Laser-Modified Arsenic Sulfide Vitreous Semiconductor Films: Structural Properties and Photoluminescence Changes

Owing to transparency in the near and middle infrared ranges, nanostructures based on arsenic sulfide (As₂S₃) are of interest for designing integrated optics elements. We investigated laser-induced structural and photoluminescence (PL) changes in thermally evaporated and spin-coated vitreous As₂S₃ films. Pulsed (λ = 515 nm, τ = 300 fs) and continuous (λ = 532 nm) laser irradiation was used as a method allowing structural modification without changing the chemical composition of As₂S₃ films. The results of our study reveal laser-induced formation of sulfur S₈ rings and polymer sulfur chains in the spin-coated films, while the local chemical composition of thermally evaporated films does not change. Laser-induced increase in the PL intensity in the range of 1.6–2.0 eV is observed, which is associated with the creation of defect states near the Urbach edge. Laser irradiation presumably increases the amount of homopolar bonds acting as radiative carrier recombination defects, while paramagnetic defects in a form of S dangling bonds do not contribute to PL.