb content. We conclude that these films are suitable for optical devices.