Impact of thickness on crystal structure and optical properties for thermally evaporated PbSe thin films

• PbSe films with varied thickness were directly prepared by thermal evaporation.
• The predominant peak is intensified with increasing film thickness.
• Optical investigation leads to a direct optical band gap ranging 2.04–2.30 eV depending on film thickness.

Nanocrystalline lead selenide (PbSe) thin films with varied thickness were deposited on glass substrates by thermal evaporation technique. Physical and surface properties of PbSe films were examined by XRD, AFM, UV–Vis spectra. It was found that the structural and optical properties of the PbSe films were strongly dependent on thickness. On one hand, the particles were uniformly distributed in the surface for the thinner samples. On the other hand, however, the particles began to aggregate and worm-like structures appeared for the thicker ones (93 nm and 127 nm). The absorption band-edge was red shifted with increasing thickness. The optical band gap ranging 2.04–2.30 eV with thickness was observed. This could be attributed to the increasing of grain size and the improvement of film uniformity.