Effect of laser-induced modification on structural properties and photoluminescence of amorphous arsenic sulfide thin films
摘要
In this study, we investigate laser-induced structural transformations in vitreous arsenic sulfide (As2S3) films deposited by thermal evaporation and spin-coating, as well as the corresponding changes in the photoluminescence (PL) properties of these films. The specified material is attractive for various applications in infrared optics and electronics, and it is important to improve its functionality by developing methods of its structural modification without changing the chemical composition. In our study pulsed (τ = 300 fs) and continuous laser irradiation at wavelengths of 515 and 532 nm respectively and a fluence of up to 56 mJ/cm2 was used as means of As2S3 films modification. The results of the study reveal that, in the spin-coated As2S3, laser-induced formation of sulfur S8 rings and polymer S chains takes place, while the local chemical composition of thermally evaporated films remains intact. PL intensity in the 1.6–2 eV range increases after laser treatment, due to creation of defect states in the Urbach edge region of the spectrum. Namely, the concentration of “wrong” homopolar bonds which act as radiative recombination centers for carriers, presumably increases, while paramagnetic defects in a form of S dangling bonds do not contribute to PL.