Journal of Luminescence, cilt.293, 2026 (SCI-Expanded, Scopus)
In this study, the nonlinear absorption (NA) and optical limiting (OL) properties of indium sulfide (In2S3) thin films prepared by physical vapor deposition (PVD) and radio-frequency (RF) magnetron sputtering were investigated. Linear optical analysis revealed distinct Urbach energies of 1.14 eV and 0.27 eV for the PVD-grown and RF-sputtered films, respectively, indicating higher defect density in the former. Photoluminescence (PL) measurements showed broader and stronger visible emission for the RF-sputtered film, while the PVD-grown film exhibited narrower near-band-edge emission. Femtosecond transient absorption spectroscopy further revealed that the PVD-grown film featured broad excited-state absorption and faster decay dynamics, whereas the RF-sputtered film displayed ground-state bleaching and longer lifetimes, consistent with fewer traps and reduced carrier loss. Open-aperture Z-scan analysis under 532 nm, 4 ns excitation indicated intensity-dependent NA dominated by defect-assisted processes. The effective nonlinear coefficients from the defect-saturation model were over an order of magnitude higher than those from the Sheik–Bahae model. The RF-sputtered film exhibited shallower defect states that enhanced sequential two-photon and free-carrier absorption, while the PVD-grown film showed early saturation due to localized-state filling. Optical limiting thresholds of 2.63 mJ/cm2 (RF) and 7.15 mJ/cm2 (PVD) confirm the superior limiting performance of the RF-sputtered In2S3 film for visible-range nonlinear photonic applications.